From: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> commit 68453767131a5deec1e8f9ac92a9042f929e585d upstream. When CONFIG_GENERIC_CPU_VULNERABILITIES is not set, references to spectre_v2_update_state() cause a build error, so provide an empty stub for that function when the Kconfig option is not set. Fixes this build error: arm-linux-gnueabi-ld: arch/arm/mm/proc-v7-bugs.o: in function `cpu_v7_bugs_init': proc-v7-bugs.c:(.text+0x52): undefined reference to `spectre_v2_update_state' arm-linux-gnueabi-ld: proc-v7-bugs.c:(.text+0x82): undefined reference to `spectre_v2_update_state' Fixes: b9baf5c8c5c3 ("ARM: Spectre-BHB workaround") Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Reported-by: kernel test robot <lkp@xxxxxxxxx> Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: patches@xxxxxxxxxxxxxxx Acked-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm/include/asm/spectre.h | 6 ++++++ 1 file changed, 6 insertions(+) --- a/arch/arm/include/asm/spectre.h +++ b/arch/arm/include/asm/spectre.h @@ -25,7 +25,13 @@ enum { SPECTRE_V2_METHOD_LOOP8 = BIT(__SPECTRE_V2_METHOD_LOOP8), }; +#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES void spectre_v2_update_state(unsigned int state, unsigned int methods); +#else +static inline void spectre_v2_update_state(unsigned int state, + unsigned int methods) +{} +#endif int spectre_bhb_update_vectors(unsigned int method); Patches currently in stable-queue which might be from rdunlap@xxxxxxxxxxxxx are queue-4.9/arm-spectre-bhb-provide-empty-stub-for-non-config.patch