[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>

4 files changed, 22 insertions, 6 deletions

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 192ee01a9ba..35f8db35f44 100644
--- a/arch/arm/Kconfig.debug
+++ b/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"
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 24e0f018769..e7ef876e574 100644
--- a/arch/arm/Makefile
+++ b/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) $(tune-y) -msoft-float
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 4305345987d..ca60d335e8f 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -29,6 +29,7 @@ obj-$(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
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 29044f50026..08275a5aa00 100644
--- a/lib/Kconfig.debug
+++ b/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