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#ifdef HAVE_RDRAND
#include <stdint.h>
#include <stdlib.h>
int 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);
}
#ifdef arch_x86_64
// Returns 1 on success
static inline int _rdrand64_step(uint64_t *therand)
{
unsigned char err;
asm volatile("rdrand %0 ; setc %1"
: "=r" (*therand), "=qm" (err));
return (int) err;
}
// Returns 0 on success, non-zero on failure.
int get_rand_bytes(uint8_t *therand, size_t len)
{
int cnt;
int fail=0;
uint8_t *p = therand;
uint8_t *end = therand + len;
if((uint64_t)p%8 != 0) {
uint64_t tmp;
fail |= !_rdrand64_step(&tmp);
while((uint64_t)p%8 != 0 && p != end) {
*p = (uint8_t)(tmp & 0xFF);
tmp = tmp >> 8;
p++;
}
}
for(; p <= end - sizeof(uint64_t); p+=sizeof(uint64_t)) {
fail |= !_rdrand64_step((uint64_t *)p);
}
if(p != end) {
uint64_t tmp;
int cnt;
fail |= !_rdrand64_step(&tmp);
while(p != end) {
*p = (uint8_t)(tmp & 0xFF);
tmp = tmp >> 8;
p++;
}
}
return fail;
}
#endif /* x86-64 */
#ifdef arch_i386
// Returns 1 on success
static inline int _rdrand32_step(uint32_t *therand)
{
unsigned char err;
asm volatile("rdrand %0 ; setc %1"
: "=r" (*therand), "=qm" (err));
return (int) err;
}
int get_rand_bytes(uint8_t *therand, size_t len)
{
int cnt;
int fail=0;
uint8_t *p = therand;
uint8_t *end = therand + len;
if((uint32_t)p % sizeof(uint32_t) != 0) {
uint32_t tmp;
fail |= !_rdrand32_step(&tmp);
while((uint32_t)p % sizeof(uint32_t) != 0 && p != end) {
*p = (uint8_t)(tmp & 0xFF);
tmp = tmp >> 8;
p++;
}
}
for(; p <= end - sizeof(uint32_t); p+=sizeof(uint32_t)) {
fail |= !_rdrand32_step((uint32_t *)p);
}
if(p != end) {
uint32_t tmp;
int cnt;
fail |= !_rdrand32_step(&tmp);
while(p != end) {
*p = (uint8_t)(tmp & 0xFF);
tmp = tmp >> 8;
p++;
}
}
return fail;
}
#endif /* i386 */
#endif // RDRAND
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