linux-kernel - [PATCH v3 5/5] x86: Always define BUG() and HAVE_ARCH_BUG, even with !CONFIG

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Date:	Sun, 9 Mar 2014 18:03:10 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 5/5] x86: Always define BUG() and HAVE_ARCH_BUG, even with
 !CONFIG_BUG

This ensures that BUG() always has a definition that causes a trap (via
an undefined instruction), and that the compiler still recognizes the
code following BUG() as unreachable, avoiding warnings that would
otherwise appear (such as on non-void functions that don't return a
value after BUG()).

In addition to saving a few bytes over the generic infinite-loop
implementation, this implementation traps rather than looping, which
potentially allows for better error-recovery behavior (such as by
rebooting).

Reported-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Josh Triplett <josh@...htriplett.org>
---
v3: New patch for x86-optimized implementation of a simple bug for
!CONFIG_BUG, based on Arnd Bergmann's proposal.

 arch/x86/include/asm/bug.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index 2f03ff0..ba38ebb 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -1,7 +1,6 @@
 #ifndef _ASM_X86_BUG_H
 #define _ASM_X86_BUG_H
 
-#ifdef CONFIG_BUG
 #define HAVE_ARCH_BUG
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
@@ -33,8 +32,6 @@ do {								\
 } while (0)
 #endif
 
-#endif /* !CONFIG_BUG */
-
 #include <asm-generic/bug.h>
 
 #endif /* _ASM_X86_BUG_H */
-- 
1.9.0

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