This is a note to let you know that I've just added the patch titled
ARM: 9197/1: spectre-bhb: fix loop8 sequence for Thumb2
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-9197-1-spectre-bhb-fix-loop8-sequence-for-thumb2.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit de15ad79ebca8d603124476ba944f8ddccf42c7b
Author: Ard Biesheuvel <ardb@xxxxxxxxxx>
Date: Wed Apr 20 09:46:17 2022 +0100
ARM: 9197/1: spectre-bhb: fix loop8 sequence for Thumb2
[ 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@xxxxxxxxxx>
Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 46b697dfa4cf..68261a83b7ad 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -1038,7 +1038,7 @@ vector_bhb_loop8_\name:
@ bhb workaround
mov r0, #8
-3: b . + 4
+3: W(b) . + 4
subs r0, r0, #1
bne 3b
dsb
