base/dispatch.c, rand/rand.c, and asm: Support `rdseed' for quick noise.

[catacomb] / base / dispatch-x86ish.S

diff --git a/base/dispatch-x86ish.S b/base/dispatch-x86ish.S
index b3b6d1c..57d8d32 100644 (file)
--- a/base/dispatch-x86ish.S
+++ b/base/dispatch-x86ish.S
@@ -158,10 +158,11 @@ ENDFUNC
 /// 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
@@ -182,13 +183,22 @@ FUNC(dispatch_x86ish_rdrand)
 #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