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

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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>
This commit is contained in:
Eric Biggers 2026-01-12 11:20:01 -08:00
parent a22fd0e3c4
commit a4e4e44649
2 changed files with 16 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

1
arch/arm/crypto/Kconfig
View file

@ -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

29
arch/arm/crypto/aes-neonbs-glue.c
View file

@ -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);