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/*
* Copyright (C) Thomas DuBuisson
* Copyright (C) 2013 Vincent Hanquez <tab@snarc.org>
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the author nor the names of his contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int crypto_random_cpu_has_rdrand()
{
uint32_t ax,bx,cx,dx,func=1;
__asm__ volatile ("cpuid": "=a" (ax), "=b" (bx), "=c" (cx), "=d" (dx) : "a" (func));
return (cx & 0x40000000);
}
/* sadly many people are still using an old binutils,
* leading to report that instruction is not recognized.
*/
#if 0
/* Returns 1 on success */
static inline int crypto_random_rdrand64_step(uint64_t *buffer)
{
unsigned char err;
asm volatile ("rdrand %0; setc %1" : "=r" (*buffer), "=qm" (err));
return (int) err;
}
#endif
/* inline encoding of 'rdrand %rax' to cover old binutils
* - no inputs
* - 'cc' to the clobber list as we modify condition code.
* - output of rdrand in rax and have a 8 bit error condition
*/
#define inline_rdrand_rax(val, err) \
asm(".byte 0x48,0x0f,0xc7,0xf0; setc %1" \
: "=a" (val), "=q" (err) \
: \
: "cc")
/* Returns the number of bytes succesfully generated */
int crypto_random_get_rand_bytes(uint8_t *buffer, size_t len)
{
uint64_t tmp;
int aligned = (unsigned long) buffer % 8;
int orig_len = len;
int to_alignment = 8 - aligned;
uint8_t ok;
if (aligned != 0) {
inline_rdrand_rax(tmp, ok);
if (!ok)
return 0;
memcpy(buffer, (uint8_t *) &tmp, to_alignment);
buffer += to_alignment;
len -= to_alignment;
}
for (; len >= 8; buffer += 8, len -= 8) {
inline_rdrand_rax(tmp, ok);
if (!ok)
return (orig_len - len);
*((uint64_t *) buffer) = tmp;
}
if (len > 0) {
inline_rdrand_rax(tmp, ok);
if (!ok)
return (orig_len - len);
memcpy(buffer, (uint8_t *) &tmp, len);
}
return orig_len;
}
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