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 21 #if !defined(_WIN32) 22 #include <sys/syscall.h> 23 #include <unistd.h> 24 #endif 25 #include "macros.h" 26 27 #if defined(__BIONIC__) 28 29 #include <atomic> 30 #include <linux/membarrier.h> 31 32 #define CHECK_MEMBARRIER_CMD(art_value, membarrier_value) \ 33 static_assert(static_cast<int>(art_value) == (membarrier_value), "Bad value for " # art_value) 34 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kQuery, MEMBARRIER_CMD_QUERY); 35 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kGlobal, MEMBARRIER_CMD_SHARED); 36 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED); 37 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kRegisterPrivateExpedited, 38 MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED); 39 CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED); 40 #undef CHECK_MEMBARRIER_CMD 41 42 #endif // __BIONIC 43 44 namespace art { 45 46 #if defined(__NR_membarrier) 47 48 int membarrier(MembarrierCommand command) { 49 #if defined(__BIONIC__) 50 // Avoid calling membarrier on older Android versions where membarrier may be barred by secomp 51 // causing the current process to be killed. The probing here could be considered expensive so 52 // endeavour not to repeat too often. 53 static int api_level = android_get_device_api_level(); 54 if (api_level < __ANDROID_API_Q__) { 55 errno = ENOSYS; 56 return -1; 57 } 58 #endif // __BIONIC__ 59 return syscall(__NR_membarrier, static_cast<int>(command), 0); 60 } 61 62 #else // __NR_membarrier 63 64 int membarrier(MembarrierCommand command ATTRIBUTE_UNUSED) { 65 // In principle this could be supported on linux, but Android's prebuilt glibc does not include 66 // the system call number defintions (b/111199492). 67 errno = ENOSYS; 68 return -1; 69 } 70 71 #endif // __NR_membarrier 72 73 } // namespace art 74
