mirror of
https://github.com/jart/cosmopolitan.git
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7e0a09feec
This change ports APE Loader to Linux AARCH64, so that Raspberry Pi users can run programs like redbean, without the executable needing to modify itself. Progress has also slipped into this change on the issue of making progress better conforming to user expectations and industry standards regarding which symbols we're allowed to declare
81 lines
3.5 KiB
C
81 lines
3.5 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 2020 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/errno.h"
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#include "libc/intrin/asmflag.h"
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#include "libc/nexgen32e/x86feature.h"
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#include "libc/stdio/rand.h"
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#include "libc/sysv/consts/grnd.h"
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__static_yoink("rdrand_init");
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static dontinline uint64_t rdrand_failover(void) {
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int f;
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size_t i;
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ssize_t r;
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volatile uint64_t b;
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register uint64_t x;
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for (f = GRND_RANDOM | GRND_NONBLOCK, i = 0; i < 8; i += r) {
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if ((r = getrandom((char *)&b + i, 8 - i, f)) <= 0) {
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if (r == -1 && errno == EINTR) {
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r = 0;
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} else if (r == -1 && errno == EAGAIN) {
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r = 0;
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f = 0;
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} else {
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return _rand64();
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}
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}
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}
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x = b;
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b = 0;
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return x;
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}
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/**
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* Retrieves 64-bits of hardware random data from RDRAND instruction.
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*
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* If RDRAND isn't available (we check CPUID and we also disable it
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* automatically for microarchitectures where it's slow or buggy) then
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* we try getrandom(), RtlGenRandom(), or sysctl(KERN_ARND). If those
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* aren't available then we try /dev/urandom and if that fails, we try
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* getauxval(AT_RANDOM), and if not we finally use RDTSC and getpid().
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*
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* @note this function could block a nontrivial time on old computers
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* @note this function is indeed intended for cryptography
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* @note this function takes around 300 cycles
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* @see rngset(), rdseed(), _rand64()
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* @asyncsignalsafe
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* @vforksafe
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*/
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uint64_t rdrand(void) {
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int i;
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char cf;
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uint64_t x;
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if (X86_HAVE(RDRND)) {
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for (i = 0; i < 10; ++i) {
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asm volatile(CFLAG_ASM("rdrand\t%1")
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: CFLAG_CONSTRAINT(cf), "=r"(x)
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: /* no inputs */
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: "cc");
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if (cf) return x;
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asm volatile("pause");
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}
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}
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return rdrand_failover();
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}
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