From: Ard Biesheuvel <ardb@xxxxxxxxxx>
Tweak the round key logic so that they can be loaded using a single
branchless sequence using overlapping loads. This is shorter and
simpler, and puts the conditional branches based on the key size further
apart, which might benefit microarchitectures that cannot record taken
branches at every instruction. For these branches, use test-bit-branch
instructions that don't clobber the condition flags.
Note that none of this has any impact on performance, positive or
otherwise (and the branch prediction benefit would only benefit AES-192
which nobody uses). It does make for nicer code, though.
While at it, use \@ to generate the labels inside the macros, which is
more robust than using fixed numbers, which could clash inadvertently.
Also, bring aes-neon.S in line with these changes, including the switch
to test-and-branch instructions, to avoid surprises in the future when
we might start relying on the condition flags being preserved in the
chaining mode wrappers in aes-modes.S
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
arch/arm64/crypto/aes-ce.S | 34 ++++++++++++++--------------------
arch/arm64/crypto/aes-neon.S | 20 ++++++++++----------
2 files changed, 24 insertions(+), 30 deletions(-)
diff --git a/arch/arm64/crypto/aes-ce.S b/arch/arm64/crypto/aes-ce.S
index 1dc5bbbfeed2..b262eaa9170c 100644
--- a/arch/arm64/crypto/aes-ce.S
+++ b/arch/arm64/crypto/aes-ce.S
@@ -25,33 +25,28 @@
.endm
/* preload all round keys */
- .macro load_round_keys, rounds, rk
- cmp \rounds, #12
- blo 2222f /* 128 bits */
- beq 1111f /* 192 bits */
- ld1 {v17.4s-v18.4s}, [\rk], #32
-1111: ld1 {v19.4s-v20.4s}, [\rk], #32
-2222: ld1 {v21.4s-v24.4s}, [\rk], #64
- ld1 {v25.4s-v28.4s}, [\rk], #64
- ld1 {v29.4s-v31.4s}, [\rk]
+ .macro load_round_keys, rk, nr, tmp
+ add \tmp, \rk, \nr, sxtw #4
+ sub \tmp, \tmp, #160
+ ld1 {v17.4s-v20.4s}, [\rk]
+ ld1 {v21.4s-v24.4s}, [\tmp], #64
+ ld1 {v25.4s-v28.4s}, [\tmp], #64
+ ld1 {v29.4s-v31.4s}, [\tmp]
.endm
/* prepare for encryption with key in rk[] */
.macro enc_prepare, rounds, rk, temp
- mov \temp, \rk
- load_round_keys \rounds, \temp
+ load_round_keys \rk, \rounds, \temp
.endm
/* prepare for encryption (again) but with new key in rk[] */
.macro enc_switch_key, rounds, rk, temp
- mov \temp, \rk
- load_round_keys \rounds, \temp
+ load_round_keys \rk, \rounds, \temp
.endm
/* prepare for decryption with key in rk[] */
.macro dec_prepare, rounds, rk, temp
- mov \temp, \rk
- load_round_keys \rounds, \temp
+ load_round_keys \rk, \rounds, \temp
.endm
.macro do_enc_Nx, de, mc, k, i0, i1, i2, i3, i4
@@ -110,14 +105,13 @@
/* up to 5 interleaved blocks */
.macro do_block_Nx, enc, rounds, i0, i1, i2, i3, i4
- cmp \rounds, #12
- blo 2222f /* 128 bits */
- beq 1111f /* 192 bits */
+ tbz \rounds, #2, .L\@ /* 128 bits */
round_Nx \enc, v17, \i0, \i1, \i2, \i3, \i4
round_Nx \enc, v18, \i0, \i1, \i2, \i3, \i4
-1111: round_Nx \enc, v19, \i0, \i1, \i2, \i3, \i4
+ tbz \rounds, #1, .L\@ /* 192 bits */
+ round_Nx \enc, v19, \i0, \i1, \i2, \i3, \i4
round_Nx \enc, v20, \i0, \i1, \i2, \i3, \i4
-2222: .irp key, v21, v22, v23, v24, v25, v26, v27, v28, v29
+.L\@: .irp key, v21, v22, v23, v24, v25, v26, v27, v28, v29
round_Nx \enc, \key, \i0, \i1, \i2, \i3, \i4
.endr
fin_round_Nx \enc, v30, v31, \i0, \i1, \i2, \i3, \i4
diff --git a/arch/arm64/crypto/aes-neon.S b/arch/arm64/crypto/aes-neon.S
index 9de7fbc797af..3a8961b6ea51 100644
--- a/arch/arm64/crypto/aes-neon.S
+++ b/arch/arm64/crypto/aes-neon.S
@@ -99,16 +99,16 @@
ld1 {v15.4s}, [\rk]
add \rkp, \rk, #16
mov \i, \rounds
-1111: eor \in\().16b, \in\().16b, v15.16b /* ^round key */
+.La\@: eor \in\().16b, \in\().16b, v15.16b /* ^round key */
movi v15.16b, #0x40
tbl \in\().16b, {\in\().16b}, v13.16b /* ShiftRows */
sub_bytes \in
- subs \i, \i, #1
+ sub \i, \i, #1
ld1 {v15.4s}, [\rkp], #16
- beq 2222f
+ cbz \i, .Lb\@
mix_columns \in, \enc
- b 1111b
-2222: eor \in\().16b, \in\().16b, v15.16b /* ^round key */
+ b .La\@
+.Lb\@: eor \in\().16b, \in\().16b, v15.16b /* ^round key */
.endm
.macro encrypt_block, in, rounds, rk, rkp, i
@@ -206,7 +206,7 @@
ld1 {v15.4s}, [\rk]
add \rkp, \rk, #16
mov \i, \rounds
-1111: eor \in0\().16b, \in0\().16b, v15.16b /* ^round key */
+.La\@: eor \in0\().16b, \in0\().16b, v15.16b /* ^round key */
eor \in1\().16b, \in1\().16b, v15.16b /* ^round key */
eor \in2\().16b, \in2\().16b, v15.16b /* ^round key */
eor \in3\().16b, \in3\().16b, v15.16b /* ^round key */
@@ -216,13 +216,13 @@
tbl \in2\().16b, {\in2\().16b}, v13.16b /* ShiftRows */
tbl \in3\().16b, {\in3\().16b}, v13.16b /* ShiftRows */
sub_bytes_4x \in0, \in1, \in2, \in3
- subs \i, \i, #1
+ sub \i, \i, #1
ld1 {v15.4s}, [\rkp], #16
- beq 2222f
+ cbz \i, .Lb\@
mix_columns_2x \in0, \in1, \enc
mix_columns_2x \in2, \in3, \enc
- b 1111b
-2222: eor \in0\().16b, \in0\().16b, v15.16b /* ^round key */
+ b .La\@
+.Lb\@: eor \in0\().16b, \in0\().16b, v15.16b /* ^round key */
eor \in1\().16b, \in1\().16b, v15.16b /* ^round key */
eor \in2\().16b, \in2\().16b, v15.16b /* ^round key */
eor \in3\().16b, \in3\().16b, v15.16b /* ^round key */
--
2.44.0.683.g7961c838ac-goog
