/// Checking `rdrand'.
FUNC(dispatch_x86ish_rdrand)
- // Enter with two arguments: a code OP requesting `rdrand' (0), and a
- // pointer X_OUT to a 32-bit word. Try to generate a random word
- // using the requested instruction. If successful, set *X_OUT to the
- // generated word, and return zero; otherwise, return -1.
+ // Enter with two arguments: a code OP requesting either `rdrand' (0)
+ // or `rdseed' (1), and a pointer X_OUT to a 32-bit word. Try to
+ // generate a random word using the requested instruction'. If
+ // successful, set *X_OUT to the generated word, and return zero;
+ // otherwise, return -1.
#if CPUFAM_X86
# define OP eax
#endif
endprologue
+ cmp OP, 0
mov COUNT, 16 // fairly persistent
+ jne 1f
+
0: rdrand eax
jc 9f
dec COUNT
jnz 0b
jmp 8f
+1: rdseed eax
+ jc 9f
+ dec COUNT
+ jnz 1b
+ jmp 8f
+
// Failed to come up with a random value.
8: mov eax, -1
ret