| // Copyright 2017 Google Inc. |
| // |
| // 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 <stdlib.h> |
| #include <string.h> |
| |
| #include "cpu_features_macros.h" |
| #include "internal/filesystem.h" |
| #include "internal/hwcaps.h" |
| #include "internal/string_view.h" |
| |
| #if defined(NDEBUG) |
| #define D(...) |
| #else |
| #include <stdio.h> |
| #define D(...) \ |
| do { \ |
| printf(__VA_ARGS__); \ |
| fflush(stdout); \ |
| } while (0) |
| #endif |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // Implementation of GetElfHwcapFromGetauxval |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| #if defined(CPU_FEATURES_MOCK_GET_ELF_HWCAP_FROM_GETAUXVAL) |
| // Implementation will be provided by test/hwcaps_for_testing.cc. |
| #elif defined(HAVE_STRONG_GETAUXVAL) |
| #include <sys/auxv.h> |
| static unsigned long GetElfHwcapFromGetauxval(uint32_t hwcap_type) { |
| return getauxval(hwcap_type); |
| } |
| #elif defined(HAVE_DLFCN_H) |
| // On Android we probe the system's C library for a 'getauxval' function and |
| // call it if it exits, or return 0 for failure. This function is available |
| // since API level 20. |
| // |
| // This code does *NOT* check for '__ANDROID_API__ >= 20' to support the edge |
| // case where some NDK developers use headers for a platform that is newer than |
| // the one really targetted by their application. This is typically done to use |
| // newer native APIs only when running on more recent Android versions, and |
| // requires careful symbol management. |
| // |
| // Note that getauxval() can't really be re-implemented here, because its |
| // implementation does not parse /proc/self/auxv. Instead it depends on values |
| // that are passed by the kernel at process-init time to the C runtime |
| // initialization layer. |
| |
| #include <dlfcn.h> |
| #define AT_HWCAP 16 |
| #define AT_HWCAP2 26 |
| #define AT_PLATFORM 15 |
| #define AT_BASE_PLATFORM 24 |
| |
| typedef unsigned long getauxval_func_t(unsigned long); |
| |
| static uint32_t GetElfHwcapFromGetauxval(uint32_t hwcap_type) { |
| uint32_t ret = 0; |
| void* libc_handle = NULL; |
| getauxval_func_t* func = NULL; |
| |
| dlerror(); // Cleaning error state before calling dlopen. |
| libc_handle = dlopen("libc.so", RTLD_NOW); |
| if (!libc_handle) { |
| D("Could not dlopen() C library: %s\n", dlerror()); |
| return 0; |
| } |
| func = (getauxval_func_t*)dlsym(libc_handle, "getauxval"); |
| if (!func) { |
| D("Could not find getauxval() in C library\n"); |
| } else { |
| // Note: getauxval() returns 0 on failure. Doesn't touch errno. |
| ret = (uint32_t)(*func)(hwcap_type); |
| } |
| dlclose(libc_handle); |
| return ret; |
| } |
| #else |
| #error "This platform does not provide hardware capabilities." |
| #endif |
| |
| // Implementation of GetHardwareCapabilities for OS that provide |
| // GetElfHwcapFromGetauxval(). |
| |
| // Fallback when getauxval is not available, retrieves hwcaps from |
| // "/proc/self/auxv". |
| static uint32_t GetElfHwcapFromProcSelfAuxv(uint32_t hwcap_type) { |
| struct { |
| uint32_t tag; |
| uint32_t value; |
| } entry; |
| uint32_t result = 0; |
| const char filepath[] = "/proc/self/auxv"; |
| const int fd = CpuFeatures_OpenFile(filepath); |
| if (fd < 0) { |
| D("Could not open %s\n", filepath); |
| return 0; |
| } |
| for (;;) { |
| const int ret = CpuFeatures_ReadFile(fd, (char*)&entry, sizeof entry); |
| if (ret < 0) { |
| D("Error while reading %s\n", filepath); |
| break; |
| } |
| // Detect end of list. |
| if (ret == 0 || (entry.tag == 0 && entry.value == 0)) { |
| break; |
| } |
| if (entry.tag == hwcap_type) { |
| result = entry.value; |
| break; |
| } |
| } |
| CpuFeatures_CloseFile(fd); |
| return result; |
| } |
| |
| // Retrieves hardware capabilities by first trying to call getauxval, if not |
| // available falls back to reading "/proc/self/auxv". |
| static unsigned long GetHardwareCapabilitiesFor(uint32_t type) { |
| unsigned long hwcaps = GetElfHwcapFromGetauxval(type); |
| if (!hwcaps) { |
| D("Parsing /proc/self/auxv to extract ELF hwcaps!\n"); |
| hwcaps = GetElfHwcapFromProcSelfAuxv(type); |
| } |
| return hwcaps; |
| } |
| |
| HardwareCapabilities CpuFeatures_GetHardwareCapabilities(void) { |
| HardwareCapabilities capabilities; |
| capabilities.hwcaps = GetHardwareCapabilitiesFor(AT_HWCAP); |
| capabilities.hwcaps2 = GetHardwareCapabilitiesFor(AT_HWCAP2); |
| return capabilities; |
| } |
| |
| PlatformType kEmptyPlatformType; |
| |
| PlatformType CpuFeatures_GetPlatformType(void) { |
| PlatformType type = kEmptyPlatformType; |
| char *platform = (char *)GetHardwareCapabilitiesFor(AT_PLATFORM); |
| char *base_platform = (char *)GetHardwareCapabilitiesFor(AT_BASE_PLATFORM); |
| |
| if (platform != NULL) |
| CpuFeatures_StringView_CopyString(str(platform), type.platform, |
| sizeof(type.platform)); |
| if (base_platform != NULL) |
| CpuFeatures_StringView_CopyString(str(base_platform), type.base_platform, |
| sizeof(type.base_platform)); |
| return type; |
| } |