Add POSIX shared memory support for Mac

base/memory/shared_memory_mac.cc

 // Copyright (c) 2012 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/memory/shared_memory.h"
 
+#include <errno.h>
 #include <mach/mach_vm.h>
+#include <stddef.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <unistd.h>
 
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
-#include "base/mac/foundation_util.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_mach_vm.h"
+#include "base/memory/shared_memory_helper.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/posix/eintr_wrapper.h"
+#include "base/posix/safe_strerror.h"
 #include "base/process/process_metrics.h"
-#include "base/profiler/scoped_tracker.h"
 #include "base/scoped_generic.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 
+#if defined(OS_MACOSX)
+#include "base/mac/foundation_util.h"
+#endif  // OS_MACOSX
+
 namespace base {
 
 namespace {
 
 // Returns whether the operation succeeded.
 // |new_handle| is an output variable, populated on success. The caller takes
 // ownership of the underlying memory object.
 // |handle| is the handle to copy.
 // If |handle| is already mapped, |mapped_addr| is its mapped location.
 // Otherwise, |mapped_addr| should be |nullptr|.
@@ skipping 30 matching lines @@
   if (kr != KERN_SUCCESS)
     return false;
 
   *new_handle = SharedMemoryHandle(named_right, size, base::GetCurrentProcId());
   return true;
 }
 
 }  // namespace
 
 SharedMemory::SharedMemory()
-    : mapped_size_(0), memory_(NULL), read_only_(false), requested_size_(0) {}
+    : mapped_memory_mechanism_(SharedMemoryHandle::MACH),
+      readonly_mapped_file_(-1),
+      mapped_size_(0),
+      memory_(NULL),
+      read_only_(false),
+      requested_size_(0) {}
 
 SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
     : shm_(handle),
+      mapped_memory_mechanism_(SharedMemoryHandle::POSIX),
+      readonly_mapped_file_(-1),
       mapped_size_(0),
       memory_(NULL),
       read_only_(read_only),
       requested_size_(0) {}
 
 SharedMemory::~SharedMemory() {
   Unmap();
   Close();
 }
 
 // static
 bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle) {
   return handle.IsValid();
 }
 
 // static
 SharedMemoryHandle SharedMemory::NULLHandle() {
   return SharedMemoryHandle();
 }
 
 // static
 void SharedMemory::CloseHandle(const SharedMemoryHandle& handle) {
   handle.Close();
 }
 
 // static
 size_t SharedMemory::GetHandleLimit() {
-  // This should be effectively unlimited on OS X.
-  return 10000;
+  return GetMaxFds();
 }
 
 // static
 SharedMemoryHandle SharedMemory::DuplicateHandle(
     const SharedMemoryHandle& handle) {
   return handle.Duplicate();
 }
 
+// static
+int SharedMemory::GetFdFromSharedMemoryHandle(
+    const SharedMemoryHandle& handle) {
+  return handle.file_descriptor_.fd;
+}
+
 bool SharedMemory::CreateAndMapAnonymous(size_t size) {
   return CreateAnonymous(size) && Map(size);
 }
 
 // static
 bool SharedMemory::GetSizeFromSharedMemoryHandle(
     const SharedMemoryHandle& handle,
     size_t* size) {
   return handle.GetSize(size);
 }
 
 // Chromium mostly only uses the unique/private shmem as specified by
 // "name == L"". The exception is in the StatsTable.
 bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
-  // TODO(erikchen): Remove ScopedTracker below once http://crbug.com/466437
-  // is fixed.
-  tracked_objects::ScopedTracker tracking_profile1(
-      FROM_HERE_WITH_EXPLICIT_FUNCTION(
-          "466437 SharedMemory::Create::Start"));
   DCHECK(!shm_.IsValid());
   if (options.size == 0) return false;
 
   if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
     return false;
 
-  shm_ = SharedMemoryHandle(options.size);
+  if (options.type == SharedMemoryHandle::MACH) {
+    shm_ = SharedMemoryHandle(options.size);
+    requested_size_ = options.size;
+    return shm_.IsValid();
+  }
+
+  // This function theoretically can block on the disk. Both profiling of real
+  // users and local instrumentation shows that this is a real problem.
+  // https://code.google.com/p/chromium/issues/detail?id=466437
+  base::ThreadRestrictions::ScopedAllowIO allow_io;
+
+  ScopedFILE fp;
+  ScopedFD readonly_fd;
+
+  FilePath path;
+  bool result = CreateAnonymousSharedMemory(options, &fp, &readonly_fd, &path);
+  if (!result)
+    return false;
+
+  if (!fp) {
+    PLOG(ERROR) << "Creating shared memory in " << path.value() << " failed";
+    return false;
+  }
+
+  // Get current size.
+  struct stat stat;
+  if (fstat(fileno(fp.get()), &stat) != 0)
+    return false;
+  const size_t current_size = stat.st_size;
+  if (current_size != options.size) {
+    if (HANDLE_EINTR(ftruncate(fileno(fp.get()), options.size)) != 0)
+      return false;
+  }
   requested_size_ = options.size;
-  return shm_.IsValid();
+
+  int mapped_file = -1;
+  result = PrepareMapFile(std::move(fp), std::move(readonly_fd), &mapped_file,
+                          &readonly_mapped_file_);

[erikchen, 2016/12/08 21:33:34]

Do we still need readonly_mapped_file_? 

[lawrencewu, 2016/12/08 23:06:30]

I think so -- we're sharing the fd as readonly:
https://cs.chromium.org/chromium/src/base/metrics/field_trial.cc?q=field_tria...

so actually readonly_mapped_file is the field getting populated.

+
+  shm_ = SharedMemoryHandle(FileDescriptor(mapped_file, false));
+  return result;
 }
 
 bool SharedMemory::MapAt(off_t offset, size_t bytes) {
   if (!shm_.IsValid())
     return false;
   if (bytes > static_cast<size_t>(std::numeric_limits<int>::max()))
     return false;
   if (memory_)
     return false;
 
   bool success = shm_.MapAt(offset, bytes, &memory_, read_only_);
   if (success) {
     mapped_size_ = bytes;
     DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
                       (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
+    mapped_memory_mechanism_ = shm_.type_;
   } else {
     memory_ = NULL;
   }
 
   return success;
 }
 
 bool SharedMemory::Unmap() {
   if (memory_ == NULL)
     return false;
 
-  mach_vm_deallocate(mach_task_self(),
-                     reinterpret_cast<mach_vm_address_t>(memory_),
-                     mapped_size_);
+  switch (mapped_memory_mechanism_) {
+    case SharedMemoryHandle::POSIX:
+      munmap(memory_, mapped_size_);
+      break;
+    case SharedMemoryHandle::MACH:
+      mach_vm_deallocate(mach_task_self(),
+                         reinterpret_cast<mach_vm_address_t>(memory_),
+                         mapped_size_);
+      break;
+  }
+
   memory_ = NULL;
   mapped_size_ = 0;
   return true;
 }
 
 SharedMemoryHandle SharedMemory::handle() const {
-  return shm_;
+  switch (shm_.type_) {
+    case SharedMemoryHandle::POSIX:
+      return SharedMemoryHandle(
+          FileDescriptor(shm_.file_descriptor_.fd, false));
+    case SharedMemoryHandle::MACH:
+      return shm_;
+  }
 }
 
 SharedMemoryHandle SharedMemory::TakeHandle() {
   SharedMemoryHandle dup = DuplicateHandle(handle());
   Close();
   return dup;
 }
 
 void SharedMemory::Close() {
   shm_.Close();
   shm_ = SharedMemoryHandle();
+  if (shm_.type_ == SharedMemoryHandle::POSIX) {
+    if (readonly_mapped_file_ > 0) {
+      if (IGNORE_EINTR(close(readonly_mapped_file_)) < 0)
+        PLOG(ERROR) << "close";
+      readonly_mapped_file_ = -1;
+    }
+  }
 }
 
 bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
                                         SharedMemoryHandle* new_handle,
                                         bool close_self,
                                         ShareMode share_mode) {
-  DCHECK(shm_.IsValid());
+  if (shm_.type_ == SharedMemoryHandle::MACH) {
+    DCHECK(shm_.IsValid());
 
-  bool success = false;
+    bool success = false;
+    switch (share_mode) {
+      case SHARE_CURRENT_MODE:
+        *new_handle = shm_.Duplicate();
+        success = true;
+        break;
+      case SHARE_READONLY:
+        success = MakeMachSharedMemoryHandleReadOnly(new_handle, shm_, memory_);
+        break;
+    }
+
+    if (success)
+      new_handle->SetOwnershipPassesToIPC(true);
+
+    if (close_self) {
+      Unmap();
+      Close();
+    }
+
+    return success;
+  }
+
+  int handle_to_dup = -1;
   switch (share_mode) {
     case SHARE_CURRENT_MODE:
-      *new_handle = shm_.Duplicate();
-      success = true;
+      handle_to_dup = shm_.file_descriptor_.fd;
       break;
     case SHARE_READONLY:
-      success = MakeMachSharedMemoryHandleReadOnly(new_handle, shm_, memory_);
+      // We could imagine re-opening the file from /dev/fd, but that can't make
+      // it readonly on Mac: https://codereview.chromium.org/27265002/#msg10
+      CHECK_GE(readonly_mapped_file_, 0);
+      handle_to_dup = readonly_mapped_file_;

[erikchen, 2016/12/08 21:33:34]

Do we still need both "readonly_mapped_file_" and "shm_.file_descriptor_"? Seems
redundant for your use case?

[lawrencewu, 2016/12/08 23:06:30]

I think so -- the browser process uses readonly_mapped_file_, while the child
process will still use shm_.file_descriptor_.

       break;
   }
 
-  if (success)
-    new_handle->SetOwnershipPassesToIPC(true);
+  const int new_fd = HANDLE_EINTR(dup(handle_to_dup));
+  if (new_fd < 0) {
+    DPLOG(ERROR) << "dup() failed.";
+    if (close_self) {

[erikchen, 2016/12/08 21:33:34]

This close_self logic is duplicated in three places in this function. Please
refactor.

[lawrencewu, 2016/12/08 23:06:30]

Done.

[erikchen, 2016/12/09 00:30:38]

Perhaps you could pull all the logic for handle duplication into a separate
method, and then in this method.

bool success = Duplicate handle().
if (close_self) {
  Unmap();
  Close();
}
return success;

This avoids a common type of error where we return from the function but forget
to call UnmapAndCloseIfNeeded.

[lawrencewu, 2016/12/09 15:21:39]

Yeah, that is cleaner. Done.

+      Unmap();
+      Close();
+    }
+    return false;
+  }
+
+  new_handle->file_descriptor_.fd = new_fd;
+  new_handle->type_ = SharedMemoryHandle::POSIX;
 
   if (close_self) {
     Unmap();
     Close();
   }
 
-  return success;
+  return true;
 }
 
 }  // namespace base