[BUG][PATCH] crypto: arm64: Avoid indirect branch to bti_c

From: Jeremy Linton
Date: Mon Oct 05 2020 - 23:49:07 EST


The AES code uses a 'br x7' as part of a function called by
a macro. That branch needs a bti_j as a target. This results
in a panic as seen below. Instead of trying to replace the branch
target with a bti_jc, lets replace the indirect branch with a
bl/ret, bl sequence that can target the existing bti_c.

Bad mode in Synchronous Abort handler detected on CPU1, code 0x34000003 -- BTI
CPU: 1 PID: 265 Comm: cryptomgr_test Not tainted 5.8.11-300.fc33.aarch64 #1
pstate: 20400c05 (nzCv daif +PAN -UAO BTYPE=j-)
pc : aesbs_encrypt8+0x0/0x5f0 [aes_neon_bs]
lr : aesbs_xts_encrypt+0x48/0xe0 [aes_neon_bs]
sp : ffff80001052b730

aesbs_encrypt8+0x0/0x5f0 [aes_neon_bs]
__xts_crypt+0xb0/0x2dc [aes_neon_bs]
xts_encrypt+0x28/0x3c [aes_neon_bs]
crypto_skcipher_encrypt+0x50/0x84
simd_skcipher_encrypt+0xc8/0xe0
crypto_skcipher_encrypt+0x50/0x84
test_skcipher_vec_cfg+0x224/0x5f0
test_skcipher+0xbc/0x120
alg_test_skcipher+0xa0/0x1b0
alg_test+0x3dc/0x47c
cryptomgr_test+0x38/0x60

Fixes: commit 0e89640b640d ("crypto: arm64 - Use modern annotations for assembly functions")
Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
---
arch/arm64/crypto/aes-neonbs-core.S | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/crypto/aes-neonbs-core.S b/arch/arm64/crypto/aes-neonbs-core.S
index b357164379f6..32f53ebe5e2c 100644
--- a/arch/arm64/crypto/aes-neonbs-core.S
+++ b/arch/arm64/crypto/aes-neonbs-core.S
@@ -788,7 +788,7 @@ SYM_FUNC_START_LOCAL(__xts_crypt8)

0: mov bskey, x21
mov rounds, x22
- br x7
+ ret
SYM_FUNC_END(__xts_crypt8)

.macro __xts_crypt, do8, o0, o1, o2, o3, o4, o5, o6, o7
@@ -806,8 +806,8 @@ SYM_FUNC_END(__xts_crypt8)
uzp1 v30.4s, v30.4s, v25.4s
ld1 {v25.16b}, [x24]

-99: adr x7, \do8
- bl __xts_crypt8
+99: bl __xts_crypt8
+ bl \do8

ldp q16, q17, [sp, #.Lframe_local_offset]
ldp q18, q19, [sp, #.Lframe_local_offset + 32]
--
2.25.4