[crypto] Separate out bigint_reduce() from bigint_mod_multiply()

Faster modular multiplication algorithms such as Montgomery
multiplication will still require the ability to perform a single
direct modular reduction.

Neaten up the implementation of direct reduction and split it out into
a separate bigint_reduce() function, complete with its own unit tests.

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

1 files changed, 34 insertions, 0 deletions

diff --git a/src/include/ipxe/bigint.h b/src/include/ipxe/bigint.h
index c556afbc1..c56b2155f 100644
--- a/src/include/ipxe/bigint.h
+++ b/src/include/ipxe/bigint.h
@@ -218,6 +218,35 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 	} while ( 0 )
 
 /**
+ * Reduce big integer
+ *
+ * @v minuend		Big integer to be reduced
+ * @v modulus		Big integer modulus
+ * @v result		Big integer to hold result
+ * @v tmp		Temporary working space
+ */
+#define bigint_reduce( minuend, modulus, result, tmp ) do {		\
+	unsigned int minuend_size = bigint_size (minuend);		\
+	unsigned int modulus_size = bigint_size (modulus);		\
+	bigint_reduce_raw ( (minuend)->element, minuend_size,		\
+			    (modulus)->element, modulus_size,		\
+			    (result)->element, tmp );			\
+	} while ( 0 )
+
+/**
+ * Calculate temporary working space required for reduction
+ *
+ * @v minuend		Big integer to be reduced
+ * @ret len		Length of temporary working space
+ */
+#define bigint_reduce_tmp_len( minuend ) ( {				\
+	unsigned int size = bigint_size (minuend);			\
+	sizeof ( struct {						\
+		bigint_t ( size ) temp_minuend;				\
+		bigint_t ( size ) temp_modulus;				\
+	} ); } )
+
+/**
  * Perform modular multiplication of big integers
  *
  * @v multiplicand	Big integer to be multiplied
@@ -339,6 +368,11 @@ void bigint_multiply_raw ( const bigint_element_t *multiplicand0,
 			   const bigint_element_t *multiplier0,
 			   unsigned int multiplier_size,
 			   bigint_element_t *result0 );
+void bigint_reduce_raw ( const bigint_element_t *minuend0,
+			 unsigned int minuend_size,
+			 const bigint_element_t *modulus0,
+			 unsigned int modulus_size,
+			 bigint_element_t *result0, void *tmp );
 void bigint_mod_multiply_raw ( const bigint_element_t *multiplicand0,
 			       const bigint_element_t *multiplier0,
 			       const bigint_element_t *modulus0,