Merged PR 785475: Resolve ptrace sandbox reports dfa in Ubuntu 22.04 on readlink

Untrack /user/local/include and /usr/x86_64-linux-gnu by default
Report Checker::Lookup for absent path in readlink
Fix a small bug when pathname is empty, we added extra slash at the end of the path

Related work items: #2137346

Public/Src/Engine/UnitTests/Processes/InterposeSandboxProcessTest.cs

@@ -100,6 +100,26 @@ namespace Test.BuildXL.Processes
             XAssert.AreEqual(1, accesses.Where(a => a.Path == realPath3).Count());
         }
 
+        [Fact]
+        public void CallBoostReadlinkAbsentPathTests()
+        {
+            var fileStorage = new TempFileStorage(canGetFileNames: true);
+            var absentFilePath = Path.Combine(fileStorage.RootDirectory, "absentFile.o");
+
+            // This test calls readlink(absentFilePath)
+            var result = RunTest("readlink_absent_path", fileStorage);
+            XAssert.IsNotNull(result.FileAccesses);
+
+            // There should be only one absent file access
+            var absentPathAccesses = result.FileAccesses!.Where(a => a.IsNonexistent);
+            XAssert.AreEqual(1, absentPathAccesses.Count());
+
+            // readlink on absent path is reported backed as probe
+            var absentFileAccess = absentPathAccesses.Single();
+            XAssert.AreEqual(absentFilePath, absentFileAccess.GetPath(Context.PathTable));
+            XAssert.AreEqual(RequestedAccess.Probe, absentFileAccess.RequestedAccess);
+        }
+
         [Fact]
         public void CallBoostObserverUtilitiesTests()
         {

Public/Src/Pips/Dll/Graph/PipGraph.UnixDefaults.cs

@@ -121,6 +121,8 @@ namespace BuildXL.Pips.Graph
                         UnixPaths.LibLinuxGnu,
                         UnixPaths.Lib64,
                         UnixPaths.Run,
+                        UnixPaths.UsrLocalInclude,
+                        UnixPaths.UsrLinuxGnu,
                     }
                     .Concat(IfMacOs(
                         MacPaths.AppleInternal,

Public/Src/Sandbox/Linux/UnitTests/BuildXL.Sandbox.Linux.UnitTests.dsc

@@ -32,6 +32,10 @@ namespace UnitTests
             exeName: a`observer_utilities_test`,
             sourceFiles: [ f`observer_utilities_test.cpp`, f`${sandboxSrcDirectory.path}/observer_utilities.cpp` ],
             includeDirectories: [ sandboxSrcDirectory ]
+        },
+        {
+            exeName: a`readlink_absent_path`,
+            sourceFiles:[f`readlink_absent_path.cpp`]
         }
     ];
 

Public/Src/Sandbox/Linux/UnitTests/readlink_absent_path.cpp

@@ -0,0 +1,34 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+#define BOOST_TEST_MODULE LinuxSandboxTest
+#define _DO_NOT_EXPORT
+
+#include <boost/test/included/unit_test.hpp>
+#include <limits.h>
+#include <string.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+using namespace std;
+
+BOOST_AUTO_TEST_SUITE(ReadlinkAbsentPath)
+
+BOOST_AUTO_TEST_CASE(TestReadlinkAbsentPath)
+{
+    // Create a absent file path under current working directory
+    char cwd[PATH_MAX] = { 0 };
+    char *res = getcwd(cwd, PATH_MAX);   
+    string newPath(res);
+    newPath.append("/absentFile.o");
+
+    // Call readlink on this absent file path
+    char buf[PATH_MAX] = { 0 };
+    auto read = readlink(newPath.c_str(), buf, PATH_MAX);
+    // readlink return -1 on absent path and error number is ENOENT
+    BOOST_CHECK(read == -1);
+    BOOST_CHECK_EQUAL(errno, ENOENT);
+}
+
+BOOST_AUTO_TEST_SUITE_END()

Public/Src/Sandbox/Linux/bxl_observer.cpp

@@ -1129,8 +1129,11 @@ void BxlObserver::relative_to_absolute(const char *pathname, int dirfd, int asso
             _fatal("['%s'] Could not get path for fd %d with path '%s'; errno: %d", systemcall, dirfd, pathname, errno);
         }
 
-        fullpath[len] = '/';
+        if (pathname[0] != '\0')
-        strcpy(fullpath + len + 1, pathname);
+        {
+            fullpath[len] = '/';
+            strcpy(fullpath + len + 1, pathname);
+        }
     }
     else
     {

Public/Src/Sandbox/MacOs/Interop/Sandbox/Handlers/IOHandler.cpp

@@ -127,7 +127,15 @@ AccessCheckResult IOHandler::HandleUnlink(const IOEvent &event, AccessReport &ac
 
 AccessCheckResult IOHandler::HandleReadlink(const IOEvent &event, AccessReport &accessToReport)
 {
-    return CheckAndCreateReport(kOpMacReadlink, event.GetEventPath(SRC_PATH), Checkers::CheckRead, event.GetPid(), false, event.GetError(), accessToReport);
+    bool isDir = S_ISDIR(event.GetMode());
+    if (!event.EventPathExists())
+    {
+        return CheckAndCreateReport(kOpMacLookup, event.GetEventPath(SRC_PATH), Checkers::CheckLookup, event.GetPid(), isDir, event.GetError(), accessToReport);
+    }
+    else
+    {
+        return CheckAndCreateReport(kOpMacReadlink, event.GetEventPath(SRC_PATH), Checkers::CheckRead, event.GetPid(), isDir, event.GetError(), accessToReport);
+    }
 }
 
 AccessCheckResult IOHandler::HandleRename(const IOEvent &event, AccessReport &sourceAccessToReport, AccessReport &destinationAccessToReport)

Public/Src/Utilities/Utilities.Core/Interop/MacOS/IO.cs

@@ -492,6 +492,8 @@ namespace BuildXL.Interop.Unix
         public const string UsrStandalone   = "/usr/standalone";
         public const string UsrSbin         = "/usr/sbin";
         public const string Var             = "/var";
+        public const string UsrLocalInclude = "/usr/local/include";
+        public const string UsrLinuxGnu     = "/usr/x86_64-linux-gnu";
     }
 
     public static class MacPaths