[tip: objtool/urgent] x86/extable: Annotate ex_handler_msr_mce() as a dead end

[tip-bot2 for Borislav Petkov]

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

Commit-ID:     2028a255f4df3af9e759f01f958d3237f825f256
Gitweb:        https://git.kernel.org/tip/2028a255f4df3af9e759f01f958d3237f825f256
Author:        Borislav Petkov <bp@xxxxxxx>
AuthorDate:    Fri, 20 May 2022 21:27:29 +02:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 27 May 2022 12:34:45 +02:00

x86/extable: Annotate ex_handler_msr_mce() as a dead end

Fix

  vmlinux.o: warning: objtool: fixup_exception+0x2d6: unreachable instruction

Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20220520192729.23969-1-bp@xxxxxxxxx
---
 arch/x86/include/asm/extable.h | 8 ++++++--
 tools/objtool/check.c          | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/extable.h b/arch/x86/include/asm/extable.h
index 155c991..eeed395 100644
--- a/arch/x86/include/asm/extable.h
+++ b/arch/x86/include/asm/extable.h
@@ -42,9 +42,13 @@ extern int ex_get_fixup_type(unsigned long ip);
 extern void early_fixup_exception(struct pt_regs *regs, int trapnr);
 
 #ifdef CONFIG_X86_MCE
-extern void ex_handler_msr_mce(struct pt_regs *regs, bool wrmsr);
+extern void __noreturn ex_handler_msr_mce(struct pt_regs *regs, bool wrmsr);
 #else
-static inline void ex_handler_msr_mce(struct pt_regs *regs, bool wrmsr) { }
+static inline void __noreturn ex_handler_msr_mce(struct pt_regs *regs, bool wrmsr)
+{
+	for (;;)
+		cpu_relax();
+}
 #endif
 
 #if defined(CONFIG_BPF_JIT) && defined(CONFIG_X86_64)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 7a187da..864bb9d 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -187,6 +187,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"__invalid_creds",
 		"cpu_startup_entry",
 		"__ubsan_handle_builtin_unreachable",
+		"ex_handler_msr_mce",
 	};
 
 	if (!func)