1 /*
2 * Copyright (C) 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "membarrier.h"
18
19 #include <errno.h>
20 #include <stdio.h>
21
22 #if !defined(_WIN32)
23 #include <sys/syscall.h>
24 #include <sys/utsname.h>
25 #include <unistd.h>
26 #endif
27 #include "macros.h"
28
29 #if defined(__BIONIC__)
30
31 #include <atomic>
32 #include <linux/membarrier.h>
33
34 #define CHECK_MEMBARRIER_CMD(art_value, membarrier_value) \
35 static_assert(static_cast<int>(art_value) == (membarrier_value), "Bad value for " # art_value)
36 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kQuery, MEMBARRIER_CMD_QUERY);
37 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kGlobal, MEMBARRIER_CMD_SHARED);
38 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED);
39 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kRegisterPrivateExpedited,
40 MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED);
41 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED);
42 #undef CHECK_MEMBARRIER_CMD
43
44 #endif // __BIONIC
45
46 namespace art {
47
48 #if defined(__NR_membarrier)
49
membarrier(MembarrierCommand command)50 int membarrier(MembarrierCommand command) {
51 // Check kernel version supports membarrier(2).
52 static constexpr int kRequiredMajor = 4;
53 static constexpr int kRequiredMinor = 16;
54 struct utsname uts;
55 int major, minor;
56 if (uname(&uts) != 0 ||
57 strcmp(uts.sysname, "Linux") != 0 ||
58 sscanf(uts.release, "%d.%d", &major, &minor) != 2 ||
59 (major < kRequiredMajor || (major == kRequiredMajor && minor < kRequiredMinor))) {
60 errno = ENOSYS;
61 return -1;
62 }
63 #if defined(__BIONIC__)
64 // Avoid calling membarrier on older Android versions where membarrier may be barred by secomp
65 // causing the current process to be killed. The probing here could be considered expensive so
66 // endeavour not to repeat too often.
67 static int api_level = android_get_device_api_level();
68 if (api_level < __ANDROID_API_Q__) {
69 errno = ENOSYS;
70 return -1;
71 }
72 #endif // __BIONIC__
73 return syscall(__NR_membarrier, static_cast<int>(command), 0);
74 }
75
76 #else // __NR_membarrier
77
78 int membarrier(MembarrierCommand command ATTRIBUTE_UNUSED) {
79 // In principle this could be supported on linux, but Android's prebuilt glibc does not include
80 // the system call number defintions (b/111199492).
81 errno = ENOSYS;
82 return -1;
83 }
84
85 #endif // __NR_membarrier
86
87 } // namespace art
88