The Tor Browser: ipc/chromium/src/base/shared_memory

ipc/chromium/src/base/shared_memory_posix.cc@6474c204b198 (annotated)

ipc/chromium/src/base/shared_memory_posix.cc

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 #include "base/shared_memory.h"
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/platform_thread.h"
 #include "base/string_util.h"
 namespace base {
 SharedMemory::SharedMemory()
     : mapped_file_(-1),
       inode_(0),
       memory_(NULL),
       read_only_(false),
       max_size_(0) {
 }
 SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only)
     : mapped_file_(handle.fd),
       inode_(0),
       memory_(NULL),
       read_only_(read_only),
       max_size_(0) {
   struct stat st;
   if (fstat(handle.fd, &st) == 0) {
     // If fstat fails, then the file descriptor is invalid and we'll learn this
     // fact when Map() fails.
     inode_ = st.st_ino;
   }
 }
 SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only,
                            ProcessHandle process)
     : mapped_file_(handle.fd),
       memory_(NULL),
       read_only_(read_only),
       max_size_(0) {
   // We don't handle this case yet (note the ignored parameter); let's die if
   // someone comes calling.
   NOTREACHED();
 }
 SharedMemory::~SharedMemory() {
   Close();
 }
 // static
 bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle) {
   return handle.fd >= 0;
 }
 // static
 SharedMemoryHandle SharedMemory::NULLHandle() {
   return SharedMemoryHandle();
 }
 bool SharedMemory::Create(const std::string &cname, bool read_only,
                           bool open_existing, size_t size) {
   read_only_ = read_only;
   std::wstring name = UTF8ToWide(cname);
   int posix_flags = 0;
   posix_flags |= read_only ? O_RDONLY : O_RDWR;
   if (!open_existing || mapped_file_ <= 0)
     posix_flags |= O_CREAT;
   if (!CreateOrOpen(name, posix_flags, size))
     return false;
   max_size_ = size;
   return true;
 }
 // Our current implementation of shmem is with mmap()ing of files.
 // These files need to be deleted explicitly.
 // In practice this call is only needed for unit tests.
 bool SharedMemory::Delete(const std::wstring& name) {
   std::wstring mem_filename;
   if (FilenameForMemoryName(name, &mem_filename) == false)
     return false;
   FilePath path(WideToUTF8(mem_filename));
   if (file_util::PathExists(path)) {
     return file_util::Delete(path, false);
   }
   // Doesn't exist, so success.
   return true;
 }
 bool SharedMemory::Open(const std::wstring &name, bool read_only) {
   read_only_ = read_only;
   int posix_flags = 0;
   posix_flags |= read_only ? O_RDONLY : O_RDWR;
   return CreateOrOpen(name, posix_flags, 0);
 }
 // For the given shmem named |memname|, return a filename to mmap()
 // (and possibly create).  Modifies |filename|.  Return false on
 // error, or true of we are happy.
 bool SharedMemory::FilenameForMemoryName(const std::wstring &memname,
                                          std::wstring *filename) {
   std::wstring mem_filename;
   // mem_name will be used for a filename; make sure it doesn't
   // contain anything which will confuse us.
   DCHECK(memname.find_first_of(L"/") == std::string::npos);
   DCHECK(memname.find_first_of(L"\0") == std::string::npos);
   FilePath temp_dir;
   if (file_util::GetShmemTempDir(&temp_dir) == false)
     return false;
   mem_filename = UTF8ToWide(temp_dir.value());
   file_util::AppendToPath(&mem_filename, L"com.google.chrome.shmem." + memname);
   *filename = mem_filename;
   return true;
 }
 namespace {
 // A class to handle auto-closing of FILE*'s.
 class ScopedFILEClose {
  public:
   inline void operator()(FILE* x) const {
     if (x) {
       fclose(x);
     }
   }
 };
 typedef scoped_ptr_malloc<FILE, ScopedFILEClose> ScopedFILE;
 }
 // Chromium mostly only use the unique/private shmem as specified by
 // "name == L"". The exception is in the StatsTable.
 // TODO(jrg): there is no way to "clean up" all unused named shmem if
 // we restart from a crash.  (That isn't a new problem, but it is a problem.)
 // In case we want to delete it later, it may be useful to save the value
 // of mem_filename after FilenameForMemoryName().
 bool SharedMemory::CreateOrOpen(const std::wstring &name,
                                 int posix_flags, size_t size) {
   DCHECK(mapped_file_ == -1);
   ScopedFILE file_closer;
   FILE *fp;
   if (name == L"") {
     // It doesn't make sense to have a read-only private piece of shmem
     DCHECK(posix_flags & (O_RDWR | O_WRONLY));
     FilePath path;
     fp = file_util::CreateAndOpenTemporaryShmemFile(&path);
     // Deleting the file prevents anyone else from mapping it in
     // (making it private), and prevents the need for cleanup (once
     // the last fd is closed, it is truly freed).
     file_util::Delete(path, false);
   } else {
     std::wstring mem_filename;
     if (FilenameForMemoryName(name, &mem_filename) == false)
       return false;
     std::string mode;
     switch (posix_flags) {
       case (O_RDWR | O_CREAT):
         // Careful: "w+" will truncate if it already exists.
         mode = "a+";
         break;
       case O_RDWR:
         mode = "r+";
         break;
       case O_RDONLY:
         mode = "r";
         break;
       default:
         NOTIMPLEMENTED();
         break;
     }
     fp = file_util::OpenFile(mem_filename, mode.c_str());
   }
   if (fp == NULL)
     return false;
   file_closer.reset(fp);  // close when we go out of scope
   // Make sure the (new) file is the right size.
   // According to the man page, "Use of truncate() to extend a file is
   // not portable."
   if (size && (posix_flags & (O_RDWR | O_CREAT))) {
     // Get current size.
     struct stat stat;
     if (fstat(fileno(fp), &stat) != 0)
       return false;
     size_t current_size = stat.st_size;
     if (current_size != size) {
       if (ftruncate(fileno(fp), size) != 0)
         return false;
       if (fseeko(fp, size, SEEK_SET) != 0)
         return false;
     }
   }
   mapped_file_ = dup(fileno(fp));
   DCHECK(mapped_file_ >= 0);
   struct stat st;
   if (fstat(mapped_file_, &st))
     NOTREACHED();
   inode_ = st.st_ino;
   return true;
 }
 bool SharedMemory::Map(size_t bytes) {
   if (mapped_file_ == -1)
     return false;
   memory_ = mmap(NULL, bytes, PROT_READ | (read_only_ ? 0 : PROT_WRITE),
                  MAP_SHARED, mapped_file_, 0);
   if (memory_)
     max_size_ = bytes;
   bool mmap_succeeded = (memory_ != (void*)-1);
   DCHECK(mmap_succeeded) << "Call to mmap failed, errno=" << errno;
   return mmap_succeeded;
 }
 bool SharedMemory::Unmap() {
   if (memory_ == NULL)
     return false;
   munmap(memory_, max_size_);
   memory_ = NULL;
   max_size_ = 0;
   return true;
 }
 bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
                                         SharedMemoryHandle *new_handle,
                                         bool close_self) {
   const int new_fd = dup(mapped_file_);
   DCHECK(new_fd >= -1);
   new_handle->fd = new_fd;
   new_handle->auto_close = true;
   if (close_self)
     Close();
   return true;
 }
 void SharedMemory::Close() {
   Unmap();
   if (mapped_file_ > 0) {
     close(mapped_file_);
     mapped_file_ = -1;
   }
 }
 #ifdef ANDROID
 void SharedMemory::LockOrUnlockCommon(int function) {
   DCHECK(mapped_file_ >= 0);
   struct flock lockreq;
   lockreq.l_type = function;
   lockreq.l_whence = SEEK_SET;
   lockreq.l_start = 0;
   lockreq.l_len = 0;
   while (fcntl(mapped_file_, F_SETLKW, &lockreq) < 0) {
     if (errno == EINTR) {
       continue;
     } else if (errno == ENOLCK) {
       // temporary kernel resource exaustion
       PlatformThread::Sleep(500);
       continue;
     } else {
       NOTREACHED() << "lockf() failed."
                    << " function:" << function
                    << " fd:" << mapped_file_
                    << " errno:" << errno
                    << " msg:" << strerror(errno);
     }
   }
 }
 void SharedMemory::Lock() {
   LockOrUnlockCommon(F_WRLCK);
 }
 void SharedMemory::Unlock() {
   LockOrUnlockCommon(F_UNLCK);
 }
 #else
 void SharedMemory::LockOrUnlockCommon(int function) {
   DCHECK(mapped_file_ >= 0);
   while (lockf(mapped_file_, function, 0) < 0) {
     if (errno == EINTR) {
       continue;
     } else if (errno == ENOLCK) {
       // temporary kernel resource exaustion
       PlatformThread::Sleep(500);
       continue;
     } else {
       NOTREACHED() << "lockf() failed."
                    << " function:" << function
                    << " fd:" << mapped_file_
                    << " errno:" << errno
                    << " msg:" << strerror(errno);
     }
   }
 }
 void SharedMemory::Lock() {
   LockOrUnlockCommon(F_LOCK);
 }
 void SharedMemory::Unlock() {
   LockOrUnlockCommon(F_ULOCK);
 }
 #endif
 SharedMemoryHandle SharedMemory::handle() const {
   return FileDescriptor(mapped_file_, false);
 }
 }  // namespace base

The Tor Browser / annotate

ipc/chromium/src/base/shared_memory_posix.cc@6474c204b198 (annotated)

ipc/chromium/src/base/shared_memory_posix.cc