[PATCH AUTOSEL 4.19 21/57] compiler.h: update definition of unreachable()

Sasha Levin
2019-03-30T01:40:13Z

From: "ndesaulniers@google.com" <ndesaulniers@google.com>

[ Upstream commit fe0640eb30b7da261ae84d252ed9ed3c7e68dfd8 ]

Fixes the objtool warning seen with Clang:
arch/x86/mm/fault.o: warning: objtool: no_context()+0x220: unreachable
instruction

Fixes commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h
mutually exclusive")

Josh noted that the fallback definition was meant to work around a
pre-gcc-4.6 bug. GCC still needs to work around
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365, so compiler-gcc.h
defines its own version of unreachable(). Clang and ICC can use this
shared definition.

Link: https://github.com/ClangBuiltLinux/linux/issues/204
Suggested-by: Andy Lutomirski <luto@amacapital.net>
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/compiler.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 269d376f5a11..81c2238b884c 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -124,7 +124,10 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
# define ASM_UNREACHABLE
#endif
#ifndef unreachable
-# define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
+# define unreachable() do { \
+ annotate_unreachable(); \
+ __builtin_unreachable(); \
+} while (0)
#endif

/*
--
2.19.1