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gecko-dev/mozglue/linker/Mappable.cpp

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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include "Mappable.h"
#include "mozilla/UniquePtr.h"
#ifdef ANDROID
#include <linux/ashmem.h>
#endif
#include <sys/stat.h>
#include <errno.h>
#include "ElfLoader.h"
#include "SeekableZStream.h"
#include "Logging.h"
using mozilla::MakeUnique;
using mozilla::UniquePtr;
Mappable *
MappableFile::Create(const char *path)
{
int fd = open(path, O_RDONLY);
if (fd != -1)
return new MappableFile(fd);
return nullptr;
}
MemoryRange
MappableFile::mmap(const void *addr, size_t length, int prot, int flags,
off_t offset)
{
MOZ_ASSERT(fd != -1);
MOZ_ASSERT(!(flags & MAP_SHARED));
flags |= MAP_PRIVATE;
return MemoryRange::mmap(const_cast<void *>(addr), length, prot, flags,
fd, offset);
}
void
MappableFile::finalize()
{
/* Close file ; equivalent to close(fd.forget()) */
fd = -1;
}
size_t
MappableFile::GetLength() const
{
struct stat st;
return fstat(fd, &st) ? 0 : st.st_size;
}
Mappable *
MappableExtractFile::Create(const char *name, Zip *zip, Zip::Stream *stream)
{
const char *cachePath = getenv("MOZ_LINKER_CACHE");
if (!cachePath || !*cachePath) {
WARN("MOZ_LINKER_EXTRACT is set, but not MOZ_LINKER_CACHE; "
"not extracting");
return nullptr;
}
UniquePtr<char[]> path =
MakeUnique<char[]>(strlen(cachePath) + strlen(name) + 2);
sprintf(path.get(), "%s/%s", cachePath, name);
struct stat cacheStat;
if (stat(path.get(), &cacheStat) == 0) {
struct stat zipStat;
stat(zip->GetName(), &zipStat);
if (cacheStat.st_mtime > zipStat.st_mtime) {
DEBUG_LOG("Reusing %s", static_cast<char *>(path.get()));
return MappableFile::Create(path.get());
}
}
DEBUG_LOG("Extracting to %s", static_cast<char *>(path.get()));
AutoCloseFD fd;
fd = open(path.get(), O_TRUNC | O_RDWR | O_CREAT | O_NOATIME,
S_IRUSR | S_IWUSR);
if (fd == -1) {
ERROR("Couldn't open %s to decompress library", path.get());
return nullptr;
}
AutoUnlinkFile file(path.release());
if (stream->GetType() == Zip::Stream::DEFLATE) {
if (ftruncate(fd, stream->GetUncompressedSize()) == -1) {
ERROR("Couldn't ftruncate %s to decompress library", file.get());
return nullptr;
}
/* Map the temporary file for use as inflate buffer */
MappedPtr buffer(MemoryRange::mmap(nullptr, stream->GetUncompressedSize(),
PROT_WRITE, MAP_SHARED, fd, 0));
if (buffer == MAP_FAILED) {
ERROR("Couldn't map %s to decompress library", file.get());
return nullptr;
}
z_stream zStream = stream->GetZStream(buffer);
/* Decompress */
if (inflateInit2(&zStream, -MAX_WBITS) != Z_OK) {
ERROR("inflateInit failed: %s", zStream.msg);
return nullptr;
}
if (inflate(&zStream, Z_FINISH) != Z_STREAM_END) {
ERROR("inflate failed: %s", zStream.msg);
return nullptr;
}
if (inflateEnd(&zStream) != Z_OK) {
ERROR("inflateEnd failed: %s", zStream.msg);
return nullptr;
}
if (zStream.total_out != stream->GetUncompressedSize()) {
ERROR("File not fully uncompressed! %ld / %d", zStream.total_out,
static_cast<unsigned int>(stream->GetUncompressedSize()));
return nullptr;
}
} else if (stream->GetType() == Zip::Stream::STORE) {
SeekableZStream zStream;
if (!zStream.Init(stream->GetBuffer(), stream->GetSize())) {
ERROR("Couldn't initialize SeekableZStream for %s", name);
return nullptr;
}
if (ftruncate(fd, zStream.GetUncompressedSize()) == -1) {
ERROR("Couldn't ftruncate %s to decompress library", file.get());
return nullptr;
}
MappedPtr buffer(MemoryRange::mmap(nullptr, zStream.GetUncompressedSize(),
PROT_WRITE, MAP_SHARED, fd, 0));
if (buffer == MAP_FAILED) {
ERROR("Couldn't map %s to decompress library", file.get());
return nullptr;
}
if (!zStream.Decompress(buffer, 0, zStream.GetUncompressedSize())) {
ERROR("%s: failed to decompress", name);
return nullptr;
}
} else {
return nullptr;
}
return new MappableExtractFile(fd.forget(), Move(file));
}
MappableExtractFile::~MappableExtractFile()
{
/* When destroying from a forked process, we don't want the file to be
* removed, as the main process is still using the file. Although it
* doesn't really matter, it helps e.g. valgrind that the file is there.
* The string still needs to be delete[]d, though */
if (pid != getpid())
delete [] path.release();
}
/**
* _MappableBuffer is a buffer which content can be mapped at different
* locations in the virtual address space.
* On Linux, uses a (deleted) temporary file on a tmpfs for sharable content.
* On Android, uses ashmem.
*/
class _MappableBuffer: public MappedPtr
{
public:
/**
* Returns a _MappableBuffer instance with the given name and the given
* length.
*/
static _MappableBuffer *Create(const char *name, size_t length)
{
AutoCloseFD fd;
#ifdef ANDROID
/* On Android, initialize an ashmem region with the given length */
fd = open("/" ASHMEM_NAME_DEF, O_RDWR, 0600);
if (fd == -1)
return nullptr;
char str[ASHMEM_NAME_LEN];
strlcpy(str, name, sizeof(str));
ioctl(fd, ASHMEM_SET_NAME, str);
if (ioctl(fd, ASHMEM_SET_SIZE, length))
return nullptr;
/* The Gecko crash reporter is confused by adjacent memory mappings of
* the same file and chances are we're going to map from the same file
* descriptor right away. To avoid problems with the crash reporter,
* create an empty anonymous page before or after the ashmem mapping,
* depending on how mappings grow in the address space.
*/
#if defined(__arm__)
void *buf = ::mmap(nullptr, length + PAGE_SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
if (buf != MAP_FAILED) {
::mmap(AlignedEndPtr(reinterpret_cast<char *>(buf) + length, PAGE_SIZE),
PAGE_SIZE, PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
DEBUG_LOG("Decompression buffer of size 0x%x in ashmem \"%s\", mapped @%p",
length, str, buf);
return new _MappableBuffer(fd.forget(), buf, length);
}
#elif defined(__i386__)
size_t anon_mapping_length = length + PAGE_SIZE;
void *buf = ::mmap(nullptr, anon_mapping_length, PROT_NONE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (buf != MAP_FAILED) {
char *first_page = reinterpret_cast<char *>(buf);
char *map_page = first_page + PAGE_SIZE;
void *actual_buf = ::mmap(map_page, length, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_SHARED, fd, 0);
if (actual_buf == MAP_FAILED) {
::munmap(buf, anon_mapping_length);
DEBUG_LOG("Fixed allocation of decompression buffer at %p failed", map_page);
return nullptr;
}
DEBUG_LOG("Decompression buffer of size 0x%x in ashmem \"%s\", mapped @%p",
length, str, actual_buf);
return new _MappableBuffer(fd.forget(), actual_buf, length);
}
#else
#error need to add a case for your CPU
#endif
#else
/* On Linux, use /dev/shm as base directory for temporary files, assuming
* it's on tmpfs */
/* TODO: check that /dev/shm is tmpfs */
char path[256];
sprintf(path, "/dev/shm/%s.XXXXXX", name);
fd = mkstemp(path);
if (fd == -1)
return nullptr;
unlink(path);
ftruncate(fd, length);
void *buf = ::mmap(nullptr, length, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
if (buf != MAP_FAILED) {
DEBUG_LOG("Decompression buffer of size %ld in \"%s\", mapped @%p",
length, path, buf);
return new _MappableBuffer(fd.forget(), buf, length);
}
#endif
return nullptr;
}
void *mmap(const void *addr, size_t length, int prot, int flags, off_t offset)
{
MOZ_ASSERT(fd != -1);
#ifdef ANDROID
/* Mapping ashmem MAP_PRIVATE is like mapping anonymous memory, even when
* there is content in the ashmem */
if (flags & MAP_PRIVATE) {
flags &= ~MAP_PRIVATE;
flags |= MAP_SHARED;
}
#endif
return ::mmap(const_cast<void *>(addr), length, prot, flags, fd, offset);
}
#ifdef ANDROID
~_MappableBuffer() {
/* Free the additional page we allocated. See _MappableBuffer::Create */
#if defined(__arm__)
::munmap(AlignedEndPtr(*this + GetLength(), PAGE_SIZE), PAGE_SIZE);
#elif defined(__i386__)
::munmap(*this - PAGE_SIZE, GetLength() + PAGE_SIZE);
#else
#error need to add a case for your CPU
#endif
}
#endif
private:
_MappableBuffer(int fd, void *buf, size_t length)
: MappedPtr(buf, length), fd(fd) { }
/* File descriptor for the temporary file or ashmem */
AutoCloseFD fd;
};
Mappable *
MappableDeflate::Create(const char *name, Zip *zip, Zip::Stream *stream)
{
MOZ_ASSERT(stream->GetType() == Zip::Stream::DEFLATE);
_MappableBuffer *buf = _MappableBuffer::Create(name, stream->GetUncompressedSize());
if (buf)
return new MappableDeflate(buf, zip, stream);
return nullptr;
}
MappableDeflate::MappableDeflate(_MappableBuffer *buf, Zip *zip,
Zip::Stream *stream)
: zip(zip), buffer(buf), zStream(stream->GetZStream(*buf)) { }
MappableDeflate::~MappableDeflate() { }
MemoryRange
MappableDeflate::mmap(const void *addr, size_t length, int prot, int flags, off_t offset)
{
MOZ_ASSERT(buffer);
MOZ_ASSERT(!(flags & MAP_SHARED));
flags |= MAP_PRIVATE;
/* The deflate stream is uncompressed up to the required offset + length, if
* it hasn't previously been uncompressed */
ssize_t missing = offset + length + zStream.avail_out - buffer->GetLength();
if (missing > 0) {
uInt avail_out = zStream.avail_out;
zStream.avail_out = missing;
if ((*buffer == zStream.next_out) &&
(inflateInit2(&zStream, -MAX_WBITS) != Z_OK)) {
ERROR("inflateInit failed: %s", zStream.msg);
return MemoryRange(MAP_FAILED, 0);
}
int ret = inflate(&zStream, Z_SYNC_FLUSH);
if (ret < 0) {
ERROR("inflate failed: %s", zStream.msg);
return MemoryRange(MAP_FAILED, 0);
}
if (ret == Z_NEED_DICT) {
ERROR("zstream requires a dictionary. %s", zStream.msg);
return MemoryRange(MAP_FAILED, 0);
}
zStream.avail_out = avail_out - missing + zStream.avail_out;
if (ret == Z_STREAM_END) {
if (inflateEnd(&zStream) != Z_OK) {
ERROR("inflateEnd failed: %s", zStream.msg);
return MemoryRange(MAP_FAILED, 0);
}
if (zStream.total_out != buffer->GetLength()) {
ERROR("File not fully uncompressed! %ld / %d", zStream.total_out,
static_cast<unsigned int>(buffer->GetLength()));
return MemoryRange(MAP_FAILED, 0);
}
}
}
#if defined(ANDROID) && defined(__arm__)
if (prot & PROT_EXEC) {
/* We just extracted data that may be executed in the future.
* We thus need to ensure Instruction and Data cache coherency. */
DEBUG_LOG("cacheflush(%p, %p)", *buffer + offset, *buffer + (offset + length));
cacheflush(reinterpret_cast<uintptr_t>(*buffer + offset),
reinterpret_cast<uintptr_t>(*buffer + (offset + length)), 0);
}
#endif
return MemoryRange(buffer->mmap(addr, length, prot, flags, offset), length);
}
void
MappableDeflate::finalize()
{
/* Free zlib internal buffers */
inflateEnd(&zStream);
/* Free decompression buffer */
buffer = nullptr;
/* Remove reference to Zip archive */
zip = nullptr;
}
size_t
MappableDeflate::GetLength() const
{
return buffer->GetLength();
}
Mappable *
MappableSeekableZStream::Create(const char *name, Zip *zip,
Zip::Stream *stream)
{
MOZ_ASSERT(stream->GetType() == Zip::Stream::STORE);
mozilla::ScopedDeletePtr<MappableSeekableZStream> mappable;
mappable = new MappableSeekableZStream(zip);
pthread_mutexattr_t recursiveAttr;
pthread_mutexattr_init(&recursiveAttr);
pthread_mutexattr_settype(&recursiveAttr, PTHREAD_MUTEX_RECURSIVE);
if (pthread_mutex_init(&mappable->mutex, &recursiveAttr))
return nullptr;
if (!mappable->zStream.Init(stream->GetBuffer(), stream->GetSize()))
return nullptr;
mappable->buffer.reset(_MappableBuffer::Create(name,
mappable->zStream.GetUncompressedSize()));
if (!mappable->buffer)
return nullptr;
mappable->chunkAvail = MakeUnique<unsigned char[]>(mappable->zStream.GetChunksNum());
return mappable.forget();
}
MappableSeekableZStream::MappableSeekableZStream(Zip *zip)
: zip(zip), chunkAvailNum(0) { }
MappableSeekableZStream::~MappableSeekableZStream()
{
pthread_mutex_destroy(&mutex);
}
MemoryRange
MappableSeekableZStream::mmap(const void *addr, size_t length, int prot,
int flags, off_t offset)
{
/* Map with PROT_NONE so that accessing the mapping would segfault, and
* bring us to ensure() */
void *res = buffer->mmap(addr, length, PROT_NONE, flags, offset);
if (res == MAP_FAILED)
return MemoryRange(MAP_FAILED, 0);
/* Store the mapping, ordered by offset and length */
std::vector<LazyMap>::reverse_iterator it;
for (it = lazyMaps.rbegin(); it < lazyMaps.rend(); ++it) {
if ((it->offset < offset) ||
((it->offset == offset) && (it->length < length)))
break;
}
LazyMap map = { res, length, prot, offset };
lazyMaps.insert(it.base(), map);
return MemoryRange(res, length);
}
void
MappableSeekableZStream::munmap(void *addr, size_t length)
{
std::vector<LazyMap>::iterator it;
for (it = lazyMaps.begin(); it < lazyMaps.end(); ++it)
if ((it->addr = addr) && (it->length == length)) {
lazyMaps.erase(it);
::munmap(addr, length);
return;
}
MOZ_CRASH("munmap called with unknown mapping");
}
void
MappableSeekableZStream::finalize() { }
class AutoLock {
public:
AutoLock(pthread_mutex_t *mutex): mutex(mutex)
{
if (pthread_mutex_lock(mutex))
MOZ_CRASH("pthread_mutex_lock failed");
}
~AutoLock()
{
if (pthread_mutex_unlock(mutex))
MOZ_CRASH("pthread_mutex_unlock failed");
}
private:
pthread_mutex_t *mutex;
};
bool
MappableSeekableZStream::ensure(const void *addr)
{
DEBUG_LOG("ensure @%p", addr);
const void *addrPage = PageAlignedPtr(addr);
/* Find the mapping corresponding to the given page */
std::vector<LazyMap>::iterator map;
for (map = lazyMaps.begin(); map < lazyMaps.end(); ++map) {
if (map->Contains(addrPage))
break;
}
if (map == lazyMaps.end())
return false;
/* Find corresponding chunk */
off_t mapOffset = map->offsetOf(addrPage);
off_t chunk = mapOffset / zStream.GetChunkSize();
/* In the typical case, we just need to decompress the chunk entirely. But
* when the current mapping ends in the middle of the chunk, we want to
* stop at the end of the corresponding page.
* However, if another mapping needs the last part of the chunk, we still
* need to continue. As mappings are ordered by offset and length, we don't
* need to scan the entire list of mappings.
* It is safe to run through lazyMaps here because the linker is never
* going to call mmap (which adds lazyMaps) while this function is
* called. */
size_t length = zStream.GetChunkSize(chunk);
off_t chunkStart = chunk * zStream.GetChunkSize();
off_t chunkEnd = chunkStart + length;
std::vector<LazyMap>::iterator it;
for (it = map; it < lazyMaps.end(); ++it) {
if (chunkEnd <= it->endOffset())
break;
}
if ((it == lazyMaps.end()) || (chunkEnd > it->endOffset())) {
/* The mapping "it" points at now is past the interesting one */
--it;
length = it->endOffset() - chunkStart;
}
length = PageAlignedSize(length);
/* The following lock can be re-acquired by the thread holding it.
* If this happens, it means the following code is interrupted somehow by
* some signal, and ends up retriggering a chunk decompression for the
* same MappableSeekableZStream.
* If the chunk to decompress is different the second time, then everything
* is safe as the only common data touched below is chunkAvailNum, and it is
* atomically updated (leaving out any chance of an interruption while it is
* updated affecting the result). If the chunk to decompress is the same, the
* worst thing that can happen is chunkAvailNum being incremented one too
* many times, which doesn't affect functionality. The chances of it
* happening being pretty slim, and the effect being harmless, we can just
* ignore the issue. Other than that, we'd just be wasting time decompressing
* the same chunk twice. */
AutoLock lock(&mutex);
/* The very first page is mapped and accessed separately of the rest, and
* as such, only the first page of the first chunk is decompressed this way.
* When we fault in the remaining pages of that chunk, we want to decompress
* the complete chunk again. Short of doing that, we would end up with
* no data between PageSize() and chunkSize, which would effectively corrupt
* symbol resolution in the underlying library. */
if (chunkAvail[chunk] < PageNumber(length)) {
if (!zStream.DecompressChunk(*buffer + chunkStart, chunk, length))
return false;
#if defined(ANDROID) && defined(__arm__)
if (map->prot & PROT_EXEC) {
/* We just extracted data that may be executed in the future.
* We thus need to ensure Instruction and Data cache coherency. */
DEBUG_LOG("cacheflush(%p, %p)", *buffer + chunkStart, *buffer + (chunkStart + length));
cacheflush(reinterpret_cast<uintptr_t>(*buffer + chunkStart),
reinterpret_cast<uintptr_t>(*buffer + (chunkStart + length)), 0);
}
#endif
/* Only count if we haven't already decompressed parts of the chunk */
if (chunkAvail[chunk] == 0)
chunkAvailNum++;
chunkAvail[chunk] = PageNumber(length);
}
/* Flip the chunk mapping protection to the recorded flags. We could
* also flip the protection for other mappings of the same chunk,
* but it's easier to skip that and let further segfaults call
* ensure again. */
const void *chunkAddr = reinterpret_cast<const void *>
(reinterpret_cast<uintptr_t>(addrPage)
- mapOffset % zStream.GetChunkSize());
const void *chunkEndAddr = reinterpret_cast<const void *>
(reinterpret_cast<uintptr_t>(chunkAddr) + length);
const void *start = std::max(map->addr, chunkAddr);
const void *end = std::min(map->end(), chunkEndAddr);
length = reinterpret_cast<uintptr_t>(end)
- reinterpret_cast<uintptr_t>(start);
if (mprotect(const_cast<void *>(start), length, map->prot) == 0) {
DEBUG_LOG("mprotect @%p, 0x%" PRIxSize ", 0x%x", start, length, map->prot);
return true;
}
ERROR("mprotect @%p, 0x%" PRIxSize ", 0x%x failed with errno %d",
start, length, map->prot, errno);
return false;
}
void
MappableSeekableZStream::stats(const char *when, const char *name) const
{
size_t nEntries = zStream.GetChunksNum();
DEBUG_LOG("%s: %s; %" PRIdSize "/%" PRIdSize " chunks decompressed",
name, when, static_cast<size_t>(chunkAvailNum), nEntries);
size_t len = 64;
UniquePtr<char[]> map = MakeUnique<char[]>(len + 3);
map[0] = '[';
for (size_t i = 0, j = 1; i < nEntries; i++, j++) {
map[j] = chunkAvail[i] ? '*' : '_';
if ((j == len) || (i == nEntries - 1)) {
map[j + 1] = ']';
map[j + 2] = '\0';
DEBUG_LOG("%s", static_cast<char *>(map.get()));
j = 0;
}
}
}
size_t
MappableSeekableZStream::GetLength() const
{
return buffer->GetLength();
}
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