linux-kernel - [PATCH 4/4] x86,objtool: Explicitly mark idtentry

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Date:   Fri, 08 Apr 2022 11:45:56 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        rick.p.edgecombe@...el.com, jpoimboe@...hat.com
Subject: [PATCH 4/4] 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@...radead.org>
---
 arch/x86/entry/entry_64.S |    3 +++
 1 file changed, 3 insertions(+)

--- 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