[PATCH 2/2] x86: Annotate WARN-related UD2 as reachable

From: Josh Poimboeuf <jpoimboe@redhat.com>
To: x86@kernel.org
Cc: Borislav Petkov <bp@alien8.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	kbuild test robot <fengguang.wu@intel.com>,
	Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org,
	Arjan van de Ven <arjan@linux.intel.com>
Subject: [PATCH 2/2] x86: Annotate WARN-related UD2 as reachable
Date: Thu,  8 Feb 2018 17:09:26 -0600	[thread overview]
Message-ID: <0e483379275a42626ba8898117f918e1bf661e40.1518130694.git.jpoimboe@redhat.com> (raw)
In-Reply-To: <cover.1518130694.git.jpoimboe@redhat.com>

By default, objtool assumes that a UD2 is a dead end.  This is mainly
because GCC 7+ sometimes inserts a UD2 when it detects a divide-by-zero
condition.

Now that WARN() is moving back to UD2, annotate the code after it as
reachable so objtool can follow the code flow.

Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/x86/include/asm/bug.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index f2da5fc90e5c..697d89d6fa76 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -74,7 +74,11 @@ do {								\
 	unreachable();						\
 } while (0)
 
-#define __WARN_FLAGS(flags)	_BUG_FLAGS(ASM_UD2, BUGFLAG_WARNING|(flags))
+#define __WARN_FLAGS(flags)					\
+do {								\
+	_BUG_FLAGS(ASM_UD2, BUGFLAG_WARNING|(flags));		\
+	annotate_reachable();					\
+} while (0)
 
 #include <asm-generic/bug.h>
 
-- 
2.14.3
