Add CONFIG_UNWIND_INFO

From: Jan Beulich <jbeulich@novell.com>

As a foundation for reliable stack unwinding, this adds a config option
(available to all architectures except IA64) to enable the generation
of frame unwind information.

Signed-Off-By: Jan Beulich <jbeulich@novell.com>

Signed-off-by: Andi Kleen <ak@suse.de>

Index: linux/Makefile
===================================================================
--- linux.orig/Makefile
+++ linux/Makefile
@@ -502,6 +502,10 @@ CFLAGS		+= $(call add-align,CONFIG_CC_AL
 CFLAGS		+= $(call add-align,CONFIG_CC_ALIGN_LOOPS,-loops)
 CFLAGS		+= $(call add-align,CONFIG_CC_ALIGN_JUMPS,-jumps)
 
+ifdef CONFIG_UNWIND_INFO
+CFLAGS		+= -fasynchronous-unwind-tables
+endif
+
 ifdef CONFIG_FRAME_POINTER
 CFLAGS		+= -fno-omit-frame-pointer $(call cc-option,-fno-optimize-sibling-calls,)
 else
Index: linux/lib/Kconfig.debug
===================================================================
--- linux.orig/lib/Kconfig.debug
+++ linux/lib/Kconfig.debug
@@ -195,6 +195,16 @@ config FRAME_POINTER
 	  some architectures or if you use external debuggers.
 	  If you don't debug the kernel, you can say N.
 
+config UNWIND_INFO
+	bool "Compile the kernel with frame unwind information"
+	depends on !IA64
+	default DEBUG_KERNEL
+	help
+	  If you say Y here the resulting kernel image will be slightly larger
+	  but not slower, and it will give very useful debugging information.
+	  If you don't debug the kernel, you can say N, but we may not be able
+	  to solve problems without frame unwind information or frame pointers.
+
 config RCU_TORTURE_TEST
 	tristate "torture tests for RCU"
 	depends on DEBUG_KERNEL