Even though the kernel's implementations of AES-XTS were updated to
implement ciphertext stealing and can operate on inputs of any size
larger than or equal to the AES block size, this feature is rarely used
in practice.
In fact, in the kernel, AES-XTS is only used to operate on 4096 or 512
byte blocks, which means that not only the ciphertext stealing is
effectively dead code, the logic in the bit sliced NEON implementation
to deal with fewer than 8 blocks at a time is also never used.
Since the bit-sliced NEON driver already depends on the plain NEON
version, which is slower but can operate on smaller data quantities more
straightforwardly, let's fallback to the plain NEON implementation of
XTS for any residual inputs that are not multiples of 128 bytes. This
allows us to remove a lot of complicated logic that rarely gets
exercised in practice.
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
arch/arm64/crypto/aes-neonbs-core.S | 132 ++++++--------------
arch/arm64/crypto/aes-neonbs-glue.c | 33 ++---
2 files changed, 57 insertions(+), 108 deletions(-)
diff --git a/arch/arm64/crypto/aes-neonbs-core.S b/arch/arm64/crypto/aes-neonbs-core.S
index f2761481181d..d427f4556b6e 100644
--- a/arch/arm64/crypto/aes-neonbs-core.S
+++ b/arch/arm64/crypto/aes-neonbs-core.S
@@ -735,119 +735,67 @@ SYM_FUNC_END(aesbs_cbc_decrypt)
* int blocks, u8 iv[])
*/
SYM_FUNC_START_LOCAL(__xts_crypt8)
- mov x6, #1
- lsl x6, x6, x23
- subs w23, w23, #8
- csel x23, x23, xzr, pl
- csel x6, x6, xzr, mi
+ movi v18.2s, #0x1
+ movi v19.2s, #0x87
+ uzp1 v18.4s, v18.4s, v19.4s
+
+ ld1 {v0.16b-v3.16b}, [x1], #64
+ ld1 {v4.16b-v7.16b}, [x1], #64
+
+ next_tweak v26, v25, v18, v19
+ next_tweak v27, v26, v18, v19
+ next_tweak v28, v27, v18, v19
+ next_tweak v29, v28, v18, v19
+ next_tweak v30, v29, v18, v19
+ next_tweak v31, v30, v18, v19
+ next_tweak v16, v31, v18, v19
+ next_tweak v17, v16, v18, v19
- ld1 {v0.16b}, [x20], #16
- next_tweak v26, v25, v30, v31
eor v0.16b, v0.16b, v25.16b
- tbnz x6, #1, 0f
-
- ld1 {v1.16b}, [x20], #16
- next_tweak v27, v26, v30, v31
eor v1.16b, v1.16b, v26.16b
- tbnz x6, #2, 0f
-
- ld1 {v2.16b}, [x20], #16
- next_tweak v28, v27, v30, v31
eor v2.16b, v2.16b, v27.16b
- tbnz x6, #3, 0f
-
- ld1 {v3.16b}, [x20], #16
- next_tweak v29, v28, v30, v31
eor v3.16b, v3.16b, v28.16b
- tbnz x6, #4, 0f
-
- ld1 {v4.16b}, [x20], #16
- str q29, [sp, #.Lframe_local_offset]
eor v4.16b, v4.16b, v29.16b
- next_tweak v29, v29, v30, v31
- tbnz x6, #5, 0f
-
- ld1 {v5.16b}, [x20], #16
- str q29, [sp, #.Lframe_local_offset + 16]
- eor v5.16b, v5.16b, v29.16b
- next_tweak v29, v29, v30, v31
- tbnz x6, #6, 0f
+ eor v5.16b, v5.16b, v30.16b
+ eor v6.16b, v6.16b, v31.16b
+ eor v7.16b, v7.16b, v16.16b
- ld1 {v6.16b}, [x20], #16
- str q29, [sp, #.Lframe_local_offset + 32]
- eor v6.16b, v6.16b, v29.16b
- next_tweak v29, v29, v30, v31
- tbnz x6, #7, 0f
+ stp q16, q17, [sp, #16]
- ld1 {v7.16b}, [x20], #16
- str q29, [sp, #.Lframe_local_offset + 48]
- eor v7.16b, v7.16b, v29.16b
- next_tweak v29, v29, v30, v31
-
-0: mov bskey, x21
- mov rounds, x22
+ mov bskey, x2
+ mov rounds, x3
br x16
SYM_FUNC_END(__xts_crypt8)
.macro __xts_crypt, do8, o0, o1, o2, o3, o4, o5, o6, o7
- frame_push 6, 64
-
- mov x19, x0
- mov x20, x1
- mov x21, x2
- mov x22, x3
- mov x23, x4
- mov x24, x5
+ stp x29, x30, [sp, #-48]!
+ mov x29, sp
- movi v30.2s, #0x1
- movi v25.2s, #0x87
- uzp1 v30.4s, v30.4s, v25.4s
- ld1 {v25.16b}, [x24]
+ ld1 {v25.16b}, [x5]
-99: adr x16, \do8
+0: adr x16, \do8
bl __xts_crypt8
- ldp q16, q17, [sp, #.Lframe_local_offset]
- ldp q18, q19, [sp, #.Lframe_local_offset + 32]
+ eor v16.16b, \o0\().16b, v25.16b
+ eor v17.16b, \o1\().16b, v26.16b
+ eor v18.16b, \o2\().16b, v27.16b
+ eor v19.16b, \o3\().16b, v28.16b
- eor \o0\().16b, \o0\().16b, v25.16b
- eor \o1\().16b, \o1\().16b, v26.16b
- eor \o2\().16b, \o2\().16b, v27.16b
- eor \o3\().16b, \o3\().16b, v28.16b
+ ldp q24, q25, [sp, #16]
- st1 {\o0\().16b}, [x19], #16
- mov v25.16b, v26.16b
- tbnz x6, #1, 1f
- st1 {\o1\().16b}, [x19], #16
- mov v25.16b, v27.16b
- tbnz x6, #2, 1f
- st1 {\o2\().16b}, [x19], #16
- mov v25.16b, v28.16b
- tbnz x6, #3, 1f
- st1 {\o3\().16b}, [x19], #16
- mov v25.16b, v29.16b
- tbnz x6, #4, 1f
-
- eor \o4\().16b, \o4\().16b, v16.16b
- eor \o5\().16b, \o5\().16b, v17.16b
- eor \o6\().16b, \o6\().16b, v18.16b
- eor \o7\().16b, \o7\().16b, v19.16b
-
- st1 {\o4\().16b}, [x19], #16
- tbnz x6, #5, 1f
- st1 {\o5\().16b}, [x19], #16
- tbnz x6, #6, 1f
- st1 {\o6\().16b}, [x19], #16
- tbnz x6, #7, 1f
- st1 {\o7\().16b}, [x19], #16
+ eor v20.16b, \o4\().16b, v29.16b
+ eor v21.16b, \o5\().16b, v30.16b
+ eor v22.16b, \o6\().16b, v31.16b
+ eor v23.16b, \o7\().16b, v24.16b
- cbz x23, 1f
- st1 {v25.16b}, [x24]
+ st1 {v16.16b-v19.16b}, [x0], #64
+ st1 {v20.16b-v23.16b}, [x0], #64
- b 99b
+ subs x4, x4, #8
+ b.gt 0b
-1: st1 {v25.16b}, [x24]
- frame_pop
+ st1 {v25.16b}, [x5]
+ ldp x29, x30, [sp], #48
ret
.endm
diff --git a/arch/arm64/crypto/aes-neonbs-glue.c b/arch/arm64/crypto/aes-neonbs-glue.c
index 3189003e1cbe..bac4cabef607 100644
--- a/arch/arm64/crypto/aes-neonbs-glue.c
+++ b/arch/arm64/crypto/aes-neonbs-glue.c
@@ -302,23 +302,18 @@ static int __xts_crypt(struct skcipher_request *req, bool encrypt,
return err;
while (walk.nbytes >= AES_BLOCK_SIZE) {
- unsigned int blocks = walk.nbytes / AES_BLOCK_SIZE;
-
- if (walk.nbytes < walk.total || walk.nbytes % AES_BLOCK_SIZE)
- blocks = round_down(blocks,
- walk.stride / AES_BLOCK_SIZE);
-
+ int blocks = (walk.nbytes / AES_BLOCK_SIZE) & ~7;
out = walk.dst.virt.addr;
in = walk.src.virt.addr;
nbytes = walk.nbytes;
kernel_neon_begin();
- if (likely(blocks > 6)) { /* plain NEON is faster otherwise */
- if (first)
+ if (blocks >= 8) {
+ if (first == 1)
neon_aes_ecb_encrypt(walk.iv, walk.iv,
ctx->twkey,
ctx->key.rounds, 1);
- first = 0;
+ first = 2;
fn(out, in, ctx->key.rk, ctx->key.rounds, blocks,
walk.iv);
@@ -327,10 +322,17 @@ static int __xts_crypt(struct skcipher_request *req, bool encrypt,
in += blocks * AES_BLOCK_SIZE;
nbytes -= blocks * AES_BLOCK_SIZE;
}
-
- if (walk.nbytes == walk.total && nbytes > 0)
- goto xts_tail;
-
+ if (walk.nbytes == walk.total && nbytes > 0) {
+ if (encrypt)
+ neon_aes_xts_encrypt(out, in, ctx->cts.key_enc,
+ ctx->key.rounds, nbytes,
+ ctx->twkey, walk.iv, first);
+ else
+ neon_aes_xts_decrypt(out, in, ctx->cts.key_dec,
+ ctx->key.rounds, nbytes,
+ ctx->twkey, walk.iv, first);
+ nbytes = first = 0;
+ }
kernel_neon_end();
err = skcipher_walk_done(&walk, nbytes);
}
@@ -355,13 +357,12 @@ static int __xts_crypt(struct skcipher_request *req, bool encrypt,
nbytes = walk.nbytes;
kernel_neon_begin();
-xts_tail:
if (encrypt)
neon_aes_xts_encrypt(out, in, ctx->cts.key_enc, ctx->key.rounds,
- nbytes, ctx->twkey, walk.iv, first ?: 2);
+ nbytes, ctx->twkey, walk.iv, first);
else
neon_aes_xts_decrypt(out, in, ctx->cts.key_dec, ctx->key.rounds,
- nbytes, ctx->twkey, walk.iv, first ?: 2);
+ nbytes, ctx->twkey, walk.iv, first);
kernel_neon_end();
return skcipher_walk_done(&walk, 0);
--
2.30.2
