linux-kernel - [PATCH 2/4] Add BUG() debugger entry points x86

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Message-Id: <1454091544-12733-1-git-send-email-jeffmerkey@gmail.com>
Date:	Fri, 29 Jan 2016 11:19:04 -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 2/4] Add BUG() debugger entry points x86

This patch series adds a config option which can be set during compile to
direct the compiler to output a breakpoint instruction anywhere a BUG()
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 anywhere in the
kernel.

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 | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index ba38ebb..6319f3e0 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -27,7 +27,11 @@ do {								\
 #else
 #define BUG()							\
 do {								\
+#ifdef CONFIG_DEBUG_BREAK
+	asm volatile("int3");					\
+#else
 	asm volatile("ud2");					\
+#endif
 	unreachable();						\
 } while (0)
 #endif
-- 
1.8.3.1