[rng] Use fixed-point calculations for min-entropy quantities

We currently perform various min-entropy calculations using build-time
floating-point arithmetic.  No floating-point code ends up in the
final binary, since the results are eventually converted to integers
and asserted to be compile-time constants.

Though this mechanism is undoubtedly cute, it inhibits us from using
"-mno-sse" to prevent the use of SSE registers by the compiler.

Fix by using fixed-point arithmetic instead.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/include/ipxe/null_entropy.h b/src/include/ipxe/null_entropy.h
index 91adefa69..5a6bb6218 100644
--- a/src/include/ipxe/null_entropy.h
+++ b/src/include/ipxe/null_entropy.h
@@ -30,14 +30,14 @@ ENTROPY_INLINE ( null, entropy_disable ) ( void ) {
 	/* Do nothing */
 }
 
-static inline __always_inline double
+static inline __always_inline min_entropy_t
 ENTROPY_INLINE ( null, min_entropy_per_sample ) ( void ) {
 	/* Actual amount of min-entropy is zero.  To avoid
 	 * division-by-zero errors and to allow compilation of
 	 * entropy-consuming code, pretend to have 1 bit of entropy in
 	 * each sample.
 	 */
-	return 1.0;
+	return MIN_ENTROPY ( 1.0 );
 }
 
 static inline __always_inline int