Replace base::SharedMemory read-only methods with GetReadOnlyHandle.

base/memory/shared_memory_posix.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 <fcntl.h>
 #include <stddef.h>
 #include <sys/mman.h>
@@ skipping 15 matching lines @@
 #include "build/build_config.h"
 
 #if defined(OS_ANDROID)
 #include "base/os_compat_android.h"
 #include "third_party/ashmem/ashmem.h"
 #endif
 
 namespace base {
 
 SharedMemory::SharedMemory()
-    : readonly_mapped_file_(-1),
-      mapped_size_(0),
-      memory_(NULL),
-      read_only_(false),
-      requested_size_(0) {}
+    : mapped_size_(0), memory_(NULL), read_only_(false), requested_size_(0) {}
 
 SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
     : shm_(handle),
-      readonly_mapped_file_(-1),
+
       mapped_size_(0),
       memory_(NULL),
       read_only_(read_only),
       requested_size_(0) {}
 
 SharedMemory::~SharedMemory() {
   Unmap();
   Close();
 }
 
@@ skipping 111 matching lines @@
             "Invalid owner when opening existing shared memory file.";
         close(fd);
         return false;
       }
 
       // An existing file was opened, so its size should not be fixed.
       fix_size = false;
     }
 
     if (options.share_read_only) {
-      // Also open as readonly so that we can ShareReadOnlyToProcess.
+      // Also open as readonly so that we can GetReadOnlyHandle.
       readonly_fd.reset(HANDLE_EINTR(open(path.value().c_str(), O_RDONLY)));
       if (!readonly_fd.is_valid()) {
         DPLOG(ERROR) << "open(\"" << path.value() << "\", O_RDONLY) failed";
         close(fd);
         fd = -1;
         return false;
       }
     }
     if (fd >= 0) {
       // "a+" is always appropriate: if it's a new file, a+ is similar to w+.
@@ skipping 19 matching lines @@
       PLOG(ERROR) << "Unable to access(W_OK|X_OK) " << dir.value();
       if (dir.value() == "/dev/shm") {
         LOG(FATAL) << "This is frequently caused by incorrect permissions on "
                    << "/dev/shm.  Try 'sudo chmod 1777 /dev/shm' to fix.";
       }
     }
     return false;
   }
 
   int mapped_file = -1;
+  int readonly_mapped_file = -1;
   bool result = PrepareMapFile(std::move(fp), std::move(readonly_fd),
-                               &mapped_file, &readonly_mapped_file_);
+                               &mapped_file, &readonly_mapped_file);
   shm_ = SharedMemoryHandle::ImportHandle(mapped_file);
+  readonly_shm_ = SharedMemoryHandle::ImportHandle(readonly_mapped_file);
   return result;
 }
 
 // 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::string& name) {
   FilePath path;
   if (!FilePathForMemoryName(name, &path))
     return false;
@@ skipping 13 matching lines @@
   read_only_ = read_only;
 
   const char *mode = read_only ? "r" : "r+";
   ScopedFILE fp(base::OpenFile(path, mode));
   ScopedFD readonly_fd(HANDLE_EINTR(open(path.value().c_str(), O_RDONLY)));
   if (!readonly_fd.is_valid()) {
     DPLOG(ERROR) << "open(\"" << path.value() << "\", O_RDONLY) failed";
     return false;
   }
   int mapped_file = -1;
+  int readonly_mapped_file = -1;
   bool result = PrepareMapFile(std::move(fp), std::move(readonly_fd),
-                               &mapped_file, &readonly_mapped_file_);
+                               &mapped_file, &readonly_mapped_file);
   shm_ = SharedMemoryHandle::ImportHandle(mapped_file);
+  readonly_shm_ = SharedMemoryHandle::ImportHandle(readonly_mapped_file);
   return result;
 }
 #endif  // !defined(OS_ANDROID)
 
 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;
@@ skipping 52 matching lines @@
   memory_ = nullptr;
   mapped_size_ = 0;
   return handle_copy;
 }
 
 void SharedMemory::Close() {
   if (shm_.IsValid()) {
     shm_.Close();
     shm_ = SharedMemoryHandle();
   }
-  if (readonly_mapped_file_ > 0) {
-    if (IGNORE_EINTR(close(readonly_mapped_file_)) < 0)
-      PLOG(ERROR) << "close";
-    readonly_mapped_file_ = -1;
+  if (readonly_shm_.IsValid()) {
+    readonly_shm_.Close();
+    readonly_shm_ = SharedMemoryHandle();
   }
 }
 
 #if !defined(OS_ANDROID)
 // For the given shmem named |mem_name|, return a filename to mmap()
 // (and possibly create).  Modifies |filename|.  Return false on
 // error, or true of we are happy.
 bool SharedMemory::FilePathForMemoryName(const std::string& mem_name,
                                          FilePath* path) {
   // mem_name will be used for a filename; make sure it doesn't
   // contain anything which will confuse us.
   DCHECK_EQ(std::string::npos, mem_name.find('/'));
   DCHECK_EQ(std::string::npos, mem_name.find('\0'));
 
   FilePath temp_dir;
   if (!GetShmemTempDir(false, &temp_dir))
     return false;
 
 #if defined(GOOGLE_CHROME_BUILD)
   std::string name_base = std::string("com.google.Chrome");
 #else
   std::string name_base = std::string("org.chromium.Chromium");
 #endif
   *path = temp_dir.AppendASCII(name_base + ".shmem." + mem_name);
   return true;
 }
 #endif  // !defined(OS_ANDROID)
 
+SharedMemoryHandle SharedMemory::GetReadOnlyHandle() {
+  CHECK(readonly_shm_.IsValid());
+  return readonly_shm_.Duplicate();
+}
+
 bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
                                         SharedMemoryHandle* new_handle,
-                                        bool close_self,
-                                        ShareMode share_mode) {
-  int handle_to_dup = -1;
-  switch(share_mode) {
-    case SHARE_CURRENT_MODE:
-      handle_to_dup = shm_.GetHandle();
-      break;
-    case SHARE_READONLY:
-      // 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_;
-      break;
-  }
-
-  const int new_fd = HANDLE_EINTR(dup(handle_to_dup));
-  if (new_fd < 0) {
-    if (close_self) {
-      Unmap();
-      Close();
-    }
-    DPLOG(ERROR) << "dup() failed.";
-    return false;
-  }
-
-  new_handle->SetHandle(new_fd);
-  new_handle->SetOwnershipPassesToIPC(true);
-
+                                        bool close_self) {
+  *new_handle = shm_.Duplicate();
   if (close_self) {
     Unmap();
     Close();
   }
-
-  return true;
+  return new_handle->IsValid();
 }
 
 bool SharedMemory::GetUniqueId(SharedMemory::UniqueId* id) const {
   // This function is called just after mmap. fstat is a system call that might
   // cause I/O. It's safe to call fstat here because mmap for shared memory is
   // called in two cases:
   // 1) To handle file-mapped memory
   // 2) To handle annonymous shared memory
   // In 1), I/O is already permitted. In 2), the backend is on page cache and
   // fstat doesn't cause I/O access to the disk. See the discussion at
   // crbug.com/604726#c41.
   base::ThreadRestrictions::ScopedAllowIO allow_io;
   struct stat file_stat;
   if (HANDLE_EINTR(
           ::fstat(static_cast<int>(handle().GetHandle()), &file_stat)) != 0)
     return false;
   id->first = file_stat.st_dev;
   id->second = file_stat.st_ino;
   return true;
 }
 
 }  // namespace base