[tip: x86/urgent] x86,objtool: Explicitly mark idtentry_body()s tail REACHABLE

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     d66e9d50ea5cd76b2c4875c758efad665283d7ad
Gitweb:        https://git.kernel.org/tip/d66e9d50ea5cd76b2c4875c758efad665283d7ad
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Fri, 08 Apr 2022 11:45:56 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 19 Apr 2022 21:58:48 +02:00

x86,objtool: Explicitly mark idtentry_body()s tail REACHABLE

Objtool can figure out that some \cfunc()s are noreturn and then
complains about certain instances having unreachable tails:

  vmlinux.o: warning: objtool: asm_exc_xen_unknown_trap()+0x16: unreachable instruction

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220408094718.441854969@xxxxxxxxxxxxx
---
 arch/x86/entry/entry_64.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 4faac48..73d9585 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -337,6 +337,9 @@ SYM_CODE_END(ret_from_fork)
 
 	call	\cfunc
 
+	/* For some configurations \cfunc ends up being a noreturn. */
+	REACHABLE
+
 	jmp	error_return
 .endm