mirror of
https://github.com/PSI-Rockin/DobieStation.git
synced 2024-06-02 19:38:33 -04:00
120 lines
3.2 KiB
C
120 lines
3.2 KiB
C
/*
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* arm/cpu_features.c - feature detection for ARM processors
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*
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* Copyright 2018 Eric Biggers
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following
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* conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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/*
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* ARM processors don't have a standard way for unprivileged programs to detect
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* processor features. But, on Linux we can read the AT_HWCAP and AT_HWCAP2
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* values from /proc/self/auxv.
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*
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* Ideally we'd use the C library function getauxval(), but it's not guaranteed
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* to be available: it was only added to glibc in 2.16, and in Android it was
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* added to API level 18 for ARM and level 21 for AArch64.
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*/
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#include "cpu_features.h"
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#if ARM_CPU_FEATURES_ENABLED
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#include <errno.h>
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#include <fcntl.h>
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#include <string.h>
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#include <unistd.h>
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#define AT_HWCAP 16
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#define AT_HWCAP2 26
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volatile u32 _cpu_features = 0;
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static void scan_auxv(unsigned long *hwcap, unsigned long *hwcap2)
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{
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int fd;
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unsigned long auxbuf[32];
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int filled = 0;
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int i;
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fd = open("/proc/self/auxv", O_RDONLY);
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if (fd < 0)
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return;
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for (;;) {
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do {
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int ret = read(fd, &((char *)auxbuf)[filled],
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sizeof(auxbuf) - filled);
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if (ret <= 0) {
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if (ret < 0 && errno == EINTR)
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continue;
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goto out;
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}
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filled += ret;
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} while (filled < 2 * sizeof(long));
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i = 0;
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do {
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unsigned long type = auxbuf[i];
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unsigned long value = auxbuf[i + 1];
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if (type == AT_HWCAP)
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*hwcap = value;
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else if (type == AT_HWCAP2)
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*hwcap2 = value;
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i += 2;
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filled -= 2 * sizeof(long);
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} while (filled >= 2 * sizeof(long));
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memmove(auxbuf, &auxbuf[i], filled);
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}
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out:
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close(fd);
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}
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void setup_cpu_features(void)
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{
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u32 features = 0;
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unsigned long hwcap = 0;
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unsigned long hwcap2 = 0;
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scan_auxv(&hwcap, &hwcap2);
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#ifdef __arm__
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STATIC_ASSERT(sizeof(long) == 4);
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if (hwcap & (1 << 12)) /* HWCAP_NEON */
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features |= ARM_CPU_FEATURE_NEON;
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if (hwcap2 & (1 << 1)) /* HWCAP2_PMULL */
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features |= ARM_CPU_FEATURE_PMULL;
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#else
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STATIC_ASSERT(sizeof(long) == 8);
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if (hwcap & (1 << 1)) /* HWCAP_ASIMD */
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features |= ARM_CPU_FEATURE_NEON;
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if (hwcap & (1 << 4)) /* HWCAP_PMULL */
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features |= ARM_CPU_FEATURE_PMULL;
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#endif
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_cpu_features = features | ARM_CPU_FEATURES_KNOWN;
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}
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#endif /* ARM_CPU_FEATURES_ENABLED */
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