[patch 2/2] kbuild: move -fno-dwarf2-cfi-asm to powerpc only

[akpm at linux-foundation.org]

From: Andi Kleen <andi at firstfloor.org>

Better dwarf2 unwind information is a good thing, it allows better
debugging with kgdb and crash and helps systemtap.

Commit 003086497f07f7f1e67c0c295e261740f822b377 ("Build with
-fno-dwarf2-cfi-asm") disabled some CFI information globally to work
around a module loader bug on powerpc.

But this disables the better unwind tables for all architectures, not just
powerpc.  Move the workaround to powerpc and also add a suitable comment
that's it really a workaround.

This improves dwarf2 unwind tables on x86 at least.

Signed-off-by: Andi Kleen <ak at linux.intel.com>
Cc: Kyle McMartin <kyle at mcmartin.ca>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Michal Marek <mmarek at suse.cz>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---

 Makefile              |    3 ---
 arch/powerpc/Makefile |    5 +++++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff -puN Makefile~kbuild-move-fno-dwarf2-cfi-asm-to-powerpc-only Makefile
--- a/Makefile~kbuild-move-fno-dwarf2-cfi-asm-to-powerpc-only
+++ a/Makefile
@@ -579,9 +579,6 @@ KBUILD_CFLAGS += $(call cc-option,-Wno-p
 # disable invalid "can't wrap" optimizations for signed / pointers
 KBUILD_CFLAGS	+= $(call cc-option,-fno-strict-overflow)
 
-# revert to pre-gcc-4.4 behaviour of .eh_frame
-KBUILD_CFLAGS	+= $(call cc-option,-fno-dwarf2-cfi-asm)
-
 # conserve stack if available
 KBUILD_CFLAGS   += $(call cc-option,-fconserve-stack)
 
diff -puN arch/powerpc/Makefile~kbuild-move-fno-dwarf2-cfi-asm-to-powerpc-only arch/powerpc/Makefile
--- a/arch/powerpc/Makefile~kbuild-move-fno-dwarf2-cfi-asm-to-powerpc-only
+++ a/arch/powerpc/Makefile
@@ -112,6 +112,11 @@ KBUILD_CFLAGS += $(call cc-option,-mspe=
 # kernel considerably.
 KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
 
+# FIXME: the module load should be taught about the additional relocs
+# generated by this.
+# revert to pre-gcc-4.4 behaviour of .eh_frame
+KBUILD_CFLAGS	+= $(call cc-option,-fno-dwarf2-cfi-asm)
+
 # Never use string load/store instructions as they are
 # often slow when they are implemented at all
 KBUILD_CFLAGS		+= -mno-string
_