[Xamarin.Android.Build.Tasks] libxamarin-app.so generation (#2718)

Xamarin.Android needs a lot of information in the runtime in order to
do its tasks.  Among this is are two bits of information that are
used during startup: type mappings (java-to-managed `.jm` files and
managed-to-java `.mj` files) and environment settings (variables and
system properties).  Historically, Xamarin.Android used these bits of
data (generated on the application build time) by writing them into
separate files (`*.mj`, `*.jm`, `environment`), storing them in the
`.apk`, and reading these files dynamically during startup.
an `environment`

However, none of this data is *actually* dynamic - it's known
beforehand and could be stored as static data right in the `.apk`.
The problem with this idea was that we had no way to put that
information into the application native bits at build time: it would
require the presence of a compiler (or native assembler) as well as
the native linker for the target platforms.  This would have required
having the Android NDK installed, which is a hefty requirement.

That said, the Android SDK currently ships a native linker within its
`build-tools` package, and we can also bundle within our packages the
`gas` native assembler for all the architectures we support.  This
allows us to generate simple native assembler code, compile it
and link into a shared library ***when packaging*** the application.

The way it works is that during the Xamarin.Android *SDK* build we
build a "stub" `libxamarin-app.so` library which the Xamarin.Android
`libmono-android.*.so` neé `libmonodroid.so` runtime libraries are
linked against.  The stub `libxamarin-app.so` library is *not*
distributed with the Xamarin.Android SDK; instead, the "real" version
is generated at build/packaging time and packaged with the runtime
within the `.apk`.  Since the "real" version is ABI-compatible with
the stub version, the dynamic loader doesn't care and loads and
resolves symbols just fine.

This allows us to dispense with memory allocation, loading
(potentially large) files from the `.apk` (lots of I/O, slow),
parsing text files to set environment variables (additional memory
allocation), etc.  All of the data is loaded for us by Android and we
simply access global variables from the `libxamarin-app.so` library.

The process, however, can be time consuming (sort of...) and in order
to allow fast deployment to work as quickly as possible, the debug
(and desktop/host - for the benefit of the UI Designer) builds of the
runtime also contain code to load both type maps and environment
variables from files stored inside one of the override directories.

The changes provide a speed-up of ~10ms, reducing the startup time
down to around 233ms for a release build of a Xamarin.Forms app on a
Pixel 3 XL.

Makefile

@@ -193,7 +193,7 @@ define CREATE_THIRD_PARTY_NOTICES_RULE
 prepare-tpn:: $(1)
 
 $(1) $(topdir)/$(1): build-tools/ThirdPartyNotices/ThirdPartyNotices.csproj \
-		$(wildcard external/*.tpnitems src/*.tpnitems) \
+		$(wildcard external/*.tpnitems src/*.tpnitems build-tools/*.tpnitems) \
 		$(TPN_LICENSE_FILES)
 	$(call CREATE_THIRD_PARTY_NOTICES,$(1),$(2),$(3),$(4))
 endef # CREATE_THIRD_PARTY_NOTICES_RULE

Xamarin.Android.sln

@@ -21,6 +21,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "api-merge", "build-tools\ap
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "remap-assembly-ref", "build-tools\remap-assembly-ref\remap-assembly-ref.csproj", "{C876DA71-8573-4CEF-9149-716D72455ED4}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "fetch-windows-assemblers", "build-tools\fetch-windows-assemblers\fetch-windows-assemblers.csproj", "{09518DF2-C7B1-4CDB-849A-9F91F4BEA925}"
+EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Core", "Core", "{04E3E11E-B47D-4599-8AFC-50515A95E715}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Java.Interop", "external\Java.Interop\src\Java.Interop\Java.Interop.csproj", "{94BD81F7-B06F-4295-9636-F8A3B6BDC762}"
@@ -197,6 +199,10 @@ Global
 		{C876DA71-8573-4CEF-9149-716D72455ED4}.Debug|AnyCPU.Build.0 = Debug|Any CPU
 		{C876DA71-8573-4CEF-9149-716D72455ED4}.Release|AnyCPU.ActiveCfg = Release|Any CPU
 		{C876DA71-8573-4CEF-9149-716D72455ED4}.Release|AnyCPU.Build.0 = Release|Any CPU
+		{09518DF2-C7B1-4CDB-849A-9F91F4BEA925}.Debug|AnyCPU.ActiveCfg = Debug|Any CPU
+		{09518DF2-C7B1-4CDB-849A-9F91F4BEA925}.Debug|AnyCPU.Build.0 = Debug|Any CPU
+		{09518DF2-C7B1-4CDB-849A-9F91F4BEA925}.Release|AnyCPU.ActiveCfg = Release|Any CPU
+		{09518DF2-C7B1-4CDB-849A-9F91F4BEA925}.Release|AnyCPU.Build.0 = Release|Any CPU
 		{94BD81F7-B06F-4295-9636-F8A3B6BDC762}.Debug|AnyCPU.ActiveCfg = Debug|Any CPU
 		{94BD81F7-B06F-4295-9636-F8A3B6BDC762}.Debug|AnyCPU.Build.0 = Debug|Any CPU
 		{94BD81F7-B06F-4295-9636-F8A3B6BDC762}.Release|AnyCPU.ActiveCfg = Release|Any CPU

build-tools/android-toolchain/android-toolchain.targets

@@ -105,7 +105,7 @@
     <ReplaceFileContents
         SourceFile="..\scripts\XABuildConfig.cs.in"
         DestinationFile="..\..\bin\Build$(Configuration)\XABuildConfig.cs"
-        Replacements="@NDK_MINIMUM_API_AVAILABLE@=$(_NDKMinimumApiAvailable);@NDK_RELEASE@=$(AndroidNdkVersion);@NDK_REVISION@=$(_NDKRevision);@NDK_VERSION_MAJOR@=$(_NDKVersionMajor);@NDK_VERSION_MINOR@=$(_NDKVersionMinor);@NDK_VERSION_MICRO@=$(_NDKVersionMicro);@NDK_ARMEABI_V7_API@=$(AndroidNdkApiLevel_ArmV7a);@NDK_ARM64_V8A_API@=$(AndroidNdkApiLevel_ArmV8a);@NDK_X86_API@=$(AndroidNdkApiLevel_X86);@NDK_X86_64_API@=$(AndroidNdkApiLevel_X86_64)">
+        Replacements="@NDK_MINIMUM_API_AVAILABLE@=$(_NDKMinimumApiAvailable);@NDK_RELEASE@=$(AndroidNdkVersion);@NDK_REVISION@=$(_NDKRevision);@NDK_VERSION_MAJOR@=$(_NDKVersionMajor);@NDK_VERSION_MINOR@=$(_NDKVersionMinor);@NDK_VERSION_MICRO@=$(_NDKVersionMicro);@NDK_ARMEABI_V7_API@=$(AndroidNdkApiLevel_ArmV7a);@NDK_ARM64_V8A_API@=$(AndroidNdkApiLevel_ArmV8a);@NDK_X86_API@=$(AndroidNdkApiLevel_X86);@NDK_X86_64_API@=$(AndroidNdkApiLevel_X86_64);@XA_SUPPORTED_ABIS@=$(AndroidSupportedTargetJitAbis.Replace(':',';'))">
     </ReplaceFileContents>
   </Target>
 </Project>

build-tools/fetch-windows-assemblers.tpnitems

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup Condition=" '$(TpnIncludeExternalDependencies)' == 'True' ">
+    <!-- The CRC32 code comes from:
+         https://github.com/force-net/Crc32.NET/blob/fbc1061b0cb53df2322d5aed33167a2e6335970b/Crc32.NET/SafeProxy.cs
+         License: MIT (https://github.com/force-net/Crc32.NET/blob/fbc1061b0cb53df2322d5aed33167a2e6335970b/LICENSE)
+    -->
+    <ThirdPartyNotice Include="force-net/crc32.net">
+      <LicenseText>
+The MIT License (MIT)
+
+Copyright (c) 2016 force
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+      </LicenseText>
+      <SourceUrl>https://github.com/force-net/Crc32.NET</SourceUrl>
+    </ThirdPartyNotice>
+  </ItemGroup>
+</Project>

build-tools/fetch-windows-assemblers/fetch-windows-assemblers.cs

@@ -0,0 +1,738 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.IO.Compression;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading.Tasks;
+
+//
+// Taken from:
+//   https://github.com/force-net/Crc32.NET/blob/fbc1061b0cb53df2322d5aed33167a2e6335970b/Crc32.NET/SafeProxy.cs
+//
+// License: MIT
+//   https://github.com/force-net/Crc32.NET/blob/fbc1061b0cb53df2322d5aed33167a2e6335970b/LICENSE
+//
+class CRC32
+{
+	const uint Poly = 0xedb88320u;
+
+	readonly uint[] _table = new uint[16 * 256];
+
+	internal CRC32 ()
+	{
+		Init (Poly);
+	}
+
+	protected void Init (uint poly)
+	{
+		var table = _table;
+		for (uint i = 0; i < 256; i++) {
+			uint res = i;
+			for (int t = 0; t < 16; t++) {
+				for (int k = 0; k < 8; k++) res = (res & 1) == 1 ? poly ^ (res >> 1) : (res >> 1);
+				table[(t * 256) + i] = res;
+			}
+		}
+	}
+
+	public uint Append (uint crc, byte[] input, int offset, int length)
+	{
+		uint crcLocal = uint.MaxValue ^ crc;
+
+		uint[] table = _table;
+		while (length >= 16) {
+			var a = table[(3 * 256) + input[offset + 12]]
+				^ table[(2 * 256) + input[offset + 13]]
+				^ table[(1 * 256) + input[offset + 14]]
+				^ table[(0 * 256) + input[offset + 15]];
+
+			var b = table[(7 * 256) + input[offset + 8]]
+				^ table[(6 * 256) + input[offset + 9]]
+				^ table[(5 * 256) + input[offset + 10]]
+				^ table[(4 * 256) + input[offset + 11]];
+
+			var c = table[(11 * 256) + input[offset + 4]]
+				^ table[(10 * 256) + input[offset + 5]]
+				^ table[(9 * 256) + input[offset + 6]]
+				^ table[(8 * 256) + input[offset + 7]];
+
+			var d = table[(15 * 256) + ((byte)crcLocal ^ input[offset])]
+				^ table[(14 * 256) + ((byte)(crcLocal >> 8) ^ input[offset + 1])]
+				^ table[(13 * 256) + ((byte)(crcLocal >> 16) ^ input[offset + 2])]
+				^ table[(12 * 256) + ((crcLocal >> 24) ^ input[offset + 3])];
+
+			crcLocal = d ^ c ^ b ^ a;
+			offset += 16;
+			length -= 16;
+		}
+
+		while (--length >= 0)
+			crcLocal = table[(byte)(crcLocal ^ input[offset++])] ^ crcLocal >> 8;
+
+		return crcLocal ^ uint.MaxValue;
+	}
+}
+
+class app
+{
+	const int EndFileChunkSize = 65535 + 22; // Maximum comment size + EOCD size
+	const uint EOCDSignature = 0x06054b50;
+	const uint CDHeaderSignature = 0x02014b50;
+	const uint LFHeaderSignature = 0x04034b50;
+
+	class EOCD
+	{
+		public uint Signature; // Signature (0x06054b50)
+		public ushort DiskNumber; // number of this disk
+		public ushort CDStartDisk; // number of the disk with the start of the central directory
+		public ushort TotalEntriesThisDisk; // total number of entries in the central directory on this disk
+		public ushort TotalEntries; // total number of entries in the central directory
+		public uint CDSize; // size of the central directory
+		public uint CDOffset; // offset of start of central	directory with respect to the starting disk number
+		public ushort CommentLength; // .ZIP file comment length
+	};
+
+	class CDHeader
+	{
+		public uint Signature; // 0x02014b50
+		public ushort VersionMadeBy;
+		public ushort VersionNeededToExtract;
+		public ushort GeneralPurposeBitFlag;
+		public ushort CompressionMethod;
+		public ushort LastModFileTime;
+		public ushort LastModFileDate;
+		public uint CRC32;
+		public uint CompressedSize;
+		public uint UncompressedSize;
+		public ushort FileNameLength;
+		public ushort ExtraFieldLength;
+		public ushort FileCommentLength;
+		public ushort DiskNumberStart;
+		public ushort InternalFileAttributes;
+		public uint ExternalFileAttributes;
+		public uint RelativeOffsetOfLocalHeader;
+		public string FileName;
+		public byte[] ExtraField;
+		public string FileComment;
+	};
+
+	class LFHeader
+	{
+		public uint Signature; // 0x04034b50
+		public ushort VersionNeededToExtract;
+		public ushort GeneralPurposeBitFlag;
+		public ushort CompressionMethod;
+		public ushort LastModFileTime;
+		public ushort LastModFileDate;
+		public uint CRC32;
+		public uint CompressedSize;
+		public uint UncompressedSize;
+		public ushort FileNameLength;
+		public ushort ExtraFieldLength;
+		public string FileName;
+		public byte[] ExtraField;
+	};
+
+	static int Main (string[] args)
+	{
+		if (args.Length < 3) {
+			Console.WriteLine ("Usage: fetch-windows-assemblers NDK_VERSION DESTINATION_DIRECTORY NDK_URL");
+			return 1;
+		}
+
+		Task<bool> fetcher = FetchFiles (
+			args [0],
+			args [1],
+			new Uri (args [2])
+		);
+
+		fetcher.Wait ();
+
+		return fetcher.Result ? 0 : 1;
+	}
+
+	static async Task<bool> FetchFiles (string ndkVersion, string destinationDirectory, Uri url)
+	{
+		var neededFiles = new HashSet<string> (StringComparer.OrdinalIgnoreCase) {
+			$"android-ndk-r{ndkVersion}/toolchains/llvm/prebuilt/windows-x86_64/bin/i686-linux-android-as.exe",
+			$"android-ndk-r{ndkVersion}/toolchains/llvm/prebuilt/windows-x86_64/bin/arm-linux-androideabi-as.exe",
+			$"android-ndk-r{ndkVersion}/toolchains/llvm/prebuilt/windows-x86_64/bin/x86_64-linux-android-as.exe",
+			$"android-ndk-r{ndkVersion}/toolchains/llvm/prebuilt/windows-x86_64/bin/aarch64-linux-android-as.exe",
+		};
+
+		using (var httpClient = new HttpClient ()) {
+			bool success;
+			long size;
+
+			Console.WriteLine ($"Retrieving {url}");
+			(success, size) = await GetFileSize (httpClient, url);
+			if (!success)
+				return false;
+
+			Console.WriteLine ($"  File size: {size}");
+
+			EOCD eocd;
+			(success, eocd) = await GetEOCD (httpClient, url, size);
+			if (!success) {
+				Console.Error.WriteLine ("Failed to find the End of Central Directory record");
+				return false;
+			}
+
+			if (eocd.DiskNumber != 0)
+				throw new NotSupportedException ("Multi-disk ZIP archives not supported");
+
+			Console.WriteLine ($"  Central Directory offset: {eocd.CDOffset} (0x{eocd.CDOffset:x})");
+			Console.WriteLine ($"  Central Directory size: {eocd.CDSize} (0x{eocd.CDSize})");
+			Console.WriteLine ($"  Total Entries: {eocd.TotalEntries}");
+
+			Stream cd;
+			(success, cd) = await ReadCD (httpClient, url, eocd.CDOffset, eocd.CDSize, size);
+			if (!success) {
+				Console.Error.WriteLine ("Failed to read the Central Directory");
+				return false;
+			}
+
+			Console.WriteLine ();
+			Console.WriteLine ("Entries:");
+			if (!await ProcessEntries (httpClient, url, eocd, cd, neededFiles, destinationDirectory))
+				return false;
+		}
+
+		return true;
+	}
+
+	static async Task<bool> ProcessEntries (HttpClient httpClient, Uri url, EOCD eocd, Stream centralDirectory, HashSet<string> neededFiles, string destinationDirectory)
+	{
+		long foundEntries = 0;
+
+		using (var br = new BinaryReader (centralDirectory)) {
+			long nread = 0;
+			long nentries = 1;
+
+			while (nread < centralDirectory.Length && nentries <= eocd.TotalEntries) {
+				(bool success, CDHeader cdh) = ReadCDHeader (br, centralDirectory.Length, ref nread);
+				nentries++;
+				if (!success) {
+					Console.Error.WriteLine ($"Failed to read a Central Directory file header for entry {nentries}");
+					return false;
+				}
+
+				if (!neededFiles.Contains (cdh.FileName))
+					continue;
+
+				if (!await ReadEntry (httpClient, url, cdh, br, destinationDirectory))
+					return false;
+				foundEntries++;
+			}
+		}
+
+		if (foundEntries < neededFiles.Count) {
+			Console.WriteLine ($"Could not find all required binaries. Found {foundEntries} out of {neededFiles.Count}");
+			return false;
+		}
+
+		return true;
+	}
+
+	static async Task<bool> ReadEntry (HttpClient httpClient, Uri url, CDHeader cdh, BinaryReader br, string destinationDirectory)
+	{
+		string compressedFilePath = Path.Combine (destinationDirectory, $"{Path.GetFileName (cdh.FileName)}.deflated");
+		Console.WriteLine ($" {cdh.FileName} (offset: {cdh.RelativeOffsetOfLocalHeader})");
+
+		(bool success, Stream contentStream) = await ReadFileData (httpClient, url, cdh);
+		if (!success) {
+			Console.Error.WriteLine ("Failed to read file data");
+			return false;
+		}
+
+		using (var destFile = new BinaryWriter (File.OpenWrite (compressedFilePath))) {
+			using (var fbr = new BinaryReader (contentStream)) {
+				if (!await DownloadAndExtract (fbr, contentStream, destFile, compressedFilePath))
+					return CleanupAndReturn (false);
+			}
+		}
+
+		return CleanupAndReturn (true);
+
+		bool CleanupAndReturn (bool retval)
+		{
+			if (File.Exists (compressedFilePath))
+				File.Delete (compressedFilePath);
+
+			return retval;
+		}
+	}
+
+	static async Task<bool> DownloadAndExtract (BinaryReader fbr, Stream contentStream, BinaryWriter destFile, string destFileName)
+	{
+		long fread = 0;
+		(bool success, LFHeader lfh) = ReadLFHeader (fbr, contentStream.Length, ref fread);
+		if (!success) {
+			Console.Error.WriteLine ("Failed to read local file header");
+			return false;
+		}
+
+		uint dread = 0;
+		var buffer = new byte [8192];
+		while (fread <= contentStream.Length && dread < lfh.CompressedSize) {
+			uint toRead;
+			if (lfh.CompressedSize - dread < buffer.Length)
+				toRead = lfh.CompressedSize - dread;
+			else
+				toRead = (uint)buffer.Length;
+
+			int bread = await contentStream.ReadAsync (buffer, 0, (int)toRead);
+			if (bread == 0)
+				break;
+			destFile.Write (buffer, 0, bread);
+			fread += bread;
+			dread += (uint)bread;
+		}
+
+		destFile.Flush ();
+		destFile.Close ();
+		destFile.Dispose ();
+		Extract (destFileName, lfh.CRC32);
+
+		if (dread != lfh.CompressedSize)
+			Console.Error.WriteLine ($"  Invalid data size: expected {lfh.CompressedSize} bytes, read {dread} bytes");
+
+		return true;
+	}
+
+	static void Extract (string compressedFilePath, uint crc32FromHeader)
+	{
+		string outputFile = Path.GetFileNameWithoutExtension (compressedFilePath);
+		using (var fs = File.OpenRead (compressedFilePath)) {
+			using (var dfs = File.OpenWrite (outputFile)) {
+				Extract (fs, dfs, crc32FromHeader);
+			}
+		}
+	}
+
+	static void Extract (Stream src, Stream dest, uint crc32FromHeader)
+	{
+		uint fileCRC = 0;
+		int fread = 0;
+		var crc32 = new CRC32 ();
+		var buffer = new byte [8192];
+
+		using (var iis = new DeflateStream (src, CompressionMode.Decompress)) {
+			while (true) {
+				fread = iis.Read(buffer, 0, buffer.Length);
+				if (fread <= 0)
+					break;
+
+				fileCRC = crc32.Append (fileCRC, buffer, 0, fread);
+				dest.Write (buffer, 0, fread);
+			}
+			dest.Flush ();
+		}
+
+		if (fileCRC != crc32FromHeader)
+			Console.Error.WriteLine ($"  Invalid CRC32: expected 0x{crc32FromHeader:x}, got 0x{fileCRC:x}");
+	}
+
+	static async Task<(bool success, Stream data)> ReadFileData (HttpClient httpClient, Uri url, CDHeader cdh)
+	{
+		long fileOffset = cdh.RelativeOffsetOfLocalHeader;
+		long dataSize =
+			cdh.CompressedSize +
+			30 + // local file header size, the static portion
+			cdh.FileName.Length + // They're the same in both haders
+			cdh.ExtraFieldLength + // This may differ between headers...
+			16384; // ...so we add some extra padding
+
+		var req = new HttpRequestMessage (HttpMethod.Get, url);
+		req.Headers.ConnectionClose = true;
+		req.Headers.Range = new RangeHeaderValue (fileOffset, fileOffset + dataSize);
+
+		HttpResponseMessage resp = await httpClient.SendAsync (req).ConfigureAwait (false);
+
+		if (!resp.IsSuccessStatusCode) {
+			Console.Error.WriteLine ($"Failed to read file data: HTTP error {resp.StatusCode}");
+			return (false, null);
+		}
+
+		Stream s = await resp.Content.ReadAsStreamAsync ().ConfigureAwait (false);
+		if (s.Length < dataSize) {
+			Console.Error.WriteLine ($"Failed to read file data: invalid data length ({s.Length} < {dataSize})");
+			s.Dispose ();
+			return (false, null);
+		}
+
+		return (true, s);
+	}
+
+	static (bool success, LFHeader lfh) ReadLFHeader (BinaryReader cdr, long dataLength, ref long nread)
+	{
+		var lfh = new LFHeader ();
+
+		bool worked;
+		string whatFailed = null;
+		lfh.Signature = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked || lfh.Signature != LFHeaderSignature) {
+			whatFailed = $"Signature ({lfh.Signature:x} != {LFHeaderSignature:x})";
+			goto failed;
+		}
+
+		lfh.VersionNeededToExtract = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "VersionNeededToExtract";
+			goto failed;
+		}
+
+		lfh.GeneralPurposeBitFlag = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "GeneralPurposeBitFlag";
+			goto failed;
+		}
+
+		lfh.CompressionMethod = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "CompressionMethod";
+			goto failed;
+		}
+
+		lfh.LastModFileTime = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "LastModFileTime";
+			goto failed;
+		}
+
+		lfh.LastModFileDate = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "LastModFileDate";
+			goto failed;
+		}
+
+		lfh.CRC32 = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "CRC32";
+			goto failed;
+		}
+
+		lfh.CompressedSize = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "CompressedSize";
+			goto failed;
+		}
+
+		lfh.UncompressedSize = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "UncompressedSize";
+			goto failed;
+		}
+
+		lfh.FileNameLength = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "FileNameLength";
+			goto failed;
+		}
+
+		lfh.ExtraFieldLength = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "ExtraFieldLength";
+			goto failed;
+		}
+
+		byte[] bytes = ReadBytes (cdr, lfh.FileNameLength, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "FileName (bytes)";
+			goto failed;
+		}
+
+		lfh.FileName = Encoding.ASCII.GetString (bytes);
+		if (!worked) {
+			whatFailed = "FileName (ASCII decode)";
+			goto failed;
+		}
+
+		if (lfh.ExtraFieldLength > 0) {
+			lfh.ExtraField = ReadBytes (cdr, lfh.ExtraFieldLength, dataLength, ref nread, out worked);
+			if (!worked) {
+				whatFailed = "ExtraField";
+				goto failed;
+			}
+		}
+
+		return (true, lfh);
+
+	  failed:
+		if (!String.IsNullOrEmpty (whatFailed))
+			Console.Error.WriteLine ($"Failed to read a local file header field: {whatFailed}");
+
+		return (false, null);
+	}
+
+	static (bool success, CDHeader cdh) ReadCDHeader (BinaryReader cdr, long dataLength, ref long nread)
+	{
+		var cdh = new CDHeader ();
+
+		bool worked;
+		string whatFailed = null;
+		cdh.Signature = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked || cdh.Signature != CDHeaderSignature) {
+			whatFailed = "Signature ({cdh.Signature:x} != {CDHeaderSignature:x})";
+			goto failed;
+		}
+
+		cdh.VersionMadeBy = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "VersionMadeBy";
+			goto failed;
+		}
+
+		cdh.VersionNeededToExtract = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "VersionNeededToExtract";
+			goto failed;
+		}
+
+		cdh.GeneralPurposeBitFlag = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "GeneralPurposeBitFlag";
+			goto failed;
+		}
+
+		cdh.CompressionMethod = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "CompressionMethod";
+			goto failed;
+		}
+
+		cdh.LastModFileTime = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "LastModFileTime";
+			goto failed;
+		}
+
+		cdh.LastModFileDate = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "LastModFileDate";
+			goto failed;
+		}
+
+		cdh.CRC32 = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "CRC32";
+			goto failed;
+		}
+
+		cdh.CompressedSize = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "CompressedSize";
+			goto failed;
+		}
+
+		cdh.UncompressedSize = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "UncompressedSize";
+			goto failed;
+		}
+
+		cdh.FileNameLength = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "FileNameLength";
+			goto failed;
+		}
+
+		cdh.ExtraFieldLength = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "ExtraFieldLength";
+			goto failed;
+		}
+
+		cdh.FileCommentLength = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "FileCommentLength";
+			goto failed;
+		}
+
+		cdh.DiskNumberStart = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "DiskNumberStart";
+			goto failed;
+		}
+
+		cdh.InternalFileAttributes = ReadUShort (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "InternalFileAttributes";
+			goto failed;
+		}
+
+		cdh.ExternalFileAttributes = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "ExternalFileAttributes";
+			goto failed;
+		}
+
+		cdh.RelativeOffsetOfLocalHeader = ReadUInt (cdr, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "RelativeOffsetOfLocalHeader";
+			goto failed;
+		}
+
+		byte[] bytes = ReadBytes (cdr, cdh.FileNameLength, dataLength, ref nread, out worked);
+		if (!worked) {
+			whatFailed = "FileName (bytes)";
+			goto failed;
+		}
+
+		cdh.FileName = Encoding.ASCII.GetString (bytes);
+		if (!worked) {
+			whatFailed = "FileName (ASCII decode)";
+			goto failed;
+		}
+
+		if (cdh.ExtraFieldLength > 0) {
+			cdh.ExtraField = ReadBytes (cdr, cdh.ExtraFieldLength, dataLength, ref nread, out worked);
+			if (!worked) {
+				whatFailed = "ExtraField";
+				goto failed;
+			}
+		}
+
+		if (cdh.FileCommentLength > 0) {
+			bytes = ReadBytes (cdr, cdh.FileCommentLength, dataLength, ref nread, out worked);
+			if (!worked) {
+				whatFailed = "FileComment (bytes)";
+				goto failed;
+			}
+			cdh.FileComment = Encoding.ASCII.GetString (bytes);
+		}
+
+		return (true, cdh);
+
+		failed:
+		if (!String.IsNullOrEmpty (whatFailed))
+			Console.Error.WriteLine ($"Failed to read a central directory header field: {whatFailed}");
+
+		return (false, null);
+	}
+
+	static ushort ReadUShort (BinaryReader br, long dataLength, ref long nread, out bool success)
+	{
+		success = false;
+		if (dataLength - nread < 2)
+			return 0;
+
+		ushort ret = br.ReadUInt16 ();
+		nread += 2;
+
+		success = true;
+		return ret;
+	}
+
+	static uint ReadUInt (BinaryReader br, long dataLength, ref long nread, out bool success)
+	{
+		success = false;
+		if (dataLength - nread < 4)
+			return 0;
+
+		uint ret = br.ReadUInt32 ();
+		nread += 4;
+
+		success = true;
+		return ret;
+	}
+
+	static byte[] ReadBytes (BinaryReader br, int neededBytes, long dataLength, ref long nread, out bool success)
+	{
+		success = false;
+		if (dataLength - nread < neededBytes)
+			return null;
+
+		byte[] ret = br.ReadBytes (neededBytes);
+		nread += neededBytes;
+
+		success = true;
+		return ret;
+	}
+
+	static async Task<(bool success, Stream cd)> ReadCD (HttpClient httpClient, Uri url, uint cdOffset, uint cdSize, long fileSize)
+	{
+		long fileOffset = cdOffset;
+		var req = new HttpRequestMessage (HttpMethod.Get, url);
+		req.Headers.ConnectionClose = true;
+		req.Headers.Range = new RangeHeaderValue (fileOffset, fileOffset + cdSize);
+
+		HttpResponseMessage resp = await httpClient.SendAsync (req).ConfigureAwait (false);
+		if (!resp.IsSuccessStatusCode) {
+			Console.Error.WriteLine ($"Failed to read Central Directory: HTTP error {resp.StatusCode}");
+			return (false, null);
+		}
+
+		Stream s = await resp.Content.ReadAsStreamAsync ().ConfigureAwait (false);
+		if (s.Length < cdSize) {
+			Console.Error.WriteLine ($"Failed to read Central Directory: invalid data length ({s.Length} < {cdSize})");
+			s.Dispose ();
+			return (false, null);
+		}
+
+		return (true, s);
+	}
+
+	static async Task<(bool success, EOCD eocd)> GetEOCD (HttpClient httpClient, Uri url, long fileSize)
+	{
+		long fileOffset = fileSize - EndFileChunkSize;
+		var req = new HttpRequestMessage (HttpMethod.Get, url);
+		req.Headers.ConnectionClose = true;
+		req.Headers.Range = new RangeHeaderValue (fileOffset, fileSize);
+
+		HttpResponseMessage resp = await httpClient.SendAsync (req).ConfigureAwait (false);
+		if (!resp.IsSuccessStatusCode)
+			return (false, null);
+
+		using (var eocdStream = await resp.Content.ReadAsStreamAsync ().ConfigureAwait (false)) {
+			using (var sr = new BinaryReader (eocdStream)) {
+				byte[] expected = {0x50, 0x4b, 0x05, 0x06};
+				int expectedPos = 0;
+
+				for (int i = 0; i < eocdStream.Length; i++) {
+					byte b = sr.ReadByte ();
+					if (b != expected [expectedPos]) {
+						expectedPos = 0;
+						continue;
+					}
+
+					if (expectedPos == expected.Length - 1) {
+						// We've found the signature
+						var eocd = new EOCD ();
+						eocd.Signature = 0x06054b50;
+						eocd.DiskNumber = sr.ReadUInt16 ();
+						eocd.CDStartDisk = sr.ReadUInt16 ();
+						eocd.TotalEntriesThisDisk = sr.ReadUInt16 ();
+						eocd.TotalEntries = sr.ReadUInt16 ();
+						eocd.CDSize = sr.ReadUInt32 ();
+						eocd.CDOffset = sr.ReadUInt32 ();
+						eocd.CommentLength = sr.ReadUInt16 ();
+
+						return (true, eocd);
+					}
+
+					expectedPos++;
+					if (expectedPos >= expected.Length)
+						expectedPos = 0;
+				}
+			}
+		}
+
+		return (false, null);
+	}
+
+	static async Task<(bool success, long size)> GetFileSize (HttpClient httpClient, Uri url)
+	{
+		var req = new HttpRequestMessage (HttpMethod.Head, url);
+		req.Headers.ConnectionClose = true;
+
+		HttpResponseMessage resp = await httpClient.SendAsync (req).ConfigureAwait (false);
+		if (!resp.IsSuccessStatusCode || !resp.Content.Headers.ContentLength.HasValue)
+			return (false, 0);
+
+		return (true, resp.Content.Headers.ContentLength.Value);
+	}
+}

build-tools/fetch-windows-assemblers/fetch-windows-assemblers.csproj

@@ -0,0 +1,40 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">x86</Platform>
+    <ProjectGuid>{09518DF2-C7B1-4CDB-849A-9F91F4BEA925}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <RootNamespace>fetchwindowsassemblers</RootNamespace>
+    <AssemblyName>fetch-windows-assemblers</AssemblyName>
+    <TargetFrameworkVersion>v4.7</TargetFrameworkVersion>
+  </PropertyGroup>
+  <Import Project="..\..\Configuration.props" />
+  <PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>..\..\bin\BuildDebug</OutputPath>
+    <DefineConstants>DEBUG;</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+    <ExternalConsole>true</ExternalConsole>
+    <PlatformTarget>x86</PlatformTarget>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
+    <Optimize>true</Optimize>
+    <OutputPath>..\..\bin\BuildRelease</OutputPath>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+    <ExternalConsole>true</ExternalConsole>
+    <PlatformTarget>x86</PlatformTarget>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="System.Net.Http" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="fetch-windows-assemblers.cs" />
+  </ItemGroup>
+  <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
+</Project>

build-tools/installers/create-installers.targets

@@ -134,12 +134,21 @@
     <_MSBuildFilesWin Include="$(MSBuildSrcDir)\proguard\bin\proguard.bat" />
     <_MSBuildFilesWin Include="$(MSBuildSrcDir)\aapt2.exe" />
     <_MSBuildFilesWin Include="$(MSBuildSrcDir)\libwinpthread-1.dll" />
+    <_MSBuildFilesWin Include="$(MSBuildSrcDir)\aarch64-linux-android-as.exe" Condition=" '$(HostOS)' != 'Windows' "/>
+    <_MSBuildFilesWin Include="$(MSBuildSrcDir)\arm-linux-androideabi-as.exe" Condition=" '$(HostOS)' != 'Windows' "/>
+    <_MSBuildFilesWin Include="$(MSBuildSrcDir)\i686-linux-android-as.exe" Condition=" '$(HostOS)' != 'Windows' "/>
+    <_MSBuildFilesWin Include="$(MSBuildSrcDir)\x86_64-linux-android-as.exe" Condition=" '$(HostOS)' != 'Windows' "/>
     <_MSBuildLibHostFilesWin Include="$(MSBuildSrcDir)\lib\host-mxe-Win64\libmono-android.debug.dll"   Condition=" '$(HostOS)' != 'Windows' " />
     <_MSBuildLibHostFilesWin Include="$(MSBuildSrcDir)\lib\host-mxe-Win64\libmono-android.release.dll" Condition=" '$(HostOS)' != 'Windows' " />
     <_MSBuildLibHostFilesWin Include="$(MSBuildSrcDir)\lib\host-mxe-Win64\libMonoPosixHelper.dll" />
     <_MSBuildLibHostFilesWin Include="$(MSBuildSrcDir)\lib\host-mxe-Win64\libmonosgen-2.0.dll" />
+    <_MSBuildLibHostFilesWin Include="$(MSBuildSrcDir)\lib\host-mxe-Win64\libxamarin-app.dll" Condition=" '$(HostOS)' != 'Windows' " />
   </ItemGroup>
   <ItemGroup>
+    <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\$(HostOS)\aarch64-linux-android-as" />
+    <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\$(HostOS)\arm-linux-androideabi-as" />
+    <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\$(HostOS)\i686-linux-android-as" />
+    <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\$(HostOS)\x86_64-linux-android-as" />
     <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\$(HostOS)\illinkanalyzer" />
     <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\$(HostOS)\jit-times" />
     <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\$(HostOS)\mono" />
@@ -153,6 +162,7 @@
     <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\lib\host-$(HostOS)\libmono-profiler-log.$(LibExtension)" />
     <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\lib\host-$(HostOS)\libMonoPosixHelper.$(LibExtension)" />
     <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\lib\host-$(HostOS)\libmonosgen-2.0.$(LibExtension)" />
+    <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\lib\host-$(HostOS)\libxamarin-app.$(LibExtension)" />
     <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\libzip.5.0.$(LibExtension)" />
     <_MSBuildFilesUnix Include="$(MSBuildSrcDir)\proguard\bin\proguard.sh" />
   </ItemGroup>

build-tools/scripts/Packaging.mk

@@ -98,7 +98,8 @@ _BUILD_STATUS_BUNDLE_INCLUDE = \
 	$(shell find . -name 'CMakeCache.txt') \
 	$(shell find . -name 'config.h') \
 	$(shell find . -name '.ninja_log') \
-	$(shell find . -name 'android-*.config.cache')
+	$(shell find . -name 'android-*.config.cache') \
+	bin/Build$(CONFIGURATION)/XABuildConfig.cs
 
 _BUILD_STATUS_BASENAME   = xa-build-status-v$(PRODUCT_VERSION).$(-num-commits-since-version-change)_$(OS_NAME)-$(OS_ARCH)_$(GIT_BRANCH)_$(GIT_COMMIT)-$(CONFIGURATION)
 _BUILD_STATUS_ZIP_OUTPUT = $(_BUILD_STATUS_BASENAME).$(ZIP_EXTENSION)

build-tools/scripts/XABuildConfig.cs.in

@@ -5,6 +5,7 @@ namespace Xamarin.Android.Tools
 {
 	static class XABuildConfig
 	{
+		public const string SupportedABIs = "@XA_SUPPORTED_ABIS@";
 		public const string NDKRevision = "@NDK_REVISION@";
 		public const string NDKRelease = "@NDK_RELEASE@";
 		public const int NDKMinimumApiAvailable = @NDK_MINIMUM_API_AVAILABLE@;
@@ -15,6 +16,7 @@ namespace Xamarin.Android.Tools
 			{        "arm", @NDK_ARMEABI_V7_API@},
 			{  "arm64-v8a", @NDK_ARM64_V8A_API@},
 			{      "arm64", @NDK_ARM64_V8A_API@},
+			{    "aarch64", @NDK_ARM64_V8A_API@},
 			{        "x86", @NDK_X86_API@},
 			{     "x86_64", @NDK_X86_64_API@},
 		};

src/Xamarin.Android.Build.Tasks.tpnitems

@@ -121,5 +121,633 @@
       </LicenseText>
       <SourceUrl>https://github.com/NuGet/NuGet.Client</SourceUrl>
     </ThirdPartyNotice>
+    <!-- `Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj` copies various NDK utilities into the SDK -->
+    <ThirdPartyNotice Include="android/platform/ndk">
+      <LicenseText>
+        GNU GENERAL PUBLIC LICENSE
+        Version 3, 29 June 2007
+
+        Copyright (C) 2007 Free Software Foundation, Inc. &lt;http://fsf.org/&gt;
+        Everyone is permitted to copy and distribute verbatim copies
+        of this license document, but changing it is not allowed.
+
+        Preamble
+
+        The GNU General Public License is a free, copyleft license for
+        software and other kinds of works.
+
+        The licenses for most software and other practical works are designed
+        to take away your freedom to share and change the works.  By contrast,
+        the GNU General Public License is intended to guarantee your freedom to
+        share and change all versions of a program--to make sure it remains free
+        software for all its users.  We, the Free Software Foundation, use the
+        GNU General Public License for most of our software; it applies also to
+        any other work released this way by its authors.  You can apply it to
+        your programs, too.
+
+        When we speak of free software, we are referring to freedom, not
+        price.  Our General Public Licenses are designed to make sure that you
+        have the freedom to distribute copies of free software (and charge for
+        them if you wish), that you receive source code or can get it if you
+        want it, that you can change the software or use pieces of it in new
+        free programs, and that you know you can do these things.
+
+        To protect your rights, we need to prevent others from denying you
+        these rights or asking you to surrender the rights.  Therefore, you have
+        certain responsibilities if you distribute copies of the software, or if
+        you modify it: responsibilities to respect the freedom of others.
+
+        For example, if you distribute copies of such a program, whether
+        gratis or for a fee, you must pass on to the recipients the same
+        freedoms that you received.  You must make sure that they, too, receive
+        or can get the source code.  And you must show them these terms so they
+        know their rights.
+
+        Developers that use the GNU GPL protect your rights with two steps:
+        (1) assert copyright on the software, and (2) offer you this License
+        giving you legal permission to copy, distribute and/or modify it.
+
+        For the developers' and authors' protection, the GPL clearly explains
+        that there is no warranty for this free software.  For both users' and
+        authors' sake, the GPL requires that modified versions be marked as
+        changed, so that their problems will not be attributed erroneously to
+        authors of previous versions.
+
+        Some devices are designed to deny users access to install or run
+        modified versions of the software inside them, although the manufacturer
+        can do so.  This is fundamentally incompatible with the aim of
+        protecting users' freedom to change the software.  The systematic
+        pattern of such abuse occurs in the area of products for individuals to
+        use, which is precisely where it is most unacceptable.  Therefore, we
+        have designed this version of the GPL to prohibit the practice for those
+        products.  If such problems arise substantially in other domains, we
+        stand ready to extend this provision to those domains in future versions
+        of the GPL, as needed to protect the freedom of users.
+
+        Finally, every program is threatened constantly by software patents.
+        States should not allow patents to restrict development and use of
+        software on general-purpose computers, but in those that do, we wish to
+        avoid the special danger that patents applied to a free program could
+        make it effectively proprietary.  To prevent this, the GPL assures that
+        patents cannot be used to render the program non-free.
+
+        The precise terms and conditions for copying, distribution and
+        modification follow.
+
+        TERMS AND CONDITIONS
+
+        0. Definitions.
+
+        "This License" refers to version 3 of the GNU General Public License.
+
+        "Copyright" also means copyright-like laws that apply to other kinds of
+        works, such as semiconductor masks.
+
+        "The Program" refers to any copyrightable work licensed under this
+        License.  Each licensee is addressed as "you".  "Licensees" and
+        "recipients" may be individuals or organizations.
+
+        To "modify" a work means to copy from or adapt all or part of the work
+        in a fashion requiring copyright permission, other than the making of an
+        exact copy.  The resulting work is called a "modified version" of the
+        earlier work or a work "based on" the earlier work.
+
+        A "covered work" means either the unmodified Program or a work based
+        on the Program.
+
+        To "propagate" a work means to do anything with it that, without
+        permission, would make you directly or secondarily liable for
+        infringement under applicable copyright law, except executing it on a
+        computer or modifying a private copy.  Propagation includes copying,
+        distribution (with or without modification), making available to the
+        public, and in some countries other activities as well.
+
+        To "convey" a work means any kind of propagation that enables other
+        parties to make or receive copies.  Mere interaction with a user through
+        a computer network, with no transfer of a copy, is not conveying.
+
+        An interactive user interface displays "Appropriate Legal Notices"
+        to the extent that it includes a convenient and prominently visible
+        feature that (1) displays an appropriate copyright notice, and (2)
+        tells the user that there is no warranty for the work (except to the
+        extent that warranties are provided), that licensees may convey the
+        work under this License, and how to view a copy of this License.  If
+        the interface presents a list of user commands or options, such as a
+        menu, a prominent item in the list meets this criterion.
+
+        1. Source Code.
+
+        The "source code" for a work means the preferred form of the work
+        for making modifications to it.  "Object code" means any non-source
+        form of a work.
+
+        A "Standard Interface" means an interface that either is an official
+        standard defined by a recognized standards body, or, in the case of
+        interfaces specified for a particular programming language, one that
+        is widely used among developers working in that language.
+
+        The "System Libraries" of an executable work include anything, other
+        than the work as a whole, that (a) is included in the normal form of
+        packaging a Major Component, but which is not part of that Major
+        Component, and (b) serves only to enable use of the work with that
+        Major Component, or to implement a Standard Interface for which an
+        implementation is available to the public in source code form.  A
+        "Major Component", in this context, means a major essential component
+        (kernel, window system, and so on) of the specific operating system
+        (if any) on which the executable work runs, or a compiler used to
+        produce the work, or an object code interpreter used to run it.
+
+        The "Corresponding Source" for a work in object code form means all
+        the source code needed to generate, install, and (for an executable
+        work) run the object code and to modify the work, including scripts to
+        control those activities.  However, it does not include the work's
+        System Libraries, or general-purpose tools or generally available free
+        programs which are used unmodified in performing those activities but
+        which are not part of the work.  For example, Corresponding Source
+        includes interface definition files associated with source files for
+        the work, and the source code for shared libraries and dynamically
+        linked subprograms that the work is specifically designed to require,
+        such as by intimate data communication or control flow between those
+        subprograms and other parts of the work.
+
+        The Corresponding Source need not include anything that users
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+        "Additional permissions" are terms that supplement the terms of this
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+        that they are valid under applicable law.  If additional permissions
+        apply only to part of the Program, that part may be used separately
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+        paragraph of section 11).
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+        your receipt of the notice.
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+        9. Acceptance Not Required for Having Copies.
+
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+
+        10. Automatic Licensing of Downstream Recipients.
+
+        Each time you convey a covered work, the recipient automatically
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+        sale, or importing the Program or any portion of it.
+
+        11. Patents.
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+        License of the Program or a work on which the Program is based.  The
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+
+        A contributor's "essential patent claims" are all patent claims
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+        consequence of further modification of the contributor version.  For
+        purposes of this definition, "control" includes the right to grant
+        patent sublicenses in a manner consistent with the requirements of
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+        patent license under the contributor's essential patent claims, to
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+        in the business of distributing software, under which you make payment
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+
+        Nothing in this License shall be construed as excluding or limiting
+        any implied license or other defenses to infringement that may
+        otherwise be available to you under applicable patent law.
+
+        12. No Surrender of Others' Freedom.
+
+        If conditions are imposed on you (whether by court order, agreement or
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+        to collect a royalty for further conveying from those to whom you convey
+        the Program, the only way you could satisfy both those terms and this
+        License would be to refrain entirely from conveying the Program.
+
+        13. Use with the GNU Affero General Public License.
+
+        Notwithstanding any other provision of this License, you have
+        permission to link or combine any covered work with a work licensed
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+        License will continue to apply to the part which is the covered work,
+        but the special requirements of the GNU Affero General Public License,
+        section 13, concerning interaction through a network will apply to the
+        combination as such.
+
+        14. Revised Versions of this License.
+
+        The Free Software Foundation may publish revised and/or new versions of
+        the GNU General Public License from time to time.  Such new versions will
+        be similar in spirit to the present version, but may differ in detail to
+        address new problems or concerns.
+
+        Each version is given a distinguishing version number.  If the
+        Program specifies that a certain numbered version of the GNU General
+        Public License "or any later version" applies to it, you have the
+        option of following the terms and conditions either of that numbered
+        version or of any later version published by the Free Software
+        Foundation.  If the Program does not specify a version number of the
+        GNU General Public License, you may choose any version ever published
+        by the Free Software Foundation.
+
+        If the Program specifies that a proxy can decide which future
+        versions of the GNU General Public License can be used, that proxy's
+        public statement of acceptance of a version permanently authorizes you
+        to choose that version for the Program.
+
+        Later license versions may give you additional or different
+        permissions.  However, no additional obligations are imposed on any
+        author or copyright holder as a result of your choosing to follow a
+        later version.
+
+        15. Disclaimer of Warranty.
+
+        THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+        APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+        HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+        OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+        THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+        PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+        IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+        ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+        16. Limitation of Liability.
+
+        IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+        WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+        THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+        GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+        USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+        DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+        PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+        EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+        SUCH DAMAGES.
+
+        17. Interpretation of Sections 15 and 16.
+
+        If the disclaimer of warranty and limitation of liability provided
+        above cannot be given local legal effect according to their terms,
+        reviewing courts shall apply local law that most closely approximates
+        an absolute waiver of all civil liability in connection with the
+        Program, unless a warranty or assumption of liability accompanies a
+        copy of the Program in return for a fee.
+
+        END OF TERMS AND CONDITIONS
+      </LicenseText>
+      <!-- binutils (source for gas) are not built as part of the NDK, see: https://android.googlesource.com/platform/ndk/+/master/docs/Toolchains.md -->
+      <SourceUrl>https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=tree;f=gas</SourceUrl>
+    </ThirdPartyNotice>
   </ItemGroup>
 </Project>

src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Designer.targets

@@ -74,7 +74,8 @@ Copyright (C) 2016 Xamarin. All rights reserved.
       PackageNamingPolicy="$(AndroidPackageNamingPolicy)"
       ApplicationJavaClass="$(AndroidApplicationJavaClass)"
       FrameworkDirectories="$(_XATargetFrameworkDirectories);$(_XATargetFrameworkDirectories)Facades"
-      AcwMapFile="$(_AcwMapFile)">
+      AcwMapFile="$(_AcwMapFile)"
+      SupportedAbis="$(_BuildTargetAbis)">
   </GenerateJavaStubs>
   <ConvertCustomView
       Condition="Exists('$(_CustomViewMapFile)')"
@@ -100,7 +101,11 @@ Copyright (C) 2016 Xamarin. All rights reserved.
       TlsProvider="$(AndroidTlsProvider)"
       Debug="$(AndroidIncludeDebugSymbols)"
       AndroidSequencePointsMode="$(_SequencePointsMode)"
-      EnableSGenConcurrent="$(AndroidEnableSGenConcurrent)">
+      EnableSGenConcurrent="$(AndroidEnableSGenConcurrent)"
+      IsBundledApplication="$(BundleAssemblies)"
+      SupportedAbis="$(_BuildTargetAbis)"
+      AndroidPackageName="$(_AndroidPackage)"
+      EnablePreloadAssembliesDefault="$(_AndroidEnablePreloadAssembliesDefault)">
     <Output TaskParameter="BuildId" PropertyName="_XamarinBuildId" />
   </GeneratePackageManagerJava>
 </Target>

src/Xamarin.Android.Build.Tasks/Resources/XamarinAndroidEnvironmentVariables.java

@@ -1,9 +0,0 @@
-package mono.android.app;
-
-public class XamarinAndroidEnvironmentVariables
-{
-	// Variables are specified the in "name", "value" pairs
-	public static final String[] Variables = new String[] {
-//@ENVVARS@
-	};
-}

src/Xamarin.Android.Build.Tasks/Tasks/Aot.cs

@@ -15,11 +15,12 @@ using Xamarin.Build;
 
 namespace Xamarin.Android.Tasks
 {
-	public enum AotMode
+	public enum AotMode : uint
 	{
-		Normal,
+		None      = 0x0000,
-		Hybrid,
+		Normal    = 0x0001,
-		Full
+		Hybrid    = 0x0002,
+		Full      = 0x0003,
 	}
 
 	public enum SequencePointsMode {
@@ -99,6 +100,9 @@ namespace Xamarin.Android.Tasks
 
 			switch ((androidAotMode ?? string.Empty).ToLowerInvariant().Trim())
 			{
+			case "none":
+				aotMode = AotMode.None;
+				return true;
 			case "normal":
 				aotMode = AotMode.Normal;
 				return true;

src/Xamarin.Android.Build.Tasks/Tasks/BuildApk.cs

@@ -43,6 +43,9 @@ namespace Xamarin.Android.Tasks
 		[Required]
 		public ITaskItem[] NativeLibraries { get; set; }
 
+		[Required]
+		public ITaskItem[] ApplicationSharedLibraries { get; set; }
+
 		public ITaskItem[] BundleNativeLibraries { get; set; }
 
 		public ITaskItem[] TypeMappings { get; set; }
@@ -356,6 +359,13 @@ namespace Xamarin.Android.Tasks
 			return CompressionMethod.Default;
 		}
 
+		void AddNativeLibraryToArchive (ZipArchiveEx apk, string abi, string filesystemPath, string inArchiveFileName)
+		{
+			string archivePath = $"lib/{abi}/{inArchiveFileName}";
+			Log.LogDebugMessage ($"Adding native library: {filesystemPath} (APK path: {archivePath})");
+			apk.Archive.AddEntry (archivePath, File.OpenRead (filesystemPath), compressionMethod: GetCompressionMethod (archivePath));
+		}
+
 		void AddNativeLibrary (ZipArchiveEx apk, string abi, string filename, string inArchiveFileName = null)
 		{
 			string libPath = Path.Combine (MSBuildXamarinAndroidDirectory, "lib", abi);
@@ -366,9 +376,7 @@ namespace Xamarin.Android.Tasks
 					path = debugPath;
 			}
 
-			string archivePath = string.Format ("lib/{0}/{1}", abi, inArchiveFileName ?? filename);
+			AddNativeLibraryToArchive (apk, abi, path, inArchiveFileName ?? filename);
-			Log.LogDebugMessage ($"Adding native library: {path} (APK path: {archivePath})");
-			apk.Archive.AddEntry (archivePath, File.OpenRead (path), compressionMethod: GetCompressionMethod (archivePath));
 		}
 
 		void AddProfilers (ZipArchiveEx apk, string abi)
@@ -399,6 +407,13 @@ namespace Xamarin.Android.Tasks
 			foreach (var abi in abis) {
 				string library = string.Format ("libmono-android.{0}.so", _Debug ? "debug" : "release");
 				AddNativeLibrary (apk, abi, library, "libmonodroid.so");
+
+				foreach (ITaskItem item in ApplicationSharedLibraries) {
+					if (String.Compare (abi, item.GetMetadata ("abi"), StringComparison.Ordinal) != 0)
+						continue;
+					AddNativeLibraryToArchive (apk, abi, item.ItemSpec, Path.GetFileName (item.ItemSpec));
+				}
+
 				if (!use_shared_runtime) {
 					// include the sgen
 					AddNativeLibrary (apk, abi, "libmonosgen-2.0.so");

src/Xamarin.Android.Build.Tasks/Tasks/CompileNativeAssembly.cs

@@ -0,0 +1,214 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Threading;
+
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+
+using Xamarin.Android.Tools;
+using Xamarin.Build;
+
+namespace Xamarin.Android.Tasks
+{
+	public class CompileNativeAssembly : AsyncTask
+	{
+		sealed class Config
+		{
+			public string AssemblerPath;
+			public string AssemblerOptions;
+			public string InputSource;
+		}
+
+		[Required]
+		public ITaskItem[] Sources { get; set; }
+
+		[Required]
+		public bool DebugBuild { get; set; }
+
+		[Required]
+		public string WorkingDirectory { get; set; }
+
+		public override bool Execute ()
+		{
+			try {
+				return DoExecute ();
+			} catch (Exception e) {
+				// We don't want to present a wall of text to the end user...
+				Log.LogCodedError ("XA3001", $"Unable to generate `libxamarin-app.so`: {e.Message}");
+
+				// ...but having the full stack trace available is important for us, so log it here
+				// int the way that will make it included in XA builds on bots or in verbose end user
+				// builds but not otherwise.
+				LogDebugMessage ($"Full exception: {e}");
+				return false;
+			}
+		}
+
+		bool DoExecute ()
+		{
+			Yield ();
+			try {
+				var task = this.RunTask ( () => RunParallelAssembler ());
+				task.ContinueWith (Complete);
+
+				base.Execute ();
+
+				if (!task.Result)
+					return false;
+			} finally {
+				Reacquire ();
+			}
+
+			return !Log.HasLoggedErrors;
+		}
+
+		bool RunParallelAssembler ()
+		{
+			try {
+				this.ParallelForEach (GetAssemblerConfigs (),
+					config => {
+						if (!RunAssembler (config)) {
+							LogCodedError ("XA3001", $"Could not compile native assembly file: {Path.GetFileName (config.InputSource)}");
+							Cancel ();
+							return;
+						}
+					}
+				);
+			} catch (OperationCanceledException) {
+				return false;
+			}
+
+			return true;
+		}
+
+		bool RunAssembler (Config config)
+		{
+			var stdout_completed = new ManualResetEvent (false);
+			var stderr_completed = new ManualResetEvent (false);
+			var psi = new ProcessStartInfo () {
+				FileName = config.AssemblerPath,
+				Arguments = config.AssemblerOptions,
+				UseShellExecute = false,
+				RedirectStandardOutput = true,
+				RedirectStandardError = true,
+				CreateNoWindow = true,
+				WindowStyle = ProcessWindowStyle.Hidden,
+				WorkingDirectory = WorkingDirectory,
+			};
+
+			string assemblerName = Path.GetFileName (config.AssemblerPath);
+			LogDebugMessage ($"[Native Assembler] {psi.FileName} {psi.Arguments}");
+			using (var proc = new Process ()) {
+				proc.OutputDataReceived += (s, e) => {
+					if (e.Data != null)
+						OnOutputData (assemblerName, s, e);
+					else
+						stdout_completed.Set ();
+				};
+
+				proc.ErrorDataReceived += (s, e) => {
+					if (e.Data != null)
+						OnErrorData (assemblerName, s, e);
+					else
+						stderr_completed.Set ();
+				};
+
+				proc.StartInfo = psi;
+				proc.Start ();
+				proc.BeginOutputReadLine ();
+				proc.BeginErrorReadLine ();
+				CancellationToken.Register (() => { try { proc.Kill (); } catch (Exception) { } });
+				proc.WaitForExit ();
+
+				if (psi.RedirectStandardError)
+					stderr_completed.WaitOne (TimeSpan.FromSeconds (30));
+
+				if (psi.RedirectStandardOutput)
+					stdout_completed.WaitOne (TimeSpan.FromSeconds (30));
+
+				return proc.ExitCode == 0;
+			}
+		}
+
+		IEnumerable<Config> GetAssemblerConfigs ()
+		{
+			string sdkBinDirectory = MonoAndroidHelper.GetOSBinPath ();
+			foreach (ITaskItem item in Sources) {
+				string abi = item.GetMetadata ("abi")?.ToLowerInvariant ();
+				string prefix = String.Empty;
+				AndroidTargetArch arch;
+
+				switch (abi) {
+					case "armeabi-v7a":
+						prefix = Path.Combine (sdkBinDirectory, "arm-linux-androideabi");
+						arch = AndroidTargetArch.Arm;
+						break;
+
+					case "arm64":
+					case "arm64-v8a":
+					case "aarch64":
+						prefix = Path.Combine (sdkBinDirectory, "aarch64-linux-android");
+						arch = AndroidTargetArch.Arm64;
+						break;
+
+					case "x86":
+						prefix = Path.Combine (sdkBinDirectory, "i686-linux-android");
+						arch = AndroidTargetArch.X86;
+						break;
+
+					case "x86_64":
+						prefix = Path.Combine (sdkBinDirectory, "x86_64-linux-android");
+						arch = AndroidTargetArch.X86_64;
+						break;
+
+					default:
+						throw new NotSupportedException ($"Unsupported Android target architecture ABI: {abi}");
+				}
+
+				// We don't need the directory since our WorkingDirectory is (and must be) where all the
+				// sources are (because of the typemap.inc file being included by the other sources with
+				// a relative path of `.`)
+				string sourceFile = Path.GetFileName (item.ItemSpec);
+				var assemblerOptions = new List<string> {
+					"--warn",
+					"-o",
+					QuoteFileName (sourceFile.Replace (".s", ".o"))
+				};
+
+				if (DebugBuild)
+					assemblerOptions.Add ("-g");
+
+				assemblerOptions.Add (QuoteFileName (sourceFile));
+
+				string baseExecutablePath = $"{prefix}-as";
+				string executableDir = Path.GetDirectoryName (baseExecutablePath);
+				string executableName = MonoAndroidHelper.GetExecutablePath (executableDir, Path.GetFileName (baseExecutablePath));
+
+				yield return new Config {
+					InputSource = item.ItemSpec,
+					AssemblerPath = Path.Combine (executableDir, executableName),
+					AssemblerOptions = String.Join (" ", assemblerOptions),
+				};
+			}
+		}
+
+		void OnOutputData (string assemblerName, object sender, DataReceivedEventArgs e)
+		{
+			LogMessage ($"[{assemblerName} stdout] {e.Data}");
+		}
+
+		void OnErrorData (string assemblerName, object sender, DataReceivedEventArgs e)
+		{
+			LogMessage ($"[{assemblerName} stderr] {e.Data}");
+		}
+
+		static string QuoteFileName (string fileName)
+		{
+			var builder = new CommandLineBuilder ();
+			builder.AppendFileNameIfNotNull (fileName);
+			return builder.ToString ();
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Tasks/GenerateJavaStubs.cs

@@ -5,6 +5,8 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
+using System.Xml.Linq;
+using System.Text;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 using Mono.Cecil;
@@ -35,6 +37,9 @@ namespace Xamarin.Android.Tasks
 		[Required]
 		public ITaskItem [] FrameworkDirectories { get; set; }
 
+		[Required]
+		public string SupportedAbis { get; set; }
+
 		public string ManifestTemplate { get; set; }
 		public string[] MergedManifestDocuments { get; set; }
 
@@ -285,13 +290,63 @@ namespace Xamarin.Android.Tasks
 			TypeNameMapGenerator createTypeMapGenerator () => UseSharedRuntime ?
 				new TypeNameMapGenerator (types, logger) :
 				new TypeNameMapGenerator (ResolvedAssemblies.Select (p => p.ItemSpec), logger);
-			using (var gen = createTypeMapGenerator ())
+			using (var gen = createTypeMapGenerator ()) {
-			using (var stream = new MemoryStream ()) {
+				using (var ms = new MemoryStream ()) {
-				gen.WriteJavaToManaged (stream);
+					UpdateWhenChanged (Path.Combine (OutputDirectory, "typemap.jm"), "jm", ms, gen.WriteJavaToManaged);
-				MonoAndroidHelper.CopyIfStreamChanged (stream, Path.Combine (OutputDirectory, "typemap.jm"));
+					UpdateWhenChanged (Path.Combine (OutputDirectory, "typemap.mj"), "mj", ms, gen.WriteManagedToJava);
-				stream.SetLength (0); //Reuse the stream
+				}
-				gen.WriteManagedToJava (stream);
+			}
-				MonoAndroidHelper.CopyIfStreamChanged (stream, Path.Combine (OutputDirectory, "typemap.mj"));
+		}
+
+		void UpdateWhenChanged (string path, string type, MemoryStream ms, Action<Stream> generator)
+		{
+			if (InstantRunEnabled) {
+				ms.SetLength (0);
+				generator (ms);
+				MonoAndroidHelper.CopyIfStreamChanged (ms, path);
+			}
+
+			string dataFilePath = $"{path}.inc";
+			using (var stream = new NativeAssemblyDataStream ()) {
+				generator (stream);
+				stream.Flush ();
+				MonoAndroidHelper.CopyIfStreamChanged (stream, dataFilePath);
+
+				var generatedFiles = new List <ITaskItem> ();
+				string mappingFieldName = $"{type}_typemap";
+				string dataFileName = Path.GetFileName (dataFilePath);
+				NativeAssemblerTargetProvider asmTargetProvider;
+				var utf8Encoding = new UTF8Encoding (false);
+				foreach (string abi in SupportedAbis.Split (new char[] { ',', ';' }, StringSplitOptions.RemoveEmptyEntries)) {
+					ms.SetLength (0);
+					switch (abi.Trim ()) {
+						case "armeabi-v7a":
+							asmTargetProvider = new ARMNativeAssemblerTargetProvider (is64Bit: false);
+							break;
+
+						case "arm64-v8a":
+							asmTargetProvider = new ARMNativeAssemblerTargetProvider (is64Bit: true);
+							break;
+
+						case "x86":
+							asmTargetProvider = new X86NativeAssemblerTargetProvider (is64Bit: false);
+							break;
+
+						case "x86_64":
+							asmTargetProvider = new X86NativeAssemblerTargetProvider (is64Bit: true);
+							break;
+
+						default:
+							throw new InvalidOperationException ($"Unknown ABI {abi}");
+					}
+
+					var asmgen = new TypeMappingNativeAssemblyGenerator (asmTargetProvider, stream, dataFileName, stream.MapByteCount, mappingFieldName);
+					string asmFileName = $"{path}.{abi.Trim ()}.s";
+					using (var sw = new StreamWriter (ms, utf8Encoding, bufferSize: 8192, leaveOpen: true)) {
+						asmgen.Write (sw, dataFileName);
+						MonoAndroidHelper.CopyIfStreamChanged (ms, asmFileName);
+					}
+				}
 			}
 		}
 	}

src/Xamarin.Android.Build.Tasks/Tasks/GeneratePackageManagerJava.cs

@@ -1,9 +1,11 @@
 // Copyright (C) 2011 Xamarin, Inc. All rights reserved.
 
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Text;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 
@@ -13,8 +15,6 @@ namespace Xamarin.Android.Tasks
 {
 	public class GeneratePackageManagerJava : Task
 	{
-		const string EnvironmentFileName = "XamarinAndroidEnvironmentVariables.java";
-
 		Guid buildId = Guid.NewGuid ();
 
 		[Required]
@@ -41,6 +41,18 @@ namespace Xamarin.Android.Tasks
 		[Required]
 		public string Manifest { get; set; }
 
+		[Required]
+		public bool IsBundledApplication { get; set; }
+
+		[Required]
+		public string SupportedAbis { get; set; }
+
+		[Required]
+		public string AndroidPackageName { get; set; }
+
+		[Required]
+		public bool EnablePreloadAssembliesDefault { get; set; }
+
 		public string Debug { get; set; }
 		public ITaskItem[] Environments { get; set; }
 		public string AndroidAotMode { get; set; }
@@ -125,17 +137,18 @@ namespace Xamarin.Android.Tasks
 
 		void AddEnvironment ()
 		{
-			var environment = new StringWriter () {
+			bool usesEmbeddedDSOs = false;
-				NewLine = "\n",
+			bool usesMonoAOT = false;
-			};
+			bool usesAssemblyPreload = EnablePreloadAssembliesDefault;
-
+			uint monoAOTMode = 0;
-			if (EnableLLVM) {
+			string androidPackageName = null;
-				WriteEnvironment ("mono.llvm", "true");
+			var environmentVariables = new Dictionary<string, string> (StringComparer.Ordinal);
-			}
+			var systemProperties = new Dictionary<string, string> (StringComparer.Ordinal);
 
 			AotMode aotMode;
 			if (AndroidAotMode != null && Aot.GetAndroidAotMode (AndroidAotMode, out aotMode)) {
-				WriteEnvironment ("mono.aot", aotMode.ToString ().ToLowerInvariant());
+				usesMonoAOT = true;
+				monoAOTMode = (uint)aotMode;
 			}
 
 			bool haveLogLevel = false;
@@ -150,7 +163,6 @@ namespace Xamarin.Android.Tasks
 				sequencePointsMode = SequencePointsMode.None;
 
 			foreach (ITaskItem env in Environments ?? new TaskItem[0]) {
-				environment.WriteLine ("\t\t// Source File: {0}", env.ItemSpec);
 				foreach (string line in File.ReadLines (env.ItemSpec)) {
 					var lineToWrite = line;
 					if (lineToWrite.StartsWith ("MONO_LOG_LEVEL=", StringComparison.Ordinal))
@@ -168,72 +180,119 @@ namespace Xamarin.Android.Tasks
 						haveHttpMessageHandler = true;
 					if (lineToWrite.StartsWith ("XA_TLS_PROVIDER=", StringComparison.Ordinal))
 						haveTlsProvider = true;
-					WriteEnvironmentLine (lineToWrite);
+					if (lineToWrite.StartsWith ("__XA_DSO_IN_APK", StringComparison.Ordinal)) {
+						usesEmbeddedDSOs = true;
+						continue;
+					}
+					if (lineToWrite.StartsWith ("mono.enable_assembly_preload=", StringComparison.Ordinal)) {
+						int idx = lineToWrite.IndexOf ('=');
+						uint val;
+						if (idx < lineToWrite.Length - 1 && UInt32.TryParse (lineToWrite.Substring (idx + 1), out val)) {
+							usesAssemblyPreload = idx == 1;
+						}
+						continue;
+					}
+
+					AddEnvironmentVariableLine (lineToWrite);
 				}
 			}
 
 			if (_Debug && !haveLogLevel) {
-				WriteEnvironment (defaultLogLevel[0], defaultLogLevel[1]);
+				AddEnvironmentVariable (defaultLogLevel[0], defaultLogLevel[1]);
 			}
 
 			if (sequencePointsMode != SequencePointsMode.None && !haveMonoDebug) {
-				WriteEnvironment (defaultMonoDebug[0], defaultMonoDebug[1]);
+				AddEnvironmentVariable (defaultMonoDebug[0], defaultMonoDebug[1]);
 			}
 
 			if (!havebuildId)
-				WriteEnvironment ("XAMARIN_BUILD_ID", BuildId);
+				AddEnvironmentVariable ("XAMARIN_BUILD_ID", BuildId);
 
 			if (!haveHttpMessageHandler) {
 				if (HttpClientHandlerType == null)
-					WriteEnvironment (defaultHttpMessageHandler[0], defaultHttpMessageHandler[1]);
+					AddEnvironmentVariable (defaultHttpMessageHandler[0], defaultHttpMessageHandler[1]);
 				else
-					WriteEnvironment ("XA_HTTP_CLIENT_HANDLER_TYPE", HttpClientHandlerType.Trim ());
+					AddEnvironmentVariable ("XA_HTTP_CLIENT_HANDLER_TYPE", HttpClientHandlerType.Trim ());
 			}
 
 			if (!haveTlsProvider) {
 				if (TlsProvider == null)
-					WriteEnvironment (defaultTlsProvider[0], defaultTlsProvider[1]);
+					AddEnvironmentVariable (defaultTlsProvider[0], defaultTlsProvider[1]);
 				else
-					WriteEnvironment ("XA_TLS_PROVIDER", TlsProvider.Trim ());
+					AddEnvironmentVariable ("XA_TLS_PROVIDER", TlsProvider.Trim ());
 			}
 
 			if (!haveMonoGCParams) {
 				if (EnableSGenConcurrent)
-					WriteEnvironment ("MONO_GC_PARAMS", "major=marksweep-conc");
+					AddEnvironmentVariable ("MONO_GC_PARAMS", "major=marksweep-conc");
 				else
-					WriteEnvironment ("MONO_GC_PARAMS", "major=marksweep");
+					AddEnvironmentVariable ("MONO_GC_PARAMS", "major=marksweep");
-			}
-
-			string environmentTemplate;
-			using (var sr = new StreamReader (typeof (BuildApk).Assembly.GetManifestResourceStream (EnvironmentFileName))) {
-				environmentTemplate = sr.ReadToEnd ();
 			}
 
 			using (var ms = new MemoryStream ()) {
-				using (var sw = new StreamWriter (ms)) {
+				var utf8Encoding = new UTF8Encoding (false);
-					sw.Write (environmentTemplate.Replace ("//@ENVVARS@", environment.ToString ()));
+				foreach (string abi in SupportedAbis.Split (new char[] { ',', ';' }, StringSplitOptions.RemoveEmptyEntries)) {
-					sw.Flush ();
+					ms.SetLength (0);
+					NativeAssemblerTargetProvider asmTargetProvider;
+					string asmFileName = Path.Combine (EnvironmentOutputDirectory, $"environment.{abi.ToLowerInvariant ()}.s");
+					switch (abi.Trim ()) {
+						case "armeabi-v7a":
+							asmTargetProvider = new ARMNativeAssemblerTargetProvider (false);
+							break;
+
+						case "arm64-v8a":
+							asmTargetProvider = new ARMNativeAssemblerTargetProvider (true);
+							break;
+
+						case "x86":
+							asmTargetProvider = new X86NativeAssemblerTargetProvider (false);
+							break;
+
+						case "x86_64":
+							asmTargetProvider = new X86NativeAssemblerTargetProvider (true);
+							break;
+
+						default:
+							throw new InvalidOperationException ($"Unknown ABI {abi}");
+					}
+
+					var asmgen = new ApplicationConfigNativeAssemblyGenerator (asmTargetProvider, environmentVariables, systemProperties) {
+						IsBundledApp = IsBundledApplication,
+						UsesEmbeddedDSOs = usesEmbeddedDSOs,
+						UsesMonoAOT = usesMonoAOT,
+						UsesMonoLLVM = EnableLLVM,
+						UsesAssemblyPreload = usesAssemblyPreload,
+						MonoAOTMode = monoAOTMode.ToString ().ToLowerInvariant (),
+						AndroidPackageName = AndroidPackageName,
+					};
+
+					using (var sw = new StreamWriter (ms, utf8Encoding, bufferSize: 8192, leaveOpen: true)) {
+						asmgen.Write (sw, asmFileName);
+						MonoAndroidHelper.CopyIfStreamChanged (ms, asmFileName);
+					}
 
-					string dest = Path.GetFullPath (Path.Combine (EnvironmentOutputDirectory, EnvironmentFileName));
-					MonoAndroidHelper.CopyIfStreamChanged (ms, dest);
 				}
 			}
 
-			void WriteEnvironment (string name, string value)
+			void AddEnvironmentVariable (string name, string value)
 			{
-				environment.WriteLine ($"\t\t\"{ValidJavaString (name)}\", \"{ValidJavaString (value)}\",");
+				if (Char.IsUpper(name [0]) || !Char.IsLetter(name [0]))
+					environmentVariables [ValidAssemblerString (name)] = ValidAssemblerString (value);
+				else
+					systemProperties [ValidAssemblerString (name)] = ValidAssemblerString (value);
 			}
 
-			void WriteEnvironmentLine (string line)
+			void AddEnvironmentVariableLine (string l)
 			{
-				if (String.IsNullOrEmpty (line))
+				string line = l?.Trim ();
+				if (String.IsNullOrEmpty (line) || line [0] == '#')
 					return;
 
 				string[] nv = line.Split (new char[]{'='}, 2);
-				WriteEnvironment (nv[0].Trim (), nv.Length < 2 ? String.Empty : nv[1].Trim ());
+				AddEnvironmentVariable (nv[0].Trim (), nv.Length < 2 ? String.Empty : nv[1].Trim ());
 			}
 
-			string ValidJavaString (string s)
+			string ValidAssemblerString (string s)
 			{
 				return s.Replace ("\"", "\\\"");
 			}

src/Xamarin.Android.Build.Tasks/Tasks/LinkApplicationSharedLibraries.cs

@@ -0,0 +1,260 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Threading;
+
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+
+using Xamarin.Android.Tools;
+using Xamarin.Build;
+
+namespace Xamarin.Android.Tasks
+{
+	public class LinkApplicationSharedLibraries : AsyncTask
+	{
+		sealed class Config
+		{
+			public string LinkerPath;
+			public string LinkerOptions;
+			public string OutputSharedLibrary;
+		}
+
+		sealed class InputFiles
+		{
+			public List<string> ObjectFiles;
+			public string OutputSharedLibrary;
+		}
+
+		[Required]
+		public ITaskItem[] ObjectFiles { get; set; }
+
+		[Required]
+		public ITaskItem[] ApplicationSharedLibraries { get; set; }
+
+		[Required]
+		public bool DebugBuild { get; set; }
+
+		[Required]
+		public string AndroidNdkDirectory { get; set; }
+
+		public override bool Execute ()
+		{
+			try {
+				return DoExecute ();
+			} catch (Exception e) {
+				// We don't want to present a wall of text to the end user...
+				Log.LogCodedError ("XA3001", $"Unable to link `libxamarin-app.so`: {e.Message}");
+
+				// ...but having the full stack trace available is important for us, so log it here
+				// int the way that will make it included in XA builds on bots or in verbose end user
+				// builds but not otherwise.
+				LogDebugMessage ($"Full exception: {e}");
+				return false;
+			}
+		}
+
+		bool DoExecute ()
+		{
+			Yield ();
+			try {
+				var task = this.RunTask ( () => RunParallelLinker ());
+				task.ContinueWith (Complete);
+
+				base.Execute ();
+
+				if (!task.Result)
+					return false;
+			} finally {
+				Reacquire ();
+			}
+
+			return !Log.HasLoggedErrors;
+		}
+
+		bool RunParallelLinker ()
+		{
+			try {
+				this.ParallelForEach (GetLinkerConfigs (),
+					 config => {
+						 if (RunLinker (config))
+							 return;
+						 LogCodedError ("XA3001", $"Could not link native shared library: {Path.GetFileName (config.OutputSharedLibrary)}");
+						 Cancel ();
+						 return;
+					 }
+				);
+			} catch (OperationCanceledException) {
+				return false;
+			}
+
+			return true;
+		}
+
+		bool RunLinker (Config config)
+		{
+			var stdout_completed = new ManualResetEvent (false);
+			var stderr_completed = new ManualResetEvent (false);
+			var psi = new ProcessStartInfo () {
+				FileName = config.LinkerPath,
+				Arguments = config.LinkerOptions,
+				UseShellExecute = false,
+				RedirectStandardOutput = true,
+				RedirectStandardError = true,
+				CreateNoWindow = true,
+				WindowStyle = ProcessWindowStyle.Hidden,
+			};
+
+			string targetDir = Path.GetDirectoryName (config.OutputSharedLibrary);
+			if (!Directory.Exists (targetDir))
+				Directory.CreateDirectory (targetDir);
+
+			string linkerName = Path.GetFileName (config.LinkerPath);
+			LogDebugMessage ($"[Native Linker] {psi.FileName} {psi.Arguments}");
+			using (var proc = new Process ()) {
+				proc.OutputDataReceived += (s, e) => {
+					if (e.Data != null)
+						OnOutputData (linkerName, s, e);
+					else
+						stdout_completed.Set ();
+				};
+
+				proc.ErrorDataReceived += (s, e) => {
+					if (e.Data != null)
+						OnErrorData (linkerName, s, e);
+					else
+						stderr_completed.Set ();
+				};
+
+				proc.StartInfo = psi;
+				proc.Start ();
+				proc.BeginOutputReadLine ();
+				proc.BeginErrorReadLine ();
+				CancellationToken.Register (() => { try { proc.Kill (); } catch (Exception) { } });
+				proc.WaitForExit ();
+
+				if (psi.RedirectStandardError)
+					stderr_completed.WaitOne (TimeSpan.FromSeconds (30));
+
+				if (psi.RedirectStandardOutput)
+					stdout_completed.WaitOne (TimeSpan.FromSeconds (30));
+
+				return proc.ExitCode == 0;
+			}
+		}
+
+		IEnumerable<Config> GetLinkerConfigs ()
+		{
+			var abis = new Dictionary <string, InputFiles> (StringComparer.Ordinal);
+			ITaskItem[] dsos = ApplicationSharedLibraries;
+			foreach (ITaskItem item in dsos) {
+				string abi = item.GetMetadata ("abi");
+				abis [abi] = GatherFilesForABI(item.ItemSpec, abi, ObjectFiles);
+			}
+
+			foreach (var kvp in abis) {
+				string abi = kvp.Key;
+				InputFiles inputs = kvp.Value;
+				AndroidTargetArch arch;
+
+				var linkerArgs = new List <string> {
+					"--unresolved-symbols=ignore-in-shared-libs",
+					"--export-dynamic",
+					"-soname", "libxamarin-app.so",
+					"-z", "relro",
+					"-z", "noexecstack",
+					"--enable-new-dtags",
+					"--eh-frame-hdr",
+					"-shared",
+					"--build-id",
+					"--warn-shared-textrel",
+					"--fatal-warnings",
+					"-o", QuoteFileName (inputs.OutputSharedLibrary),
+				};
+
+				string elf_arch;
+				switch (abi) {
+					case "armeabi-v7a":
+						arch = AndroidTargetArch.Arm;
+						linkerArgs.Add ("-X");
+						elf_arch = "armelf_linux_eabi";
+						break;
+
+					case "arm64":
+					case "arm64-v8a":
+					case "aarch64":
+						arch = AndroidTargetArch.Arm64;
+						linkerArgs.Add ("--fix-cortex-a53-843419");
+						elf_arch = "aarch64linux";
+						break;
+
+					case "x86":
+						arch = AndroidTargetArch.X86;
+						elf_arch = "elf_i386";
+						break;
+
+					case "x86_64":
+						arch = AndroidTargetArch.X86_64;
+						elf_arch = "elf_x86_64";
+						break;
+
+					default:
+						throw new NotSupportedException ($"Unsupported Android target architecture ABI: {abi}");
+				}
+
+				linkerArgs.Add ("-m");
+				linkerArgs.Add (elf_arch);
+
+				foreach (string file in inputs.ObjectFiles) {
+					linkerArgs.Add (QuoteFileName (file));
+				}
+
+				yield return new Config {
+					LinkerPath = NdkUtil.GetNdkTool (AndroidNdkDirectory, arch, "ld", XABuildConfig.ArchAPILevels [abi]),
+					LinkerOptions = String.Join (" ", linkerArgs),
+					OutputSharedLibrary = inputs.OutputSharedLibrary,
+				};
+			}
+		}
+
+		InputFiles GatherFilesForABI (string runtimeSharedLibrary, string abi, ITaskItem[] objectFiles)
+		{
+			return new InputFiles {
+				OutputSharedLibrary = runtimeSharedLibrary,
+				ObjectFiles = GetItemsForABI (abi, objectFiles),
+			};
+		}
+
+		List<string> GetItemsForABI (string abi, ITaskItem[] items)
+		{
+			var ret = new List <string> ();
+			foreach (ITaskItem item in items) {
+				if (String.Compare (abi, item.GetMetadata ("abi"), StringComparison.Ordinal) != 0)
+					continue;
+				ret.Add (item.ItemSpec);
+			}
+
+			return ret;
+		}
+
+		void OnOutputData (string linkerName, object sender, DataReceivedEventArgs e)
+		{
+			if (e.Data != null)
+				LogMessage ($"[{linkerName} stdout] {e.Data}");
+		}
+
+		void OnErrorData (string linkerName, object sender, DataReceivedEventArgs e)
+		{
+			if (e.Data != null)
+				LogMessage ($"[{linkerName} stderr] {e.Data}");
+		}
+
+		static string QuoteFileName (string fileName)
+		{
+			var builder = new CommandLineBuilder ();
+			builder.AppendFileNameIfNotNull (fileName);
+			return builder.ToString ();
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Tasks/NdkUtils.cs

@@ -6,6 +6,7 @@ using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Text.RegularExpressions;
+using System.Threading;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 
@@ -16,17 +17,24 @@ namespace Xamarin.Android.Tasks
 {
 	public static class NdkUtil
 	{
+		// We need it to work fine during our tests which are executed at the same time in various threads.
+		[ThreadStatic]
 		static bool usingClangNDK;
 
 		public static bool UsingClangNDK => usingClangNDK;
 
+		public static bool Init (string ndkPath)
+		{
+			return Init (null, ndkPath); // For tests which don't have access to a TaskLoggingHelper
+		}
+
 		public static bool Init (TaskLoggingHelper log, string ndkPath)
 		{
 			Version ndkVersion;
 			bool hasNdkVersion = GetNdkToolchainRelease (ndkPath ?? "", out ndkVersion);
 
 			if (!hasNdkVersion) {
-				log.LogCodedError ("XA5101",
+				log?.LogCodedError ("XA5101",
 						"Could not locate the Android NDK. Please make sure the Android NDK is installed in the Android SDK Manager, " +
 						"or if using a custom NDK path, please ensure the $(AndroidNdkDirectory) MSBuild property is set to the custom path.");
 				return false;

src/Xamarin.Android.Build.Tasks/Tasks/PrepareAbiItems.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+
+namespace Xamarin.Android.Tasks
+{
+	public class PrepareAbiItems : Task
+	{
+		[Required]
+		public string BuildTargetAbis { get; set; }
+
+		[Required]
+		public string ItemNamePattern { get; set; }
+
+		[Output]
+		public ITaskItem[] OutputItems { get; set; }
+
+		public override bool Execute ()
+		{
+			string[] abis = BuildTargetAbis.Split (new [] { ';', ',' }, StringSplitOptions.RemoveEmptyEntries);
+			var items = new List<ITaskItem> ();
+			foreach (string abi in abis) {
+				var item = new TaskItem (ItemNamePattern.Replace ("@abi@", abi));
+				item.SetMetadata ("abi", abi);
+				items.Add (item);
+			}
+
+			OutputItems = items.ToArray ();
+			return !Log.HasLoggedErrors;
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest.cs

@@ -444,8 +444,15 @@ namespace UnamedProject
 				start = DateTime.UtcNow;
 				Assert.IsTrue (b.Build (proj), "second build should have succeeded.");
 
+				// These files won't exist in OSS Xamarin.Android, thus the existence check and
+				// Assert.Ignore below. They will also not exist in the commercial version of
+				// Xamarin.Android unless fastdev is enabled.
 				foreach (var file in new [] { "typemap.mj", "typemap.jm" }) {
 					var info = new FileInfo (Path.Combine (intermediate, "android", file));
+					if (!info.Exists) {
+						Assert.Ignore ($"{info.Name} does not exist, timestamp check skipped");
+						continue;
+					}
 					Assert.IsTrue (info.LastWriteTimeUtc > start, $"`{file}` is older than `{start}`, with a timestamp of `{info.LastWriteTimeUtc}`!");
 				}
 
@@ -1784,6 +1791,8 @@ namespace App1
 		[Test]
 		public void BuildApplicationWithMonoEnvironment ([Values ("", "Normal", "Offline")] string sequencePointsMode)
 		{
+			const string supportedAbis = "armeabi-v7a;x86";
+
 			var lib = new XamarinAndroidLibraryProject {
 				ProjectName = "Library1",
 				IsRelease = true,
@@ -1803,25 +1812,27 @@ namespace App1
 			string linkSkip = KnownPackages.SupportV7AppCompat_27_0_2_1.Id;
 			app.SetProperty ("AndroidLinkSkip", linkSkip);
 			app.SetProperty ("_AndroidSequencePointsMode", sequencePointsMode);
+			app.SetProperty (app.ReleaseProperties, KnownProperties.AndroidSupportedAbis, supportedAbis);
 			using (var libb = CreateDllBuilder (Path.Combine ("temp", TestName, lib.ProjectName)))
 			using (var appb = CreateApkBuilder (Path.Combine ("temp", TestName, app.ProjectName))) {
 				Assert.IsTrue (libb.Build (lib), "Library build should have succeeded.");
 				Assert.IsTrue (appb.Build (app), "App should have succeeded.");
 				Assert.IsTrue (StringAssertEx.ContainsText (appb.LastBuildOutput, $"Save assembly: {linkSkip}"), $"{linkSkip} should be saved, and not linked!");
-				string javaEnv = Path.Combine (Root, appb.ProjectDirectory,
-							       app.IntermediateOutputPath, "android", "src", "mono", "android", "app", "XamarinAndroidEnvironmentVariables.java");
-				Assert.IsTrue (File.Exists (javaEnv), $"Java environment source does not exist at {javaEnv}");
 
-				string[] lines = File.ReadAllLines (javaEnv);
+				string intermediateOutputDir = Path.Combine (Root, appb.ProjectDirectory, app.IntermediateOutputPath);
-				Assert.IsTrue (lines.Any (x => x.Contains ("MONO_DEBUG") &&
+				List<string> envFiles = EnvironmentHelper.GatherEnvironmentFiles (intermediateOutputDir, supportedAbis, true);
-						x.Contains ("soft-breakpoints") &&
+				Dictionary<string, string> envvars = EnvironmentHelper.ReadEnvironmentVariables (envFiles);
-						string.IsNullOrEmpty (sequencePointsMode) ? true : x.Contains ("gen-compact-seq-points")),
+				Assert.IsTrue (envvars.Count > 0, $"No environment variables defined");
-						"The values from Mono.env should have been merged into environment");
 
-				string dexFile = Path.Combine (Root, appb.ProjectDirectory, app.IntermediateOutputPath, "android", "bin", "classes.dex");
+				string monoDebugVar;
-				Assert.IsTrue (File.Exists (dexFile), $"dex file does not exist at {dexFile}");
+				Assert.IsTrue (envvars.TryGetValue ("MONO_DEBUG", out monoDebugVar), "Environment should contain MONO_DEBUG");
-				Assert.IsTrue (DexUtils.ContainsClass ("Lmono/android/app/XamarinAndroidEnvironmentVariables;", dexFile, appb.AndroidSdkDirectory),
+				Assert.IsFalse (String.IsNullOrEmpty (monoDebugVar), "Environment must contain MONO_DEBUG with a value");
-					       $"dex file {dexFile} does not contain the XamarinAndroidEnvironmentVariables class");
+				Assert.IsTrue (monoDebugVar.IndexOf ("soft-breakpoints") >= 0, "Environment must contain MONO_DEBUG with 'soft-breakpoints' in its value");
+
+				if (!String.IsNullOrEmpty (sequencePointsMode))
+					Assert.IsTrue (monoDebugVar.IndexOf ("gen-compact-seq-points") >= 0, "The values from Mono.env should have been merged into environment");
+
+				EnvironmentHelper.AssertValidEnvironmentSharedLibrary (intermediateOutputDir, AndroidSdkPath, AndroidNdkPath, supportedAbis);
 
 				var assemblyDir = Path.Combine (Root, appb.ProjectDirectory, app.IntermediateOutputPath, "android", "assets");
 				var rp = new ReaderParameters { ReadSymbols = false };
@@ -1841,29 +1852,32 @@ namespace App1
 		[Test]
 		public void CheckMonoDebugIsAddedToEnvironment ([Values ("", "Normal", "Offline")] string sequencePointsMode)
 		{
+			const string supportedAbis = "armeabi-v7a;x86";
+
 			var proj = new XamarinAndroidApplicationProject () {
 				IsRelease = true,
 			};
 			proj.SetProperty ("_AndroidSequencePointsMode", sequencePointsMode);
+			proj.SetProperty (proj.ReleaseProperties, KnownProperties.AndroidSupportedAbis, supportedAbis);
 			using (var b = CreateApkBuilder (Path.Combine ("temp", TestName))) {
 				b.Verbosity = LoggerVerbosity.Diagnostic;
 				Assert.IsTrue (b.Build (proj), "Build should have succeeded.");
-				string javaEnv = Path.Combine (Root, b.ProjectDirectory,
-							       proj.IntermediateOutputPath, "android", "src", "mono", "android", "app", "XamarinAndroidEnvironmentVariables.java");
-				Assert.IsTrue (File.Exists (javaEnv), $"Java environment source does not exist at {javaEnv}");
 
-				string[] lines = File.ReadAllLines (javaEnv);
+				string intermediateOutputDir = Path.Combine (Root, b.ProjectDirectory, proj.IntermediateOutputPath);
-				Assert.IsTrue (lines.Any (x =>
+				List<string> envFiles = EnvironmentHelper.GatherEnvironmentFiles (intermediateOutputDir, supportedAbis, true);
-							  string.IsNullOrEmpty (sequencePointsMode)
+				Dictionary<string, string> envvars = EnvironmentHelper.ReadEnvironmentVariables (envFiles);
-							  ? !x.Contains ("MONO_DEBUG")
+				Assert.IsTrue (envvars.Count > 0, $"No environment variables defined");
-							  : x.Contains ("MONO_DEBUG") && x.Contains ("gen-compact-seq-points")),
-					       "environment {0} contain MONO_DEBUG=gen-compact-seq-points",
-					       string.IsNullOrEmpty (sequencePointsMode) ? "should not" : "should");
 
-				string dexFile = Path.Combine (Root, b.ProjectDirectory, proj.IntermediateOutputPath, "android", "bin", "classes.dex");
+				string monoDebugVar;
-				Assert.IsTrue (File.Exists (dexFile), $"dex file does not exist at {dexFile}");
+				bool monoDebugVarFound = envvars.TryGetValue ("MONO_DEBUG", out monoDebugVar);
-				Assert.IsTrue (DexUtils.ContainsClass ("Lmono/android/app/XamarinAndroidEnvironmentVariables;", dexFile, b.AndroidSdkDirectory),
+				if (String.IsNullOrEmpty (sequencePointsMode))
-					       $"dex file {dexFile} does not contain the XamarinAndroidEnvironmentVariables class");
+					Assert.IsFalse (monoDebugVarFound, $"environment should not contain MONO_DEBUG={monoDebugVar}");
+				else {
+					Assert.IsTrue (monoDebugVarFound, "environment should contain MONO_DEBUG");
+					Assert.AreEqual ("gen-compact-seq-points", monoDebugVar, "environment should contain MONO_DEBUG=gen-compact-seq-points");
+				}
+
+				EnvironmentHelper.AssertValidEnvironmentSharedLibrary (intermediateOutputDir, AndroidSdkPath, AndroidNdkPath, supportedAbis);
 			}
 		}
 

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/PackagingTest.cs

@@ -46,6 +46,8 @@ namespace Xamarin.Android.Build.Tests
 		[Test]
 		public void CheckBuildIdIsUnique ()
 		{
+			const string supportedAbis = "armeabi-v7a;x86";
+
 			Dictionary<string, string> buildIds = new Dictionary<string, string> ();
 			var proj = new XamarinAndroidApplicationProject () {
 				IsRelease = true,
@@ -54,7 +56,7 @@ namespace Xamarin.Android.Build.Tests
 			proj.SetProperty (proj.ReleaseProperties, "DebugSymbols", "true");
 			proj.SetProperty (proj.ReleaseProperties, "DebugType", "PdbOnly");
 			proj.SetProperty (proj.ReleaseProperties, KnownProperties.AndroidCreatePackagePerAbi, "true");
-			proj.SetProperty (proj.ReleaseProperties, KnownProperties.AndroidSupportedAbis, "armeabi-v7a;x86");
+			proj.SetProperty (proj.ReleaseProperties, KnownProperties.AndroidSupportedAbis, supportedAbis);
 			using (var b = CreateApkBuilder (Path.Combine ("temp", TestContext.CurrentContext.Test.Name))) {
 				b.Verbosity = Microsoft.Build.Framework.LoggerVerbosity.Diagnostic;
 				b.ThrowOnBuildFailure = false;
@@ -67,27 +69,16 @@ namespace Xamarin.Android.Build.Tests
 				//NOTE: Windows is still generating mdb files here
 				extension = IsWindows ? "dll.mdb" : "pdb";
 				Assert.IsTrue (allFilesInArchive.Any (x => Path.GetFileName (x) == $"{proj.ProjectName}.{extension}"), $"{proj.ProjectName}.{extension} should exist in {archivePath}");
-				string javaEnv = Path.Combine (Root, b.ProjectDirectory,
-							       proj.IntermediateOutputPath, "android", "src", "mono", "android", "app", "XamarinAndroidEnvironmentVariables.java");
-				Assert.IsTrue (File.Exists (javaEnv), $"Java environment source does not exist at {javaEnv}");
 
-				string[] lines = File.ReadAllLines (javaEnv);
+				string intermediateOutputDir = Path.Combine (Root, b.ProjectDirectory, proj.IntermediateOutputPath);
+				List<string> envFiles = EnvironmentHelper.GatherEnvironmentFiles (intermediateOutputDir, supportedAbis, true);
+				Dictionary<string, string> envvars = EnvironmentHelper.ReadEnvironmentVariables (envFiles);
+				Assert.IsTrue (envvars.Count > 0, $"No environment variables defined");
 
-				Assert.IsTrue (lines.Any (x => x.Contains ("\"XAMARIN_BUILD_ID\",")),
+				string buildID;
-					       "The environment should contain a XAMARIN_BUILD_ID");
+				Assert.IsTrue (envvars.TryGetValue ("XAMARIN_BUILD_ID", out buildID), "The environment should contain a XAMARIN_BUILD_ID");
-
-				string buildID = lines.First (x => x.Contains ("\"XAMARIN_BUILD_ID\","))
-					.Trim ()
-					.Replace ("\", \"", "=")
-					.Replace ("\",", String.Empty)
-					.Replace ("\"", String.Empty);
 				buildIds.Add ("all", buildID);
 
-				string dexFile = Path.Combine (Root, b.ProjectDirectory, proj.IntermediateOutputPath, "android", "bin", "classes.dex");
-				Assert.IsTrue (File.Exists (dexFile), $"dex file does not exist at {dexFile}");
-				Assert.IsTrue (DexUtils.ContainsClass ("Lmono/android/app/XamarinAndroidEnvironmentVariables;", dexFile, b.AndroidSdkDirectory),
-					       $"dex file {dexFile} does not contain the XamarinAndroidEnvironmentVariables class");
-
 				var msymDirectory = Path.Combine (Root, b.ProjectDirectory, proj.OutputPath, proj.PackageName + ".apk.mSYM");
 				Assert.IsTrue (File.Exists (Path.Combine (msymDirectory, "manifest.xml")), "manifest.xml should exist in", msymDirectory);
 				var doc = XDocument.Load (Path.Combine (msymDirectory, "manifest.xml"));
@@ -98,7 +89,9 @@ namespace Xamarin.Android.Build.Tests
 				var buildId = buildIds.First ().Value;
 				Assert.IsTrue (doc.Element ("mono-debug")
 					.Elements ()
-					.Any (x => x.Name == "build-id" && x.Value == buildId.Replace ("XAMARIN_BUILD_ID=", "")), "build-id is has an incorrect value.");
+					.Any (x => x.Name == "build-id" && x.Value == buildId), "build-id is has an incorrect value.");
+
+				EnvironmentHelper.AssertValidEnvironmentSharedLibrary (intermediateOutputDir, AndroidSdkPath, AndroidNdkPath, supportedAbis);
 			}
 		}
 

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Tasks/BundleToolTests.cs

@@ -63,10 +63,12 @@ namespace Xamarin.Android.Build.Tests
 				"lib/arm64-v8a/libmonodroid.so",
 				"lib/arm64-v8a/libmono-native.so",
 				"lib/arm64-v8a/libmonosgen-2.0.so",
+				"lib/arm64-v8a/libxamarin-app.so",
 				"lib/armeabi-v7a/libmono-btls-shared.so",
 				"lib/armeabi-v7a/libmonodroid.so",
 				"lib/armeabi-v7a/libmono-native.so",
 				"lib/armeabi-v7a/libmonosgen-2.0.so",
+				"lib/armeabi-v7a/libxamarin-app.so",
 				"manifest/AndroidManifest.xml",
 				"res/drawable-hdpi-v4/icon.png",
 				"res/drawable-mdpi-v4/icon.png",
@@ -83,8 +85,6 @@ namespace Xamarin.Android.Build.Tests
 				"root/assemblies/System.Runtime.Serialization.dll",
 				"root/assemblies/UnnamedProject.dll",
 				"root/NOTICE",
-				"root/typemap.jm",
-				"root/typemap.mj",
 				//These are random files from Google Play Services .jar/.aar files
 				"root/build-data.properties",
 				"root/com/google/api/client/repackaged/org/apache/commons/codec/language/dmrules.txt",
@@ -108,10 +108,12 @@ namespace Xamarin.Android.Build.Tests
 				"base/lib/arm64-v8a/libmonodroid.so",
 				"base/lib/arm64-v8a/libmono-native.so",
 				"base/lib/arm64-v8a/libmonosgen-2.0.so",
+				"base/lib/arm64-v8a/libxamarin-app.so",
 				"base/lib/armeabi-v7a/libmono-btls-shared.so",
 				"base/lib/armeabi-v7a/libmonodroid.so",
 				"base/lib/armeabi-v7a/libmono-native.so",
 				"base/lib/armeabi-v7a/libmonosgen-2.0.so",
+				"base/lib/armeabi-v7a/libxamarin-app.so",
 				"base/manifest/AndroidManifest.xml",
 				"base/native.pb",
 				"base/res/drawable-hdpi-v4/icon.png",
@@ -129,8 +131,6 @@ namespace Xamarin.Android.Build.Tests
 				"base/root/assemblies/System.Runtime.Serialization.dll",
 				"base/root/assemblies/UnnamedProject.dll",
 				"base/root/NOTICE",
-				"base/root/typemap.jm",
-				"base/root/typemap.mj",
 				"BundleConfig.pb",
 				//These are random files from Google Play Services .jar/.aar files
 				"base/root/build-data.properties",

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/EnvironmentHelper.cs

@@ -0,0 +1,458 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Text.RegularExpressions;
+using System.Threading;
+
+using NUnit.Framework;
+using Xamarin.Android.Tasks;
+using Xamarin.Android.Tools;
+
+namespace Xamarin.Android.Build.Tests
+{
+	class EnvironmentHelper
+	{
+		// This must be identical to the like-named structure in src/monodroid/jni/xamarin-app.h
+		public sealed class ApplicationConfig
+		{
+			public bool   uses_mono_llvm;
+			public bool   uses_mono_aot;
+			public bool   uses_embedded_dsos;
+			public bool   uses_assembly_preload;
+			public bool   is_a_bundled_app;
+			public uint   environment_variable_count;
+			public uint   system_property_count;
+			public string android_package_name;
+		};
+		const uint ApplicationConfigFieldCount = 8;
+
+		static readonly object ndkInitLock = new object ();
+		static readonly char[] readElfFieldSeparator = new [] { ' ', '\t' };
+		static readonly Regex stringLabelRegex = new Regex ("^\\.L\\.str\\.[0-9]+:", RegexOptions.Compiled);
+
+		static readonly HashSet <string> expectedPointerTypes = new HashSet <string> (StringComparer.Ordinal) {
+			".long",
+			".quad",
+			".xword",
+		};
+
+		static readonly HashSet <string> expectedUInt32Types = new HashSet <string> (StringComparer.Ordinal) {
+			".word",
+			".long",
+		};
+
+		static readonly string[] requiredSharedLibrarySymbols = {
+			"app_environment_variables",
+			"app_system_properties",
+			"application_config",
+			"jm_typemap",
+			"jm_typemap_header",
+			"mj_typemap",
+			"mj_typemap_header",
+			"mono_aot_mode_name",
+		};
+
+		// Reads all the environment files, makes sure they all have identical contents in the
+		// `application_config` structure and returns the config if the condition is true
+		public static ApplicationConfig ReadApplicationConfig (List<string> envFilePaths)
+		{
+			if (envFilePaths.Count == 0)
+				return null;
+
+			ApplicationConfig app_config = ReadApplicationConfig (envFilePaths [0]);
+
+			for (int i = 1; i < envFilePaths.Count; i++) {
+				AssertApplicationConfigIsIdentical (app_config, envFilePaths [0], ReadApplicationConfig (envFilePaths[i]), envFilePaths[i]);
+			}
+
+			return app_config;
+		}
+
+		static ApplicationConfig ReadApplicationConfig (string envFile)
+		{
+			string[] lines = File.ReadAllLines (envFile, Encoding.UTF8);
+			var strings = new Dictionary<string, string> (StringComparer.Ordinal);
+			var pointers = new List <string> ();
+
+			var ret = new ApplicationConfig ();
+			bool gatherFields = false;
+			uint fieldCount = 0;
+			for (int i = 0; i < lines.Length; i++) {
+				string line = lines [i];
+				if (IsCommentLine (line))
+					continue;
+
+				string[] field;
+				if (stringLabelRegex.IsMatch (line)) {
+					string label = line.Substring (0, line.Length - 1);
+
+					line = lines [++i];
+					field = GetField (envFile, line, i);
+
+					AssertFieldType (envFile, ".asciz", field [0], i);
+					strings [label] = AssertIsAssemblerString (envFile, field [1], i);
+					continue;
+				}
+
+				if (String.Compare ("application_config:", line.Trim (), StringComparison.Ordinal) == 0) {
+					gatherFields = true;
+					continue;
+				}
+
+				if (!gatherFields)
+					continue;
+
+				field = GetField (envFile, line, i);
+				if (String.Compare (".zero", field [0], StringComparison.Ordinal) == 0)
+					continue; // structure padding
+
+				switch (fieldCount) {
+					case 0: // uses_mono_llvm: bool / .byte
+						AssertFieldType (envFile, ".byte", field [0], i);
+						ret.uses_mono_llvm = ConvertFieldToBool ("uses_mono_llvm", envFile, i, field [1]);
+						break;
+
+					case 1: // uses_mono_aot: bool / .byte
+						AssertFieldType (envFile, ".byte", field [0], i);
+						ret.uses_mono_aot = ConvertFieldToBool ("uses_mono_aot", envFile, i, field [1]);
+						break;
+
+					case 2: // uses_embedded_dsos: bool / .byte
+						AssertFieldType (envFile, ".byte", field [0], i);
+						ret.uses_embedded_dsos = ConvertFieldToBool ("uses_embedded_dsos", envFile, i, field [1]);
+						break;
+
+					case 3: // uses_assembly_preload: bool / .byte
+						AssertFieldType (envFile, ".byte", field [0], i);
+						ret.uses_assembly_preload = ConvertFieldToBool ("uses_assembly_preload", envFile, i, field [1]);
+						break;
+
+					case 4: // is_a_bundled_app: bool / .byte
+						AssertFieldType (envFile, ".byte", field [0], i);
+						ret.is_a_bundled_app = ConvertFieldToBool ("is_a_bundled_app", envFile, i, field [1]);
+						break;
+
+					case 5: // environment_variable_count: uint32_t / .word | .long
+						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile}:{i}': {field [0]}");
+						ret.environment_variable_count = ConvertFieldToUInt32 ("environment_variable_count", envFile, i, field [1]);
+						break;
+
+					case 6: // system_property_count: uint32_t / .word | .long
+						Assert.IsTrue (expectedUInt32Types.Contains (field [0]), $"Unexpected uint32_t field type in '{envFile}:{i}': {field [0]}");
+						ret.system_property_count = ConvertFieldToUInt32 ("system_property_count", envFile, i, field [1]);
+						break;
+
+					case 7: // android_package_name: string / [pointer type]
+						Assert.IsTrue (expectedPointerTypes.Contains (field [0]), $"Unexpected pointer field type in '{envFile}:{i}': {field [0]}");
+						pointers.Add (field [1].Trim ());
+						break;
+				}
+				fieldCount++;
+
+				if (String.Compare (".size", field [0], StringComparison.Ordinal) == 0) {
+					fieldCount--;
+					Assert.IsTrue (field [1].StartsWith ("application_config", StringComparison.Ordinal), $"Mismatched .size directive in '{envFile}:{i}'");
+					break; // We've reached the end of the application_config structure
+				}
+			}
+			Assert.AreEqual (ApplicationConfigFieldCount, fieldCount, $"Invalid 'application_config' field count in environment file '{envFile}'");
+			Assert.AreEqual (1, pointers.Count, $"Invalid number of string pointers in 'application_config' structure in environment file '{envFile}'");
+			Assert.IsTrue (strings.TryGetValue (pointers [0], out ret.android_package_name), $"Invalid package name string pointer in 'application_config' structure in environment file '{envFile}'");
+			Assert.IsFalse (String.IsNullOrEmpty (ret.android_package_name), $"Package name field in 'application_config' in environment file '{envFile}' must not be null or empty");
+
+			return ret;
+		}
+
+		// Reads all the environment files, makes sure they contain the same environment variables (both count
+		// and contents) and then returns a dictionary filled with the variables.
+		public static Dictionary<string, string> ReadEnvironmentVariables (List<string> envFilePaths)
+		{
+			if (envFilePaths.Count == 0)
+				return null;
+
+			Dictionary<string, string> envvars = ReadEnvironmentVariables (envFilePaths [0]);
+			if (envFilePaths.Count == 1)
+				return envvars;
+
+			for (int i = 1; i < envFilePaths.Count; i++) {
+				AssertDictionariesAreEqual (envvars, envFilePaths [0], ReadEnvironmentVariables (envFilePaths[i]), envFilePaths[i]);
+			}
+
+			return envvars;
+		}
+
+		static Dictionary<string, string> ReadEnvironmentVariables (string envFile)
+		{
+			string[] lines = File.ReadAllLines (envFile, Encoding.UTF8);
+			var strings = new Dictionary<string, string> (StringComparer.Ordinal);
+			var pointers = new List <string> ();
+
+			bool gatherPointers = false;
+			for (int i = 0; i < lines.Length; i++) {
+				string line = lines [i];
+				if (IsCommentLine (line))
+					continue;
+
+				string[] field;
+				if (stringLabelRegex.IsMatch (line)) {
+					string label = line.Substring (0, line.Length - 1);
+
+					line = lines [++i];
+					field = GetField (envFile, line, i);
+
+					AssertFieldType (envFile, ".asciz", field [0], i);
+					strings [label] = AssertIsAssemblerString (envFile, field [1], i);
+					continue;
+				}
+
+				if (String.Compare ("app_environment_variables:", line.Trim (), StringComparison.Ordinal) == 0) {
+					gatherPointers = true;
+					continue;
+				}
+
+				if (!gatherPointers)
+					continue;
+
+				field = GetField (envFile, line, i);
+				if (String.Compare (".size", field [0], StringComparison.Ordinal) == 0) {
+					Assert.IsTrue (field [1].StartsWith ("app_environment_variables", StringComparison.Ordinal), $"Mismatched .size directive in '{envFile}:{i}'");
+					break; // We've reached the end of the environment variable array
+				}
+
+				Assert.IsTrue (expectedPointerTypes.Contains (field [0]), $"Unexpected pointer field type in '{envFile}:{i}': {field [0]}");
+				pointers.Add (field [1].Trim ());
+			}
+
+			var ret = new Dictionary <string, string> (StringComparer.Ordinal);
+			if (pointers.Count == 0)
+				return ret;
+
+			Assert.IsTrue (pointers.Count % 2 == 0, "Environment variable array must have an even number of elements");
+			for (int i = 0; i < pointers.Count; i += 2) {
+				string name;
+
+				Assert.IsTrue (strings.TryGetValue (pointers [i], out name), $"[name] String with label '{pointers [i]}' not found in '{envFile}'");
+				Assert.IsFalse (String.IsNullOrEmpty (name), $"Environment variable name must not be null or empty in {envFile} for string label '{pointers [i]}'");
+
+				string value;
+				Assert.IsTrue (strings.TryGetValue (pointers [i + 1], out value), $"[value] String with label '{pointers [i + 1]}' not found in '{envFile}'");
+				Assert.IsNotNull (value, $"Environnment variable value must not be null in '{envFile}' for string label '{pointers [i + 1]}'");
+
+				ret [name] = value;
+			}
+
+			return ret;
+		}
+
+		static bool IsCommentLine (string line)
+		{
+			string l = line?.Trim ();
+			return !String.IsNullOrEmpty (l) && l.StartsWith ("/*", StringComparison.Ordinal);
+		}
+
+		static string[] GetField (string file, string line, int lineNumber)
+		{
+			string[] ret = line?.Trim ()?.Split ('\t');
+			Assert.AreEqual (2, ret.Length, $"Invalid assembler field format in file '{file}:{lineNumber}': '{line}'");
+
+			return ret;
+		}
+
+		static void AssertFieldType (string file, string expectedType, string value, int lineNumber)
+		{
+			Assert.AreEqual (expectedType, value, $"Expected the '{expectedType}' field type in file '{file}:{lineNumber}': {value}");
+		}
+
+		static string AssertIsAssemblerString (string file, string value, int lineNumber)
+		{
+			string v = value.Trim ();
+			Assert.IsTrue (v.StartsWith ("\"") && v.EndsWith("\""), $"Field value is not a valid assembler string in '{file}:{lineNumber}': {v}");
+			return v.Trim ('"');
+		}
+
+		static void AssertDictionariesAreEqual (Dictionary <string, string> d1, string d1FileName, Dictionary <string, string> d2, string d2FileName)
+		{
+			Assert.AreEqual (d1.Count, d2.Count, $"File '{d2FileName}' has a different number of environment variables than file '{d2FileName}'");
+
+			foreach (var kvp in d1) {
+				string value;
+
+				Assert.IsTrue (d2.TryGetValue (kvp.Key, out value), $"File '{d2FileName}' does not contain environment variable '{kvp.Key}'");
+				Assert.AreEqual (kvp.Value, value, $"Value of environnment variable '{kvp.Key}' is different in file '{d2FileName}' than in file '{d1FileName}'");
+			}
+		}
+
+		static void AssertApplicationConfigIsIdentical (ApplicationConfig firstAppConfig, string firstEnvFile, ApplicationConfig secondAppConfig, string secondEnvFile)
+		{
+			Assert.AreEqual (firstAppConfig.uses_mono_llvm, secondAppConfig.uses_mono_llvm, $"Field 'uses_mono_llvm' has different value in environment file '{secondEnvFile}' than in environment file '{firstEnvFile}'");
+			Assert.AreEqual (firstAppConfig.uses_mono_aot, secondAppConfig.uses_mono_aot, $"Field 'uses_mono_aot' has different value in environment file '{secondEnvFile}' than in environment file '{firstEnvFile}'");
+			Assert.AreEqual (firstAppConfig.uses_embedded_dsos, secondAppConfig.uses_embedded_dsos, $"Field 'uses_embedded_dsos' has different value in environment file '{secondEnvFile}' than in environment file '{firstEnvFile}'");
+			Assert.AreEqual (firstAppConfig.is_a_bundled_app, secondAppConfig.is_a_bundled_app, $"Field 'is_a_bundled_app' has different value in environment file '{secondEnvFile}' than in environment file '{firstEnvFile}'");
+			Assert.AreEqual (firstAppConfig.environment_variable_count, secondAppConfig.environment_variable_count, $"Field 'environment_variable_count' has different value in environment file '{secondEnvFile}' than in environment file '{firstEnvFile}'");
+			Assert.AreEqual (firstAppConfig.system_property_count, secondAppConfig.system_property_count, $"Field 'system_property_count' has different value in environment file '{secondEnvFile}' than in environment file '{firstEnvFile}'");
+			Assert.AreEqual (firstAppConfig.android_package_name, secondAppConfig.android_package_name, $"Field 'android_package_name' has different value in environment file '{secondEnvFile}' than in environment file '{firstEnvFile}'");
+		}
+
+		public static List<string> GatherEnvironmentFiles (string outputDirectoryRoot, string supportedAbis, bool required)
+		{
+			var environmentFiles = new List <string> ();
+
+			foreach (string abi in supportedAbis.Split (';')) {
+				string envFilePath = Path.Combine (outputDirectoryRoot, "android", $"environment.{abi}.s");
+
+				Assert.IsTrue (File.Exists (envFilePath), $"Environment file {envFilePath} does not exist");
+				environmentFiles.Add (envFilePath);
+			}
+
+			if (required)
+				Assert.AreNotEqual (0, environmentFiles.Count, "No environment files found");
+
+			return environmentFiles;
+		}
+
+		public static void AssertValidEnvironmentSharedLibrary (string outputDirectoryRoot, string sdkDirectory, string ndkDirectory, string supportedAbis)
+		{
+			NdkUtil.Init (ndkDirectory);
+			MonoAndroidHelper.AndroidSdk = new AndroidSdkInfo ((arg1, arg2) => {}, sdkDirectory, ndkDirectory);
+
+			AndroidTargetArch arch;
+
+			foreach (string abi in supportedAbis.Split (';')) {
+				switch (abi) {
+					case "armeabi-v7a":
+						arch = AndroidTargetArch.Arm;
+						break;
+
+					case "arm64":
+					case "arm64-v8a":
+					case "aarch64":
+						arch = AndroidTargetArch.Arm64;
+						break;
+
+					case "x86":
+						arch = AndroidTargetArch.X86;
+						break;
+
+					case "x86_64":
+						arch = AndroidTargetArch.X86_64;
+						break;
+
+					default:
+						throw new Exception ("Unsupported Android target architecture ABI: " + abi);
+				}
+
+				string envSharedLibrary = Path.Combine (outputDirectoryRoot, "app_shared_libraries", abi, "libxamarin-app.so");
+				Assert.IsTrue (File.Exists (envSharedLibrary), $"Application environment SharedLibrary '{envSharedLibrary}' must exist");
+
+				// API level doesn't matter in this case
+				AssertSharedLibraryHasRequiredSymbols (envSharedLibrary, NdkUtil.GetNdkTool (ndkDirectory, arch, "readelf", 0));
+			}
+		}
+
+		static void AssertSharedLibraryHasRequiredSymbols (string dsoPath, string readElfPath)
+		{
+			var psi = new ProcessStartInfo {
+				FileName = readElfPath,
+				Arguments = $"--dyn-syms \"{dsoPath}\"",
+				CreateNoWindow = true,
+				WindowStyle = ProcessWindowStyle.Hidden,
+				UseShellExecute = false,
+				RedirectStandardError = true,
+				RedirectStandardOutput = true,
+			};
+
+			psi.StandardOutputEncoding = Encoding.UTF8;
+			psi.StandardErrorEncoding = Encoding.UTF8;
+
+			var stdout_completed = new ManualResetEventSlim (false);
+			var stderr_completed = new ManualResetEventSlim (false);
+			var stdout_lines = new List <string> ();
+			var stderr_lines = new List <string> ();
+
+			using (var process = new Process ()) {
+				process.StartInfo = psi;
+				process.OutputDataReceived += (s, e) => {
+					if (e.Data != null)
+						stdout_lines.Add (e.Data);
+					else
+						stdout_completed.Set ();
+				};
+
+				process.ErrorDataReceived += (s, e) => {
+					if (e.Data != null)
+						stderr_lines.Add (e.Data);
+					else
+						stderr_completed.Set ();
+				};
+
+				process.Start ();
+				process.BeginOutputReadLine ();
+				process.BeginErrorReadLine ();
+				bool exited = process.WaitForExit ((int)TimeSpan.FromSeconds (60).TotalMilliseconds);
+				bool stdout_done = stdout_completed.Wait (TimeSpan.FromSeconds (30));
+				bool stderr_done = stderr_completed.Wait (TimeSpan.FromSeconds (30));
+
+				if (!exited)
+					TestContext.Out.WriteLine ($"{psi.FileName} {psi.Arguments} timed out");
+				if (process.ExitCode != 0)
+					TestContext.Out.WriteLine ($"{psi.FileName} {psi.Arguments} returned with error code {process.ExitCode}");
+
+				if (!exited || process.ExitCode != 0) {
+					DumpLines ("stdout", stdout_lines);
+					DumpLines ("stderr", stderr_lines);
+					Assert.Fail ($"Failed to validate application environment SharedLibrary '{dsoPath}'");
+				}
+			}
+
+			var symbols = new HashSet<string> (StringComparer.Ordinal);
+			foreach (string line in stdout_lines) {
+				string[] fields = line.Split (readElfFieldSeparator, StringSplitOptions.RemoveEmptyEntries);
+				if (fields.Length < 8 || !fields [0].EndsWith (":", StringComparison.Ordinal))
+					continue;
+				string symbolName = fields [7].Trim ();
+				if (String.IsNullOrEmpty (symbolName))
+					continue;
+
+				symbols.Add (symbolName);
+			}
+
+			foreach (string symbol in requiredSharedLibrarySymbols) {
+				Assert.IsTrue (symbols.Contains (symbol), $"Symbol '{symbol}' is missing from '{dsoPath}'");
+			}
+		}
+
+		static void DumpLines (string streamName, List <string> lines)
+		{
+			if (lines == null || lines.Count == 0)
+				return;
+
+			TestContext.Out.WriteLine ($"{streamName}:");
+			foreach (string line in lines) {
+				TestContext.Out.WriteLine (line);
+			}
+		}
+
+		static bool ConvertFieldToBool (string fieldName, string envFile, int fileLine, string value)
+		{
+			Assert.AreEqual (1, value.Length, $"Field '{fieldName}' in {envFile}:{fileLine} is not a valid boolean value (too long)");
+
+			uint fv;
+			Assert.IsTrue (UInt32.TryParse (value, out fv), $"Field '{fieldName}' in {envFile}:{fileLine} is not a valid boolean value (not a valid integer)");
+			Assert.IsTrue (fv == 0 || fv == 1, $"Field '{fieldName}' in {envFile}:{fileLine} is not a valid boolean value (not a valid boolean value 0 or 1)");
+
+			return fv == 1;
+		}
+
+		static uint ConvertFieldToUInt32 (string fieldName, string envFile, int fileLine, string value)
+		{
+			Assert.IsTrue (value.Length > 0, $"Field '{fieldName}' in {envFile}:{fileLine} is not a valid uint32_t value (not long enough)");
+
+			uint fv;
+			Assert.IsTrue (UInt32.TryParse (value, out fv), $"Field '{fieldName}' in {envFile}:{fileLine} is not a valid uint32_t value (not a valid integer)");
+
+			return fv;
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Xamarin.Android.Build.Tests.Shared.projitems

@@ -29,5 +29,6 @@
     <Compile Include="$(MSBuildThisFileDirectory)Utilities\FilesTests.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Utilities\MockBuildEngine.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Utilities\MonoAndroidHelperTests.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Utilities\EnvironmentHelper.cs" />
   </ItemGroup>
 </Project>

src/Xamarin.Android.Build.Tasks/Utilities/ARMNativeAssemblerTargetProvider.cs

@@ -0,0 +1,57 @@
+using System;
+using System.IO;
+
+namespace Xamarin.Android.Tasks
+{
+	class ARMNativeAssemblerTargetProvider : NativeAssemblerTargetProvider
+	{
+		public override bool Is64Bit { get; }
+		public override string PointerFieldType { get; }
+		public override string TypePrefix { get; }
+
+		public ARMNativeAssemblerTargetProvider (bool is64Bit)
+		{
+			Is64Bit = is64Bit;
+			PointerFieldType = is64Bit ? ".xword" : ".long";
+			TypePrefix = is64Bit ? "@" : "%";
+		}
+
+		public override string MapType <T> ()
+		{
+			if (typeof(T) == typeof(Int32) || typeof(T) == typeof(UInt32))
+				return Is64Bit ? ".word" : ".long";
+			return base.MapType <T> ();
+		}
+
+		public override void WriteFileHeader (StreamWriter output, string indent)
+		{
+			output.Write ($"{indent}.arch{indent}");
+			output.WriteLine (Is64Bit ? "armv8-a" : "armv7-a");
+
+			if (!Is64Bit) {
+				output.WriteLine ($"{indent}.syntax unified");
+				output.WriteLine ($"{indent}.eabi_attribute 67, \"2.09\"{indent}@ Tag_conformance");
+				output.WriteLine ($"{indent}.eabi_attribute 6, 10{indent}@ Tag_CPU_arch");
+				output.WriteLine ($"{indent}.eabi_attribute 7, 65{indent}@ Tag_CPU_arch_profile");
+				output.WriteLine ($"{indent}.eabi_attribute 8, 1{indent}@ Tag_ARM_ISA_use");
+				output.WriteLine ($"{indent}.eabi_attribute 9, 2{indent}@ Tag_THUMB_ISA_use");
+				output.WriteLine ($"{indent}.fpu{indent}vfpv3-d16");
+				output.WriteLine ($"{indent}.eabi_attribute 34, 1{indent}@ Tag_CPU_unaligned_access");
+				output.WriteLine ($"{indent}.eabi_attribute 15, 1{indent}@ Tag_ABI_PCS_RW_data");
+				output.WriteLine ($"{indent}.eabi_attribute 16, 1{indent}@ Tag_ABI_PCS_RO_data");
+				output.WriteLine ($"{indent}.eabi_attribute 17, 2{indent}@ Tag_ABI_PCS_GOT_use");
+				output.WriteLine ($"{indent}.eabi_attribute 20, 2{indent}@ Tag_ABI_FP_denormal");
+				output.WriteLine ($"{indent}.eabi_attribute 21, 0{indent}@ Tag_ABI_FP_exceptions");
+				output.WriteLine ($"{indent}.eabi_attribute 23, 3{indent}@ Tag_ABI_FP_number_model");
+				output.WriteLine ($"{indent}.eabi_attribute 24, 1{indent}@ Tag_ABI_align_needed");
+				output.WriteLine ($"{indent}.eabi_attribute 25, 1{indent}@ Tag_ABI_align_preserved");
+				output.WriteLine ($"{indent}.eabi_attribute 38, 1{indent}@ Tag_ABI_FP_16bit_format");
+				output.WriteLine ($"{indent}.eabi_attribute 18, 4{indent}@ Tag_ABI_PCS_wchar_t");
+				output.WriteLine ($"{indent}.eabi_attribute 26, 2{indent}@ Tag_ABI_enum_size");
+				output.WriteLine ($"{indent}.eabi_attribute 14, 0{indent}@ Tag_ABI_PCS_R9_use");
+			}
+
+			base.WriteFileHeader (output, indent);
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGenerator.cs

@@ -0,0 +1,126 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace Xamarin.Android.Tasks
+{
+	class ApplicationConfigNativeAssemblyGenerator : NativeAssemblyGenerator
+	{
+		SortedDictionary <string, string> environmentVariables;
+		SortedDictionary <string, string> systemProperties;
+		uint stringCounter = 0;
+
+		public bool IsBundledApp { get; set; }
+		public bool UsesEmbeddedDSOs { get; set; }
+		public bool UsesMonoAOT { get; set; }
+		public bool UsesMonoLLVM { get; set; }
+		public bool UsesAssemblyPreload { get; set; }
+		public string MonoAOTMode { get; set; }
+		public string AndroidPackageName { get; set; }
+
+		public ApplicationConfigNativeAssemblyGenerator (NativeAssemblerTargetProvider targetProvider, IDictionary<string, string> environmentVariables, IDictionary<string, string> systemProperties)
+			: base (targetProvider)
+		{
+			if (environmentVariables != null)
+				this.environmentVariables = new SortedDictionary<string, string> (environmentVariables, StringComparer.Ordinal);
+			if (systemProperties != null)
+				this.systemProperties = new SortedDictionary<string, string> (systemProperties, StringComparer.Ordinal);
+		}
+
+		protected override void WriteSymbols (StreamWriter output)
+		{
+			if (String.IsNullOrEmpty (AndroidPackageName))
+				throw new InvalidOperationException ("Android package name must be set");
+
+			if (UsesMonoAOT && String.IsNullOrEmpty (MonoAOTMode))
+				throw new InvalidOperationException ("Mono AOT enabled but no AOT mode specified");
+
+			string stringLabel = GetStringLabel ();
+			WriteData (output, AndroidPackageName, stringLabel);
+
+			WriteDataSection (output, "application_config");
+			WriteSymbol (output, "application_config", TargetProvider.GetStructureAlignment (true), fieldAlignBytes: 4, isGlobal: true, alwaysWriteSize: true, structureWriter: () => {
+				// Order of fields and their type must correspond *exactly* to that in
+				// src/monodroid/jni/xamarin-app.h ApplicationConfig structure
+				WriteCommentLine (output, "uses_mono_llvm");
+				uint size = WriteData (output, UsesMonoLLVM);
+
+				WriteCommentLine (output, "uses_mono_aot");
+				size += WriteData (output, UsesMonoAOT);
+
+				WriteCommentLine (output, "uses_embedded_dsos");
+				size += WriteData (output, UsesEmbeddedDSOs);
+
+				WriteCommentLine (output, "uses_assembly_preload");
+				size += WriteData (output, UsesAssemblyPreload);
+
+				WriteCommentLine (output, "is_a_bundled_app");
+				size += WriteData (output, IsBundledApp);
+
+				WriteCommentLine (output, "environment_variable_count");
+				size += WriteData (output, environmentVariables == null ? 0 : environmentVariables.Count * 2);
+
+				WriteCommentLine (output, "system_property_count");
+				size += WriteData (output, systemProperties == null ? 0 : systemProperties.Count * 2);
+
+				WriteCommentLine (output, "android_package_name");
+				size += WritePointer (output, stringLabel);
+
+				return size;
+			});
+
+			stringLabel = GetStringLabel ();
+			WriteData (output, MonoAOTMode ?? String.Empty, stringLabel);
+			WriteDataSection (output, "mono_aot_mode_name");
+			WritePointer (output, stringLabel, "mono_aot_mode_name", isGlobal: true);
+
+			WriteNameValueStringArray (output, "app_environment_variables", environmentVariables);
+			WriteNameValueStringArray (output, "app_system_properties", systemProperties);
+		}
+
+		void WriteNameValueStringArray (StreamWriter output, string label, SortedDictionary<string, string> entries)
+		{
+			if (entries == null || entries.Count == 0) {
+				WriteDataSection (output, label);
+				WriteSymbol (output, label, TargetProvider.GetStructureAlignment (true), fieldAlignBytes: 4, isGlobal: true, alwaysWriteSize: true, structureWriter: null);
+				return;
+			}
+
+			var entry_labels = new List <string> ();
+			foreach (var kvp in entries) {
+				string name = kvp.Key;
+				string value = kvp.Value ?? String.Empty;
+				string stringLabel = GetStringLabel ();
+				WriteData (output, name, stringLabel);
+				entry_labels.Add (stringLabel);
+
+				stringLabel = GetStringLabel ();
+				WriteData (output, value, stringLabel);
+				entry_labels.Add (stringLabel);
+
+			}
+
+			WriteDataSection (output, label);
+			WriteSymbol (output, label, TargetProvider.GetStructureAlignment (true), fieldAlignBytes: 4, isGlobal: true, alwaysWriteSize: true, structureWriter: () => {
+				uint size = 0;
+
+				foreach (string l in entry_labels) {
+					size += WritePointer (output, l);
+				}
+
+				return size;
+			});
+		}
+
+		void WriteDataSection (StreamWriter output, string tag)
+		{
+			WriteSection (output, $".data.{tag}", hasStrings: false, writable: true);
+		}
+
+		string GetStringLabel ()
+		{
+			stringCounter++;
+			return $".L.str.{stringCounter}";
+		}
+	};
+}

src/Xamarin.Android.Build.Tasks/Utilities/NativeAssemblerTargetProvider.cs

@@ -0,0 +1,65 @@
+using System;
+using System.IO;
+
+namespace Xamarin.Android.Tasks
+{
+	abstract class NativeAssemblerTargetProvider
+	{
+		public abstract bool Is64Bit { get; }
+		public abstract string PointerFieldType { get; }
+		public abstract string TypePrefix { get; }
+
+		public virtual string MapType <T> ()
+		{
+			if (typeof(T) == typeof(byte))
+				return ".byte";
+
+			if (typeof(T) == typeof(bool))
+				return ".byte";
+
+			if (typeof(T) == typeof(string))
+				return ".asciz";
+
+			throw new InvalidOperationException ($"Unable to map managed type {typeof(T)} to native assembly type");
+		}
+
+		public virtual uint GetTypeSize <T> (T field)
+		{
+			return GetTypeSize <T> ();
+		}
+
+		public virtual uint GetTypeSize <T> ()
+		{
+			if (typeof(T) == typeof(byte))
+				return 1u;
+
+			if (typeof(T) == typeof(bool))
+				return 1u;
+
+			if (typeof(T) == typeof(string))
+				return GetPointerSize();
+
+			if (typeof(T) == typeof(Int32) || typeof(T) == typeof(UInt32))
+				return 4u;
+
+			if (typeof(T) == typeof(Int64) || typeof(T) == typeof(UInt64))
+				return 8u;
+
+			throw new InvalidOperationException ($"Unable to map managed type {typeof(T)} to native assembly type");
+		}
+
+		public virtual uint GetStructureAlignment (bool hasPointers)
+		{
+			return (!hasPointers || !Is64Bit) ? 2u : 3u;
+		}
+
+		public virtual uint GetPointerSize ()
+		{
+			return Is64Bit ? 8u : 4u;
+		}
+
+		public virtual void WriteFileHeader (StreamWriter output, string indent)
+		{
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Utilities/NativeAssemblyDataStream.cs

@@ -0,0 +1,220 @@
+using System;
+using System.Collections.Generic;
+using System.Security.Cryptography;
+using System.IO;
+using System.Text;
+
+namespace Xamarin.Android.Tasks
+{
+	class NativeAssemblyDataStream : Stream
+	{
+		const uint MapVersionFound     = 0x0001;
+		const uint MapEntryCountFound  = 0x0002;
+		const uint MapEntryLengthFound = 0x0004;
+		const uint MapValueOffsetFound = 0x0008;
+		const uint MapEverythingFound  = MapVersionFound | MapEntryCountFound | MapEntryLengthFound | MapValueOffsetFound;
+
+		const string MapFieldVersion     = "version";
+		const string MapFieldEntryCount  = "entry-count";
+		const string MapFieldEntryLength = "entry-len";
+		const string MapFieldValueOffset = "value-offset";
+
+		const uint MaxFieldsInRow = 32;
+
+		MemoryStream outputStream;
+		StreamWriter outputWriter;
+		bool firstWrite = true;
+		uint rowFieldCounter;
+		SHA1CryptoServiceProvider sha1;
+		bool hashingFinished;
+		uint byteCount = 0;
+
+		public int MapVersion     { get; set; } = -1;
+		public int MapEntryCount  { get; set; } = -1;
+		public int MapEntryLength { get; set; } = -1;
+		public int MapValueOffset { get; set; } = -1;
+		public uint MapByteCount => byteCount;
+
+		public override bool CanRead => outputStream.CanRead;
+		public override bool CanSeek => outputStream.CanSeek;
+		public override bool CanWrite => outputStream.CanWrite;
+		public override long Length => outputStream.Length;
+
+		public override long Position {
+			get => outputStream.Position;
+			set => outputStream.Position = value;
+		}
+
+		public NativeAssemblyDataStream ()
+		{
+			outputStream = new MemoryStream ();
+			outputWriter = new StreamWriter (outputStream, new UTF8Encoding (false));
+			sha1 = new SHA1CryptoServiceProvider ();
+			sha1.Initialize ();
+		}
+
+		public byte[] GetStreamHash ()
+		{
+			if (!hashingFinished) {
+				sha1.TransformFinalBlock (new byte[0], 0, 0);
+				hashingFinished = true;
+			}
+
+			return sha1.Hash;
+		}
+
+		protected override void Dispose (bool disposing)
+		{
+			base.Dispose (disposing);
+			if (!disposing)
+				return;
+
+			outputWriter.Dispose ();
+			outputWriter = null;
+			outputStream = null;
+		}
+
+		public override void Flush ()
+		{
+			outputWriter.Flush ();
+			outputStream.Flush ();
+		}
+
+		public override int Read (byte[] buffer, int offset, int count)
+		{
+			return outputStream.Read (buffer, offset, count);
+		}
+
+		public override long Seek (long offset, SeekOrigin origin)
+		{
+			return outputStream.Seek (offset, origin);
+		}
+
+		public override void SetLength (long value)
+		{
+			outputStream.SetLength (value);
+		}
+
+		public override void Write (byte[] buffer, int offset, int count)
+		{
+			if (buffer == null)
+				throw new ArgumentNullException (nameof (buffer));
+			if (offset < 0)
+				throw new ArgumentOutOfRangeException (nameof (offset));
+			if (count < 0)
+				throw new ArgumentOutOfRangeException (nameof (count));
+			if (offset + count > buffer.Length)
+				throw new ArgumentException ($"The sum of the '{nameof (offset)}' and '{nameof (count)}' arguments is greater than the buffer length");
+			if (outputWriter == null)
+				throw new ObjectDisposedException (this.GetType ().Name);
+
+			if (!hashingFinished)
+				sha1.TransformBlock (buffer, offset, count, null, 0);
+
+			if (firstWrite) {
+				// Kind of a backward thing to do, but I wanted to avoid having to modfy (and bump the
+				// submodule of) Java.Interop. This should be Safe Enough™ (until it's not)
+				string line = Encoding.UTF8.GetString (buffer, offset, count);
+
+				// Format used by Java.Interop.Tools.JavaCallableWrappers.TypeNameMapGenerator:
+				//
+				//  "version=1\u0000entry-count={0}\u0000entry-len={1}\u0000value-offset={2}\u0000"
+				//
+				string[] parts = line.Split ('\u0000');
+				if (parts.Length != 5)
+					HeaderFormatError ("invalid number of fields");
+
+				// Let's be just slightly flexible :P
+				uint foundMask = 0;
+				foreach (string p in parts) {
+					string field = p.Trim ();
+					if (String.IsNullOrEmpty (field))
+						continue;
+
+					string[] fieldParts = field.Split(new char[]{'='}, 2);
+					if (fieldParts.Length != 2)
+						HeaderFormatError ($"invalid field format '{field}'");
+
+					switch (fieldParts [0]) {
+						case MapFieldVersion:
+							foundMask |= MapVersionFound;
+							MapVersion = GetHeaderInteger (fieldParts[0], fieldParts [1]);
+							break;
+
+						case MapFieldEntryCount:
+							foundMask |= MapEntryCountFound;
+							MapEntryCount = GetHeaderInteger (fieldParts[0], fieldParts [1]);
+							break;
+
+						case MapFieldEntryLength:
+							foundMask |= MapEntryLengthFound;
+							MapEntryLength = GetHeaderInteger (fieldParts[0], fieldParts [1]);
+							break;
+
+						case MapFieldValueOffset:
+							foundMask |= MapValueOffsetFound;
+							MapValueOffset = GetHeaderInteger (fieldParts[0], fieldParts [1]);
+							break;
+
+						default:
+							HeaderFormatError ($"unknown field '{fieldParts [0]}'");
+							break;
+					}
+				}
+
+				if (foundMask != MapEverythingFound) {
+					var missingFields = new List <string> ();
+					if ((foundMask & MapVersionFound) == 0)
+						missingFields.Add (MapFieldVersion);
+					if ((foundMask & MapEntryCountFound) == 0)
+						missingFields.Add (MapFieldEntryCount);
+					if ((foundMask & MapEntryLengthFound) == 0)
+						missingFields.Add (MapFieldEntryLength);
+					if ((foundMask & MapValueOffsetFound) == 0)
+						missingFields.Add (MapFieldValueOffset);
+
+					var sb = new StringBuilder ("missing header field");
+					if (missingFields.Count > 1)
+						sb.Append ('s');
+					sb.Append (": ");
+					sb.Append (String.Join (", ", missingFields));
+					HeaderFormatError (sb.ToString ());
+				}
+
+				firstWrite = false;
+				rowFieldCounter = 0;
+				return;
+			}
+
+			for (int i = 0; i < count; i++) {
+				byteCount++;
+				if (rowFieldCounter == 0)
+					outputWriter.Write ("\t.byte ");
+
+				byte b = buffer [offset + i];
+				if (rowFieldCounter > 0)
+					outputWriter.Write (", ");
+				outputWriter.Write ($"0x{b:x02}");
+
+				rowFieldCounter++;
+				if (rowFieldCounter > MaxFieldsInRow) {
+					rowFieldCounter = 0;
+					outputWriter.WriteLine ();
+				}
+			}
+
+			void HeaderFormatError (string whatsWrong)
+			{
+				throw new InvalidOperationException ($"Java.Interop.Tools.JavaCallableWrappers.TypeNameMapGenerator header format changed: {whatsWrong}");
+			}
+
+			int GetHeaderInteger (string name, string value)
+			{
+				int ret;
+				if (!Int32.TryParse (value, out ret))
+					HeaderFormatError ($"failed to parse integer value from '{value}' for field '{name}'");
+				return ret;
+			}
+		}
+	};
+}

src/Xamarin.Android.Build.Tasks/Utilities/NativeAssemblyGenerator.cs

@@ -0,0 +1,239 @@
+using System;
+using System.IO;
+using System.Text;
+
+namespace Xamarin.Android.Tasks
+{
+	abstract class NativeAssemblyGenerator
+	{
+		uint structureByteCount;
+		uint structureAlignBytes;
+		bool writingStructure = false;
+
+		protected string Indent { get; } = "\t";
+		protected NativeAssemblerTargetProvider TargetProvider { get; }
+
+		protected NativeAssemblyGenerator (NativeAssemblerTargetProvider targetProvider)
+		{
+			if (targetProvider == null)
+				throw new ArgumentNullException (nameof (targetProvider));
+			TargetProvider = targetProvider;
+		}
+
+		public void Write (StreamWriter output, string outputFileName)
+		{
+			if (output == null)
+				throw new ArgumentNullException (nameof (output));
+
+			WriteFileHeader (output, outputFileName);
+			WriteSymbols (output);
+			output.Flush ();
+		}
+
+		protected virtual void WriteSymbols (StreamWriter output)
+		{
+		}
+
+		protected string HashToHex (byte[] dataHash)
+		{
+			var sb = new StringBuilder ();
+			foreach (byte b in dataHash)
+				sb.Append ($"{b:x02}");
+			return sb.ToString ();
+		}
+
+		protected void WriteEndLine (StreamWriter output, string comment = null, bool indent = true)
+		{
+			if (!String.IsNullOrEmpty (comment)) {
+				if (indent)
+					output.Write (Indent);
+				WriteComment (output, comment);
+			}
+			output.WriteLine ();
+		}
+
+		protected void WriteComment (StreamWriter output, string comment, bool indent = true)
+		{
+			output.Write ($"{(indent ? Indent : String.Empty)}/* {comment} */");
+		}
+
+		protected void WriteCommentLine (StreamWriter output, string comment, bool indent = true)
+		{
+			WriteComment (output, comment);
+			output.WriteLine ();
+		}
+
+		protected virtual void WriteFileHeader (StreamWriter output, string outputFileName)
+		{
+			TargetProvider.WriteFileHeader (output, Indent);
+			output.WriteLine ($"{Indent}.file{Indent}\"{Path.GetFileName (outputFileName)}\"");
+		}
+
+		protected virtual void WriteSection (StreamWriter output, string sectionName, bool hasStrings, bool writable)
+		{
+			output.Write ($"{Indent}.section{Indent}{sectionName},\"a"); // a - section is allocatable
+			if (hasStrings)
+				output.Write ("MS"); // M - section is mergeable, S - section contains zero-terminated strings
+			else if (writable)
+				output.Write ("w");
+
+			output.Write ($"\",{TargetProvider.TypePrefix}progbits");
+			if (hasStrings)
+				output.Write (",1");
+			output.WriteLine ();
+		}
+
+		// `alignBits` indicates the number of lowest bits that have to be cleared to 0 in order to align the
+		// following data structure, thus `2` would mean "align to 4 bytes", `3' would be "align to 8 bytes"
+		// etc. In general, if the data field contains a pointer the alignment should be to the platform's
+		// native pointer size, if not it should be 2 (for 4-byte alignment) in the case of the targets we
+		// support. Alignment is not necessary for standalone fields (i.e. not parts of a structure)
+		protected void WriteSymbol <T> (StreamWriter output, T symbolValue, string symbolName, ulong size, uint alignBits, bool isGlobal, bool isObject, bool alwaysWriteSize)
+		{
+			WriteSymbol (output, TargetProvider.MapType<T>(), QuoteValue (symbolValue), symbolName, size, alignBits, isGlobal, isObject, alwaysWriteSize);
+		}
+
+		protected void WriteSymbol (StreamWriter output, string symbolType, string symbolValue, string symbolName, ulong size, uint alignBits, bool isGlobal, bool isObject, bool alwaysWriteSize)
+		{
+			if (isObject)
+				output.WriteLine ($"{Indent}.type{Indent}{symbolName}, {TargetProvider.TypePrefix}object");
+			if (alignBits > 0)
+				output.WriteLine ($"{Indent}.p2align{Indent}{alignBits}");
+			if (isGlobal)
+				output.WriteLine ($"{Indent}.global{Indent}{symbolName}");
+			if (!String.IsNullOrEmpty (symbolName))
+				output.WriteLine ($"{symbolName}:");
+			if (!String.IsNullOrEmpty (symbolType) && !String.IsNullOrEmpty (symbolValue))
+				output.WriteLine ($"{Indent}{symbolType}{Indent}{symbolValue}");
+			if (alwaysWriteSize || size > 0)
+				output.WriteLine ($"{Indent}.size{Indent}{symbolName}, {size}");
+		}
+
+		protected void WriteSymbol (StreamWriter output, string label, uint size, bool isGlobal, bool isObject, bool alwaysWriteSize)
+		{
+			WriteSymbol (output, null, null, label, size, alignBits: 0, isGlobal: isGlobal, isObject: isObject, alwaysWriteSize: alwaysWriteSize);
+		}
+
+		protected void WriteSymbol (StreamWriter output, string symbolName, uint alignBits, uint fieldAlignBytes, bool isGlobal, bool alwaysWriteSize, Func<uint> structureWriter)
+		{
+			output.WriteLine ($"{Indent}.type{Indent}{symbolName}, {TargetProvider.TypePrefix}object");
+			if (alignBits > 0)
+				output.WriteLine ($"{Indent}.p2align{Indent}{alignBits}");
+			if (isGlobal)
+				output.WriteLine ($"{Indent}.global{Indent}{symbolName}");
+			if (!String.IsNullOrEmpty (symbolName))
+				output.WriteLine ($"{symbolName}:");
+
+			writingStructure = true;
+			structureByteCount = 0;
+			structureAlignBytes = fieldAlignBytes;
+			uint size = structureWriter != null ? structureWriter () : 0u;
+			writingStructure = false;
+			if (alwaysWriteSize || size > 0)
+				output.WriteLine ($"{Indent}.size{Indent}{symbolName}, {size}");
+		}
+
+		protected virtual string QuoteValue <T> (T value)
+		{
+			if (typeof(T) == typeof(string))
+				return $"\"{value}\"";
+
+			if (typeof(T) == typeof(bool))
+				return (bool)((object)value) ? "1" : "0";
+
+			return $"{value}";
+		}
+
+		protected uint WritePointer (StreamWriter output, string targetName, string label = null, bool isGlobal = false)
+		{
+			if (String.IsNullOrEmpty (targetName))
+				throw new ArgumentException ("must not be null or empty", nameof (targetName));
+
+			uint fieldSize = UpdateSize (output, targetName);
+			WriteSymbol (output, TargetProvider.PointerFieldType, targetName, label, size: 0, alignBits: 0, isGlobal: isGlobal, isObject: false, alwaysWriteSize: false);
+			return fieldSize;
+		}
+
+		uint WriteDataPadding (StreamWriter output, uint nextFieldSize, uint sizeSoFar)
+		{
+			if (!writingStructure || structureAlignBytes <= 1 || nextFieldSize == 1)
+				return 0;
+
+			uint alignment = sizeSoFar % structureAlignBytes;
+			if (alignment == 0)
+				return 0;
+
+			uint nbytes = structureAlignBytes - alignment;
+			output.WriteLine ($"{Indent}.zero{Indent}{nbytes}");
+			return nbytes;
+		}
+
+		protected uint WriteData (StreamWriter output, string value, string label, bool isGlobal = false)
+		{
+			if (String.IsNullOrEmpty (label))
+				throw new ArgumentException ("must not be null or empty", nameof (label));
+			if (value == null)
+				value = String.Empty;
+
+			WriteSection (output, $".rodata.{label}", hasStrings: true, writable: false);
+			WriteSymbol (output, value, label, size: (ulong)(value.Length + 1), alignBits: 0, isGlobal: isGlobal, isObject: true, alwaysWriteSize: true);
+			return TargetProvider.GetTypeSize (value);
+		}
+
+		uint UpdateSize <T> (StreamWriter output, T value)
+		{
+			uint fieldSize;
+
+			if (typeof (T) == typeof (string))
+				fieldSize = TargetProvider.GetPointerSize ();
+			else
+				fieldSize = TargetProvider.GetTypeSize (value);
+			fieldSize += WriteDataPadding (output, fieldSize, structureByteCount);
+			structureByteCount += fieldSize;
+
+			return fieldSize;
+		}
+
+		protected uint WriteData (StreamWriter output, byte value, string label = null, bool isGlobal = false)
+		{
+			uint fieldSize = UpdateSize (output, value);
+			WriteSymbol (output, value, label, size: 0, alignBits: 0, isGlobal: isGlobal, isObject: false, alwaysWriteSize: false);
+			return fieldSize;
+		}
+
+		protected uint WriteData (StreamWriter output, Int32 value, string label = null, bool isGlobal = false)
+		{
+			uint fieldSize = UpdateSize (output, value);
+			WriteSymbol (output, value, label, size: 0, alignBits: 0, isGlobal: isGlobal, isObject: false, alwaysWriteSize: false);
+			return fieldSize;
+		}
+
+		protected uint WriteData (StreamWriter output, UInt32 value, string label = null, bool isGlobal = false)
+		{
+			uint fieldSize = UpdateSize (output, value);
+			WriteSymbol (output, value, label, size: 0, alignBits: 0, isGlobal: isGlobal, isObject: false, alwaysWriteSize: false);
+			return fieldSize;
+		}
+
+		protected uint WriteData (StreamWriter output, Int64 value, string label = null, bool isGlobal = false)
+		{
+			uint fieldSize = UpdateSize (output, value);
+			WriteSymbol (output, value, label, size: 0, alignBits: 0, isGlobal: isGlobal, isObject: false, alwaysWriteSize: false);
+			return fieldSize;
+		}
+
+		protected uint WriteData (StreamWriter output, UInt64 value, string label = null, bool isGlobal = false)
+		{
+			uint fieldSize = UpdateSize (output, value);
+			WriteSymbol (output, value, label, size: 0, alignBits: 0, isGlobal: isGlobal, isObject: false, alwaysWriteSize: false);
+			return fieldSize;
+		}
+
+		protected uint WriteData (StreamWriter output, bool value, string label = null, bool isGlobal = false)
+		{
+			uint fieldSize = UpdateSize (output, value);
+			WriteSymbol (output, value, label, size: 0, alignBits: 0, isGlobal: isGlobal, isObject: false, alwaysWriteSize: false);
+			return fieldSize;
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Utilities/TypeMappingNativeAssemblyGenerator.cs

@@ -0,0 +1,71 @@
+using System;
+using System.IO;
+using System.Text;
+
+namespace Xamarin.Android.Tasks
+{
+	class TypeMappingNativeAssemblyGenerator : NativeAssemblyGenerator
+	{
+		NativeAssemblyDataStream dataStream;
+		string dataFileName;
+		uint dataSize;
+		string mappingFieldName;
+
+		public TypeMappingNativeAssemblyGenerator (NativeAssemblerTargetProvider targetProvider, NativeAssemblyDataStream dataStream, string dataFileName, uint dataSize, string mappingFieldName)
+			: base (targetProvider)
+		{
+			if (dataStream == null)
+				throw new ArgumentNullException (nameof (dataStream));
+			if (String.IsNullOrEmpty (dataFileName))
+				throw new ArgumentException ("must not be null or empty", nameof (dataFileName));
+			if (String.IsNullOrEmpty (mappingFieldName))
+				throw new ArgumentException ("must not be null or empty", nameof (mappingFieldName));
+
+			this.dataStream = dataStream;
+			this.dataFileName = dataFileName;
+			this.dataSize = dataSize;
+			this.mappingFieldName = mappingFieldName;
+		}
+
+		protected override void WriteFileHeader (StreamWriter output, string outputFileName)
+		{
+			// The hash is written to make sure the assembly file which includes the data one is
+			// actually different whenever the data changes. Relying on mapping header values for this
+			// purpose would not be enough since the only change to the mapping might be a single-character
+			// change in one of the type names and we must be sure the assembly is rebuilt in all cases,
+			// thus the SHA1.
+			WriteEndLine (output, $"Data SHA1: {HashToHex (dataStream.GetStreamHash ())}", false);
+			base.WriteFileHeader (output, outputFileName);
+		}
+
+		protected override void WriteSymbols (StreamWriter output)
+		{
+			WriteMappingHeader (output, dataStream, mappingFieldName);
+			WriteCommentLine (output, "Mapping data");
+			WriteSymbol (output, mappingFieldName, dataSize, isGlobal: true, isObject: true, alwaysWriteSize: true);
+			output.WriteLine ($"{Indent}.include{Indent}\"{dataFileName}\"");
+		}
+
+		void WriteMappingHeader (StreamWriter output, NativeAssemblyDataStream dataStream, string mappingFieldName)
+		{
+			output.WriteLine ();
+			WriteCommentLine (output, "Mapping header");
+			WriteSection (output, $".data.{mappingFieldName}", hasStrings: false, writable: true);
+			WriteSymbol (output, $"{mappingFieldName}_header", alignBits: 2, fieldAlignBytes: 4, isGlobal: true, alwaysWriteSize: true, structureWriter: () => {
+				WriteCommentLine (output, "version");
+				WriteData (output, dataStream.MapVersion);
+
+				WriteCommentLine (output, "entry-count");
+				WriteData (output, dataStream.MapEntryCount);
+
+				WriteCommentLine (output, "entry-length");
+				WriteData (output, dataStream.MapEntryLength);
+
+				WriteCommentLine (output, "value-offset");
+				WriteData (output, dataStream.MapValueOffset);
+				return 16;
+			});
+			output.WriteLine ();
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Utilities/X86NativeAssemblerTargetProvider.cs

@@ -0,0 +1,24 @@
+using System;
+
+namespace Xamarin.Android.Tasks
+{
+	class X86NativeAssemblerTargetProvider : NativeAssemblerTargetProvider
+	{
+		public override bool Is64Bit { get; }
+		public override string PointerFieldType { get; }
+		public override string TypePrefix { get; } = "@";
+
+		public X86NativeAssemblerTargetProvider (bool is64Bit)
+		{
+			Is64Bit = is64Bit;
+			PointerFieldType = is64Bit ? ".quad" : ".long";
+		}
+
+		public override string MapType <T> ()
+		{
+			if (typeof(T) == typeof(Int32) || typeof(T) == typeof(UInt32))
+				return ".long";
+			return base.MapType <T> ();
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj

@@ -163,6 +163,7 @@
     <Compile Include="Tasks\ResolveSdksTask.cs" />
     <Compile Include="Tasks\CompileToDalvik.cs" />
     <Compile Include="Tasks\AndroidToolTask.cs" />
+    <Compile Include="Tasks\PrepareAbiItems.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Mono.Android\ApplicationAttribute.Partial.cs" />
     <Compile Include="Mono.Android\BroadcastReceiverAttribute.Partial.cs" />
@@ -599,6 +600,15 @@
     <Compile Include="Tasks\LayoutWidget.cs" />
     <Compile Include="..\..\bin\Build$(Configuration)\XABuildConfig.cs" />
     <Compile Include="Tasks\CheckGoogleSdkRequirements.cs" />
+    <Compile Include="Utilities\NativeAssemblyDataStream.cs" />
+    <Compile Include="Utilities\NativeAssemblyGenerator.cs" />
+    <Compile Include="Utilities\NativeAssemblerTargetProvider.cs" />
+    <Compile Include="Utilities\ARMNativeAssemblerTargetProvider.cs" />
+    <Compile Include="Utilities\X86NativeAssemblerTargetProvider.cs" />
+    <Compile Include="Utilities\TypeMappingNativeAssemblyGenerator.cs" />
+    <Compile Include="Utilities\ApplicationConfigNativeAssemblyGenerator.cs" />
+    <Compile Include="Tasks\CompileNativeAssembly.cs" />
+    <Compile Include="Tasks\LinkApplicationSharedLibraries.cs" />
     <None Include="Resources\desugar_deploy.jar">
       <Link>desugar_deploy.jar</Link>
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
@@ -696,9 +706,6 @@
     <EmbeddedResource Include="Resources\ApplicationRegistration.java">
       <LogicalName>ApplicationRegistration.java</LogicalName>
     </EmbeddedResource>
-    <EmbeddedResource Include="Resources\XamarinAndroidEnvironmentVariables.java">
-      <LogicalName>XamarinAndroidEnvironmentVariables.java</LogicalName>
-    </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Xamarin.Android.Tools.Aidl\Xamarin.Android.Tools.Aidl.csproj">
@@ -788,6 +795,10 @@
       <Project>{94BD81F7-B06F-4295-9636-F8A3B6BDC762}</Project>
       <Name>Java.Interop</Name>
     </ProjectReference>
+    <ProjectReference Include="..\..\build-tools\fetch-windows-assemblers\fetch-windows-assemblers.csproj">
+      <Project>{09518DF2-C7B1-4CDB-849A-9F91F4BEA925}</Project>
+      <Name>fetch-windows-assemblers</Name>
+    </ProjectReference>
   </ItemGroup>
   <Import Project="ILRepack.targets" />
 </Project>

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.targets

@@ -3,12 +3,15 @@
   <UsingTask TaskName="Xamarin.Android.Tools.BootstrapTasks.GenerateProfile" AssemblyFile="..\..\bin\Build$(Configuration)\Xamarin.Android.Tools.BootstrapTasks.dll" />
   <UsingTask TaskName="Xamarin.Android.Tools.BootstrapTasks.UnzipDirectoryChildren" AssemblyFile="..\..\bin\Build$(Configuration)\Xamarin.Android.Tools.BootstrapTasks.dll" />
   <UsingTask AssemblyFile="..\..\bin\Build$(Configuration)\xa-prep-tasks.dll"       TaskName="Xamarin.Android.BuildTools.PrepTasks.ReplaceFileContents" />
+  <UsingTask AssemblyFile="..\..\bin\Build$(Configuration)\xa-prep-tasks.dll"       TaskName="Xamarin.Android.BuildTools.PrepTasks.Which" />
+
   <Import Project="..\..\src\mono-runtimes\ProfileAssemblies.projitems" />
   <Import Project="..\..\build-tools\scripts\XAVersionInfo.targets" />
   <PropertyGroup>
     <_SharedRuntimeBuildPath Condition=" '$(_SharedRuntimeBuildPath)' == '' ">$(XAInstallPrefix)xbuild-frameworks\MonoAndroid\</_SharedRuntimeBuildPath>
     <_GeneratedProfileClass>$(MSBuildThisFileDirectory)$(IntermediateOutputPath)Profile.g.cs</_GeneratedProfileClass>
     <BuildDependsOn>
+      _CopyNDKTools;
       _GenerateXACommonProps;
       $(BuildDependsOn);
       _CopyExtractedMultiDexJar;
@@ -128,6 +131,74 @@
     <_SharedRuntimeAssemblies Include="$(_SharedRuntimeBuildPath)$(AndroidFrameworkVersion)\OpenTK.dll" />
     <_SharedRuntimeAssemblies Include="$(_SharedRuntimeBuildPath)$(AndroidFrameworkVersion)\OpenTK-1.0.dll" />
   </ItemGroup>
+  <Target Name="_PrepareNDKToolsItems">
+    <PropertyGroup>
+      <_PrebuiltToolchainDir Condition=" '$(HostOS)' == 'Linux' ">linux-x86_64</_PrebuiltToolchainDir>
+      <_PrebuiltToolchainDir Condition=" '$(HostOS)' == 'Darwin' ">darwin-x86_64</_PrebuiltToolchainDir>
+      <_PrebuiltToolchainDir Condition=" '$(HostOS)' == 'Windows' And '$(HostBits)' == '64' ">windows-x86_64</_PrebuiltToolchainDir>
+      <_PrebuiltToolchainDir Condition=" '$(HostOS)' == 'Windows' And '$(HostBits)' == '32' ">windows</_PrebuiltToolchainDir>
+    </PropertyGroup>
+    <ItemGroup>
+      <_ToolchainPrefix Include="aarch64-linux-android">
+        <ToolPrefix>aarch64-linux-android</ToolPrefix>
+      </_ToolchainPrefix>
+      <_ToolchainPrefix Include="arm-linux-androideabi">
+        <ToolPrefix>arm-linux-androideabi</ToolPrefix>
+      </_ToolchainPrefix>
+      <_ToolchainPrefix Include="x86">
+        <ToolPrefix>i686-linux-android</ToolPrefix>
+      </_ToolchainPrefix>
+      <_ToolchainPrefix Include="x86_64">
+        <ToolPrefix>x86_64-linux-android</ToolPrefix>
+      </_ToolchainPrefix>
+    </ItemGroup>
+
+    <Which
+        HostOS="$(HostOS)"
+        HostOSName="$(HostOsName)"
+        Program="$(AndroidNdkFullPath)/toolchains/%(_ToolchainPrefix.Identity)-4.9/prebuilt/$(_PrebuiltToolchainDir)/bin/%(_ToolchainPrefix.ToolPrefix)-as"
+        Required="True">
+      <Output TaskParameter="Location" PropertyName="_NDKToolLocation%(_ToolchainPrefix.Identity)" />
+    </Which>
+
+    <PropertyGroup>
+      <_NDKToolFileName>$([System.IO.Path]::GetFileName ('$(_NDKToolLocation)'))</_NDKToolFileName>
+      <_NDKToolDestinationBase>$(XAInstallPrefix)xbuild\Xamarin\Android</_NDKToolDestinationBase>
+      <_WinAsmDestDir>$(XAInstallPrefix)xbuild\Xamarin\Android</_WinAsmDestDir>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <_NDKToolSource Include="$(_NDKToolLocation%(_ToolchainPrefix.Identity))" />
+      <_NDKToolDestination Condition=" '$(HostOS)' != 'Windows' " Include="$(_NDKToolDestinationBase)\$(HostOS)\$([System.IO.Path]::GetFileName ('$(_NDKToolLocation%(_ToolchainPrefix.Identity))'))" />
+      <_NDKToolDestination Condition=" '$(HostOS)' == 'Windows' " Include="$(_NDKToolDestinationBase)\$([System.IO.Path]::GetFileName ('$(_NDKToolLocation%(_ToolchainPrefix.Identity))'))" />
+    </ItemGroup>
+  </Target>
+
+  <Target Name="_FetchWindowsAssemblers"
+      Condition=" '$(HostOS)' != 'Windows' "
+      DependsOnTargets="_PrepareNDKToolsItems"
+      AfterTargets="Build"
+      Inputs="..\..\build-tools\scripts\Ndk.targets"
+      Outputs="$(_WinAsmDestDir)\%(_ToolchainPrefix.Identity)-as.exe">
+    <MakeDir
+        Directories="$(_WinAsmDestDir)"
+    />
+    <Exec
+        Command="$(ManagedRuntime) $(MSBuildThisFileDirectory)..\..\bin\Build$(Configuration)\fetch-windows-assemblers.exe $(AndroidNdkVersion) &quot;$(_WinAsmDestDir)&quot; https://dl.google.com/android/repository/android-ndk-r$(AndroidNdkVersion)-windows-x86_64.zip"
+        WorkingDirectory="$(_WinAsmDestDir)"
+    />
+  </Target>
+
+  <Target Name="_CopyNDKTools"
+      DependsOnTargets="_PrepareNDKToolsItems"
+      Inputs="@(_NDKToolSource)"
+      Outputs="@(_NDKToolDestination)">
+    <Copy
+        SourceFiles="@(_NDKToolSource)"
+        DestinationFiles="@(_NDKToolDestination)"
+        />
+  </Target>
+
   <Target Name="_GenerateMonoAndroidEnums"
       BeforeTargets="CoreCompile"
       Inputs="..\Mono.Android\obj\$(Configuration)\android-$(AndroidLatestStableApiLevel)\mcw\api.xml"

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets

@@ -111,6 +111,9 @@ Copyright (C) 2011-2012 Xamarin. All rights reserved.
 <UsingTask TaskName="Xamarin.Android.Tasks.Proguard" AssemblyFile="Xamarin.Android.Build.Tasks.dll" />
 <UsingTask TaskName="Xamarin.Android.Tasks.DetermineJavaLibrariesToCompile" AssemblyFile="Xamarin.Android.Build.Tasks.dll" />
 <UsingTask TaskName="Xamarin.Android.Tasks.CreateMultiDexMainDexClassList" AssemblyFile="Xamarin.Android.Build.Tasks.dll" />
+<UsingTask TaskName="Xamarin.Android.Tasks.CompileNativeAssembly" AssemblyFile="Xamarin.Android.Build.Tasks.dll" />
+<UsingTask TaskName="Xamarin.Android.Tasks.LinkApplicationSharedLibraries" AssemblyFile="Xamarin.Android.Build.Tasks.dll" />
+<UsingTask TaskName="Xamarin.Android.Tasks.PrepareAbiItems" AssemblyFile="Xamarin.Android.Build.Tasks.dll" />
 
 <!--
 *******************************************
@@ -286,6 +289,7 @@ Copyright (C) 2011-2012 Xamarin. All rights reserved.
 	<_AndroidLibraryFlatArchivesDirectory>$(IntermediateOutputPath)flata\</_AndroidLibraryFlatArchivesDirectory>
 	<_AndroidStampDirectory>$(IntermediateOutputPath)stamp\</_AndroidStampDirectory>
 	<_AndroidBuildIdFile>$(IntermediateOutputPath)buildid.txt</_AndroidBuildIdFile>
+        <_AndroidApplicationSharedLibraryPath>$(IntermediateOutputPath)app_shared_libraries\</_AndroidApplicationSharedLibraryPath>
 	<_ResolvedUserAssembliesHashFile>$(IntermediateOutputPath)resolvedassemblies.hash</_ResolvedUserAssembliesHashFile>
 
 	<!-- $(EnableProguard) is an obsolete property that should be removed at some stage. -->
@@ -335,7 +339,9 @@ Copyright (C) 2011-2012 Xamarin. All rights reserved.
 	<AndroidMakeBundleKeepTemporaryFiles Condition=" '$(AndroidMakeBundleKeepTemporaryFiles)' == '' ">False</AndroidMakeBundleKeepTemporaryFiles>
 
 	<!-- If true it will cause all the assemblies in the apk to be preloaded on startup time -->
-	<AndroidEnablePreloadAssemblies Condition=" '$(AndroidEnablePreloadAssemblies)' == '' ">True</AndroidEnablePreloadAssemblies>
+        <_AndroidEnablePreloadAssembliesDefault>True</_AndroidEnablePreloadAssembliesDefault>
+	<AndroidEnablePreloadAssemblies Condition=" '$(AndroidEnablePreloadAssemblies)' == '' ">$(_AndroidEnablePreloadAssembliesDefault)</AndroidEnablePreloadAssemblies>
+        <_NativeAssemblySourceDir>$(IntermediateOutputPath)android\</_NativeAssemblySourceDir>
 </PropertyGroup>
 
 <Choose>
@@ -2243,8 +2249,22 @@ because xbuild doesn't support framework reference assemblies.
   </CreateItem>
 </Target>
 
+<Target Name="_PrepareNativeAssemblySources">
+  <PrepareAbiItems
+    BuildTargetAbis="$(_BuildTargetAbis)"
+    ItemNamePattern="$(_NativeAssemblySourceDir)typemap.jm.@abi@.s">
+      <Output TaskParameter="OutputItems" ItemName="_TypeMapAssemblySource" />
+  </PrepareAbiItems>
+
+  <PrepareAbiItems
+    BuildTargetAbis="$(_BuildTargetAbis)"
+    ItemNamePattern="$(_NativeAssemblySourceDir)typemap.mj.@abi@.s" >
+      <Output TaskParameter="OutputItems" ItemName="_TypeMapAssemblySource" />
+  </PrepareAbiItems>
+</Target>
+
 <Target Name="_GenerateJavaStubs"
-  DependsOnTargets="_SetLatestTargetFrameworkVersion;_PrepareAssemblies;$(_AfterPrepareAssemblies)"
+  DependsOnTargets="_SetLatestTargetFrameworkVersion;_PrepareAssemblies;$(_AfterPrepareAssemblies);_PrepareNativeAssemblySources"
   Inputs="$(MSBuildAllProjects);@(_ResolvedUserMonoAndroidAssemblies);$(_AndroidManifestAbs);$(_AndroidBuildPropertiesCache);@(_AndroidResourceDest)"
   Outputs="$(_AndroidStampDirectory)_GenerateJavaStubs.stamp">
   <GenerateJavaStubs
@@ -2270,8 +2290,10 @@ because xbuild doesn't support framework reference assemblies.
 	PackageNamingPolicy="$(AndroidPackageNamingPolicy)"
 	ApplicationJavaClass="$(AndroidApplicationJavaClass)"
 	FrameworkDirectories="$(_XATargetFrameworkDirectories);$(_XATargetFrameworkDirectories)Facades"
-	AcwMapFile="$(_AcwMapFile)">
+	AcwMapFile="$(_AcwMapFile)"
+	SupportedAbis="$(_BuildTargetAbis)">
   </GenerateJavaStubs>
+
   <ConvertCustomView
 	Condition="Exists('$(_CustomViewMapFile)')"
 	CustomViewMapFile="$(_CustomViewMapFile)"
@@ -2350,6 +2372,14 @@ because xbuild doesn't support framework reference assemblies.
   </ItemGroup>
 </Target>
 
+<Target Name="_PrepareEnvironmentAssemblySources">
+  <PrepareAbiItems
+    BuildTargetAbis="$(_BuildTargetAbis)"
+    ItemNamePattern="$(_NativeAssemblySourceDir)environment.@abi@.s">
+      <Output TaskParameter="OutputItems" ItemName="_EnvironmentAssemblySource" />
+  </PrepareAbiItems>
+</Target>
+
 <Target Name="_GenerateEnvironmentFiles" DependsOnTargets="_ReadAndroidManifest;_SetupEmbeddedDSOs;_SetupAssemblyPreload" />
 
 <PropertyGroup>
@@ -2359,20 +2389,22 @@ because xbuild doesn't support framework reference assemblies.
     _AddStaticResources;
     $(_AfterAddStaticResources);
     _PrepareAssemblies;
+    _PrepareEnvironmentAssemblySources;
+    _SetupAssemblyPreload;
   </_GeneratePackageManagerJavaDependsOn>
 </PropertyGroup>
 
 <Target Name="_GeneratePackageManagerJava"
   DependsOnTargets="$(_GeneratePackageManagerJavaDependsOn)"
   Inputs="$(MSBuildAllProjects);$(_ResolvedUserAssembliesHashFile);$(MSBuildProjectFile);$(_AndroidBuildPropertiesCache)"
-  Outputs="$(_AndroidStampDirectory)_GeneratePackageManagerJava.stamp">
+  Outputs="$(_AndroidStampDirectory)_GeneratePackageManagerJava.stamp;@(_EnvironmentAssemblySource)">
   <!-- Create java needed for Mono runtime -->
   <GeneratePackageManagerJava
     ResolvedAssemblies="@(_ResolvedAssemblies)"
     ResolvedUserAssemblies="@(_ResolvedUserAssemblies)"
     MainAssembly="$(MonoAndroidLinkerInputDir)$(TargetFileName)"
     OutputDirectory="$(IntermediateOutputPath)android\src\mono"
-    EnvironmentOutputDirectory="$(IntermediateOutputPath)android\src\mono\android\app"
+    EnvironmentOutputDirectory="$(IntermediateOutputPath)android"
     UseSharedRuntime="$(AndroidUseSharedRuntime)"
     TargetFrameworkVersion="$(TargetFrameworkVersion)" 
     Manifest="$(IntermediateOutputPath)android\AndroidManifest.xml"
@@ -2384,6 +2416,10 @@ because xbuild doesn't support framework reference assemblies.
     Debug="$(AndroidIncludeDebugSymbols)"
     AndroidSequencePointsMode="$(_SequencePointsMode)"
     EnableSGenConcurrent="$(AndroidEnableSGenConcurrent)"
+    IsBundledApplication="$(BundleAssemblies)"
+    SupportedAbis="$(_BuildTargetAbis)"
+    AndroidPackageName="$(_AndroidPackage)"
+    EnablePreloadAssembliesDefault="$(_AndroidEnablePreloadAssembliesDefault)"
   >
     <Output TaskParameter="BuildId" PropertyName="_XamarinBuildId" />
   </GeneratePackageManagerJava>
@@ -2834,6 +2870,55 @@ because xbuild doesn't support framework reference assemblies.
   </ItemGroup>
 </Target>
 
+<Target Name="_PrepareNativeAssemblyItems">
+  <ItemGroup>
+    <_NativeAssemblyTarget Include="@(_TypeMapAssemblySource->Replace('.s', '.o'))">
+      <abi>%(_TypeMapAssemblySource.abi)</abi>
+    </_NativeAssemblyTarget>
+    <_NativeAssemblyTarget Include="@(_EnvironmentAssemblySource->Replace('.s', '.o'))">
+      <abi>%(_EnvironmentAssemblySource.abi)</abi>
+    </_NativeAssemblyTarget>
+  </ItemGroup>
+</Target>
+
+<Target Name="_CompileNativeAssemblySources"
+    DependsOnTargets="_PrepareNativeAssemblyItems"
+    Inputs="@(_TypeMapAssemblySource);@(_EnvironmentAssemblySource)"
+    Outputs="@(_NativeAssemblyTarget)">
+  <CompileNativeAssembly
+      Sources="@(_TypeMapAssemblySource);@(_EnvironmentAssemblySource)"
+      DebugBuild="$(AndroidIncludeDebugSymbols)"
+      WorkingDirectory="$(_NativeAssemblySourceDir)"
+  />
+</Target>
+
+<Target Name="_PrepareApplicationSharedLibraryItems">
+  <ItemGroup>
+    <_XARuntimeArchitecture Include="$(_BuildTargetAbis)"/>
+  </ItemGroup>
+
+  <ItemGroup>
+    <_ApplicationSharedLibrary Include="$(_AndroidApplicationSharedLibraryPath)%(_XARuntimeArchitecture.Identity)\libxamarin-app.so">
+      <abi>%(_XARuntimeArchitecture.Identity)</abi>
+    </_ApplicationSharedLibrary>
+  </ItemGroup>
+</Target>
+
+<Target Name="_CreateApplicationSharedLibraries"
+    DependsOnTargets="_CompileNativeAssemblySources;_PrepareApplicationSharedLibraryItems"
+    Inputs="@(_NativeAssemblyTarget)"
+    Outputs="@(_ApplicationSharedLibrary)">
+  <LinkApplicationSharedLibraries
+      ObjectFiles="@(_NativeAssemblyTarget)"
+      ApplicationSharedLibraries="@(_ApplicationSharedLibrary)"
+      DebugBuild="$(AndroidIncludeDebugSymbols)"
+      AndroidNdkDirectory="$(_AndroidNdkDirectory)"
+  />
+  <ItemGroup>
+    <FileWrites Include="@(_ApplicationSharedLibrary)" />
+  </ItemGroup>
+</Target>
+
 <PropertyGroup>
 	<_PrepareBuildApkDependsOnTargets>
 		_SetLatestTargetFrameworkVersion;
@@ -2851,7 +2936,8 @@ because xbuild doesn't support framework reference assemblies.
 		_CreateBaseApk;
 		_PrepareAssemblies;
 		_ResolveSatellitePaths;
-		_CheckApkPerAbiFlag
+		_CheckApkPerAbiFlag;
+		_CreateApplicationSharedLibraries;
 		;_LintChecks
 		;_IncludeNativeSystemLibraries
 		;_CheckGoogleSdkRequirements
@@ -2878,9 +2964,8 @@ because xbuild doesn't support framework reference assemblies.
 		;@(_ShrunkFrameworkAssemblies)
 		;@(AndroidNativeLibrary)
 		;@(_DexFile)
-		;$(_AndroidTypeMappingJavaToManaged)
-		;$(_AndroidTypeMappingManagedToJava)
 		;$(_AndroidBuildPropertiesCache)
+                ;@(_ApplicationSharedLibrary)
 	</_BuildApkEmbedInputs>
 </PropertyGroup>
 
@@ -2953,6 +3038,7 @@ because xbuild doesn't support framework reference assemblies.
     ResolvedUserAssemblies="@(_ResolvedUserAssemblies);@(_AndroidResolvedSatellitePaths)"
     ResolvedFrameworkAssemblies="@(_ShrunkFrameworkAssemblies)"
     NativeLibraries="@(AndroidNativeLibrary)"
+    ApplicationSharedLibraries="@(_ApplicationSharedLibrary)"
     AdditionalNativeLibraryReferences="@(_AdditionalNativeLibraryReferences)"
     EmbeddedNativeLibraryAssemblies="$(OutDir)$(TargetFileName);@(_ReferencePath);@(_ReferenceDependencyPaths)"
     DalvikClasses="@(_DexFile)"
@@ -2961,7 +3047,6 @@ because xbuild doesn't support framework reference assemblies.
     UseSharedRuntime="$(AndroidUseSharedRuntime)"
     Debug="$(AndroidIncludeDebugSymbols)"
     PreferNativeLibrariesWithDebugSymbols="$(AndroidPreferNativeLibrariesWithDebugSymbols)"
-    TypeMappings="$(_AndroidTypeMappingJavaToManaged);$(_AndroidTypeMappingManagedToJava)"
     JavaSourceFiles="@(AndroidJavaSource)"
     JavaLibraries="@(AndroidJavaLibrary)"
     AndroidSequencePointsMode="$(_SequencePointsMode)"
@@ -2982,6 +3067,7 @@ because xbuild doesn't support framework reference assemblies.
       ResolvedUserAssemblies="@(_ResolvedUserAssemblies);@(_AndroidResolvedSatellitePaths)"
       ResolvedFrameworkAssemblies="@(_ShrunkFrameworkAssemblies)"
       NativeLibraries="@(AndroidNativeLibrary)"
+      ApplicationSharedLibraries="@(_ApplicationSharedLibrary)"
       AdditionalNativeLibraryReferences="@(_AdditionalNativeLibraryReferences)"
       EmbeddedNativeLibraryAssemblies="$(OutDir)$(TargetFileName);@(ReferencePath);@(ReferenceDependencyPaths)"
       DalvikClasses="@(_DexFile)"
@@ -2990,7 +3076,6 @@ because xbuild doesn't support framework reference assemblies.
       UseSharedRuntime="$(AndroidUseSharedRuntime)"
       Debug="$(AndroidIncludeDebugSymbols)"
       PreferNativeLibrariesWithDebugSymbols="$(AndroidPreferNativeLibrariesWithDebugSymbols)"
-      TypeMappings="$(_AndroidTypeMappingJavaToManaged);$(_AndroidTypeMappingManagedToJava)"
       JavaSourceFiles="@(AndroidJavaSource)"
       JavaLibraries="@(AndroidJavaLibrary)"
       AndroidSequencePointsMode="$(_SequencePointsMode)"
@@ -3344,6 +3429,7 @@ because xbuild doesn't support framework reference assemblies.
 	<RemoveDirFixed Directories="$(_AndroidAotBinDirectory)" Condition="Exists ('$(_AndroidAotBinDirectory)')" />
 	<RemoveDirFixed Directories="$(_AndroidLibraryFlatArchivesDirectory)" Condition="Exists ('$(_AndroidLibraryFlatArchivesDirectory)')" />
 	<RemoveDirFixed Directories="$(_AndroidStampDirectory)" Condition="Exists ('$(_AndroidStampDirectory)')" />
+	<RemoveDirFixed Directories="$(_AndroidApplicationSharedLibraryPath)" Condition="Exists ('$(_AndroidApplicationSharedLibraryPath)')" />
  	<Delete Files="$(MonoAndroidIntermediate)R.cs.flag" />
 	<Delete Files="$(MonoAndroidIntermediate)acw-map.txt" />
 	<Delete Files="$(MonoAndroidIntermediate)customview-map.txt" />

src/java-runtime/java/mono/android/MonoPackageManager.java

@@ -46,6 +46,12 @@ public class MonoPackageManager {
 							external0,
 							"../legacy/Android/data/" + context.getPackageName () + "/files/.__override__").getAbsolutePath ();
 
+				// Preload DSOs libmonodroid.so depends on so that the dynamic
+				// linker can resolve them when loading monodroid. This is not
+				// needed in the latest Android versions but is required in at least
+				// API 16 and since there's no inherent negative effect of doing it,
+				// we can do it unconditionally.
+				System.loadLibrary("xamarin-app");
 				System.loadLibrary("monodroid");
 
 				Runtime.init (
@@ -63,9 +69,10 @@ public class MonoPackageManager {
 							externalLegacyDir
 						},
 						MonoPackageManager_Resources.Assemblies,
-						context.getPackageName (),
+						null, // unused
 						android.os.Build.VERSION.SDK_INT,
-						mono.android.app.XamarinAndroidEnvironmentVariables.Variables);
+						null // unused
+					);
 				
 				mono.android.app.ApplicationRegistration.registerApplications ();
 				

src/monodroid/CMakeLists.txt

@@ -104,6 +104,7 @@ else()
   add_definitions("-D_GNU_SOURCE")
   if(APPLE)
     add_definitions("-DAPPLE_OS_X")
+    set(CMAKE_MACOSX_RPATH 1)
     set(HOST_BUILD_NAME "host-Darwin")
   elseif(CMAKE_HOST_SYSTEM_NAME STREQUAL Linux)
     if(NOT MINGW AND NOT WIN32)
@@ -221,6 +222,9 @@ if(UNIX)
     )
 endif()
 
+set(XAMARIN_APP_STUB_SOURCES ${SOURCES_DIR}/application_dso_stub.cc)
+add_library(xamarin-app SHARED ${XAMARIN_APP_STUB_SOURCES})
+
 set(SOURCES_FRAGMENT_FILE "sources.projitems")
 file(WRITE ${SOURCES_FRAGMENT_FILE} "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n\
 <Project xmlns=\"http://schemas.microsoft.com/developer/msbuild/2003\">\n\
@@ -236,6 +240,13 @@ file(APPEND ${SOURCES_FRAGMENT_FILE} "  </ItemGroup>\n\
 string(TOLOWER ${CMAKE_BUILD_TYPE} MONO_ANDROID_SUFFIX)
 set(MONO_ANDROID_LIB "mono-android.${MONO_ANDROID_SUFFIX}")
 add_library(${MONO_ANDROID_LIB} SHARED ${MONODROID_SOURCES})
+if(APPLE)
+  add_custom_command(
+    TARGET ${MONO_ANDROID_LIB}
+    POST_BUILD
+    COMMAND xcrun install_name_tool -change "@rpath/libxamarin-app.dylib" "@loader_path/libxamarin-app.dylib" $<TARGET_FILE:${MONO_ANDROID_LIB}>
+  )
+endif()
 
 if(MINGW_ZLIB_LIBRARY_PATH)
   set(LINK_LIBS "${MINGW_ZLIB_LIBRARY_PATH} ${EXTRA_LINKER_FLAGS}")
@@ -249,4 +260,5 @@ elseif(NOT ANDROID)
   set(LINK_LIBS "-pthread ${LINK_LIBS} -ldl")
 endif()
 
-target_link_libraries(${MONO_ANDROID_LIB} ${LINK_LIBS})
+target_link_libraries(${MONO_ANDROID_LIB} ${LINK_LIBS} xamarin-app)
+

src/monodroid/jni/android-system.cc

@@ -1,9 +1,11 @@
 #include <limits.h>
 #include <string.h>
+#include <stdlib.h>
 #include <errno.h>
 #include <assert.h>
 #include <ctype.h>
 #include <dlfcn.h>
+#include <fcntl.h>
 
 #ifdef ANDROID
 #include <sys/system_properties.h>
@@ -24,20 +26,27 @@
 #include "monodroid.h"
 #include "monodroid-glue-internal.h"
 #include "jni-wrappers.h"
+#include "xamarin-app.h"
 
+#if defined (DEBUG) || !defined (ANDROID)
 namespace xamarin { namespace android { namespace internal {
 	struct BundledProperty {
 		char     *name;
 		char     *value;
-		int   value_len;
+		uint32_t  value_len;
 		struct BundledProperty *next;
 	};
 }}}
+#endif // DEBUG || !ANDROID
 
 using namespace xamarin::android;
 using namespace xamarin::android::internal;
 
+#if defined (DEBUG) || !defined (ANDROID)
 BundledProperty *AndroidSystem::bundled_properties = nullptr;
+constexpr char AndroidSystem::OVERRIDE_ENVIRONMENT_FILE_NAME[];
+#endif // DEBUG || !ANDROID
+
 char* AndroidSystem::override_dirs [MAX_OVERRIDES];
 const char **AndroidSystem::app_lib_directories;
 size_t AndroidSystem::app_lib_directories_size = 0;
@@ -70,6 +79,7 @@ static constexpr uint32_t PROP_NAME_MAX = 32;
 static constexpr uint32_t PROP_VALUE_MAX = 92;
 #endif
 
+#if defined (DEBUG) || !defined (ANDROID)
 BundledProperty*
 AndroidSystem::lookup_system_property (const char *name)
 {
@@ -79,7 +89,51 @@ AndroidSystem::lookup_system_property (const char *name)
 			return p;
 	return nullptr;
 }
+#endif // DEBUG || !ANDROID
 
+const char*
+AndroidSystem::lookup_system_property (const char *name, uint32_t &value_len)
+{
+	value_len = 0;
+#if defined (DEBUG) || !defined (ANDROID)
+	BundledProperty *p = lookup_system_property (name);
+	if (p != nullptr) {
+		value_len = p->value_len;
+		return p->name;
+	}
+#endif // DEBUG || !ANDROID
+
+	if (application_config.system_property_count == 0)
+		return nullptr;
+
+	if (application_config.system_property_count % 2 != 0) {
+		log_warn (LOG_DEFAULT, "Corrupted environment variable array: does not contain an even number of entries (%u)", application_config.environment_variable_count);
+		return nullptr;
+	}
+
+	const char *prop_name;
+	const char *prop_value;
+	for (size_t i = 0; i < application_config.system_property_count; i += 2) {
+		prop_name = app_system_properties[i];
+		if (prop_name == nullptr || *prop_name == '\0')
+			continue;
+
+		if (strcmp (prop_name, name) == 0) {
+			prop_value = app_system_properties [i + 1];
+			if (prop_value == nullptr || *prop_value == '\0') {
+				value_len = 0;
+				return "";
+			}
+
+			value_len = strlen (prop_value);
+			return prop_value;
+		}
+	}
+
+	return nullptr;
+}
+
+#if defined (DEBUG) || !defined (ANDROID)
 void
 AndroidSystem::add_system_property (const char *name, const char *value)
 {
@@ -114,6 +168,7 @@ AndroidSystem::add_system_property (const char *name, const char *value)
 	p->next             = bundled_properties;
 	bundled_properties  = p;
 }
+#endif // DEBUG || !ANDROID
 
 #ifndef ANDROID
 void
@@ -187,10 +242,13 @@ AndroidSystem::monodroid_get_system_property (const char *name, char **value)
 	char *pvalue = sp_value;
 	int len = _monodroid__system_property_get (name, sp_value, sizeof (sp_value));
 
-	BundledProperty *p;
+	if (len <= 0) {
-	if (len <= 0 && (p = lookup_system_property (name)) != nullptr) {
+		uint32_t plen;
-		pvalue  = p->value;
+		const char *v = lookup_system_property (name, plen);
-		len     = p->value_len;
+		if (v != nullptr) {
+			pvalue  = const_cast<char*> (v);
+			len     = static_cast<int> (plen);
+		}
 	}
 
 	if (len >= 0 && value) {
@@ -225,6 +283,7 @@ AndroidSystem::monodroid_read_file_into_memory (const char *path, char **value)
 	return r;
 }
 
+#if defined (DEBUG) || !defined (ANDROID)
 int
 AndroidSystem::_monodroid_get_system_property_from_file (const char *path, char **value)
 {
@@ -262,10 +321,12 @@ AndroidSystem::_monodroid_get_system_property_from_file (const char *path, char
 	}
 	return len;
 }
+#endif
 
 int
 AndroidSystem::monodroid_get_system_property_from_overrides (const char *name, char ** value)
 {
+#if defined (DEBUG) || !defined (ANDROID)
 	int result = -1;
 
 	for (size_t oi = 0; oi < MAX_OVERRIDES; ++oi) {
@@ -281,6 +342,7 @@ AndroidSystem::monodroid_get_system_property_from_overrides (const char *name, c
 			return result;
 		}
 	}
+#endif
 	return 0;
 }
 
@@ -718,95 +780,184 @@ AndroidSystem::get_gref_gc_threshold ()
 	return static_cast<int> ((max_gref_count * 90LL) / 100LL);
 }
 
+#if defined (DEBUG) || !defined (ANDROID)
 void
-AndroidSystem::setup_environment (jstring_wrapper& name, jstring_wrapper& value)
+AndroidSystem::setup_environment (const char *name, const char *value)
 {
-	const char *k = name.get_cstr ();
+	if (name == nullptr || *name == '\0')
-
-	if (k == nullptr || *k == '\0')
 		return;
 
-	const char *v = value.get_cstr ();
+	const char *v = value;
-	if (v == nullptr || *v == '\0')
+	if (v == nullptr)
 		v = "";
 
-	if (isupper (k [0]) || k [0] == '_') {
+	if (isupper (name [0]) || name [0] == '_') {
-		if (k [0] == '_') {
+		if (setenv (name, v, 1) < 0)
-			if (strcmp (k, "__XA_DSO_IN_APK") == 0) {
+			log_warn (LOG_DEFAULT, "(Debug) Failed to set environment variable: %s", strerror (errno));
-				knownEnvVars.DSOInApk = true;
-				return;
-			}
-		}
-
-		setenv (k, v, 1);
 		return;
 	}
 
-	if (k [0] == 'm') {
+	add_system_property (name, v);
-		if (strcmp (k, "mono.aot") == 0) {
-			if (*v == '\0') {
-				knownEnvVars.MonoAOT = MonoAotMode::MONO_AOT_MODE_NONE;
-				return;
-			}
-
-			switch (v [0]) {
-				case 'n':
-					knownEnvVars.MonoAOT = MonoAotMode::MONO_AOT_MODE_NORMAL;
-					break;
-
-				case 'h':
-					knownEnvVars.MonoAOT = MonoAotMode::MONO_AOT_MODE_HYBRID;
-					break;
-
-				case 'f':
-					knownEnvVars.MonoAOT = MonoAotMode::MONO_AOT_MODE_FULL;
-					break;
-
-				default:
-					knownEnvVars.MonoAOT = MonoAotMode::MONO_AOT_MODE_UNKNOWN;
-					break;
-			}
-
-			if (knownEnvVars.MonoAOT != MonoAotMode::MONO_AOT_MODE_UNKNOWN)
-				log_info (LOG_DEFAULT, "Mono AOT mode: %s", v);
-			else
-				log_warn (LOG_DEFAULT, "Unknown Mono AOT mode: %s", v);
-
-			return;
-		}
-
-		if (strcmp (k, "mono.llvm") == 0) {
-			knownEnvVars.MonoLLVM = true;
-			return;
-		}
-
-		if (strcmp (k, "mono.enable_assembly_preload") == 0) {
-			if (*v == '\0')
-				knownEnvVars.EnableAssemblyPreload = KnownEnvironmentVariables::AssemblyPreloadDefault;
-			else if (v[0] == '1')
-				knownEnvVars.EnableAssemblyPreload = true;
-			else
-				knownEnvVars.EnableAssemblyPreload = false;
-			return;
-		}
-	}
-
-	add_system_property (k, v);
 }
 
 void
-AndroidSystem::setup_environment (JNIEnv *env, jobjectArray environmentVariables)
+AndroidSystem::setup_environment_from_override_file (const char *path)
 {
-	jsize envvarsLength = env->GetArrayLength (environmentVariables);
+	monodroid_stat_t sbuf;
-	if (envvarsLength == 0)
+	if (utils.monodroid_stat (path, &sbuf) < 0) {
+		log_warn (LOG_DEFAULT, "Failed to stat the environment override file %s: %s", path, strerror (errno));
+		return;
+	}
+
+	int fd = open (path, O_RDONLY);
+	if (fd < 0) {
+		log_warn (LOG_DEFAULT, "Failed to open the environment override file %s: %s", path, strerror (errno));
+		return;
+	}
+
+	char    *buf = new char [sbuf.st_size];
+	ssize_t  nread = 0;
+	ssize_t  r;
+	do {
+		int i = nread;
+		r = read (fd, buf + i, sbuf.st_size - i);
+		if (r > 0)
+			nread += r;
+	} while (r < 0 && errno == EINTR);
+
+	if (nread < 0) {
+		log_warn (LOG_DEFAULT, "Failed to read the environment override file %s: %s", path, strerror (errno));
+		delete[] buf;
+		return;
+	}
+
+	// The file format is as follows (no newlines are used, this is just for illustration
+	// purposes, comments aren't part of the file either):
+	//
+	// # 10 ASCII characters formattted as a C++ hexadecimal number terminated with NUL: name
+	// # width (including the terminating NUL)
+	// 0x00000000\0
+	//
+	// # 10 ASCII characters formattted as a C++ hexadecimal number terminated with NUL: value
+	// # width (including the terminating NUL)
+	// 0x00000000\0
+	//
+	// # Variable name, terminated with NUL and padded to [name width] with NUL characters
+	// name\0
+	//
+	// # Variable value, terminated with NUL and padded to [value width] with NUL characters
+	// value\0
+	if (nread < OVERRIDE_ENVIRONMENT_FILE_HEADER_SIZE) {
+		log_warn (LOG_DEFAULT, "Invalid format of the environment override file %s: malformatted header", path);
+		delete[] buf;
+		return;
+	}
+
+	char *endptr;
+	unsigned long name_width = strtoul (buf, &endptr, 16);
+	if ((name_width == ULONG_MAX && errno == ERANGE) || (*buf != '\0' && *endptr != '\0')) {
+		log_warn (LOG_DEFAULT, "Malformed header of the environment override file %s: name width has invalid format", path);
+		delete[] buf;
+		return;
+	}
+
+	unsigned long value_width = strtoul (buf + 11, &endptr, 16);
+	if ((value_width == ULONG_MAX && errno == ERANGE) || (*buf != '\0' && *endptr != '\0')) {
+		log_warn (LOG_DEFAULT, "Malformed header of the environment override file %s: value width has invalid format", path);
+		delete[] buf;
+		return;
+	}
+
+	uint64_t data_width = name_width + value_width;
+	if (data_width > sbuf.st_size - OVERRIDE_ENVIRONMENT_FILE_HEADER_SIZE || (sbuf.st_size - OVERRIDE_ENVIRONMENT_FILE_HEADER_SIZE) % data_width != 0) {
+		log_warn (LOG_DEFAULT, "Malformed environment override file %s: invalid data size", path);
+		delete[] buf;
+		return;
+	}
+
+	uint64_t data_size = sbuf.st_size;
+	char *name = buf + OVERRIDE_ENVIRONMENT_FILE_HEADER_SIZE;
+	while (data_size > 0 && data_size >= data_width) {
+		if (*name == '\0') {
+			log_warn (LOG_DEFAULT, "Malformed environment override file %s: name at offset %lu is empty", path, name - buf);
+			delete[] buf;
+			return;
+		}
+
+		log_debug (LOG_DEFAULT, "Setting environment variable from the override file %s: '%s' = '%s'", path, name, name + name_width);
+		setup_environment (name, name + name_width);
+		name += data_width;
+		data_size -= data_width;
+	}
+
+	delete[] buf;
+
+}
+#endif // DEBUG || !ANDROID
+
+void
+AndroidSystem::setup_environment ()
+{
+	if (is_mono_aot_enabled () && *mono_aot_mode_name != '\0') {
+		switch (mono_aot_mode_name [0]) {
+			case 'n':
+				aotMode = MonoAotMode::MONO_AOT_MODE_NORMAL;
+				break;
+
+			case 'h':
+				aotMode = MonoAotMode::MONO_AOT_MODE_HYBRID;
+				break;
+
+			case 'f':
+				aotMode = MonoAotMode::MONO_AOT_MODE_FULL;
+				break;
+
+			default:
+				aotMode = MonoAotMode::MONO_AOT_MODE_UNKNOWN;
+				break;
+		}
+
+		if (aotMode != MonoAotMode::MONO_AOT_MODE_UNKNOWN)
+			log_info (LOG_DEFAULT, "Mono AOT mode: %s", mono_aot_mode_name);
+		else
+			log_warn (LOG_DEFAULT, "Unknown Mono AOT mode: %s", mono_aot_mode_name);
+	}
+
+	if (application_config.environment_variable_count == 0)
 		return;
 
-	jstring_wrapper name (env), value (env);
+	if (application_config.environment_variable_count % 2 != 0) {
-	for (jsize i = 0; (i + 1) < envvarsLength; i += 2) {
+		log_warn (LOG_DEFAULT, "Corrupted environment variable array: does not contain an even number of entries (%u)", application_config.environment_variable_count);
-		name = reinterpret_cast<jstring> (env->GetObjectArrayElement (environmentVariables, i));
+		return;
-		value = reinterpret_cast<jstring> (env->GetObjectArrayElement (environmentVariables, i + 1));
-		setup_environment (name, value);
 	}
+
+	const char *var_name;
+	const char *var_value;
+	for (size_t i = 0; i < application_config.environment_variable_count; i += 2) {
+		var_name = app_environment_variables [i];
+		if (var_name == nullptr || *var_name == '\0')
+			continue;
+
+		var_value = app_environment_variables [i + 1];
+		if (var_value == nullptr)
+			var_value = "";
+
+#if defined (DEBUG)
+		log_info (LOG_DEFAULT, "Setting environment variable '%s' to '%s'", var_name, var_value);
+#endif
+		if (setenv (var_name, var_value, 1) < 0)
+			log_warn (LOG_DEFAULT, "Failed to set environment variable: %s", strerror (errno));
+	}
+#if defined (DEBUG) || !defined (ANDROID)
+	// TODO: for debug read from file in the override directory named `environment`
+	for (size_t oi = 0; oi < MAX_OVERRIDES; oi++) {
+		char *env_override_file = utils.path_combine (override_dirs [oi], OVERRIDE_ENVIRONMENT_FILE_NAME);
+		if (utils.file_exists (env_override_file)) {
+			setup_environment_from_override_file (env_override_file);
+		}
+		delete[] env_override_file;
+	}
+#endif
 }
 
 void

src/monodroid/jni/android-system.h

@@ -11,6 +11,7 @@
 #include "util.h"
 #include "cpu-arch.h"
 #include "cppcompat.h"
+#include "xamarin-app.h"
 
 namespace xamarin { namespace android {
 	class jstring_wrapper;
@@ -19,22 +20,18 @@ namespace xamarin { namespace android {
 
 namespace xamarin { namespace android { namespace internal
 {
+#if defined (DEBUG) || !defined (ANDROID)
 	struct BundledProperty;
-
+#endif
-	struct KnownEnvironmentVariables
-	{
-		static constexpr bool AssemblyPreloadDefault = true;
-
-		bool        DSOInApk = false;
-		MonoAotMode MonoAOT = MonoAotMode::MONO_AOT_MODE_NONE;
-		bool        MonoLLVM = false;
-		bool        EnableAssemblyPreload = AssemblyPreloadDefault;
-	};
 
 	class AndroidSystem
 	{
 	private:
+#if defined (DEBUG) || !defined (ANDROID)
+		static constexpr char OVERRIDE_ENVIRONMENT_FILE_NAME[] = "environment";
+		static constexpr uint32_t OVERRIDE_ENVIRONMENT_FILE_HEADER_SIZE = 22;
 		static BundledProperty *bundled_properties;
+#endif
 		static const char* android_abi_names[CPU_KIND_X86_64+1];
 #if defined (WINDOWS)
 		static std::mutex readdir_mutex;
@@ -92,7 +89,7 @@ namespace xamarin { namespace android { namespace internal
 		static size_t app_lib_directories_size;
 
 	public:
-		void  setup_environment (JNIEnv *env, jobjectArray environmentVariables);
+		void  setup_environment ();
 		void  setup_process_args (JNIEnv *env, jstring_array_wrapper &runtimeApks);
 		int   monodroid_get_system_property (const char *name, char **value);
 		int   monodroid_get_system_property_from_overrides (const char *name, char ** value);
@@ -139,32 +136,43 @@ namespace xamarin { namespace android { namespace internal
 #endif
 		bool is_assembly_preload_enabled () const
 		{
-			return knownEnvVars.EnableAssemblyPreload;
+			return application_config.uses_assembly_preload;
 		}
 
 		bool is_mono_llvm_enabled () const
 		{
-			return knownEnvVars.MonoLLVM;
+			return application_config.uses_mono_llvm;
+		}
+
+		bool is_mono_aot_enabled () const
+		{
+			return application_config.uses_mono_aot;
 		}
 
 		bool is_embedded_dso_mode_enabled () const
 		{
-			return knownEnvVars.DSOInApk;
+			return application_config.uses_embedded_dsos;
 		}
 
 		MonoAotMode get_mono_aot_mode () const
 		{
-			return knownEnvVars.MonoAOT;
+			return aotMode;
 		}
 
 	private:
+#if defined (DEBUG) || !defined (ANDROID)
 		void add_system_property (const char *name, const char *value);
-		int  get_max_gref_count_from_system ();
+		void setup_environment (const char *name, const char *value);
-		void setup_environment (jstring_wrapper& name, jstring_wrapper& value);
+		void setup_environment_from_override_file (const char *path);
 		BundledProperty* lookup_system_property (const char *name);
+#endif
+		const char* lookup_system_property (const char *name, uint32_t &value_len);
+		int  get_max_gref_count_from_system ();
 		void setup_process_args_apk (const char *apk, int index, int apk_count, void *user_data);
 		int  _monodroid__system_property_get (const char *name, char *sp_value, size_t sp_value_len);
+#if defined (DEBUG) || !defined (ANDROID)
 		int  _monodroid_get_system_property_from_file (const char *path, char **value);
+#endif
 		void  copy_native_libraries_to_internal_location ();
 		void  copy_file_to_internal_location (char *to_dir, char *from_dir, char *file);
 		void  add_apk_libdir (const char *apk, int index, int apk_count, void *user_data);
@@ -188,7 +196,7 @@ namespace xamarin { namespace android { namespace internal
 #endif // !ANDROID
 	private:
 		int max_gref_count = 0;
-		KnownEnvironmentVariables knownEnvVars;
+		MonoAotMode aotMode = MonoAotMode::MONO_AOT_MODE_NONE;
 	};
 }}}
 #endif // !__ANDROID_SYSTEM_H

src/monodroid/jni/application_dso_stub.cc

@@ -0,0 +1,28 @@
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "xamarin-app.h"
+
+// This file MUST have valid values everywhere - the DSO it is compiled into is loaded by the
+// designer on desktop.
+
+TypeMapHeader jm_typemap_header = { 1, 0, 0, 0 };
+uint8_t jm_typemap[] = { 0 };
+
+TypeMapHeader mj_typemap_header = { 1, 0, 0, 0 };
+uint8_t mj_typemap[] = { 0 };
+
+ApplicationConfig application_config = {
+	.uses_mono_llvm = false,
+	.uses_mono_aot = false,
+	.uses_embedded_dsos = false,
+	.uses_assembly_preload = false,
+	.is_a_bundled_app = false,
+	.environment_variable_count = 0,
+	.system_property_count = 0,
+	.android_package_name = "com.xamarin.test",
+};
+
+const char* mono_aot_mode_name = "";
+const char* app_environment_variables[] = {};
+const char* app_system_properties[] = {};

src/monodroid/jni/embedded-assemblies.cc

@@ -19,8 +19,10 @@ extern "C" {
 #include "embedded-assemblies.h"
 #include "globals.h"
 #include "monodroid-glue.h"
+#include "xamarin-app.h"
 
 namespace xamarin { namespace android { namespace internal {
+#if defined (DEBUG) || !defined (ANDROID)
 	struct TypeMappingInfo {
 		char                     *source_apk;
 		char                     *source_entry;
@@ -30,6 +32,7 @@ namespace xamarin { namespace android { namespace internal {
 		const   char             *mapping;
 		TypeMappingInfo          *next;
 	};
+#endif // DEBUG || !ANDROID
 
 	struct md_mmap_info {
 		void   *area;
@@ -47,8 +50,9 @@ const char *EmbeddedAssemblies::suffixes[] = {
 };
 
 constexpr char EmbeddedAssemblies::assemblies_prefix[];
+#if defined (DEBUG) || !defined (ANDROID)
 constexpr char EmbeddedAssemblies::override_typemap_entry_name[];
-
+#endif
 
 void EmbeddedAssemblies::set_assemblies_prefix (const char *prefix)
 {
@@ -131,9 +135,19 @@ EmbeddedAssemblies::TypeMappingInfo_compare_key (const void *a, const void *b)
 	return strcmp (reinterpret_cast <const char*> (a), reinterpret_cast <const char*> (b));
 }
 
+inline const char*
+EmbeddedAssemblies::find_entry_in_type_map (const char *name, uint8_t map[], TypeMapHeader& header)
+{
+	const char *e = reinterpret_cast<const char*> (bsearch (name, map, header.entry_count, header.entry_length, TypeMappingInfo_compare_key ));
+	if (e == nullptr)
+		return nullptr;
+	return e + header.value_offset;
+}
+
 inline const char*
 EmbeddedAssemblies::typemap_java_to_managed (const char *java)
 {
+#if defined (DEBUG) || !defined (ANDROID)
 	for (TypeMappingInfo *info = java_to_managed_maps; info != nullptr; info = info->next) {
 		/* log_warn (LOG_DEFAULT, "# jonp: checking file: %s!%s for type '%s'", info->source_apk, info->source_entry, java); */
 		const char *e = reinterpret_cast<const char*> (bsearch (java, info->mapping, info->num_entries, info->entry_length, TypeMappingInfo_compare_key));
@@ -141,12 +155,14 @@ EmbeddedAssemblies::typemap_java_to_managed (const char *java)
 			continue;
 		return e + info->value_offset;
 	}
-	return nullptr;
+#endif
+	return find_entry_in_type_map (java, jm_typemap, jm_typemap_header);
 }
 
 inline const char*
 EmbeddedAssemblies::typemap_managed_to_java (const char *managed)
 {
+#if defined (DEBUG) || !defined (ANDROID)
 	for (TypeMappingInfo *info = managed_to_java_maps; info != nullptr; info = info->next) {
 		/* log_warn (LOG_DEFAULT, "# jonp: checking file: %s!%s for type '%s'", info->source_apk, info->source_entry, managed); */
 		const char *e = reinterpret_cast <const char*> (bsearch (managed, info->mapping, info->num_entries, info->entry_length, TypeMappingInfo_compare_key));
@@ -154,7 +170,8 @@ EmbeddedAssemblies::typemap_managed_to_java (const char *managed)
 			continue;
 		return e + info->value_offset;
 	}
-	return nullptr;
+#endif
+	return find_entry_in_type_map (managed, mj_typemap, mj_typemap_header);
 }
 
 MONO_API const char *
@@ -169,6 +186,7 @@ monodroid_typemap_managed_to_java (const char *managed)
 	return embeddedAssemblies.typemap_managed_to_java (managed);
 }
 
+#if defined (DEBUG) || !defined (ANDROID)
 void
 EmbeddedAssemblies::extract_int (const char **header, const char *source_apk, const char *source_entry, const char *key_name, int *value)
 {
@@ -235,6 +253,7 @@ EmbeddedAssemblies::add_type_mapping (TypeMappingInfo **info, const char *source
 	}
 	return true;
 }
+#endif // DEBUG || !ANDROID
 
 md_mmap_info
 EmbeddedAssemblies::md_mmap_apk_file (int fd, uLong offset, uLong size, const char* filename, const char* apk)
@@ -381,17 +400,6 @@ EmbeddedAssemblies::gather_bundled_assemblies_from_apk (const char* apk, monodro
 				continue;
 			}
 
-			if (utils.ends_with (cur_entry_name, ".jm")) {
-				md_mmap_info map_info   = md_mmap_apk_file (fd, offset, info.uncompressed_size, cur_entry_name, apk);
-				add_type_mapping (&java_to_managed_maps, apk, cur_entry_name, (const char*)map_info.area);
-				continue;
-			}
-			if (utils.ends_with (cur_entry_name, ".mj")) {
-				md_mmap_info map_info   = md_mmap_apk_file (fd, offset, info.uncompressed_size, cur_entry_name, apk);
-				add_type_mapping (&managed_to_java_maps, apk, cur_entry_name, (const char*)map_info.area);
-				continue;
-			}
-
 			const char *prefix = get_assemblies_prefix();
 			if (strncmp (prefix, cur_entry_name, strlen (prefix)) != 0)
 				continue;
@@ -469,6 +477,7 @@ EmbeddedAssemblies::gather_bundled_assemblies_from_apk (const char* apk, monodro
 	return true;
 }
 
+#if defined (DEBUG) || !defined (ANDROID)
 void
 EmbeddedAssemblies::try_load_typemaps_from_directory (const char *path)
 {
@@ -514,6 +523,7 @@ EmbeddedAssemblies::try_load_typemaps_from_directory (const char *path)
 	free (dir_path);
 	return;
 }
+#endif
 
 size_t
 EmbeddedAssemblies::register_from (const char *apk_file, monodroid_should_register should_register)

src/monodroid/jni/embedded-assemblies.h

@@ -7,15 +7,21 @@
 #include "unzip.h"
 #include "ioapi.h"
 
+struct TypeMapHeader;
+
 namespace xamarin { namespace android { namespace internal {
+#if defined (DEBUG) || !defined (ANDROID)
 	struct TypeMappingInfo;
+#endif
 	struct md_mmap_info;
 
 	class EmbeddedAssemblies
 	{
 	private:
 		static constexpr char assemblies_prefix[] = "assemblies/";
+#if defined (DEBUG) || !defined (ANDROID)
 		static constexpr char override_typemap_entry_name[] = ".__override__";
+#endif
 		static const char *suffixes[];
 
 	public:
@@ -23,7 +29,9 @@ namespace xamarin { namespace android { namespace internal {
 		using monodroid_should_register = bool (*)(const char *filename);
 
 	public:
+#if defined (DEBUG) || !defined (ANDROID)
 		void try_load_typemaps_from_directory (const char *path);
+#endif
 		void install_preload_hooks ();
 		const char* typemap_java_to_managed (const char *java);
 		const char* typemap_managed_to_java (const char *managed);
@@ -53,7 +61,9 @@ namespace xamarin { namespace android { namespace internal {
 		bool gather_bundled_assemblies_from_apk (const char* apk, monodroid_should_register should_register);
 		MonoAssembly* open_from_bundles (MonoAssemblyName* aname, bool ref_only);
 		void extract_int (const char **header, const char *source_apk, const char *source_entry, const char *key_name, int *value);
+#if defined (DEBUG) || !defined (ANDROID)
 		bool add_type_mapping (TypeMappingInfo **info, const char *source_apk, const char *source_entry, const char *addr);
+#endif // DEBUG || !ANDROID
 		bool register_debug_symbols_for_assembly (const char *entry_name, MonoBundledAssembly *assembly, const mono_byte *debug_contents, int debug_size);
 
 		static md_mmap_info md_mmap_apk_file (int fd, uLong offset, uLong size, const char* filename, const char* apk);
@@ -67,6 +77,7 @@ namespace xamarin { namespace android { namespace internal {
 		static MonoAssembly* open_from_bundles_full (MonoAssemblyName *aname, char **assemblies_path, void *user_data);
 		static MonoAssembly* open_from_bundles_refonly (MonoAssemblyName *aname, char **assemblies_path, void *user_data);
 		static int TypeMappingInfo_compare_key (const void *a, const void *b);
+		const char *find_entry_in_type_map (const char *name, uint8_t map[], TypeMapHeader& header);
 
 		const char* get_assemblies_prefix () const
 		{
@@ -77,8 +88,10 @@ namespace xamarin { namespace android { namespace internal {
 		bool                   register_debug_symbols;
 		MonoBundledAssembly  **bundled_assemblies;
 		size_t                 bundled_assemblies_count;
+#if defined (DEBUG) || !defined (ANDROID)
 		TypeMappingInfo       *java_to_managed_maps;
 		TypeMappingInfo       *managed_to_java_maps;
+#endif // DEBUG || !ANDROID
 		const char            *assemblies_prefix_override = nullptr;
 	};
 }}}

src/monodroid/jni/monodroid-glue.cc

@@ -65,6 +65,7 @@ extern "C" {
 #include "mkbundle-api.h"
 #include "monodroid-glue-internal.h"
 #include "globals.h"
+#include "xamarin-app.h"
 
 #ifndef WINDOWS
 #include "xamarin_getifaddrs.h"
@@ -215,6 +216,9 @@ mono_mkbundle_initialize_mono_api_ptr mono_mkbundle_initialize_mono_api;
 static void
 setup_bundled_app (const char *dso_name)
 {
+	if (!application_config.is_a_bundled_app)
+		return;
+
 	static int dlopen_flags = RTLD_LAZY;
 	void *libapp = nullptr;
 
@@ -481,7 +485,7 @@ should_register_file (const char *filename)
 static void
 gather_bundled_assemblies (JNIEnv *env, jstring_array_wrapper &runtimeApks, bool register_debug_symbols, int *out_user_assemblies_count)
 {
-#ifndef RELEASE
+#if defined(DEBUG) || !defined (ANDROID)
 	for (size_t i = 0; i < AndroidSystem::MAX_OVERRIDES; ++i) {
 		const char *p = androidSystem.get_override_dir (i);
 		if (!utils.directory_exists (p))
@@ -1177,6 +1181,7 @@ init_android_runtime (MonoDomain *domain, JNIEnv *env, jclass runtimeClass, jobj
 		lookup_bridge_info (domain, image, &osBridge.get_java_gc_bridge_type (i), &osBridge.get_java_gc_bridge_info (i));
 	}
 
+	// TODO: try looking up the method by its token
 	runtime                             = utils.monodroid_get_class_from_image (domain, image, "Android.Runtime", "JNIEnv");
 	method                              = monoFunctions.class_get_method_from_name (runtime, "Initialize", 1);
 
@@ -1877,13 +1882,12 @@ Java_mono_android_Runtime_init (JNIEnv *env, jclass klass, jstring lang, jobject
 
 	TimeZone_class = utils.get_class_from_runtime_field (env, klass, "java_util_TimeZone", true);
 
-	jstring_wrapper jstr (env, packageName);
+	utils.monodroid_store_package_name (application_config.android_package_name);
-	utils.monodroid_store_package_name (jstr.get_cstr ());
 
-	jstr = lang;
+	jstring_wrapper jstr (env, lang);
 	set_environment_variable (env, "LANG", jstr);
 
-	androidSystem.setup_environment (env, environmentVariables);
+	androidSystem.setup_environment ();
 
 	jstr = reinterpret_cast <jstring> (env->GetObjectArrayElement (appDirs, 1));
 	set_environment_variable_for_directory (env, "TMPDIR", jstr);
@@ -2008,6 +2012,7 @@ Java_mono_android_Runtime_init (JNIEnv *env, jclass klass, jstring lang, jobject
 
 	log_info (LOG_DEFAULT, "Probing for Mono AOT mode\n");
 
+	if (androidSystem.is_mono_aot_enabled ()) {
 		MonoAotMode mode = androidSystem.get_mono_aot_mode ();
 		if (mode == MonoAotMode::MONO_AOT_MODE_UNKNOWN)
 			mode = MonoAotMode::MONO_AOT_MODE_NONE;
@@ -2016,6 +2021,7 @@ Java_mono_android_Runtime_init (JNIEnv *env, jclass klass, jstring lang, jobject
 			log_info (LOG_DEFAULT, "Enabling AOT mode in Mono");
 			monoFunctions.jit_set_aot_mode (mode);
 		}
+	}
 
 	log_info (LOG_DEFAULT, "Probing if we should use LLVM\n");
 

src/monodroid/jni/util.h

@@ -26,16 +26,6 @@ constexpr int FALSE = 0;
 #define MONODROID_PATH_SEPARATOR_CHAR '/'
 #endif
 
-#if WINDOWS
-typedef struct _stat monodroid_stat_t;
-#define monodroid_dir_t _WDIR
-typedef struct _wdirent monodroid_dirent_t;
-#else
-typedef struct stat monodroid_stat_t;
-#define monodroid_dir_t DIR
-typedef struct dirent monodroid_dirent_t;
-#endif
-
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -50,6 +40,16 @@ typedef struct dirent monodroid_dirent_t;
 #include "dylib-mono.h"
 #include "jni-wrappers.h"
 
+#if WINDOWS
+typedef struct _stat monodroid_stat_t;
+#define monodroid_dir_t _WDIR
+typedef struct _wdirent monodroid_dirent_t;
+#else
+typedef struct stat monodroid_stat_t;
+#define monodroid_dir_t DIR
+typedef struct dirent monodroid_dirent_t;
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif // __cplusplus

src/monodroid/jni/xamarin-app.h

@@ -0,0 +1,40 @@
+// Dear Emacs, this is a -*- C++ -*- header
+#ifndef __XAMARIN_ANDROID_TYPEMAP_H
+#define __XAMARIN_ANDROID_TYPEMAP_H
+
+#include <stdint.h>
+
+#include "monodroid.h"
+
+struct TypeMapHeader
+{
+	uint32_t version;
+	uint32_t entry_count;
+	uint32_t entry_length;
+	uint32_t value_offset;
+};
+
+struct ApplicationConfig
+{
+	bool uses_mono_llvm;
+	bool uses_mono_aot;
+	bool uses_embedded_dsos;
+	bool uses_assembly_preload;
+	bool is_a_bundled_app;
+	uint32_t environment_variable_count;
+	uint32_t system_property_count;
+	const char *android_package_name;
+};
+
+MONO_API TypeMapHeader jm_typemap_header;
+MONO_API uint8_t jm_typemap[];
+
+MONO_API TypeMapHeader mj_typemap_header;
+MONO_API uint8_t mj_typemap[];
+
+MONO_API ApplicationConfig application_config;
+MONO_API const char* app_environment_variables[];
+MONO_API const char* app_system_properties[];
+
+MONO_API const char* mono_aot_mode_name;
+#endif // __XAMARIN_ANDROID_TYPEMAP_H

src/monodroid/monodroid.targets

@@ -31,13 +31,13 @@
     <!-- CMAKE_RUNTIME_OUTPUT_DIRECTORY is provided for the mingw cross builds. DLL outputs are treated as _runtime_ objects (as opposed to _library_ ones for .so, .dylib etc) by cmake
          and so in order to put libmono-android.*.dll in the output dir we need to set this property. Since we build no executables here, it won't affect the non-DLL outputs.  -->
     <Exec
-        Command="$(CmakePath) %(_HostRuntime.CmakeFlags) -DCONFIGURATION=Release -DCMAKE_BUILD_TYPE=Debug -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) -DCMAKE_RUNTIME_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) $(MSBuildThisFileDirectory)"
+        Command="$(CmakePath) %(_HostRuntime.CmakeFlags) -DCONFIGURATION=Release -DCMAKE_BUILD_TYPE=Debug -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) -DCMAKE_RUNTIME_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) $(MSBuildThisFileDirectory)"
         WorkingDirectory="$(IntermediateOutputPath)%(_HostRuntime.OutputDirectory)-Debug"
     />
 
     <MakeDir Directories="$(IntermediateOutputPath)%(_HostRuntime.OutputDirectory)-Release" />
     <Exec
-        Command="$(CmakePath) %(_HostRuntime.CmakeFlags) -DSTRIP_DEBUG=ON -DCONFIGURATION=Debug -DCMAKE_BUILD_TYPE=Release -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) -DCMAKE_RUNTIME_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) $(MSBuildThisFileDirectory)"
+        Command="$(CmakePath) %(_HostRuntime.CmakeFlags) -DSTRIP_DEBUG=ON -DCONFIGURATION=Debug -DCMAKE_BUILD_TYPE=Release -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) -DCMAKE_RUNTIME_OUTPUT_DIRECTORY=$(OutputPath)/%(_HostRuntime.OutputDirectory) $(MSBuildThisFileDirectory)"
         WorkingDirectory="$(IntermediateOutputPath)%(_HostRuntime.OutputDirectory)-Release"
     />
   </Target>
@@ -47,13 +47,13 @@
       Outputs="@(AndroidSupportedTargetJitAbi->'$(IntermediateOutputPath)\%(Identity)-Debug\CMakeCache.txt');@(AndroidSupportedTargetJitAbi->'$(IntermediateOutputPath)\%(Identity)-Release\CMakeCache.txt')">
     <MakeDir Directories="$(IntermediateOutputPath)%(AndroidSupportedTargetJitAbi.Identity)-Debug" />
     <Exec
-        Command="$(CmakePath) $(_CmakeAndroidFlags) -DCONFIGURATION=Release -DCMAKE_BUILD_TYPE=Debug -DANDROID_NATIVE_API_LEVEL=%(AndroidSupportedTargetJitAbi.ApiLevel) -DANDROID_PLATFORM=android-%(AndroidSupportedTargetJitAbi.ApiLevel) -DANDROID_ABI=%(AndroidSupportedTargetJitAbi.Identity) -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=$(OutputPath)%(AndroidSupportedTargetJitAbi.Identity) $(MSBuildThisFileDirectory)"
+        Command="$(CmakePath) $(_CmakeAndroidFlags) -DCONFIGURATION=Release -DCMAKE_BUILD_TYPE=Debug -DANDROID_NATIVE_API_LEVEL=%(AndroidSupportedTargetJitAbi.ApiLevel) -DANDROID_PLATFORM=android-%(AndroidSupportedTargetJitAbi.ApiLevel) -DANDROID_ABI=%(AndroidSupportedTargetJitAbi.Identity) -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY=$(OutputPath)%(AndroidSupportedTargetJitAbi.Identity) -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=$(OutputPath)%(AndroidSupportedTargetJitAbi.Identity) $(MSBuildThisFileDirectory)"
         WorkingDirectory="$(IntermediateOutputPath)%(AndroidSupportedTargetJitAbi.Identity)-Debug"
     />
 
     <MakeDir Directories="$(IntermediateOutputPath)%(AndroidSupportedTargetJitAbi.Identity)-Release" />
     <Exec
-        Command="$(CmakePath) $(_CmakeAndroidFlags) -DSTRIP_DEBUG=ON -DCONFIGURATION=Debug -DCMAKE_BUILD_TYPE=Release -DANDROID_NATIVE_API_LEVEL=%(AndroidSupportedTargetJitAbi.ApiLevel) -DANDROID_PLATFORM=android-%(AndroidSupportedTargetJitAbi.ApiLevel) -DANDROID_ABI=%(AndroidSupportedTargetJitAbi.Identity) -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=$(OutputPath)%(AndroidSupportedTargetJitAbi.Identity) $(MSBuildThisFileDirectory)"
+        Command="$(CmakePath) $(_CmakeAndroidFlags) -DSTRIP_DEBUG=ON -DCONFIGURATION=Debug -DCMAKE_BUILD_TYPE=Release -DANDROID_NATIVE_API_LEVEL=%(AndroidSupportedTargetJitAbi.ApiLevel) -DANDROID_PLATFORM=android-%(AndroidSupportedTargetJitAbi.ApiLevel) -DANDROID_ABI=%(AndroidSupportedTargetJitAbi.Identity) -DCMAKE_ARCHIVE_OUTPUT_DIRECTORY=$(OutputPath)%(AndroidSupportedTargetJitAbi.Identity) -DCMAKE_LIBRARY_OUTPUT_DIRECTORY=$(OutputPath)%(AndroidSupportedTargetJitAbi.Identity) $(MSBuildThisFileDirectory)"
         WorkingDirectory="$(IntermediateOutputPath)%(AndroidSupportedTargetJitAbi.Identity)-Release"
     />
   </Target>
@@ -61,7 +61,7 @@
   <Target Name="_BuildAndroidRuntimes"
       DependsOnTargets="_ConfigureAndroidRuntimes"
       Inputs="@(_MonodroidSource);@(AndroidSupportedTargetJitAbi->'$(IntermediateOutputPath)\%(Identity)-Debug\CMakeCache.txt');@(AndroidSupportedTargetJitAbi->'$(IntermediateOutputPath)\%(Identity)-Release\CMakeCache.txt');jni\*.cc;jni\*.h;jni\**\*.c;;..\..\build-tools\scripts\Ndk.targets"
-      Outputs="@(AndroidSupportedTargetJitAbi->'$(OutputPath)\%(Identity)\libmono-android.debug.so');@(AndroidSupportedTargetJitAbi->'$(OutputPath)\%(Identity)\libmono-android.release.so')">
+      Outputs="@(AndroidSupportedTargetJitAbi->'$(OutputPath)\%(Identity)\libmono-android.debug.so');@(AndroidSupportedTargetJitAbi->'$(OutputPath)\%(Identity)\libmono-android.release.so');@(AndroidSupportedTargetJitAbi->'$(IntermediateOutputPath)\%(Identity)-Debug\libxamarin-app.so');@(AndroidSupportedTargetJitAbi->'$(IntermediateOutputPath)\%(Identity)-Release\libxamarin-app.so')">
     <Exec
         Command="$(NinjaPath) -v"
         WorkingDirectory="$(IntermediateOutputPath)%(AndroidSupportedTargetJitAbi.Identity)-Debug"
@@ -76,7 +76,7 @@
   <Target Name="_BuildHostRuntimes"
       DependsOnTargets="_GetBuildHostRuntimes;_CreateJavaInteropDllConfigs;_ConfigureHostRuntimes"
       Inputs="@(_MonodroidSource);@(_HostRuntime->'$(IntermediatePath)%(OutputDirectory)-Debug\CMakeCache.txt');@(_HostRuntime->'$(IntermediatePath)%(OutputDirectory)-Release\CMakeCache.txt');jni\*.cc;jni\*.h;jni\**\*.c;"
-      Outputs="@(_HostRuntime->'$(OutputPath)%(OutputDirectory)\libmono-android.debug.%(NativeLibraryExtension)');@(_HostRuntime->'$(OutputPath)%(OutputDirectory)\libmono-android.release.%(NativeLibraryExtension)')">
+      Outputs="@(_HostRuntime->'$(OutputPath)%(OutputDirectory)\libmono-android.debug.%(NativeLibraryExtension)');@(_HostRuntime->'$(OutputPath)%(OutputDirectory)\libmono-android.release.%(NativeLibraryExtension)');@(_HostRuntime->'$(OutputPath)%(OutputDirectory)\libxamarin-app.%(NativeLibraryExtension)')">
     <Message Text="Building host runtime %(_HostRuntime.Identity) in $(OutputPath)%(_HostRuntime.OutputDirectory)"/>
     <MakeDir Directories="$(OutputPath)%(_HostRuntime.OutputDirectory)" />
 
@@ -97,6 +97,7 @@
         SourceFiles="@(_HostRuntime->'$(OutputPath)%(OutputDirectory)\libmono-android.release.%(NativeLibraryExtension)')"
         DestinationFiles="@(_HostRuntime->'$(OutputPath)%(OutputDirectory)\libmono-android.release.d.%(NativeLibraryExtension)')"
     />
+
   </Target>
   <Target Name="_CleanRuntimes"
       DependsOnTargets="_GetBuildHostRuntimes"

tests/EmbeddedDSOs/EmbeddedDSO-UnitTests/BuildTests.cs

@@ -11,6 +11,7 @@ using System.Xml.XPath;
 
 using Microsoft.Build.Framework;
 using NUnit.Framework;
+using Xamarin.Android.Build.Tests;
 using Xamarin.ProjectTools;
 using Xamarin.Tools.Zip;
 
@@ -18,9 +19,9 @@ using XABuildPaths = global::Xamarin.Android.Build.Paths;
 
 namespace EmbeddedDSOUnitTests
 {
-	sealed class LocalBuilder : Builder
+	sealed class LocalBuilder : ProjectBuilder
 	{
-		public LocalBuilder ()
+		public LocalBuilder (string projectDir) : base (projectDir)
 		{
 			BuildingInsideVisualStudio = false;
 		}
@@ -71,8 +72,13 @@ namespace EmbeddedDSOUnitTests
 		{
 			testProjectPath = PrepareProject (ProjectName);
 			string projectPath = Path.Combine (testProjectPath, $"{ProjectName}.csproj");
-			LocalBuilder builder = GetBuilder ("EmbeddedDSO");
+			LocalBuilder builder = GetBuilder ("EmbeddedDSO", testProjectPath);
-			bool success = builder.Build (projectPath, "SignAndroidPackage", new [] { "UnitTestsMode=true" });
+			string targetAbis = Xamarin.Android.Tools.XABuildConfig.SupportedABIs.Replace (";", ":");
+			bool success = builder.Build (projectPath, "SignAndroidPackage", new [] {
+					"UnitTestsMode=true",
+					$"Configuration={XABuildPaths.Configuration}",
+					$"AndroidSupportedTargetJitAbis=\"{targetAbis}\"",
+				});
 
 			Assert.That (success, Is.True, "Should have been built");
 
@@ -102,28 +108,11 @@ namespace EmbeddedDSOUnitTests
 		[Test]
 		public void EnvironmentFileContents ()
 		{
-			string javaEnv = Path.Combine (testProjectPath, "obj", XABuildPaths.Configuration, "android", "src", "mono", "android", "app", "XamarinAndroidEnvironmentVariables.java");
+			string intermediateOutputDir = Path.Combine (testProjectPath, "obj", XABuildPaths.Configuration);
-			Assert.That (new FileInfo (javaEnv), Does.Exist, $"File {javaEnv} should exist");
+			List<string> envFiles = EnvironmentHelper.GatherEnvironmentFiles (intermediateOutputDir, Xamarin.Android.Tools.XABuildConfig.SupportedABIs, true);
-
+			EnvironmentHelper.ApplicationConfig app_config = EnvironmentHelper.ReadApplicationConfig (envFiles);
-			string[] envLines = File.ReadAllLines (javaEnv);
+			Assert.That (app_config, Is.Not.Null, "application_config must be present in the environment files");
-			Assert.That (envLines.Any (l => !String.IsNullOrEmpty (l)), Is.True, $"Environment file {javaEnv} must contain at least one non-empty line");
+			Assert.That (app_config.uses_embedded_dsos, Is.True, "'uses_embedded_dsos' must be true in application_config");
-
-			bool found = false;
-			foreach (string line in envLines) {
-				if (String.IsNullOrEmpty (line))
-					continue;
-
-				if (line.IndexOf ("\"__XA_DSO_IN_APK\",") >= 0) {
-					found = true;
-					break;
-				}
-			}
-
-			Assert.That (found, Is.True, $"The `__XA_DSO_IN_APK` variable wasn't found in the environment file {javaEnv}");
-
-			string dexFile = Path.Combine (testProjectPath, "obj", XABuildPaths.Configuration, "android", "bin", "classes.dex");
-			Assert.That (new FileInfo (dexFile), Does.Exist, $"File {dexFile} should exist");
-			Assert.That (DexUtils.ContainsClass ("Lmono/android/app/XamarinAndroidEnvironmentVariables;", dexFile, androidSdkDir), Is.True, $"Dex file {dexFile} should contain the XamarinAndroidEnvironmentVariables class");
 		}
 
 		[Test]
@@ -283,9 +272,9 @@ namespace EmbeddedDSOUnitTests
 			File.Copy (from, to, true);
 		}
 
-		LocalBuilder GetBuilder (string baseLogFileName)
+		LocalBuilder GetBuilder (string baseLogFileName, string projectDir)
 		{
-			return new LocalBuilder {
+			return new LocalBuilder (projectDir) {
 				Verbosity = LoggerVerbosity.Diagnostic,
 				BuildLogFile = $"{baseLogFileName}.log"
 			};

tests/EmbeddedDSOs/EmbeddedDSO-UnitTests/EmbeddedDSO-UnitTests.csproj

@@ -34,6 +34,14 @@
     <Reference Include="nunit.framework">
       <HintPath>..\..\..\packages\NUnit.3.11.0\lib\net45\nunit.framework.dll</HintPath>
     </Reference>
+    <Reference Include="Xamarin.Android.Build.Tasks">
+      <HintPath>..\..\..\bin\$(Configuration)\lib/xamarin.android\xbuild\Xamarin\Android\Xamarin.Android.Build.Tasks.dll</HintPath>
+      <Private>True</Private>
+    </Reference>
+    <Reference Include="Xamarin.Android.Tools.AndroidSdk">
+      <HintPath>..\..\..\bin\$(Configuration)\lib/xamarin.android\xbuild\Xamarin\Android\Xamarin.Android.Tools.AndroidSdk.dll</HintPath>
+      <Private>True</Private>
+    </Reference>
   </ItemGroup>
   <ItemGroup>
     <Compile Include="BuildTests.cs" />
@@ -41,6 +49,10 @@
     <Compile Include="..\..\..\bin\Test$(CONFIGURATION)/XABuildPaths.cs">
        <Link>XABuildPaths.cs</Link>
     </Compile>
+    <Compile Include="..\..\..\bin\Build$(CONFIGURATION)/XABuildConfig.cs">
+       <Link>XABuildConfig.cs</Link>
+    </Compile>
+    <Compile Include="..\..\..\src\Xamarin.Android.Build.Tasks\Tests\Xamarin.Android.Build.Tests\Utilities\EnvironmentHelper.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="packages.config" />

tests/EmbeddedDSOs/EmbeddedDSO-UnitTests/run.sh

@@ -2,6 +2,7 @@
 export MONO_ENV_OPTIONS="--debug"
 export USE_MSBUILD=1
 export MSBUILD=msbuild
-msbuild EmbeddedDSO-UnitTests.csproj
+CONFIGURATION=${1:-Debug}
+msbuild /p:Configuration=${CONFIGURATION} EmbeddedDSO-UnitTests.csproj
 cd ../../../
-exec mono --debug packages/NUnit.ConsoleRunner.3.9.0/tools/nunit3-console.exe bin/TestDebug/EmbeddedDSO/EmbeddedDSOUnitTests.dll
+exec mono --debug packages/NUnit.ConsoleRunner.3.9.0/tools/nunit3-console.exe bin/Test${CONFIGURATION}/EmbeddedDSO/EmbeddedDSOUnitTests.dll

tests/EmbeddedDSOs/EmbeddedDSO/EmbeddedDSO.csproj

@@ -17,7 +17,6 @@
     <MonoAndroidAssetsPrefix>Assets</MonoAndroidAssetsPrefix>
     <AndroidUseLatestPlatformSdk>true</AndroidUseLatestPlatformSdk>
     <AndroidUseSharedRuntime>false</AndroidUseSharedRuntime>
-    <AndroidSupportedAbis>armeabi-v7a;x86</AndroidSupportedAbis>
   </PropertyGroup>
 
   <PropertyGroup Condition=" '$(UnitTestsMode)' == 'true' ">
@@ -29,6 +28,13 @@
   </PropertyGroup>
 
   <Import Project="$(RelativeRootPath)\Configuration.props" />
+
+  <PropertyGroup>
+    <!-- We have to limit the supported abis to the currently enabled set, since the PR builders don't build all architectures but,
+         eventually, we have to build for all the ABIs unconditionally here -->
+    <AndroidSupportedAbis>$(AndroidSupportedTargetJitAbisSplit)</AndroidSupportedAbis>
+  </PropertyGroup>
+
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
     <Optimize>false</Optimize>