From: D Scott Phillips scott@os.amperecomputing.com
commit 8ec8490a1950efeccb00967698cf7cb2fcd25ca7 upstream.
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@linux-m68k.org Signed-off-by: D Scott Phillips scott@os.amperecomputing.com Link: https://lore.kernel.org/r/20221102160106.1096948-1-scott@os.amperecomputing.... Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com --- arch/arm64/include/asm/cputype.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h index 08241810cfea..892fc0ceccb8 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))