crypto: arm/aes-neonbs - Use AES library for single blocks

aes-neonbs-glue.c calls __aes_arm_encrypt() and __aes_arm_decrypt() to
en/decrypt single blocks for CBC encryption, XTS tweak encryption, and
XTS ciphertext stealing.  In preparation for making the AES library use
this same ARM-optimized single-block AES en/decryption code and making
it an internal implementation detail of the AES library, replace the
calls to these functions with calls to the AES library.

Note that this reduces the size of the aesbs_cbc_ctx and aesbs_xts_ctx
structs, since unnecessary decryption round keys are no longer included.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260112192035.10427-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

2 files changed, 16 insertions, 14 deletions

diff --git a/arch/arm/crypto/Kconfig b/arch/arm/crypto/Kconfig
index 3eb5071bea14..167a648a9def 100644
--- a/arch/arm/crypto/Kconfig
+++ b/arch/arm/crypto/Kconfig
@@ -44,7 +44,6 @@ config CRYPTO_AES_ARM
 config CRYPTO_AES_ARM_BS
 	tristate "Ciphers: AES, modes: ECB/CBC/CTR/XTS (bit-sliced NEON)"
 	depends on KERNEL_MODE_NEON
-	select CRYPTO_AES_ARM
 	select CRYPTO_SKCIPHER
 	select CRYPTO_LIB_AES
 	help
diff --git a/arch/arm/crypto/aes-neonbs-glue.c b/arch/arm/crypto/aes-neonbs-glue.c
index df5afe601e4a..c49ddafc54f3 100644
--- a/arch/arm/crypto/aes-neonbs-glue.c
+++ b/arch/arm/crypto/aes-neonbs-glue.c
@@ -12,7 +12,6 @@
 #include <crypto/scatterwalk.h>
 #include <crypto/xts.h>
 #include <linux/module.h>
-#include "aes-cipher.h"
 
 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
 MODULE_DESCRIPTION("Bit sliced AES using NEON instructions");
@@ -48,13 +47,13 @@ struct aesbs_ctx {
 
 struct aesbs_cbc_ctx {
 	struct aesbs_ctx	key;
-	struct crypto_aes_ctx	fallback;
+	struct aes_enckey	fallback;
 };
 
 struct aesbs_xts_ctx {
 	struct aesbs_ctx	key;
-	struct crypto_aes_ctx	fallback;
-	struct crypto_aes_ctx	tweak_key;
+	struct aes_key		fallback;
+	struct aes_enckey	tweak_key;
 };
 
 static int aesbs_setkey(struct crypto_skcipher *tfm, const u8 *in_key,
@@ -122,14 +121,19 @@ static int aesbs_cbc_setkey(struct crypto_skcipher *tfm, const u8 *in_key,
 	struct aesbs_cbc_ctx *ctx = crypto_skcipher_ctx(tfm);
 	int err;
 
-	err = aes_expandkey(&ctx->fallback, in_key, key_len);
+	err = aes_prepareenckey(&ctx->fallback, in_key, key_len);
 	if (err)
 		return err;
 
 	ctx->key.rounds = 6 + key_len / 4;
 
+	/*
+	 * Note: this assumes that the arm implementation of the AES library
+	 * stores the standard round keys in k.rndkeys.
+	 */
 	kernel_neon_begin();
-	aesbs_convert_key(ctx->key.rk, ctx->fallback.key_enc, ctx->key.rounds);
+	aesbs_convert_key(ctx->key.rk, ctx->fallback.k.rndkeys,
+			  ctx->key.rounds);
 	kernel_neon_end();
 
 	return 0;
@@ -152,8 +156,7 @@ static int cbc_encrypt(struct skcipher_request *req)
 
 		do {
 			crypto_xor_cpy(dst, src, prev, AES_BLOCK_SIZE);
-			__aes_arm_encrypt(ctx->fallback.key_enc,
-					  ctx->key.rounds, dst, dst);
+			aes_encrypt(&ctx->fallback, dst, dst);
 			prev = dst;
 			src += AES_BLOCK_SIZE;
 			dst += AES_BLOCK_SIZE;
@@ -239,10 +242,10 @@ static int aesbs_xts_setkey(struct crypto_skcipher *tfm, const u8 *in_key,
 		return err;
 
 	key_len /= 2;
-	err = aes_expandkey(&ctx->fallback, in_key, key_len);
+	err = aes_preparekey(&ctx->fallback, in_key, key_len);
 	if (err)
 		return err;
-	err = aes_expandkey(&ctx->tweak_key, in_key + key_len, key_len);
+	err = aes_prepareenckey(&ctx->tweak_key, in_key + key_len, key_len);
 	if (err)
 		return err;
 
@@ -279,7 +282,7 @@ static int __xts_crypt(struct skcipher_request *req, bool encrypt,
 	if (err)
 		return err;
 
-	__aes_arm_encrypt(ctx->tweak_key.key_enc, rounds, walk.iv, walk.iv);
+	aes_encrypt(&ctx->tweak_key, walk.iv, walk.iv);
 
 	while (walk.nbytes >= AES_BLOCK_SIZE) {
 		unsigned int blocks = walk.nbytes / AES_BLOCK_SIZE;
@@ -311,9 +314,9 @@ static int __xts_crypt(struct skcipher_request *req, bool encrypt,
 	crypto_xor(buf, req->iv, AES_BLOCK_SIZE);
 
 	if (encrypt)
-		__aes_arm_encrypt(ctx->fallback.key_enc, rounds, buf, buf);
+		aes_encrypt(&ctx->fallback, buf, buf);
 	else
-		__aes_arm_decrypt(ctx->fallback.key_dec, rounds, buf, buf);
+		aes_decrypt(&ctx->fallback, buf, buf);
 
 	crypto_xor(buf, req->iv, AES_BLOCK_SIZE);