From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> [ Upstream commit be0075951fde739f14ee2b659e2fd6e2499c46c0 ] vmlinux.o: warning: objtool: page_fault_oops()+0x13c: unreachable instruction 0000 000000000005b460 <page_fault_oops>: ... 0128 5b588: 49 89 23 mov %rsp,(%r11) 012b 5b58b: 4c 89 dc mov %r11,%rsp 012e 5b58e: 4c 89 f2 mov %r14,%rdx 0131 5b591: 48 89 ee mov %rbp,%rsi 0134 5b594: 4c 89 e7 mov %r12,%rdi 0137 5b597: e8 00 00 00 00 call 5b59c <page_fault_oops+0x13c> 5b598: R_X86_64_PLT32 handle_stack_overflow-0x4 013c 5b59c: 5c pop %rsp vmlinux.o: warning: objtool: sysvec_reboot()+0x6d: unreachable instruction 0000 00000000000033f0 <sysvec_reboot>: ... 005d 344d: 4c 89 dc mov %r11,%rsp 0060 3450: e8 00 00 00 00 call 3455 <sysvec_reboot+0x65> 3451: R_X86_64_PLT32 irq_enter_rcu-0x4 0065 3455: 48 89 ef mov %rbp,%rdi 0068 3458: e8 00 00 00 00 call 345d <sysvec_reboot+0x6d> 3459: R_X86_64_PC32 .text+0x47d0c 006d 345d: e8 00 00 00 00 call 3462 <sysvec_reboot+0x72> 345e: R_X86_64_PLT32 irq_exit_rcu-0x4 0072 3462: 5c pop %rsp Both cases are due to a call_on_stack() calling a __noreturn function. Since that's an inline asm, GCC can't do anything about the instructions after the CALL. Therefore put in an explicit ASM_REACHABLE annotation to make sure objtool and gcc are consistently confused about control flow. Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220308154319.468805622@xxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- arch/x86/include/asm/irq_stack.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/irq_stack.h b/arch/x86/include/asm/irq_stack.h index ae9d40f6c706..05af249d6bec 100644 --- a/arch/x86/include/asm/irq_stack.h +++ b/arch/x86/include/asm/irq_stack.h @@ -99,7 +99,8 @@ } #define ASM_CALL_ARG0 \ - "call %P[__func] \n" + "call %P[__func] \n" \ + ASM_REACHABLE #define ASM_CALL_ARG1 \ "movq %[arg1], %%rdi \n" \ -- 2.35.1
