Implement CPU feature detection for ARM Linux.
BUG=webrtc:5057
NOTRY=True
Review URL: https://codereview.webrtc.org/1820133002
Cr-Commit-Position: refs/heads/master@{#12270}
diff --git a/webrtc/system_wrappers/source/cpu_features_linux.c b/webrtc/system_wrappers/source/cpu_features_linux.c
new file mode 100644
index 0000000..f23d827
--- /dev/null
+++ b/webrtc/system_wrappers/source/cpu_features_linux.c
@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ * Use of this source code is governed by a BSD-style license
+ * that can be found in the LICENSE file in the root of the source
+ * tree. An additional intellectual property rights grant can be found
+ * in the file PATENTS. All contributing project authors may
+ * be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <features.h>
+#if __GLIBC_PREREQ(2, 16)
+#include <sys/auxv.h>
+#else
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <link.h>
+#endif
+#include "webrtc/system_wrappers/include/cpu_features_wrapper.h"
+
+#if defined(WEBRTC_ARCH_ARM_FAMILY)
+#include <asm/hwcap.h>
+
+uint64_t WebRtc_GetCPUFeaturesARM(void) {
+ uint64_t result = 0;
+ int architecture = 0;
+ unsigned long hwcap = 0;
+ const char* platform = NULL;
+#if __GLIBC_PREREQ(2, 16)
+ hwcap = getauxval(AT_HWCAP);
+ platform = (const char*)getauxval(AT_PLATFORM);
+#else
+ ElfW(auxv_t) auxv;
+ int fd = open("/proc/self/auxv", O_RDONLY);
+ if (fd >= 0) {
+ while (hwcap == 0 || platform == NULL) {
+ if (read(fd, &auxv, sizeof(auxv)) < (ssize_t)sizeof(auxv)) {
+ if (errno == EINTR)
+ continue;
+ break;
+ }
+ switch (auxv.a_type) {
+ case AT_HWCAP:
+ hwcap = auxv.a_un.a_val;
+ break;
+ case AT_PLATFORM:
+ platform = (const char*)auxv.a_un.a_val;
+ break;
+ }
+ }
+ close(fd);
+ }
+#endif // __GLIBC_PREREQ(2,16)
+#if defined(__aarch64__)
+ architecture = 8;
+ if ((hwcap & HWCAP_FP) != 0)
+ result |= kCPUFeatureVFPv3;
+ if ((hwcap & HWCAP_ASIMD) != 0)
+ result |= kCPUFeatureNEON;
+#else
+ if (platform != NULL) {
+ /* expect a string in the form "v6l" or "v7l", etc.
+ */
+ if (platform[0] == 'v' && '0' <= platform[1] && platform[1] <= '9' &&
+ (platform[2] == 'l' || platform[2] == 'b')) {
+ architecture = platform[1] - '0';
+ }
+ }
+ if ((hwcap & HWCAP_VFPv3) != 0)
+ result |= kCPUFeatureVFPv3;
+ if ((hwcap & HWCAP_NEON) != 0)
+ result |= kCPUFeatureNEON;
+#endif
+ if (architecture >= 7)
+ result |= kCPUFeatureARMv7;
+ if (architecture >= 6)
+ result |= kCPUFeatureLDREXSTREX;
+ return result;
+}
+#endif // WEBRTC_ARCH_ARM_FAMILY