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/* $OpenBSD: mdrandom.c,v 1.3 2020/06/19 15:00:45 naddy Exp $ */
/*
* Copyright (c) 2020 Theo de Raadt
*
* Permission to use, copy, modify, and 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 <sys/param.h>
#include <machine/psl.h>
#include <machine/specialreg.h>
#include "libsa.h"
int
mdrandom(char *buf, size_t buflen)
{
u_int eax, ebx, ecx, edx;
int i;
for (i = 0; i < buflen; i++) {
uint32_t hi, lo, acc;
__asm volatile("rdtsc" : "=d" (hi), "=a" (lo));
acc = hi ^ lo;
acc ^= acc >> 16;
acc ^= acc >> 8;
buf[i] ^= acc;
}
CPUID(1, eax, ebx, ecx, edx);
if (ecx & CPUIDECX_RDRAND) {
unsigned long rand;
int retries;
uint8_t valid;
for (i = 0; i < buflen / sizeof(rand); i++) {
retries = 10;
do {
__asm volatile(
"rdrand %0;"
"setc %1;"
: "=r" (rand), "=qm" (valid));
} while (!valid && --retries > 0);
((unsigned long *)buf)[i] ^= rand;
}
}
CPUID(0, eax, ebx, ecx, edx);
if (eax >= 7) {
CPUID_LEAF(7, 0, eax, ebx, ecx, edx);
if (ebx & SEFF0EBX_RDSEED) {
unsigned long rand;
int retries;
uint8_t valid;
for (i = 0; i < buflen / sizeof(rand); i++) {
retries = 10;
do {
__asm volatile(
"rdseed %0;"
"setc %1;"
: "=r" (rand), "=qm" (valid));
} while (!valid && --retries > 0);
((unsigned long *)buf)[i] ^= rand;
}
}
}
return (0);
}
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