linux-kernel - [PATCH 4.9 19/20] ARM: fix Thumb2 regression with Spectre BHB

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Message-Id: <20220314112731.062892656@linuxfoundation.org>
Date:   Mon, 14 Mar 2022 12:34:20 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.9 19/20] ARM: fix Thumb2 regression with Spectre BHB

From: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

commit 6c7cb60bff7aec24b834343ff433125f469886a3 upstream.

When building for Thumb2, the vectors make use of a local label. Sadly,
the Spectre BHB code also uses a local label with the same number which
results in the Thumb2 reference pointing at the wrong place. Fix this
by changing the number used for the Spectre BHB local label.

Fixes: b9baf5c8c5c3 ("ARM: Spectre-BHB workaround")
Tested-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm/kernel/entry-armv.S |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -1074,9 +1074,9 @@ vector_bhb_loop8_\name:
 
 	@ bhb workaround
 	mov	r0, #8
-1:	b	. + 4
+3:	b	. + 4
 	subs	r0, r0, #1
-	bne	1b
+	bne	3b
 	dsb
 	isb
 	b	2b