[PATCH 17/18] lib/crypto: sha256: Sync sha256_update() with sha512_update()

[Eric Biggers]

The BLOCK_HASH_UPDATE_BLOCKS macro is difficult to read.  For now, let's
just write the update explicitly in the straightforward way, mirroring
sha512_update().  It's possible that we'll bring back a macro for this
later, but it needs to be properly justified and hopefully a bit more
readable.

Signed-off-by: Eric Biggers <ebiggers at kernel.org>
---
 lib/crypto/sha256.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/lib/crypto/sha256.c b/lib/crypto/sha256.c
index 0de49bf8e8b8b..c93bf4699160c 100644
--- a/lib/crypto/sha256.c
+++ b/lib/crypto/sha256.c
@@ -8,11 +8,10 @@
  * Copyright (c) 2014 Red Hat Inc.
  * Copyright 2025 Google LLC
  */
 
 #include <crypto/hmac.h>
-#include <crypto/internal/blockhash.h>
 #include <crypto/sha2.h>
 #include <linux/export.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/unaligned.h>
@@ -177,12 +176,35 @@ EXPORT_SYMBOL_GPL(sha256_init);
 void __sha256_update(struct __sha256_ctx *ctx, const u8 *data, size_t len)
 {
 	size_t partial = ctx->bytecount % SHA256_BLOCK_SIZE;
 
 	ctx->bytecount += len;
-	BLOCK_HASH_UPDATE_BLOCKS(sha256_blocks, &ctx->state, data, len,
-				 SHA256_BLOCK_SIZE, ctx->buf, partial);
+
+	if (partial + len >= SHA256_BLOCK_SIZE) {
+		size_t nblocks;
+
+		if (partial) {
+			size_t l = SHA256_BLOCK_SIZE - partial;
+
+			memcpy(&ctx->buf[partial], data, l);
+			data += l;
+			len -= l;
+
+			sha256_blocks(&ctx->state, ctx->buf, 1);
+		}
+
+		nblocks = len / SHA256_BLOCK_SIZE;
+		len %= SHA256_BLOCK_SIZE;
+
+		if (nblocks) {
+			sha256_blocks(&ctx->state, data, nblocks);
+			data += nblocks * SHA256_BLOCK_SIZE;
+		}
+		partial = 0;
+	}
+	if (len)
+		memcpy(&ctx->buf[partial], data, len);
 }
 EXPORT_SYMBOL(__sha256_update);
 
 static void __sha256_final(struct __sha256_ctx *ctx,
 			   u8 *out, size_t digest_size)
-- 
2.50.0