crypto: sun4i-ss - linearize buffers content must be kept

When running the non-optimized cipher function, SS produce partial random
output.
This is due to linearize buffers being reseted after each loop.

For preserving stack, instead of moving them back to start of function,
I move them in sun4i_ss_ctx.

Fixes: 8d3bcb99 ("crypto: sun4i-ss - reduce stack usage")
Signed-off-by: NCorentin Labbe <clabbe@baylibre.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/allwinner/sun4i-ss/sun4i-ss-cipher.c

@@ -233,8 +233,6 @@ static int sun4i_ss_cipher_poll(struct skcipher_request *areq)
 
 	while (oleft) {
 		if (ileft) {
-			char buf[4 * SS_RX_MAX];/* buffer for linearize SG src */
-
 			/*
 			 * todo is the number of consecutive 4byte word that we
 			 * can read from current SG
@@ -256,12 +254,12 @@ static int sun4i_ss_cipher_poll(struct skcipher_request *areq)
 				 */
 				todo = min(rx_cnt * 4 - ob, ileft);
 				todo = min_t(size_t, todo, mi.length - oi);
-				memcpy(buf + ob, mi.addr + oi, todo);
+				memcpy(ss->buf + ob, mi.addr + oi, todo);
 				ileft -= todo;
 				oi += todo;
 				ob += todo;
 				if (!(ob % 4)) {
-					writesl(ss->base + SS_RXFIFO, buf,
+					writesl(ss->base + SS_RXFIFO, ss->buf,
 						ob / 4);
 					ob = 0;
 				}
@@ -295,13 +293,11 @@ static int sun4i_ss_cipher_poll(struct skcipher_request *areq)
 				oo = 0;
 			}
 		} else {
-			char bufo[4 * SS_TX_MAX]; /* buffer for linearize SG dst */
-
 			/*
 			 * read obl bytes in bufo, we read at maximum for
 			 * emptying the device
 			 */
-			readsl(ss->base + SS_TXFIFO, bufo, tx_cnt);
+			readsl(ss->base + SS_TXFIFO, ss->bufo, tx_cnt);
 			obl = tx_cnt * 4;
 			obo = 0;
 			do {
@@ -313,7 +309,7 @@ static int sun4i_ss_cipher_poll(struct skcipher_request *areq)
 				 */
 				todo = min_t(size_t,
 					     mo.length - oo, obl - obo);
-				memcpy(mo.addr + oo, bufo + obo, todo);
+				memcpy(mo.addr + oo, ss->bufo + obo, todo);
 				oleft -= todo;
 				obo += todo;
 				oo += todo;

drivers/crypto/allwinner/sun4i-ss/sun4i-ss.h

@@ -148,6 +148,8 @@ struct sun4i_ss_ctx {
 	struct reset_control *reset;
 	struct device *dev;
 	struct resource *res;
+	char buf[4 * SS_RX_MAX];/* buffer for linearize SG src */
+	char bufo[4 * SS_TX_MAX]; /* buffer for linearize SG dst */
 	spinlock_t slock; /* control the use of the device */
 #ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
 	u32 seed[SS_SEED_LEN / BITS_PER_LONG];