[PATCH 4.14 21/33] ARM: 9197/1: spectre-bhb: fix loop8 sequence for Thumb2

Greg Kroah-Hartman
2022-05-23T17:09:43Z

From: Ard Biesheuvel <ardb@kernel.org>

[ Upstream commit 3cfb3019979666bdf33a1010147363cf05e0f17b ]

In Thumb2, 'b . + 4' produces a branch instruction that uses a narrow
encoding, and so it does not jump to the following instruction as
expected. So use W(b) instead.

Fixes: 6c7cb60bff7a ("ARM: fix Thumb2 regression with Spectre BHB")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm/kernel/entry-armv.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index b54084f9b77a..e1b3c5c96560 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -1071,7 +1071,7 @@ vector_bhb_loop8_\name:

@ bhb workaround
mov r0, #8
-3: b . + 4
+3: W(b) . + 4
subs r0, r0, #1
bne 3b
dsb
--
2.35.1