linux-kernel - [PATCH] cris: Mark end of BUG() implementation as unreachable

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Date:   Thu, 11 Jan 2018 12:32:57 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Mikael Starvik <starvik@...s.com>,
        Jesper Nilsson <jesper.nilsson@...s.com>
Cc:     kbuild test robot <fengguang.wu@...el.com>,
        linux-cris-kernel@...s.com, linux-kernel@...r.kernel.org
Subject: [PATCH] cris: Mark end of BUG() implementation as unreachable

When building the cris v10 architecture, the compiler doesn't realize that
BUG() doesn't return, so it will complain about functions using BUG()
that are marked with the noreturn attribute:

   mm/usercopy.c: In function 'usercopy_abort':
>> mm/usercopy.c:86:1: warning: 'noreturn' function does return
    }
    ^

This fixes it for v10, similar to how it already works on v32.

Reported-by: kbuild test robot <fengguang.wu@...el.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/cris/include/arch-v10/arch/bug.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/cris/include/arch-v10/arch/bug.h b/arch/cris/include/arch-v10/arch/bug.h
index 905afeacfedf..ca9de0b250de 100644
--- a/arch/cris/include/arch-v10/arch/bug.h
+++ b/arch/cris/include/arch-v10/arch/bug.h
@@ -44,18 +44,26 @@ struct bug_frame {
  * not be used like this with newer versions of gcc.
  */
 #define BUG()								\
+do {									\
 	__asm__ __volatile__ ("clear.d [" __stringify(BUG_MAGIC) "]\n\t"\
 			      "movu.w " __stringify(__LINE__) ",$r0\n\t"\
 			      "jump 0f\n\t"				\
 			      ".section .rodata\n"			\
 			      "0:\t.string \"" __FILE__ "\"\n\t"	\
-			      ".previous")
+			      ".previous");				\
+	unreachable();							\
+} while (0)
 #endif
 
 #else
 
 /* This just causes an oops. */
-#define BUG() (*(int *)0 = 0)
+#define BUG()								\
+do {									\
+	(*(int *)0 = 0);						\
+	do {} while (1);						\
+	unreachable();							\
+} while (0)
 
 #endif
 
-- 
2.7.4


-- 
Kees Cook
Pixel Security