Mojo: Implement passing of shared buffers across processes on POSIX.

mojo/system/raw_shared_buffer_posix.cc

 // Copyright 2014 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 "mojo/system/raw_shared_buffer.h"
 
 #include <stdint.h>
 #include <stdio.h>  // For |fileno()|.
 #include <sys/mman.h>  // For |mmap()|/|munmap()|.
+#include <sys/stat.h>
 #include <sys/types.h>  // For |off_t|.
 #include <unistd.h>
 
 #include <limits>
 
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/sys_info.h"
 #include "base/threading/thread_restrictions.h"
 #include "mojo/embedder/platform_handle.h"
 
 // We assume that |size_t| and |off_t| (type for |ftruncate()|) fits in a
 // |uint64_t|.
 COMPILE_ASSERT(sizeof(size_t) <= sizeof(uint64_t), size_t_too_big);
 COMPILE_ASSERT(sizeof(off_t) <= sizeof(uint64_t), off_t_too_big);
 
 namespace mojo {
 namespace system {
 
 // RawSharedBuffer -------------------------------------------------------------
 
-bool RawSharedBuffer::InitNoLock() {
+bool RawSharedBuffer::Init() {
   DCHECK(!handle_.is_valid());
 
   base::ThreadRestrictions::ScopedAllowIO allow_io;
 
   if (static_cast<uint64_t>(num_bytes_) >
           static_cast<uint64_t>(std::numeric_limits<off_t>::max())) {
     return false;
   }
 
   // TODO(vtl): This is stupid. The implementation of
@@ skipping 29 matching lines @@
 
   if (HANDLE_EINTR(ftruncate(fd.get(), static_cast<off_t>(num_bytes_))) != 0) {
     PLOG(ERROR) << "ftruncate";
     return false;
   }
 
   handle_.reset(embedder::PlatformHandle(fd.release()));
   return true;
 }
 
-scoped_ptr<RawSharedBufferMapping> RawSharedBuffer::MapImplNoLock(
-    size_t offset,
-    size_t length) {
-  lock_.AssertAcquired();
+bool RawSharedBuffer::InitFromPlatformHandle(
+    embedder::ScopedPlatformHandle platform_handle) {
+  DCHECK(!handle_.is_valid());
 
+  if (static_cast<uint64_t>(num_bytes_) >
+          static_cast<uint64_t>(std::numeric_limits<off_t>::max())) {
+    return false;
+  }
+
+  struct stat sb = {};
+  // Note: |fstat()| isn't interruptible.
+  if (fstat(platform_handle.get().fd, &sb) != 0) {
+    PLOG(ERROR) << "fstat";
+    return false;
+  }
+
+  if (!S_ISREG(sb.st_mode)) {
+    LOG(ERROR) << "Platform handle not to a regular file";
+    return false;
+  }
+
+  if (sb.st_size != static_cast<off_t>(num_bytes_)) {
+    LOG(ERROR) << "Shared memory file has the wrong size";
+    return false;
+  }
+
+  // TODO(vtl): More checks?
+
+  handle_ = platform_handle.Pass();
+  return true;
+}
+
+scoped_ptr<RawSharedBufferMapping> RawSharedBuffer::MapImpl(size_t offset,
+                                                            size_t length) {
   size_t offset_rounding = offset % base::SysInfo::VMAllocationGranularity();
   size_t real_offset = offset - offset_rounding;
   size_t real_length = length + offset_rounding;
 
   // This should hold (since we checked |num_bytes| versus the maximum value of
   // |off_t| on creation, but it never hurts to be paranoid.
   DCHECK_LE(static_cast<uint64_t>(real_offset),
             static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
 
   void* real_base = mmap(NULL, real_length, PROT_READ | PROT_WRITE, MAP_SHARED,
@@ skipping 12 matching lines @@
 
 // RawSharedBufferMapping ------------------------------------------------------
 
 void RawSharedBufferMapping::Unmap() {
   int result = munmap(real_base_, real_length_);
   PLOG_IF(ERROR, result != 0) << "munmap";
 }
 
 }  // namespace system
 }  // namespace mojo