1 // Copyright 2017 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.
4
5 #include "base/memory/shared_memory_handle.h"
6
7 #include <sys/mman.h>
8 #include <unistd.h>
9
10 #include "base/logging.h"
11 #include "base/posix/eintr_wrapper.h"
12 #include "base/posix/unix_domain_socket.h"
13 #include "base/unguessable_token.h"
14 #include "third_party/ashmem/ashmem.h"
15
16 namespace base {
17
GetAshmemRegionProtectionMask(int fd)18 static int GetAshmemRegionProtectionMask(int fd) {
19 int prot = ashmem_get_prot_region(fd);
20 if (prot < 0) {
21 DPLOG(ERROR) << "ashmem_get_prot_region";
22 return -1;
23 }
24 return prot;
25 }
26
27 SharedMemoryHandle::SharedMemoryHandle() = default;
28
SharedMemoryHandle(const base::FileDescriptor & file_descriptor,size_t size,const base::UnguessableToken & guid)29 SharedMemoryHandle::SharedMemoryHandle(
30 const base::FileDescriptor& file_descriptor,
31 size_t size,
32 const base::UnguessableToken& guid)
33 : guid_(guid), size_(size) {
34 DCHECK_GE(file_descriptor.fd, 0);
35 file_descriptor_ = file_descriptor;
36 }
37
38 // static
ImportHandle(int fd,size_t size)39 SharedMemoryHandle SharedMemoryHandle::ImportHandle(int fd, size_t size) {
40 SharedMemoryHandle handle;
41 handle.file_descriptor_.fd = fd;
42 handle.file_descriptor_.auto_close = false;
43 handle.guid_ = UnguessableToken::Create();
44 handle.size_ = size;
45 return handle;
46 }
47
GetHandle() const48 int SharedMemoryHandle::GetHandle() const {
49 DCHECK(IsValid());
50 return file_descriptor_.fd;
51 }
52
IsValid() const53 bool SharedMemoryHandle::IsValid() const {
54 return file_descriptor_.fd >= 0;
55 }
56
Close() const57 void SharedMemoryHandle::Close() const {
58 DCHECK(IsValid());
59 if (IGNORE_EINTR(close(file_descriptor_.fd)) < 0)
60 PLOG(ERROR) << "close";
61 }
62
Release()63 int SharedMemoryHandle::Release() {
64 int old_fd = file_descriptor_.fd;
65 file_descriptor_.fd = -1;
66 return old_fd;
67 }
68
Duplicate() const69 SharedMemoryHandle SharedMemoryHandle::Duplicate() const {
70 DCHECK(IsValid());
71 SharedMemoryHandle result;
72 int duped_handle = HANDLE_EINTR(dup(file_descriptor_.fd));
73 if (duped_handle >= 0) {
74 result = SharedMemoryHandle(FileDescriptor(duped_handle, true), GetSize(),
75 GetGUID());
76 if (IsReadOnly())
77 result.SetReadOnly();
78 }
79 return result;
80 }
81
SetOwnershipPassesToIPC(bool ownership_passes)82 void SharedMemoryHandle::SetOwnershipPassesToIPC(bool ownership_passes) {
83 file_descriptor_.auto_close = ownership_passes;
84 }
85
OwnershipPassesToIPC() const86 bool SharedMemoryHandle::OwnershipPassesToIPC() const {
87 return file_descriptor_.auto_close;
88 }
89
IsRegionReadOnly() const90 bool SharedMemoryHandle::IsRegionReadOnly() const {
91 int prot = GetAshmemRegionProtectionMask(file_descriptor_.fd);
92 return (prot >= 0 && (prot & PROT_WRITE) == 0);
93 }
94
SetRegionReadOnly() const95 bool SharedMemoryHandle::SetRegionReadOnly() const {
96 int fd = file_descriptor_.fd;
97 int prot = GetAshmemRegionProtectionMask(fd);
98 if (prot < 0)
99 return false;
100
101 if ((prot & PROT_WRITE) == 0) {
102 // Region is already read-only.
103 return true;
104 }
105
106 prot &= ~PROT_WRITE;
107 int ret = ashmem_set_prot_region(fd, prot);
108 if (ret != 0) {
109 DPLOG(ERROR) << "ashmem_set_prot_region";
110 return false;
111 }
112 return true;
113 }
114
115 } // namespace base
116