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/*
* Entropy Source Using Intel's rdrand instruction
* (C) 2012,2015 Jack Lloyd
* (C) 2015 Daniel Neus
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/rdrand.h>
#include <botan/cpuid.h>
#include <botan/build.h>
#if !defined(BOTAN_USE_GCC_INLINE_ASM)
#include <immintrin.h>
#endif
namespace Botan {
size_t Intel_Rdrand::poll(RandomNumberGenerator& rng) {
if(CPUID::has_rdrand())
{
for(size_t p = 0; p != BOTAN_ENTROPY_INTEL_RNG_POLLS; ++p)
{
for(size_t i = 0; i != BOTAN_ENTROPY_RDRAND_RETRIES; ++i)
{
uint32_t r = 0;
#if defined(BOTAN_USE_GCC_INLINE_ASM)
int cf = 0;
// Encoding of rdrand %eax
asm(".byte 0x0F, 0xC7, 0xF0; adcl $0,%1" :
"=a" (r), "=r" (cf) : "0" (r), "1" (cf) : "cc");
#else
int cf = _rdrand32_step(&r);
#endif
if(1 == cf)
{
rng.add_entropy_T(r);
break;
}
}
}
}
// RDRAND is used but not trusted
return 0;
}
}
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