You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
47 lines
2.6 KiB
47 lines
2.6 KiB
/*-*- 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 │ |
|
│ │ |
|
│ This program is free software; you can redistribute it and/or modify │ |
|
│ it under the terms of the GNU General Public License as published by │ |
|
│ the Free Software Foundation; version 2 of the License. │ |
|
│ │ |
|
│ This program is distributed in the hope that it will be useful, but │ |
|
│ WITHOUT ANY WARRANTY; without even the implied warranty of │ |
|
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │ |
|
│ General Public License for more details. │ |
|
│ │ |
|
│ You should have received a copy of the GNU General Public License │ |
|
│ along with this program; if not, write to the Free Software │ |
|
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │ |
|
│ 02110-1301 USA │ |
|
╚─────────────────────────────────────────────────────────────────────────────*/ |
|
#include "libc/assert.h" |
|
#include "libc/bits/bits.h" |
|
#include "libc/calls/calls.h" |
|
#include "libc/nexgen32e/x86feature.h" |
|
#include "libc/rand/rand.h" |
|
|
|
/** |
|
* Intel Secure Key Digital Random Number Generator |
|
* Introduced w/ Ivy Bridge c. 2013 and Excavator c. 2015 |
|
* @see rand32(), rand64(), and randcpy() |
|
*/ |
|
uint64_t rdrand(void) { |
|
char cf; |
|
size_t i; |
|
uint64_t res; |
|
assert(X86_HAVE(RDRND)); |
|
for (;;) { |
|
for (i = 0; i < 10; ++i) { |
|
/* CF=1: Destination register valid. Quoth Intel DRNG-SIG 4.1.3 */ |
|
asm volatile(CFLAG_ASM("rdrand\t%1") |
|
: CFLAG_CONSTRAINT(cf), "=r"(res) |
|
: /* no inputs */ |
|
: "cc"); |
|
if (cf) return res; |
|
} |
|
asm volatile("rep nop"); /* unlikely 140 cycle spin */ |
|
} |
|
}
|
|
|