linux-kernel - [PATCH 1/4] Add BUG_XX() debugging options

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Message-Id: <1454356886-12334-1-git-send-email-jeffmerkey@gmail.com>
Date:	Mon,  1 Feb 2016 13:01:26 -0700
From:	Jeffrey Merkey <jeffmerkey@...il.com>
To:	hpa@...or.com, jeffmerkey@...il.com, linux-kernel@...r.kernel.org,
	mingo@...hat.com, tglx@...utronix.de, x86@...nel.org
Subject: [PATCH 1/4] Add BUG_XX() debugging options

This patch series adds config options which can be set during compile to
direct the compiler to output a breakpoint instruction anywhere a BUG()
or WARN() macro has been placed in the kernel to trigger the system to
enter a debugger if a bug is detected by the system.  Use of this
compile time option also allows conditional breakpoints to be set in the
kernel with these currently used macros.

This addition is extremely useful for debugging hard and soft lockups
real time and quickly from a console debugger, and other areas of the
kernel.

Signed-off-by: Jeffrey Merkey <jeffmerkey@...il.com>
---
 arch/x86/include/asm/bug.h | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index ba38ebb..debbbfd 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -11,6 +11,13 @@
 # define __BUG_C0	"2:\t.long 1b - 2b, %c0 - 2b\n"
 #endif
 
+#if CONFIG_DEBUG_BUG
+#define BUG()							\
+do {								\
+	asm volatile("int3");					\
+	unreachable();						\
+} while (0)
+#else
 #define BUG()							\
 do {								\
 	asm volatile("1:\tud2\n"				\
@@ -23,7 +30,14 @@ do {								\
 		     "i" (sizeof(struct bug_entry)));		\
 	unreachable();						\
 } while (0)
-
+#endif
+#else
+#if CONFIG_DEBUG_BUG
+#define BUG()							\
+do {								\
+	asm volatile("int3");					\
+	unreachable();						\
+} while (0)
 #else
 #define BUG()							\
 do {								\
@@ -31,6 +45,7 @@ do {								\
 	unreachable();						\
 } while (0)
 #endif
+#endif
 
 #include <asm-generic/bug.h>
 
-- 
1.8.3.1