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When running on a 64 bit kernel, /proc/cpuinfo lists different optional features than on 32 bit kernels (because some of them are mandatory in the 64 bit implemenations). The kernel does list the old features properly if they are queried via /proc/self/auxv though - however this file is not always readable (e.g. on most android systems). The getauxval function could also provide the same info as /proc/self/auxv even if this file isn't readable, but this function is not always available (and thus would need to be loaded with dlsym for compatibility with older android versions). The android cpufeatures library does this slightly differently, by assuming that these are available if the "CPU architecture" line is >= 8, see [1] for details. It has been suggested to include the old, non-optional features in /proc/cpuinfo as well, but that suggested patch never was merged. See [2] for the discussion around this suggestion. [1] https://android-review.googlesource.com/91380 [2] http://marc.info/?l=linux-arm-kernel&m=139087240101974 Signed-off-by: Martin Storsjö <martin@martin.st>
150 lines
4.2 KiB
C
150 lines
4.2 KiB
C
/*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "libavutil/cpu.h"
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#include "libavutil/cpu_internal.h"
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#include "config.h"
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#define CORE_FLAG(f) \
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(AV_CPU_FLAG_ ## f * (HAVE_ ## f ## _EXTERNAL || HAVE_ ## f ## _INLINE))
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#define CORE_CPU_FLAGS \
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(CORE_FLAG(ARMV5TE) | \
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CORE_FLAG(ARMV6) | \
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CORE_FLAG(ARMV6T2) | \
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CORE_FLAG(VFP) | \
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CORE_FLAG(VFPV3) | \
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CORE_FLAG(NEON))
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#if defined __linux__ || defined __ANDROID__
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#include <stdint.h>
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#include <stdio.h>
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#include <string.h>
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#include "libavutil/avstring.h"
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#define AT_HWCAP 16
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/* Relevant HWCAP values from kernel headers */
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#define HWCAP_VFP (1 << 6)
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#define HWCAP_EDSP (1 << 7)
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#define HWCAP_THUMBEE (1 << 11)
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#define HWCAP_NEON (1 << 12)
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#define HWCAP_VFPv3 (1 << 13)
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#define HWCAP_TLS (1 << 15)
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static int get_hwcap(uint32_t *hwcap)
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{
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struct { uint32_t a_type; uint32_t a_val; } auxv;
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FILE *f = fopen("/proc/self/auxv", "r");
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int err = -1;
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if (!f)
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return -1;
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while (fread(&auxv, sizeof(auxv), 1, f) > 0) {
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if (auxv.a_type == AT_HWCAP) {
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*hwcap = auxv.a_val;
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err = 0;
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break;
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}
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}
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fclose(f);
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return err;
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}
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static int get_cpuinfo(uint32_t *hwcap)
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{
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FILE *f = fopen("/proc/cpuinfo", "r");
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char buf[200];
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if (!f)
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return -1;
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*hwcap = 0;
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while (fgets(buf, sizeof(buf), f)) {
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if (av_strstart(buf, "Features", NULL)) {
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if (strstr(buf, " edsp "))
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*hwcap |= HWCAP_EDSP;
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if (strstr(buf, " tls "))
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*hwcap |= HWCAP_TLS;
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if (strstr(buf, " thumbee "))
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*hwcap |= HWCAP_THUMBEE;
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if (strstr(buf, " vfp "))
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*hwcap |= HWCAP_VFP;
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if (strstr(buf, " vfpv3 "))
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*hwcap |= HWCAP_VFPv3;
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if (strstr(buf, " neon ") || strstr(buf, " asimd "))
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*hwcap |= HWCAP_NEON;
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if (strstr(buf, " fp ")) // Listed on 64 bit ARMv8 kernels
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*hwcap |= HWCAP_VFP | HWCAP_VFPv3;
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break;
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}
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}
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fclose(f);
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return 0;
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}
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int ff_get_cpu_flags_arm(void)
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{
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int flags = CORE_CPU_FLAGS;
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uint32_t hwcap;
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if (get_hwcap(&hwcap) < 0)
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if (get_cpuinfo(&hwcap) < 0)
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return flags;
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#define check_cap(cap, flag) do { \
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if (hwcap & HWCAP_ ## cap) \
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flags |= AV_CPU_FLAG_ ## flag; \
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} while (0)
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/* No flags explicitly indicate v6 or v6T2 so check others which
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imply support. */
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check_cap(EDSP, ARMV5TE);
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check_cap(TLS, ARMV6);
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check_cap(THUMBEE, ARMV6T2);
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check_cap(VFP, VFP);
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check_cap(VFPv3, VFPV3);
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check_cap(NEON, NEON);
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/* The v6 checks above are not reliable so let higher flags
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trickle down. */
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if (flags & (AV_CPU_FLAG_VFPV3 | AV_CPU_FLAG_NEON))
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flags |= AV_CPU_FLAG_ARMV6T2;
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if (flags & AV_CPU_FLAG_ARMV6T2)
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flags |= AV_CPU_FLAG_ARMV6;
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return flags;
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}
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#else
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int ff_get_cpu_flags_arm(void)
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{
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return AV_CPU_FLAG_ARMV5TE * HAVE_ARMV5TE |
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AV_CPU_FLAG_ARMV6 * HAVE_ARMV6 |
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AV_CPU_FLAG_ARMV6T2 * HAVE_ARMV6T2 |
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AV_CPU_FLAG_VFP * HAVE_VFP |
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AV_CPU_FLAG_VFPV3 * HAVE_VFPV3 |
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AV_CPU_FLAG_NEON * HAVE_NEON;
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}
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#endif
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