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Date: Wed, 12 Jul 2017 15:44:16 +0100
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: linux-arm-kernel@...ts.infradead.org,
kernel-hardening@...ts.openwall.com
Cc: mark.rutland@....com,
labbott@...oraproject.org,
will.deacon@....com,
dave.martin@....com,
catalin.marinas@....com,
Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [RFC PATCH 03/10] arm64: crypto: avoid register x18 in scalar AES code
Register x18 is the platform register, and is not unconditionally
classified as a caller save register by the AAPCS64 ABI. So avoid
using it in our AES assembler code, to allow the kernel to use it
as a task_struct pointer.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
arch/arm64/crypto/aes-cipher-core.S | 55 ++++++++++----------
1 file changed, 28 insertions(+), 27 deletions(-)
diff --git a/arch/arm64/crypto/aes-cipher-core.S b/arch/arm64/crypto/aes-cipher-core.S
index f2f9cc519309..62c91b9fcd56 100644
--- a/arch/arm64/crypto/aes-cipher-core.S
+++ b/arch/arm64/crypto/aes-cipher-core.S
@@ -17,8 +17,7 @@
out .req x1
in .req x2
rounds .req x3
- tt .req x4
- lt .req x2
+ tt .req x2
.macro __pair, enc, reg0, reg1, in0, in1e, in1d, shift
ubfx \reg0, \in0, #\shift, #8
@@ -34,17 +33,17 @@
.macro __hround, out0, out1, in0, in1, in2, in3, t0, t1, enc
ldp \out0, \out1, [rk], #8
- __pair \enc, w13, w14, \in0, \in1, \in3, 0
- __pair \enc, w15, w16, \in1, \in2, \in0, 8
- __pair \enc, w17, w18, \in2, \in3, \in1, 16
+ __pair \enc, w12, w13, \in0, \in1, \in3, 0
+ __pair \enc, w14, w15, \in1, \in2, \in0, 8
+ __pair \enc, w16, w17, \in2, \in3, \in1, 16
__pair \enc, \t0, \t1, \in3, \in0, \in2, 24
- eor \out0, \out0, w13
- eor \out1, \out1, w14
- eor \out0, \out0, w15, ror #24
- eor \out1, \out1, w16, ror #24
- eor \out0, \out0, w17, ror #16
- eor \out1, \out1, w18, ror #16
+ eor \out0, \out0, w12
+ eor \out1, \out1, w13
+ eor \out0, \out0, w14, ror #24
+ eor \out1, \out1, w15, ror #24
+ eor \out0, \out0, w16, ror #16
+ eor \out1, \out1, w17, ror #16
eor \out0, \out0, \t0, ror #8
eor \out1, \out1, \t1, ror #8
.endm
@@ -60,42 +59,44 @@
.endm
.macro do_crypt, round, ttab, ltab
- ldp w5, w6, [in]
- ldp w7, w8, [in, #8]
- ldp w9, w10, [rk], #16
- ldp w11, w12, [rk, #-8]
+ ldp w4, w5, [in]
+ ldp w6, w7, [in, #8]
+ ldp w8, w9, [rk], #16
+ ldp w10, w11, [rk, #-8]
+CPU_BE( rev w4, w4 )
CPU_BE( rev w5, w5 )
CPU_BE( rev w6, w6 )
CPU_BE( rev w7, w7 )
-CPU_BE( rev w8, w8 )
+ eor w4, w4, w8
eor w5, w5, w9
eor w6, w6, w10
eor w7, w7, w11
- eor w8, w8, w12
adr_l tt, \ttab
- adr_l lt, \ltab
tbnz rounds, #1, 1f
-0: \round w9, w10, w11, w12, w5, w6, w7, w8
- \round w5, w6, w7, w8, w9, w10, w11, w12
+0: \round w8, w9, w10, w11, w4, w5, w6, w7
+ \round w4, w5, w6, w7, w8, w9, w10, w11
1: subs rounds, rounds, #4
- \round w9, w10, w11, w12, w5, w6, w7, w8
- csel tt, tt, lt, hi
- \round w5, w6, w7, w8, w9, w10, w11, w12
- b.hi 0b
+ \round w8, w9, w10, w11, w4, w5, w6, w7
+ b.ls 2f
+ \round w4, w5, w6, w7, w8, w9, w10, w11
+ b 0b
+2: adr_l tt, \ltab
+ \round w4, w5, w6, w7, w8, w9, w10, w11
+
+CPU_BE( rev w4, w4 )
CPU_BE( rev w5, w5 )
CPU_BE( rev w6, w6 )
CPU_BE( rev w7, w7 )
-CPU_BE( rev w8, w8 )
- stp w5, w6, [out]
- stp w7, w8, [out, #8]
+ stp w4, w5, [out]
+ stp w6, w7, [out, #8]
ret
.endm
--
2.9.3
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