x86: Annotate idtentry_df()
Without CONFIG_X86_ESPFIX64 exc_double_fault() is noreturn and objtool
is clever enough to figure that out.
vmlinux.o: warning: objtool: asm_exc_double_fault()+0x22: unreachable instruction
0000000000001260 <asm_exc_double_fault>:
1260: f3 0f 1e fa endbr64
1264: 90 nop
1265: 90 nop
1266: 90 nop
1267: e8 84 03 00 00 call 15f0 <paranoid_entry>
126c: 48 89 e7 mov %rsp,%rdi
126f: 48 8b 74 24 78 mov 0x78(%rsp),%rsi
1274: 48 c7 44 24 78 ff ff ff ff movq $0xffffffffffffffff,0x78(%rsp)
127d: e8 00 00 00 00 call 1282 <asm_exc_double_fault+0x22> 127e: R_X86_64_PLT32 exc_double_fault-0x4
1282: e9 09 04 00 00 jmp 1690 <paranoid_exit>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/Yi9gOW9f1GGwwUD6@hirez.programming.kicks-ass.net
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 6e53991..4faac48 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -551,6 +551,9 @@
movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
call \cfunc
+ /* For some configurations \cfunc ends up being a noreturn. */
+ REACHABLE
+
jmp paranoid_exit
_ASM_NOKPROBE(\asmsym)
