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// Copyright 2017 Google LLC
//
// 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 "internal/hwcaps.h"
#include <stdlib.h>
#include <string.h>
#include "cpu_features_macros.h"
#include "internal/filesystem.h"
#include "internal/string_view.h"
static bool IsSet(const uint32_t mask, const uint32_t value) {
if (mask == 0) return false;
return (value & mask) == mask;
}
bool CpuFeatures_IsHwCapsSet(const HardwareCapabilities hwcaps_mask,
const HardwareCapabilities hwcaps) {
return IsSet(hwcaps_mask.hwcaps, hwcaps.hwcaps) ||
IsSet(hwcaps_mask.hwcaps2, hwcaps.hwcaps2);
}
#ifdef CPU_FEATURES_TEST
// In test mode, hwcaps_for_testing will define the following functions.
HardwareCapabilities CpuFeatures_GetHardwareCapabilities(void);
const char* CpuFeatures_GetPlatformPointer(void);
const char* CpuFeatures_GetBasePlatformPointer(void);
#else
// Debug facilities
#if defined(NDEBUG)
#define D(...)
#else
#include <stdio.h>
#define D(...) \
do { \
printf(__VA_ARGS__); \
fflush(stdout); \
} while (0)
#endif
////////////////////////////////////////////////////////////////////////////////
// Implementation of GetElfHwcapFromGetauxval
////////////////////////////////////////////////////////////////////////////////
#define AT_HWCAP 16
#define AT_HWCAP2 26
#define AT_PLATFORM 15
#define AT_BASE_PLATFORM 24
#if 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 18.
//
// 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>
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;
}
const char *CpuFeatures_GetPlatformPointer(void) {
return (const char *)GetHardwareCapabilitiesFor(AT_PLATFORM);
}
const char *CpuFeatures_GetBasePlatformPointer(void) {
return (const char *)GetHardwareCapabilitiesFor(AT_BASE_PLATFORM);
}
#endif // CPU_FEATURES_TEST
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