[PATCH v2 6/6] crypto: lib/sha - Combine round constants and message schedule

Arvind Sankar
2020-10-20T20:40:22Z

Putting the round constants and the message schedule arrays together in
one structure saves one register, which can be a significant benefit on
register-constrained architectures. On x86-32 (tested on Broadwell
Xeon), this gives a 10% performance benefit.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Suggested-by: David Laight <David.Laight@ACULAB.COM>
---
lib/crypto/sha256.c | 49 ++++++++++++++++++++++++++-------------------
1 file changed, 28 insertions(+), 21 deletions(-)

diff --git a/lib/crypto/sha256.c b/lib/crypto/sha256.c
index 3a8802d5f747..985cd0560d79 100644
--- a/lib/crypto/sha256.c
+++ b/lib/crypto/sha256.c
@@ -29,6 +29,11 @@ static const u32 SHA256_K[] = {
0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
};

+struct KW {
+ u32 K[64];
+ u32 W[64];
+};
+
static inline u32 Ch(u32 x, u32 y, u32 z)
{
return z ^ (x & (y ^ z));
@@ -56,39 +61,39 @@ static inline void BLEND_OP(int I, u32 *W)

#define SHA256_ROUND(i, a, b, c, d, e, f, g, h) do { \
u32 t1, t2; \
- t1 = h + e1(e) + Ch(e, f, g) + SHA256_K[i] + W[i]; \
+ t1 = h + e1(e) + Ch(e, f, g) + KW->K[i] + KW->W[i]; \
t2 = e0(a) + Maj(a, b, c); \
d += t1; \
h = t1 + t2; \
} while (0)

-static void sha256_transform(u32 *state, const u8 *input, u32 *W)
+static void sha256_transform(u32 *state, const u8 *input, struct KW *KW)
{
u32 a, b, c, d, e, f, g, h;
int i;

/* load the input */
for (i = 0; i < 16; i += 8) {
- LOAD_OP(i + 0, W, input);
- LOAD_OP(i + 1, W, input);
- LOAD_OP(i + 2, W, input);
- LOAD_OP(i + 3, W, input);
- LOAD_OP(i + 4, W, input);
- LOAD_OP(i + 5, W, input);
- LOAD_OP(i + 6, W, input);
- LOAD_OP(i + 7, W, input);
+ LOAD_OP(i + 0, KW->W, input);
+ LOAD_OP(i + 1, KW->W, input);
+ LOAD_OP(i + 2, KW->W, input);
+ LOAD_OP(i + 3, KW->W, input);
+ LOAD_OP(i + 4, KW->W, input);
+ LOAD_OP(i + 5, KW->W, input);
+ LOAD_OP(i + 6, KW->W, input);
+ LOAD_OP(i + 7, KW->W, input);
}

/* now blend */
for (i = 16; i < 64; i += 8) {
- BLEND_OP(i + 0, W);
- BLEND_OP(i + 1, W);
- BLEND_OP(i + 2, W);
- BLEND_OP(i + 3, W);
- BLEND_OP(i + 4, W);
- BLEND_OP(i + 5, W);
- BLEND_OP(i + 6, W);
- BLEND_OP(i + 7, W);
+ BLEND_OP(i + 0, KW->W);
+ BLEND_OP(i + 1, KW->W);
+ BLEND_OP(i + 2, KW->W);
+ BLEND_OP(i + 3, KW->W);
+ BLEND_OP(i + 4, KW->W);
+ BLEND_OP(i + 5, KW->W);
+ BLEND_OP(i + 6, KW->W);
+ BLEND_OP(i + 7, KW->W);
}

/* load the state into our registers */
@@ -115,7 +120,7 @@ void sha256_update(struct sha256_state *sctx, const u8 *data, unsigned int len)
{
unsigned int partial, done;
const u8 *src;
- u32 W[64];
+ struct KW KW;

partial = sctx->count & 0x3f;
sctx->count += len;
@@ -129,13 +134,15 @@ void sha256_update(struct sha256_state *sctx, const u8 *data, unsigned int len)
src = sctx->buf;
}

+ memcpy(KW.K, SHA256_K, sizeof(KW.K));
+
do {
- sha256_transform(sctx->state, src, W);
+ sha256_transform(sctx->state, src, &KW);
done += 64;
src = data + done;
} while (done + 63 < len);

- memzero_explicit(W, sizeof(W));
+ memzero_explicit(KW.W, sizeof(KW.W));

partial = 0;
}
--
2.26.2