lib/crypto: arm64/aes: Remove obsolete chunking logic

Since commit aefbab8 ("arm64: fpsimd: Preserve/restore kernel mode
NEON at context switch"), kernel-mode NEON sections have been
preemptible on arm64.  And since commit 7dadeaa ("sched: Further
restrict the preemption modes"), voluntary preemption is no longer
supported on arm64 either.  Therefore, there's no longer any need to
limit the length of kernel-mode NEON sections on arm64.

Simplify the AES-CBC-MAC code accordingly.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260401000548.133151-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

Author: Eric Biggers

arch/arm64/crypto/aes-ce-ccm-glue.c

@@ -101,16 +101,11 @@ static u32 ce_aes_ccm_auth_data(u8 mac[], u8 const in[], u32 abytes,
 		u32 blocks = abytes / AES_BLOCK_SIZE;
 
 		if (macp == AES_BLOCK_SIZE || (!macp && blocks > 0)) {
-			u32 rem = ce_aes_mac_update(in, rk, rounds, blocks, mac,
-						    macp, enc_after);
-			u32 adv = (blocks - rem) * AES_BLOCK_SIZE;
-
+			ce_aes_mac_update(in, rk, rounds, blocks, mac, macp,
+					  enc_after);
 			macp = enc_after ? 0 : AES_BLOCK_SIZE;
-			in += adv;
-			abytes -= adv;
-
-			if (unlikely(rem))
-				macp = 0;
+			in += blocks * AES_BLOCK_SIZE;
+			abytes -= blocks * AES_BLOCK_SIZE;
 		} else {
 			u32 l = min(AES_BLOCK_SIZE - macp, abytes);
 

include/crypto/aes.h

@@ -230,9 +230,9 @@ asmlinkage void ce_aes_essiv_cbc_encrypt(u8 out[], u8 const in[],
 asmlinkage void ce_aes_essiv_cbc_decrypt(u8 out[], u8 const in[],
 					 u32 const rk1[], int rounds,
 					 int blocks, u8 iv[], u32 const rk2[]);
-asmlinkage size_t ce_aes_mac_update(u8 const in[], u32 const rk[], int rounds,
-				    size_t blocks, u8 dg[], int enc_before,
-				    int enc_after);
+asmlinkage void ce_aes_mac_update(u8 const in[], u32 const rk[], int rounds,
+				  size_t blocks, u8 dg[], int enc_before,
+				  int enc_after);
 #elif defined(CONFIG_PPC)
 void ppc_expand_key_128(u32 *key_enc, const u8 *key);
 void ppc_expand_key_192(u32 *key_enc, const u8 *key);

lib/crypto/arm64/aes-modes.S

@@ -817,9 +817,9 @@ AES_FUNC_END(aes_xts_decrypt)
 
 #if IS_ENABLED(CONFIG_CRYPTO_LIB_AES_CBC_MACS)
 	/*
-	 * size_t aes_mac_update(u8 const in[], u32 const rk[], int rounds,
-	 *			 size_t blocks, u8 dg[], int enc_before,
-	 *			 int enc_after);
+	 * void aes_mac_update(u8 const in[], u32 const rk[], int rounds,
+	 *		       size_t blocks, u8 dg[], int enc_before,
+	 *		       int enc_after);
 	 */
 AES_FUNC_START(aes_mac_update)
 	ld1		{v0.16b}, [x4]			/* get dg */
@@ -844,7 +844,6 @@ AES_FUNC_START(aes_mac_update)
 	cbz		w5, .Lmacout
 	encrypt_block	v0, w2, x1, x7, w8
 	st1		{v0.16b}, [x4]			/* return dg */
-	cond_yield	.Lmacout, x7, x8
 	b		.Lmacloop4x
 .Lmac1x:
 	add		x3, x3, #4
@@ -863,7 +862,6 @@ AES_FUNC_START(aes_mac_update)
 
 .Lmacout:
 	st1		{v0.16b}, [x4]			/* return dg */
-	mov		x0, x3
 	ret
 AES_FUNC_END(aes_mac_update)
 #endif /* CONFIG_CRYPTO_LIB_AES_CBC_MACS */

lib/crypto/arm64/aes.h

@@ -29,9 +29,9 @@ asmlinkage void __aes_ce_decrypt(const u32 inv_rk[], u8 out[AES_BLOCK_SIZE],
 asmlinkage u32 __aes_ce_sub(u32 l);
 asmlinkage void __aes_ce_invert(struct aes_block *out,
 				const struct aes_block *in);
-asmlinkage size_t neon_aes_mac_update(u8 const in[], u32 const rk[], int rounds,
-				      size_t blocks, u8 dg[], int enc_before,
-				      int enc_after);
+asmlinkage void neon_aes_mac_update(u8 const in[], u32 const rk[], int rounds,
+				    size_t blocks, u8 dg[], int enc_before,
+				    int enc_after);
 
 /*
  * Expand an AES key using the crypto extensions if supported and usable or
@@ -192,25 +192,16 @@ static bool aes_cbcmac_blocks_arch(u8 h[AES_BLOCK_SIZE],
 				   bool enc_after)
 {
 	if (static_branch_likely(&have_neon) && likely(may_use_simd())) {
-		do {
-			size_t rem;
-
-			scoped_ksimd() {
-				if (static_branch_likely(&have_aes))
-					rem = ce_aes_mac_update(
-						data, key->k.rndkeys,
-						key->nrounds, nblocks, h,
-						enc_before, enc_after);
-				else
-					rem = neon_aes_mac_update(
-						data, key->k.rndkeys,
-						key->nrounds, nblocks, h,
-						enc_before, enc_after);
-			}
-			data += (nblocks - rem) * AES_BLOCK_SIZE;
-			nblocks = rem;
-			enc_before = false;
-		} while (nblocks);
+		scoped_ksimd() {
+			if (static_branch_likely(&have_aes))
+				ce_aes_mac_update(data, key->k.rndkeys,
+						  key->nrounds, nblocks, h,
+						  enc_before, enc_after);
+			else
+				neon_aes_mac_update(data, key->k.rndkeys,
+						    key->nrounds, nblocks, h,
+						    enc_before, enc_after);
+		}
 		return true;
 	}
 	return false;