1 // Copyright 2014 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #include "mojo/system/raw_shared_buffer.h"
8 #include <stdio.h> // For |fileno()|.
9 #include <sys/mman.h> // For |mmap()|/|munmap()|.
10 #include <sys/types.h> // For |off_t|.
15 #include "base/file_util.h"
16 #include "base/files/file_path.h"
17 #include "base/files/scoped_file.h"
18 #include "base/logging.h"
19 #include "base/macros.h"
20 #include "base/posix/eintr_wrapper.h"
21 #include "base/sys_info.h"
22 #include "base/threading/thread_restrictions.h"
23 #include "mojo/embedder/platform_handle.h"
25 // We assume that |size_t| and |off_t| (type for |ftruncate()|) fits in a
27 COMPILE_ASSERT(sizeof(size_t) <= sizeof(uint64_t), size_t_too_big);
28 COMPILE_ASSERT(sizeof(off_t) <= sizeof(uint64_t), off_t_too_big);
33 // RawSharedBuffer -------------------------------------------------------------
35 bool RawSharedBuffer::InitNoLock() {
36 DCHECK(!handle_.is_valid());
38 base::ThreadRestrictions::ScopedAllowIO allow_io;
40 if (static_cast<uint64_t>(num_bytes_) >
41 static_cast<uint64_t>(std::numeric_limits<off_t>::max())) {
45 // TODO(vtl): This is stupid. The implementation of
46 // |CreateAndOpenTemporaryFileInDir()| starts with an FD, |fdopen()|s to get a
47 // |FILE*|, and then we have to |dup(fileno(fp))| to get back to an FD that we
48 // can own. (base/memory/shared_memory_posix.cc does this too, with more
49 // |fstat()|s thrown in for good measure.)
50 base::FilePath shared_buffer_dir;
51 if (!base::GetShmemTempDir(false, &shared_buffer_dir)) {
52 LOG(ERROR) << "Failed to get temporary directory for shared memory";
55 base::FilePath shared_buffer_file;
56 base::ScopedFILE fp(base::CreateAndOpenTemporaryFileInDir(
57 shared_buffer_dir, &shared_buffer_file));
59 LOG(ERROR) << "Failed to create/open temporary file for shared memory";
62 // Note: |unlink()| is not interruptible.
63 if (unlink(shared_buffer_file.value().c_str()) != 0) {
64 PLOG(WARNING) << "unlink";
65 // This isn't "fatal" (e.g., someone else may have unlinked the file first),
66 // so we may as well continue.
69 // Note: |dup()| is not interruptible (but |dup2()|/|dup3()| are).
70 base::ScopedFD fd(dup(fileno(fp.get())));
76 if (HANDLE_EINTR(ftruncate(fd.get(), static_cast<off_t>(num_bytes_))) != 0) {
77 PLOG(ERROR) << "ftruncate";
81 handle_.reset(embedder::PlatformHandle(fd.release()));
85 scoped_ptr<RawSharedBufferMapping> RawSharedBuffer::MapImplNoLock(
88 lock_.AssertAcquired();
90 size_t offset_rounding = offset % base::SysInfo::VMAllocationGranularity();
91 size_t real_offset = offset - offset_rounding;
92 size_t real_length = length + offset_rounding;
94 // This should hold (since we checked |num_bytes| versus the maximum value of
95 // |off_t| on creation, but it never hurts to be paranoid.
96 DCHECK_LE(static_cast<uint64_t>(real_offset),
97 static_cast<uint64_t>(std::numeric_limits<off_t>::max()));
99 void* real_base = mmap(NULL, real_length, PROT_READ | PROT_WRITE, MAP_SHARED,
100 handle_.get().fd, static_cast<off_t>(real_offset));
101 // |mmap()| should return |MAP_FAILED| (a.k.a. -1) on error. But it shouldn't
102 // return null either.
103 if (real_base == MAP_FAILED || !real_base) {
104 PLOG(ERROR) << "mmap";
105 return scoped_ptr<RawSharedBufferMapping>();
108 void* base = static_cast<char*>(real_base) + offset_rounding;
109 return make_scoped_ptr(
110 new RawSharedBufferMapping(base, length, real_base, real_length));
113 // RawSharedBufferMapping ------------------------------------------------------
115 void RawSharedBufferMapping::Unmap() {
116 int result = munmap(real_base_, real_length_);
117 PLOG_IF(ERROR, result != 0) << "munmap";
120 } // namespace system