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ARM: 9197/1: spectre-bhb: fix loop8 sequence for Thumb2
authorArd Biesheuvel <ardb@kernel.org>
Wed, 20 Apr 2022 08:46:17 +0000 (09:46 +0100)
committerRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Wed, 18 May 2022 10:38:47 +0000 (11:38 +0100)
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>
arch/arm/kernel/entry-armv.S patch | blob | history

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 0650869..7a86824 100644 (file)
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -1145,7 +1145,7 @@ vector_bhb_loop8_\name:
 
        @ bhb workaround
        mov     r0, #8
-3:     b       . + 4
+3:     W(b)    . + 4
        subs    r0, r0, #1
        bne     3b
        dsb
Domain: System / Kernel;