Resurrect POSIX shared memory support on mac

mojo/edk/embedder/platform_shared_buffer.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/edk/embedder/platform_shared_buffer.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 15 matching lines @@
 namespace {
 
 // Takes ownership of |memory_handle|.
 ScopedPlatformHandle SharedMemoryToPlatformHandle(
     base::SharedMemoryHandle memory_handle) {
 #if defined(OS_POSIX) && !(defined(OS_MACOSX) && !defined(OS_IOS))
   return ScopedPlatformHandle(PlatformHandle(memory_handle.fd));
 #elif defined(OS_WIN)
   return ScopedPlatformHandle(PlatformHandle(memory_handle.GetHandle()));
 #else
-  return ScopedPlatformHandle(PlatformHandle(memory_handle.GetMemoryObject()));
+  if (memory_handle.GetType() == base::SharedMemoryHandle::MACH) {

[erikchen, 2016/12/06 17:32:32]

we never pass posix SHM on Mac over Chrome/Mojo IPC, so the only changes to
mojo/ should be adding a bunch of NOTREACHED(), or perhaps even CHECK(false) to
make sure this doesn't happen in the wild.

+    return ScopedPlatformHandle(PlatformHandle(
+        memory_handle.GetMemoryObject()));
+  } else {
+    DCHECK(memory_handle.GetType() == base::SharedMemoryHandle::POSIX);
+    return ScopedPlatformHandle(PlatformHandle(
+        memory_handle.GetFileDescriptor().fd));
+  }
 #endif
 }
 
 }  // namespace
 
 // static
 PlatformSharedBuffer* PlatformSharedBuffer::Create(size_t num_bytes) {
   DCHECK_GT(num_bytes, 0u);
 
   PlatformSharedBuffer* rv = new PlatformSharedBuffer(num_bytes, false);
@@ skipping 172 matching lines @@
 PlatformSharedBuffer::~PlatformSharedBuffer() {}
 
 bool PlatformSharedBuffer::Init() {
   DCHECK(!shared_memory_);
   DCHECK(!read_only_);
 
   base::SharedMemoryCreateOptions options;
   options.size = num_bytes_;
   // By default, we can share as read-only.
   options.share_read_only = true;
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  options.type = base::SharedMemoryHandle::MACH;
+#endif
 
   shared_memory_.reset(new base::SharedMemory);
   return shared_memory_->Create(options);
 }
 
 bool PlatformSharedBuffer::InitFromPlatformHandle(
     ScopedPlatformHandle platform_handle) {
   DCHECK(!shared_memory_);
 
 #if defined(OS_WIN)
   base::SharedMemoryHandle handle(platform_handle.release().handle,
                                   base::GetCurrentProcId());
 #elif defined(OS_MACOSX) && !defined(OS_IOS)
   base::SharedMemoryHandle handle;
-  handle = base::SharedMemoryHandle(platform_handle.release().port, num_bytes_,
-                                    base::GetCurrentProcId());
+  if (platform_handle.get().type == PlatformHandle::Type::MACH) {
+    handle = base::SharedMemoryHandle(
+        platform_handle.release().port, num_bytes_, base::GetCurrentProcId());
+  } else {
+    handle = base::SharedMemoryHandle(platform_handle.release().handle, false);
+  }
 #else
   base::SharedMemoryHandle handle(platform_handle.release().handle, false);
 #endif
 
   shared_memory_.reset(new base::SharedMemory(handle, read_only_));
   return true;
 }
 
 bool PlatformSharedBuffer::InitFromPlatformHandlePair(
     ScopedPlatformHandle rw_platform_handle,
@@ skipping 61 matching lines @@
   base_ = static_cast<char*>(shared_memory_.memory()) + offset_rounding;
   return true;
 }
 
 void PlatformSharedBufferMapping::Unmap() {
   shared_memory_.Unmap();
 }
 
 }  // namespace edk
 }  // namespace mojo