This is a note to let you know that I've just added the patch titled
arm64: Fix bit-shifting UB in the MIDR_CPU_MODEL() macro
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:
arm64-fix-bit-shifting-ub-in-the-midr_cpu_model-macr.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 c4b50f6fa4c7625fc8d20d37dee29a479ec7cdb9
Author: D Scott Phillips <scott@xxxxxxxxxxxxxxxxxxxxxx>
Date: Wed Nov 2 09:01:06 2022 -0700
arm64: Fix bit-shifting UB in the MIDR_CPU_MODEL() macro
[ Upstream commit 8ec8490a1950efeccb00967698cf7cb2fcd25ca7 ]
CONFIG_UBSAN_SHIFT with gcc-5 complains that the shifting of
ARM_CPU_IMP_AMPERE (0xC0) into bits [31:24] by MIDR_CPU_MODEL() is
undefined behavior. Well, sort of, it actually spells the error as:
arch/arm64/kernel/proton-pack.c: In function 'spectre_bhb_loop_affected':
arch/arm64/include/asm/cputype.h:44:2: error: initializer element is not constant
(((imp) << MIDR_IMPLEMENTOR_SHIFT) | \
^
This isn't an issue for other Implementor codes, as all the other codes
have zero in the top bit and so are representable as a signed int.
Cast the implementor code to unsigned in MIDR_CPU_MODEL to remove the
undefined behavior.
Fixes: 0e5d5ae837c8 ("arm64: Add AMPERE1 to the Spectre-BHB affected list")
Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Signed-off-by: D Scott Phillips <scott@xxxxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221102160106.1096948-1-scott@xxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
index 457b6bb276bb..9cf5d9551e99 100644
--- a/arch/arm64/include/asm/cputype.h
+++ b/arch/arm64/include/asm/cputype.h
@@ -41,7 +41,7 @@
(((midr) & MIDR_IMPLEMENTOR_MASK) >> MIDR_IMPLEMENTOR_SHIFT)
#define MIDR_CPU_MODEL(imp, partnum) \
- (((imp) << MIDR_IMPLEMENTOR_SHIFT) | \
+ ((_AT(u32, imp) << MIDR_IMPLEMENTOR_SHIFT) | \
(0xf << MIDR_ARCHITECTURE_SHIFT) | \
((partnum) << MIDR_PARTNUM_SHIFT))
