[PATCH v2 13/14] 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 <ebigg...@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 68936d5cd7745..808438d4f4278 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/string.h>
@@ -178,12 +177,35 @@ 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