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Fold LIBC_RAND into LIBC_STDIO/TINYMATH/INTRIN

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Justine Tunney 2022-08-11 12:26:30 -07:00
parent 05b8f82371
commit 8a0a2c0c36
183 changed files with 149 additions and 322 deletions
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libc/stdio/rdseed.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/intrin/asmflag.h"
#include "libc/nexgen32e/x86feature.h"
#include "libc/stdio/rand.h"
#include "libc/stdio/stdio.h"
#include "libc/sysv/consts/grnd.h"
/**
* Retrieves 64-bits of true random data from RDSEED instruction.
*
* If RDSEED isn't available, we'll try RDRAND (which we automatically
* disable for microarchitectures where it's known to be slow or buggy).
* If RDRAND isn't available then we try getrandom(), RtlGenRandom(), or
* sysctl(KERN_ARND). If those aren't available then we try /dev/urandom
* and if that fails, we use RDTSC and getpid().
*
* @note this function could block a nontrivial time on old computers
* @note this function is indeed intended for cryptography
* @note this function takes around 800 cycles
* @see rngset(), rdrand(), rand64()
* @asyncsignalsafe
* @vforksafe
*/
uint64_t rdseed(void) {
int i;
char cf;
uint64_t x;
if (X86_HAVE(RDSEED)) {
for (i = 0; i < 10; ++i) {
asm volatile(CFLAG_ASM("rdseed\t%1")
: CFLAG_CONSTRAINT(cf), "=r"(x)
: /* no inputs */
: "cc");
if (cf) return x;
asm volatile("pause");
}
}
return rdrand();
}