/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Scalar AES core transform
*
* Copyright (C) 2017 Linaro Ltd.
* Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/cache.h>
.text
.
align 5
rk .req r0
rounds .req r1
in .req r2
out .req r3
ttab .req ip
t0 .req lr
t1 .req r2
t2 .req r3
.macro __select, out, in, idx
.if __LINUX_ARM_ARCH__ < 7
and \out, \in, #0xff << (8 * \idx)
.else
ubfx \out, \in, #(8 * \idx), #8
.endif
.endm
.macro __load, out, in, idx, sz, op
.if __LINUX_ARM_ARCH__ < 7 && \idx > 0
ldr\op \out, [ttab, \in, lsr #(8 * \idx) - \sz]
.else
ldr\op \out, [ttab, \in, lsl #\sz]
.endif
.endm
.macro __hround, out0, out1, in0, in1, in2, in3, t3, t4, enc, sz, op, oldcpsr
__select \out0, \in0, 0
__select t0, \in1, 1
__load \out0, \out0, 0, \sz, \op
__load t0, t0, 1, \sz, \op
.if \enc
__select \out1, \in1, 0
__select t1, \in2, 1
.else
__select \out1, \in3, 0
__select t1, \in0, 1
.endif
__load \out1, \out1, 0, \sz, \op
__select t2, \in2, 2
__load t1, t1, 1, \sz, \op
__load t2, t2, 2, \sz, \op
eor \out0, \out0, t0, ror #24
__select t0, \in3, 3
.if \enc
__select \t3, \in3, 2
__select \t4, \in0, 3
.else
__select \t3, \in1, 2
__select \t4, \in2, 3
.endif
__load \t3, \t3, 2, \sz, \op
__load t0, t0, 3, \sz, \op
__load \t4, \t4, 3, \sz, \op
.ifnb \oldcpsr
/*
* This is the final round and we're done with all data-dependent table
* lookups, so we can safely re-enable interrupts.
*/
restore_irqs \oldcpsr
.endif
eor \out1, \out1, t1, ror #24
eor \out0, \out0, t2, ror #16
ldm rk
!, {t1, t2}
eor \out1, \out1, \t3, ror #16
eor \out0, \out0, t0, ror #8
eor \out1, \out1, \t4, ror #8
eor \out0, \out0, t1
eor \out1, \out1, t2
.endm
.macro fround, out0, out1, out2, out3, in0, in1, in2, in3, sz=2, op, oldcpsr
__hround \out0, \out1, \in0, \in1, \in2, \in3, \out2, \out3, 1, \sz, \op
__hround \out2, \out3, \in2, \in3, \in0, \in1, \in1, \in2, 1, \sz, \op, \oldcpsr
.endm
.macro iround, out0, out1, out2, out3, in0, in1, in2, in3, sz=2, op, oldcpsr
__hround \out0, \out1, \in0, \in3, \in2, \in1, \out2, \out3, 0, \sz, \op
__hround \out2, \out3, \in2, \in1, \in0, \in3, \in1, \in0, 0, \sz, \op, \oldcpsr
.endm
.macro do_crypt, round, ttab, ltab, bsz
push {r3-r11, lr}
// Load keys first, to reduce latency in case they
're not cached yet.
ldm rk
!, {r8-r11}
ldr r4, [in]
ldr r5, [in, #4]
ldr r6, [in, #8]
ldr r7, [in, #12]
#ifdef CONFIG_CPU_BIG_ENDIAN
rev_l r4, t0
rev_l r5, t0
rev_l r6, t0
rev_l r7, t0
#endif
eor r4, r4, r8
eor r5, r5, r9
eor r6, r6, r10
eor r7, r7, r11
mov_l ttab, \ttab
/*
* Disable interrupts and prefetch the 1024-byte 'ft' or 'it' table into
* L1 cache, assuming cacheline size >= 32. This is a hardening measure
* intended to make cache-timing attacks more difficult. They may not
* be fully prevented, however; see the paper
* https://cr.yp.to/antiforgery/cachetiming-20050414.pdf
* ("Cache-timing attacks on AES") for a discussion of the many
* difficulties involved in writing truly constant-time AES software.
*/
save_and_disable_irqs t0
.
set i, 0
.rept 1024 / 128
ldr r8, [ttab, #i + 0]
ldr r9, [ttab, #i + 32]
ldr r10, [ttab, #i + 64]
ldr r11, [ttab, #i + 96]
.
set i, i + 128
.endr
push {t0} // oldcpsr
tst rounds, #2
bne 1f
0: \round r8, r9, r10, r11, r4, r5, r6, r7
\round r4, r5, r6, r7, r8, r9, r10, r11
1: subs rounds, rounds, #4
\round r8, r9, r10, r11, r4, r5, r6, r7
bls 2f
\round r4, r5, r6, r7, r8, r9, r10, r11
b 0b
2: .ifb \ltab
add ttab, ttab, #1
.else
mov_l ttab, \ltab
// Prefetch inverse S-box for final round; see explanation above
.
set i, 0
.rept 256 / 64
ldr t0, [ttab, #i + 0]
ldr t1, [ttab, #i + 32]
.
set i, i + 64
.endr
.endif
pop {rounds} // oldcpsr
\round r4, r5, r6, r7, r8, r9, r10, r11, \bsz, b, rounds
#ifdef CONFIG_CPU_BIG_ENDIAN
rev_l r4, t0
rev_l r5, t0
rev_l r6, t0
rev_l r7, t0
#endif
ldr out, [sp]
str r4, [out]
str r5, [out, #4]
str r6, [out, #8]
str r7, [out, #12]
pop {r3-r11, pc}
.
align 3
.ltorg
.endm
ENTRY(__aes_arm_encrypt)
do_crypt fround, crypto_ft_tab,, 2
ENDPROC(__aes_arm_encrypt)
.
align 5
ENTRY(__aes_arm_decrypt)
do_crypt iround, crypto_it_tab, crypto_aes_inv_sbox, 0
ENDPROC(__aes_arm_decrypt)
