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https://github.com/jart/cosmopolitan.git
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44 lines
2.7 KiB
C
44 lines
2.7 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2021 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/nexgen32e/kcpuids.h"
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#include "libc/nexgen32e/vendor.internal.h"
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#include "libc/nexgen32e/x86feature.h"
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#include "libc/nexgen32e/x86info.h"
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#include "libc/stdio/rand.h"
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textstartup void rdrand_init(int argc, char **argv, char **envp,
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intptr_t *auxv) {
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extern unsigned kMutableCpuids[KCPUIDS_LEN][4] asm("kCpuids");
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/*
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* Clear RDRAND on AMD models before Zen and then some
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* since it's not only slow but can freeze after sleep
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* https://bugzilla.redhat.com/show_bug.cgi?id=1150286
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*/
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if ((X86_HAVE(RDRND) || X86_HAVE(RDSEED)) &&
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(IsAuthenticAMD() &&
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(kX86CpuFamily < 0x17 ||
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(kX86CpuFamily == 0x17 &&
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(0x70 <= kX86CpuModel && kX86CpuModel <= 0x7F))))) {
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kMutableCpuids[KCPUIDS_1H][KCPUIDS_ECX] &= ~(1u << 30);
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kMutableCpuids[KCPUIDS_7H][KCPUIDS_EBX] &= ~(1u << 18);
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}
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}
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const void *const g_rdrand_init[] initarray = {rdrand_init};
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