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

9af207c random: fix crash on some 64bit platforms (Cory Fields)

Tree-SHA512: c9516b69bec224c7e650dfc7c50f04cdd93a1006d515699bc64a311a03662d4ad33a834861194a1649ed212b37fb50aadfb004954cdf8b9bc1dc82f3ea962897

Author: sipa

src/random.cpp

@@ -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;