From: Josh Poimboeuf <jpoimboe@redhat.com>
Date: Thu, 27 Jul 2017 15:56:54 -0500
Subject: objtool: Skip unreachable warnings for 'alt' instructions
Git-commit: 0e2bb2bc14b3df754b0a86e87cd8923df0701a1b
Patch-mainline: v4.14-rc1
References: bnc#1058115

When a whitelisted function uses one of the ALTERNATIVE macros, it
produces false positive warnings like:

  arch/x86/kvm/vmx.o: warning: objtool: .altinstr_replacement+0x0: unreachable instruction
  arch/x86/kvm/svm.o: warning: objtool: .altinstr_replacement+0x6e: unreachable instruction

There's no easy way to whitelist alternative instructions, so instead
just skip any 'unreachable' warnings associated with them.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a5d0a8c60155f03b36a31fac871e12cf75f35fd0.1501188854.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 tools/objtool/check.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1746,8 +1746,13 @@ static bool ignore_unreachable_insn(stru
 	/*
 	 * Ignore any unused exceptions.  This can happen when a whitelisted
 	 * function has an exception table entry.
+	 *
+	 * Also ignore alternative replacement instructions.  This can happen
+	 * when a whitelisted function uses one of the ALTERNATIVE macros.
 	 */
-	if (!strcmp(insn->sec->name, ".fixup"))
+	if (!strcmp(insn->sec->name, ".fixup") ||
+	    !strcmp(insn->sec->name, ".altinstr_replacement") ||
+	    !strcmp(insn->sec->name, ".altinstr_aux"))
 		return true;
 
 	/*