[otbn] change calling convention for modexp
Gets rid of the clunky calling convention with the four
descriptors.
Expects the following layout in the 1st dmem cell now:
[p_out|p_exp|p_in|p_m|p_rr|p_m0d|N|reserved]
2nd dmem cell is reserved for future use
(blinding parameters).
Signed-off-by: Felix Miller <felix.miller@gi-de.com>
diff --git a/sw/otbn/code-snippets/rsa_1024_dec_test.s b/sw/otbn/code-snippets/rsa_1024_dec_test.s
index 5a7c2ac..6e125c6 100644
--- a/sw/otbn/code-snippets/rsa_1024_dec_test.s
+++ b/sw/otbn/code-snippets/rsa_1024_dec_test.s
@@ -18,7 +18,7 @@
jal x1, modload
jal x1, modexp
/* pointer to out buffer */
- lw x21, 116(x0)
+ lw x21, 28(x0)
/* copy all limbs of result to wide reg file */
li x8, 0
@@ -31,52 +31,35 @@
.data
-/* descriptor 1: a=in, b=RR, c=in
- convert to Montgomery */
-.word 0x00000080
-.word 0x00000280
-.word 0x000002c0
-.word 0x000004c0
-.word 0x000002c0
-.word 0x000004c0
-.word 0x00000004
-.word 0x00000003
+/* reserved */
+.word 0x00000000
-/* descriptor 2: a=out, b=out, c=out
- square */
-.word 0x00000080
-.word 0x00000280
-.word 0x000002c0
-.word 0x000008e0
-.word 0x000008e0
-.word 0x000008e0
+/* number of limbs (N) */
.word 0x00000004
-.word 0x00000003
-/* descriptor 3: a=in, b=out, c=out
- multiply */
-.word 0x00000080
+/* pointer to m0' (dptr_m0d) */
.word 0x00000280
+
+/* pointer to RR (dptr_rr) */
.word 0x000002c0
+
+/* load pointer to modulus (dptr_m) */
+.word 0x00000080
+
+/* pointer to base bignum buffer (dptr_in) */
.word 0x000004c0
-.word 0x000008e0
-.word 0x000008e0
-.word 0x00000004
-.word 0x00000003
-/* descriptor 4: a=in, b=exp, c=out
- shift exponent and convert back */
-.word 0x00000080
-.word 0x00000280
-.word 0x000002c0
-.word 0x000008e0
+/* pointer to exponent buffer (dptr_exp) */
.word 0x000006c0
-.word 0x000008e0
-.word 0x00000004
-.word 0x00000003
+
+/* pointer to out buffer (dptr_out) */
+.word 0x000008c0
-/* modulus */
+/* Modulus */
+/* skip to 128 */
+.skip 96
+
.word 0xc28cf49f
.word 0xb6e64c3b
.word 0xa21417f1
