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Merge #10614: random: fix crash on some 64bit platforms

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9af207c81 random: fix crash on some 64bit platforms (Cory Fields)

Tree-SHA512: c9516b69bec224c7e650dfc7c50f04cdd93a1006d515699bc64a311a03662d4ad33a834861194a1649ed212b37fb50aadfb004954cdf8b9bc1dc82f3ea962897
This commit is contained in:
Pieter Wuille 2017-06-16 17:36:22 -07:00
commit cafe24f039
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1 changed files with 8 additions and 2 deletions
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10
src/random.cpp
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@ -72,10 +72,16 @@ static bool rdrand_supported = false;
static constexpr uint32_t CPUID_F1_ECX_RDRAND = 0x40000000;
static void RDRandInit()
{
//! When calling cpuid function #1, ecx register will have this set if RDRAND is available.
uint32_t eax, ecx, edx;
#if defined(__i386__) && ( defined(__PIC__) || defined(__PIE__))
// Avoid clobbering ebx, as that is used for PIC on x86.
uint32_t eax, tmp, ecx, edx;
uint32_t tmp;
__asm__ ("mov %%ebx, %1; cpuid; mov %1, %%ebx": "=a"(eax), "=g"(tmp), "=c"(ecx), "=d"(edx) : "a"(1));
#else
uint32_t ebx;
__asm__ ("cpuid": "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx) : "a"(1));
#endif
//! When calling cpuid function #1, ecx register will have this set if RDRAND is available.
if (ecx & CPUID_F1_ECX_RDRAND) {
LogPrintf("Using RdRand as entropy source\n");
rdrand_supported = true;