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/*
* Entropy Source Using Intel's rdseed instruction
* (C) 2015 Jack Lloyd, Daniel Neus
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/rdseed.h>
#include <botan/cpuid.h>
#include <botan/build.h>
#if !defined(BOTAN_USE_GCC_INLINE_ASM)
#include <immintrin.h>
#endif
namespace Botan {
namespace {
/// @returns 0 if RdSeed failed after @param max_retries otherwise the 32 bit random number generated by RdSeed
uint32_t get_32bit_random(const uint32_t max_retries) {
for(size_t i = 0; i != max_retries; ++i)
{
uint32_t r = 0;
#if defined(BOTAN_USE_GCC_INLINE_ASM)
int cf = 0;
// Encoding of rdseed %eax
asm(".byte 0x0F, 0xC7, 0xF8; adcl $0,%1" :
"=a" (r), "=r" (cf) : "0" (r), "1" (cf) : "cc");
#else
int cf = _rdseed32_step(&r);
#endif
if(1 == cf)
{
return r;
}
}
return 0;
}
}
void Intel_Rdseed::poll(Entropy_Accumulator& accum) {
if(!CPUID::has_rdseed())
return;
for(size_t i = 0; i != BOTAN_ENTROPY_INTEL_RNG_POLLS; ++i)
{
uint32_t random = get_32bit_random(BOTAN_ENTROPY_RDSEED_RETRIES);
if(random)
{
accum.add(random, BOTAN_ENTROPY_ESTIMATE_HARDWARE_RNG);
}
}
}
}
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