[PATCH] CONFIG_UNWIND_INFO

As a foundation for reliable stack unwinding, this adds a config option
(available to all architectures except IA64 and those where the module
loader might have problems with the resulting relocations) to enable the
generation of frame unwind information.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Miles Bader <uclinux-v850@lsi.nec.co.jp>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Paul Mundt <lethal@linux-sh.org>,
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Makefile

@@ -517,6 +517,10 @@ else
 CFLAGS		+= -fomit-frame-pointer
 endif
 
+ifdef CONFIG_UNWIND_INFO
+CFLAGS		+= -fasynchronous-unwind-tables
+endif
+
 ifdef CONFIG_DEBUG_INFO
 CFLAGS		+= -g
 endif

lib/Kconfig.debug

@@ -195,6 +195,17 @@ 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
+	depends on !MODULES || !(MIPS || PARISC || PPC || SUPERH || SPARC64 || V850)
+	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 FORCED_INLINING
 	bool "Force gcc to inline functions marked 'inline'"
 	depends on DEBUG_KERNEL