mirror of https://github.com/gnss-sdr/gnss-sdr
170 lines
5.2 KiB
C
170 lines
5.2 KiB
C
// SPDX-FileCopyrightText: 2017 Google Inc.
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// SPDX-License-Identifier: Apache-2.0
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#include "internal/hwcaps.h"
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#include "cpu_features_macros.h"
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#include "internal/filesystem.h"
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#include "internal/string_view.h"
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#include <stdlib.h>
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#include <string.h>
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#if defined(NDEBUG)
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#define D(...)
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#else
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#include <stdio.h>
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#define D(...) \
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do \
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{ \
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printf(__VA_ARGS__); \
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fflush(stdout); \
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} \
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while (0)
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#endif
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////////////////////////////////////////////////////////////////////////////////
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// Implementation of GetElfHwcapFromGetauxval
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////////////////////////////////////////////////////////////////////////////////
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#if defined(CPU_FEATURES_MOCK_GET_ELF_HWCAP_FROM_GETAUXVAL)
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// Implementation will be provided by test/hwcaps_for_testing.cc.
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#elif defined(HAVE_STRONG_GETAUXVAL)
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#include <sys/auxv.h>
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static unsigned long GetElfHwcapFromGetauxval(uint32_t hwcap_type)
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{
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return getauxval(hwcap_type);
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}
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#elif defined(HAVE_DLFCN_H)
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// On Android we probe the system's C library for a 'getauxval' function and
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// call it if it exits, or return 0 for failure. This function is available
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// since API level 20.
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//
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// This code does *NOT* check for '__ANDROID_API__ >= 20' to support the edge
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// case where some NDK developers use headers for a platform that is newer than
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// the one really targetted by their application. This is typically done to use
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// newer native APIs only when running on more recent Android versions, and
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// requires careful symbol management.
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//
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// Note that getauxval() can't really be re-implemented here, because its
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// implementation does not parse /proc/self/auxv. Instead it depends on values
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// that are passed by the kernel at process-init time to the C runtime
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// initialization layer.
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#include <dlfcn.h>
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#define AT_HWCAP 16
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#define AT_HWCAP2 26
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#define AT_PLATFORM 15
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#define AT_BASE_PLATFORM 24
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typedef unsigned long getauxval_func_t(unsigned long);
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static uint32_t GetElfHwcapFromGetauxval(uint32_t hwcap_type)
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{
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uint32_t ret = 0;
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void *libc_handle = NULL;
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getauxval_func_t *func = NULL;
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dlerror(); // Cleaning error state before calling dlopen.
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libc_handle = dlopen("libc.so", RTLD_NOW);
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if (!libc_handle)
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{
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D("Could not dlopen() C library: %s\n", dlerror());
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return 0;
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}
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func = (getauxval_func_t *)dlsym(libc_handle, "getauxval");
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if (!func)
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{
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D("Could not find getauxval() in C library\n");
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}
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else
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{
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// Note: getauxval() returns 0 on failure. Doesn't touch errno.
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ret = (uint32_t)(*func)(hwcap_type);
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}
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dlclose(libc_handle);
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return ret;
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}
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#else
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#error "This platform does not provide hardware capabilities."
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#endif
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// Implementation of GetHardwareCapabilities for OS that provide
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// GetElfHwcapFromGetauxval().
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// Fallback when getauxval is not available, retrieves hwcaps from
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// "/proc/self/auxv".
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static uint32_t GetElfHwcapFromProcSelfAuxv(uint32_t hwcap_type)
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{
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struct
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{
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uint32_t tag;
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uint32_t value;
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} entry;
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uint32_t result = 0;
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const char filepath[] = "/proc/self/auxv";
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const int fd = CpuFeatures_OpenFile(filepath);
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if (fd < 0)
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{
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D("Could not open %s\n", filepath);
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return 0;
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}
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for (;;)
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{
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const int ret = CpuFeatures_ReadFile(fd, (char *)&entry, sizeof entry);
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if (ret < 0)
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{
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D("Error while reading %s\n", filepath);
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break;
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}
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// Detect end of list.
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if (ret == 0 || (entry.tag == 0 && entry.value == 0))
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{
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break;
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}
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if (entry.tag == hwcap_type)
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{
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result = entry.value;
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break;
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}
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}
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CpuFeatures_CloseFile(fd);
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return result;
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}
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// Retrieves hardware capabilities by first trying to call getauxval, if not
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// available falls back to reading "/proc/self/auxv".
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static unsigned long GetHardwareCapabilitiesFor(uint32_t type)
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{
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unsigned long hwcaps = GetElfHwcapFromGetauxval(type);
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if (!hwcaps)
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{
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D("Parsing /proc/self/auxv to extract ELF hwcaps!\n");
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hwcaps = GetElfHwcapFromProcSelfAuxv(type);
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}
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return hwcaps;
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}
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HardwareCapabilities CpuFeatures_GetHardwareCapabilities(void)
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{
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HardwareCapabilities capabilities;
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capabilities.hwcaps = GetHardwareCapabilitiesFor(AT_HWCAP);
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capabilities.hwcaps2 = GetHardwareCapabilitiesFor(AT_HWCAP2);
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return capabilities;
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}
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PlatformType kEmptyPlatformType;
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PlatformType CpuFeatures_GetPlatformType(void)
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{
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PlatformType type = kEmptyPlatformType;
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char *platform = (char *)GetHardwareCapabilitiesFor(AT_PLATFORM);
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char *base_platform = (char *)GetHardwareCapabilitiesFor(AT_BASE_PLATFORM);
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if (platform != NULL)
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CpuFeatures_StringView_CopyString(str(platform), type.platform,
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sizeof(type.platform));
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if (base_platform != NULL)
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CpuFeatures_StringView_CopyString(str(base_platform), type.base_platform,
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sizeof(type.base_platform));
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return type;
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}
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