Below error was reported in a 32-bit kernel build:

static_call.c:(.ref.text+0x46): undefined reference to `cpu_wants_rethunk_at' make[1]: [Makefile:1234: vmlinux] Error

This is because the definition of cpu_wants_rethunk_at() depends on CONFIG_STACK_VALIDATION which is only enabled in 64-bit mode.

Define the empty function for CONFIG_STACK_VALIDATION=n, rethunk mitigation is anyways not supported without it.

Reported-by: Guenter Roeck linux@roeck-us.net Fixes: 5d19a0574b75 ("x86/its: Add support for ITS-safe return thunk") Signed-off-by: Pawan Gupta pawan.kumar.gupta@linux.intel.com Link: https://lore.kernel.org/stable/0f597436-5da6-4319-b918-9f57bde5634a@roeck-us... --- arch/x86/include/asm/alternative.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 1797f80c10de..a5f704dbb4a1 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -98,7 +98,7 @@ static inline u8 *its_static_thunk(int reg) } #endif

-#ifdef CONFIG_RETHUNK +#if defined(CONFIG_RETHUNK) && defined(CONFIG_STACK_VALIDATION) extern bool cpu_wants_rethunk(void); extern bool cpu_wants_rethunk_at(void *addr); #else