ref: 2bbc75bddc6f2a07056ff017108e35f14061041b
dir: /third_party/boringssl/src/crypto/cpu-arm-linux.c/
/* Copyright (c) 2016, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#include <openssl/cpu.h>
#if defined(OPENSSL_ARM) && !defined(OPENSSL_STATIC_ARMCAP)
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>
#include <unistd.h>
#include <openssl/arm_arch.h>
#include <openssl/mem.h>
#include "cpu-arm-linux.h"
#define AT_HWCAP 16
#define AT_HWCAP2 26
// |getauxval| is not available on Android until API level 20. Link it as a weak
// symbol and use other methods as fallback.
unsigned long getauxval(unsigned long type) __attribute__((weak));
static int open_eintr(const char *path, int flags) {
int ret;
do {
ret = open(path, flags);
} while (ret < 0 && errno == EINTR);
return ret;
}
static ssize_t read_eintr(int fd, void *out, size_t len) {
ssize_t ret;
do {
ret = read(fd, out, len);
} while (ret < 0 && errno == EINTR);
return ret;
}
// read_full reads exactly |len| bytes from |fd| to |out|. On error or end of
// file, it returns zero.
static int read_full(int fd, void *out, size_t len) {
char *outp = out;
while (len > 0) {
ssize_t ret = read_eintr(fd, outp, len);
if (ret <= 0) {
return 0;
}
outp += ret;
len -= ret;
}
return 1;
}
// read_file opens |path| and reads until end-of-file. On success, it returns
// one and sets |*out_ptr| and |*out_len| to a newly-allocated buffer with the
// contents. Otherwise, it returns zero.
static int read_file(char **out_ptr, size_t *out_len, const char *path) {
int fd = open_eintr(path, O_RDONLY);
if (fd < 0) {
return 0;
}
static const size_t kReadSize = 1024;
int ret = 0;
size_t cap = kReadSize, len = 0;
char *buf = OPENSSL_malloc(cap);
if (buf == NULL) {
goto err;
}
for (;;) {
if (cap - len < kReadSize) {
size_t new_cap = cap * 2;
if (new_cap < cap) {
goto err;
}
char *new_buf = OPENSSL_realloc(buf, new_cap);
if (new_buf == NULL) {
goto err;
}
buf = new_buf;
cap = new_cap;
}
ssize_t bytes_read = read_eintr(fd, buf + len, kReadSize);
if (bytes_read < 0) {
goto err;
}
if (bytes_read == 0) {
break;
}
len += bytes_read;
}
*out_ptr = buf;
*out_len = len;
ret = 1;
buf = NULL;
err:
OPENSSL_free(buf);
close(fd);
return ret;
}
// getauxval_proc behaves like |getauxval| but reads from /proc/self/auxv.
static unsigned long getauxval_proc(unsigned long type) {
int fd = open_eintr("/proc/self/auxv", O_RDONLY);
if (fd < 0) {
return 0;
}
struct {
unsigned long tag;
unsigned long value;
} entry;
for (;;) {
if (!read_full(fd, &entry, sizeof(entry)) ||
(entry.tag == 0 && entry.value == 0)) {
break;
}
if (entry.tag == type) {
close(fd);
return entry.value;
}
}
close(fd);
return 0;
}
extern uint32_t OPENSSL_armcap_P;
static int g_has_broken_neon, g_needs_hwcap2_workaround;
void OPENSSL_cpuid_setup(void) {
// We ignore the return value of |read_file| and proceed with an empty
// /proc/cpuinfo on error. If |getauxval| works, we will still detect
// capabilities. There may be a false positive due to
// |crypto_cpuinfo_has_broken_neon|, but this is now rare.
char *cpuinfo_data = NULL;
size_t cpuinfo_len = 0;
read_file(&cpuinfo_data, &cpuinfo_len, "/proc/cpuinfo");
STRING_PIECE cpuinfo;
cpuinfo.data = cpuinfo_data;
cpuinfo.len = cpuinfo_len;
// |getauxval| is not available on Android until API level 20. If it is
// unavailable, read from /proc/self/auxv as a fallback. This is unreadable
// on some versions of Android, so further fall back to /proc/cpuinfo.
//
// See
// https://android.googlesource.com/platform/ndk/+/882ac8f3392858991a0e1af33b4b7387ec856bd2
// and b/13679666 (Google-internal) for details.
unsigned long hwcap = 0;
if (getauxval != NULL) {
hwcap = getauxval(AT_HWCAP);
}
if (hwcap == 0) {
hwcap = getauxval_proc(AT_HWCAP);
}
if (hwcap == 0) {
hwcap = crypto_get_arm_hwcap_from_cpuinfo(&cpuinfo);
}
// Clear NEON support if known broken. Note, if NEON is available statically,
// the non-NEON code is dropped and this workaround is a no-op.
//
// TODO(davidben): The Android NDK now builds with NEON statically available
// by default. Cronet still has some consumers that support NEON-less devices
// (b/150371744). Get metrics on whether they still see this CPU and, if not,
// remove this check entirely.
g_has_broken_neon = crypto_cpuinfo_has_broken_neon(&cpuinfo);
if (g_has_broken_neon) {
hwcap &= ~HWCAP_NEON;
}
// Matching OpenSSL, only report other features if NEON is present.
if (hwcap & HWCAP_NEON) {
OPENSSL_armcap_P |= ARMV7_NEON;
// Some ARMv8 Android devices don't expose AT_HWCAP2. Fall back to
// /proc/cpuinfo. See https://crbug.com/boringssl/46. As of February 2021,
// this is now rare (see Chrome's Net.NeedsHWCAP2Workaround metric), but AES
// and PMULL extensions are very useful, so we still carry the workaround
// for now.
unsigned long hwcap2 = 0;
if (getauxval != NULL) {
hwcap2 = getauxval(AT_HWCAP2);
}
if (hwcap2 == 0) {
hwcap2 = crypto_get_arm_hwcap2_from_cpuinfo(&cpuinfo);
g_needs_hwcap2_workaround = hwcap2 != 0;
}
if (hwcap2 & HWCAP2_AES) {
OPENSSL_armcap_P |= ARMV8_AES;
}
if (hwcap2 & HWCAP2_PMULL) {
OPENSSL_armcap_P |= ARMV8_PMULL;
}
if (hwcap2 & HWCAP2_SHA1) {
OPENSSL_armcap_P |= ARMV8_SHA1;
}
if (hwcap2 & HWCAP2_SHA2) {
OPENSSL_armcap_P |= ARMV8_SHA256;
}
}
OPENSSL_free(cpuinfo_data);
}
int CRYPTO_has_broken_NEON(void) { return g_has_broken_neon; }
int CRYPTO_needs_hwcap2_workaround(void) { return g_needs_hwcap2_workaround; }
#endif // OPENSSL_ARM && !OPENSSL_STATIC_ARMCAP