[ARM] 5386/2: unwind: Add Makefile and Kconfig entries for ARM stack unwinding

This patch also makes the frame pointer default to y only if
!ARM_UNWIND. LOCKDEP no longer selects FRAME_POINTER if ARM_UNWIND is
enabled.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig.debug

@@ -2,18 +2,29 @@ menu "Kernel hacking"
 
 source "lib/Kconfig.debug"
 
-# RMK wants arm kernels compiled with frame pointers so hardwire this to y.
+# RMK wants arm kernels compiled with frame pointers or stack unwinding.
 # If you know what you are doing and are willing to live without stack
 # traces, you can get a slightly smaller kernel by setting this option to
 # n, but then RMK will have to kill you ;).
 config FRAME_POINTER
 	bool
-	default y
+	default y if !ARM_UNWIND
 	help
 	  If you say N here, the resulting kernel will be slightly smaller and
-	  faster. However, when a problem occurs with the kernel, the
-	  information that is reported is severely limited. Most people
-	  should say Y here.
+	  faster. However, if neither FRAME_POINTER nor ARM_UNWIND are enabled,
+	  when a problem occurs with the kernel, the information that is
+	  reported is severely limited.
+
+config ARM_UNWIND
+	bool "Enable stack unwinding support"
+	depends on AEABI && EXPERIMENTAL
+	default y
+	help
+	  This option enables stack unwinding support in the kernel
+	  using the information automatically generated by the
+	  compiler. The resulting kernel image is slightly bigger but
+	  the performance is not affected. Currently, this feature
+	  only works with EABI compilers. If unsure say Y.
 
 config DEBUG_USER
 	bool "Verbose user fault messages"

arch/arm/Makefile

@@ -85,6 +85,10 @@ else
 CFLAGS_ABI	:=$(call cc-option,-mapcs-32,-mabi=apcs-gnu) $(call cc-option,-mno-thumb-interwork,)
 endif
 
+ifeq ($(CONFIG_ARM_UNWIND),y)
+CFLAGS_ABI	+=-funwind-tables
+endif
+
 # Need -Uarm for gcc < 3.x
 KBUILD_CFLAGS	+=$(CFLAGS_ABI) $(arch-y) $(tune-y) $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) -msoft-float -Uarm
 KBUILD_AFLAGS	+=$(CFLAGS_ABI) $(arch-y) $(tune-y) -msoft-float

arch/arm/kernel/Makefile

@@ -29,6 +29,7 @@ obj-$(CONFIG_ATAGS_PROC)	+= atags.o
 obj-$(CONFIG_OABI_COMPAT)	+= sys_oabi-compat.o
 obj-$(CONFIG_ARM_THUMBEE)	+= thumbee.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
+obj-$(CONFIG_ARM_UNWIND)	+= unwind.o
 
 obj-$(CONFIG_CRUNCH)		+= crunch.o crunch-bits.o
 AFLAGS_crunch-bits.o		:= -Wa,-mcpu=ep9312

lib/Kconfig.debug

@@ -402,7 +402,7 @@ config LOCKDEP
 	bool
 	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 	select STACKTRACE
-	select FRAME_POINTER if !X86 && !MIPS && !PPC
+	select FRAME_POINTER if !X86 && !MIPS && !PPC && !ARM_UNWIND
 	select KALLSYMS
 	select KALLSYMS_ALL