linux-kernel - [PATCH] Move -fno-dwarf2-cfi-asm to powerpc only

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Date:	Mon, 21 Dec 2009 02:23:51 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	akpm@...l.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, kyle@...hat.com,
	benh@...nel.crashing.org, mmarek@...e.cz
Subject: [PATCH] Move -fno-dwarf2-cfi-asm to powerpc only

Move -fno-dwarf2-cfi-asm to powerpc only

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

commit 003086497f07f7f1e67c0c295e261740f822b377 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.

Cc: kyle@...hat.com
Cc: benh@...nel.crashing.org
Cc: mmarek@...e.cz

Signed-off-by: Andi Kleen <ak@...ux.intel.com>

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

Index: linux-2.6.33-rc1-ak/Makefile
===================================================================
--- linux-2.6.33-rc1-ak.orig/Makefile
+++ linux-2.6.33-rc1-ak/Makefile
@@ -570,9 +570,6 @@ 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)
 
Index: linux-2.6.33-rc1-ak/arch/powerpc/Makefile
===================================================================
--- linux-2.6.33-rc1-ak.orig/arch/powerpc/Makefile
+++ linux-2.6.33-rc1-ak/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
--
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