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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "membarrier.h"
#include <errno.h>
#include <stdio.h>
#include <cstring>
#if !defined(_WIN32)
#include <sys/syscall.h>
#include <sys/utsname.h>
#include <unistd.h>
#endif
#include "macros.h"
#if defined(__BIONIC__)
#include <atomic>
#include <linux/membarrier.h>
#define CHECK_MEMBARRIER_CMD(art_value, membarrier_value) \
static_assert(static_cast<int>(art_value) == (membarrier_value), "Bad value for " # art_value)
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kQuery, MEMBARRIER_CMD_QUERY);
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kGlobal, MEMBARRIER_CMD_SHARED);
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED);
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kRegisterPrivateExpedited,
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED);
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED);
#undef CHECK_MEMBARRIER_CMD
#endif // __BIONIC
namespace art {
#if defined(__NR_membarrier)
int membarrier(MembarrierCommand command) {
// Check kernel version supports membarrier(2).
static constexpr int kRequiredMajor = 4;
static constexpr int kRequiredMinor = 16;
struct utsname uts;
int major, minor;
if (uname(&uts) != 0 ||
strcmp(uts.sysname, "Linux") != 0 ||
sscanf(uts.release, "%d.%d", &major, &minor) != 2 ||
(major < kRequiredMajor || (major == kRequiredMajor && minor < kRequiredMinor))) {
errno = ENOSYS;
return -1;
}
#if defined(__BIONIC__)
// Avoid calling membarrier on older Android versions where membarrier may be barred by secomp
// causing the current process to be killed. The probing here could be considered expensive so
// endeavour not to repeat too often.
static int api_level = android_get_device_api_level();
if (api_level < __ANDROID_API_Q__) {
errno = ENOSYS;
return -1;
}
#endif // __BIONIC__
return syscall(__NR_membarrier, static_cast<int>(command), 0);
}
#else // __NR_membarrier
int membarrier(MembarrierCommand command ATTRIBUTE_UNUSED) {
// In principle this could be supported on linux, but Android's prebuilt glibc does not include
// the system call number defintions (b/111199492).
errno = ENOSYS;
return -1;
}
#endif // __NR_membarrier
} // namespace art
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