Re: [PATCH 1/3] powerpc, Makefile: Make it possible to safely select CONFIG_FRAME_POINTER

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Sat, 2009-03-28 at 13:48 +0300, Anton Vorontsov wrote:
> On Fri, Mar 20, 2009 at 11:49:29PM -0400, Steven Rostedt wrote:
> > Ben,
> > 
> > Can you ACK this patch? Or even take it in your tree?
> 
> Benjamin, have you had a chance to look into this? Sam, could
> you also take a look?

Those patches look ok. I'm a little bit surprised that -mno-sched-epilog
isn't needed, gcc weirdness never ceases to amaze me, but the
Makefile/Kconfig churning isn't for me to judge. If Sam is happy, then
let's merge it.

Ben.

> Thanks!
> 
> > On Fri, 2009-03-20 at 19:44 +0300, Anton Vorontsov wrote:
> > > This patch introduces ARCH_HAS_NORMAL_FRAME_POINTERS Kconfig symbol.
> > > When defined, the top level Makefile won't add -fno-omit-frame-pointer
> > > cflag (the flag is useless in PowerPC kernels, and also makes gcc
> > > generate wrong code).
> > > 
> > > Also move ARCH_WANT_FRAME_POINTERS's help text.
> > > 
> > > Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
> > > ---
> > >  Makefile             |    7 +++++--
> > >  arch/powerpc/Kconfig |    1 +
> > >  lib/Kconfig.debug    |   16 ++++++++++------
> > >  3 files changed, 16 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/Makefile b/Makefile
> > > index 46c04c5..bf41b05 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -538,9 +538,12 @@ KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
> > >  endif
> > >  
> > >  ifdef CONFIG_FRAME_POINTER
> > > -KBUILD_CFLAGS	+= -fno-omit-frame-pointer -fno-optimize-sibling-calls
> > > +  KBUILD_CFLAGS	+= -fno-optimize-sibling-calls
> > > +  ifndef ARCH_HAS_NORMAL_FRAME_POINTERS
> > > +    KBUILD_CFLAGS	+= -fno-omit-frame-pointer
> > > +  endif
> > >  else
> > > -KBUILD_CFLAGS	+= -fomit-frame-pointer
> > > +  KBUILD_CFLAGS	+= -fomit-frame-pointer
> > >  endif
> > >  
> > >  ifdef CONFIG_DEBUG_INFO
> > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > > index 97f9a64..4587e66 100644
> > > --- a/arch/powerpc/Kconfig
> > > +++ b/arch/powerpc/Kconfig
> > > @@ -113,6 +113,7 @@ config PPC
> > >  	select HAVE_FUNCTION_TRACER
> > >  	select HAVE_FUNCTION_GRAPH_TRACER
> > >  	select ARCH_WANT_OPTIONAL_GPIOLIB
> > > +	select ARCH_HAS_NORMAL_FRAME_POINTERS
> > >  	select HAVE_IDE
> > >  	select HAVE_IOREMAP_PROT
> > >  	select HAVE_EFFICIENT_UNALIGNED_ACCESS
> > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > > index 4b63b6b..fc8cd1f 100644
> > > --- a/lib/Kconfig.debug
> > > +++ b/lib/Kconfig.debug
> > > @@ -661,20 +661,24 @@ config DEBUG_NOTIFIERS
> > >  	  This is a relatively cheap check but if you care about maximum
> > >  	  performance, say N.
> > >  
> > > -#
> > > -# Select this config option from the architecture Kconfig, if it
> > > -# it is preferred to always offer frame pointers as a config
> > > -# option on the architecture (regardless of KERNEL_DEBUG):
> > > -#
> > >  config ARCH_WANT_FRAME_POINTERS
> > >  	bool
> > >  	help
> > > +	  Select this config option from the architecture Kconfig, if it
> > > +	  it is preferred to always offer frame pointers as a config
> > > +	  option on the architecture (regardless of KERNEL_DEBUG).
> > > +
> > > +config ARCH_HAS_NORMAL_FRAME_POINTERS
> > > +	bool
> > > +	help
> > > +	  Architectures should select this symbol if their ABI implies
> > > +	  having a frame pointer.
> > >  
> > >  config FRAME_POINTER
> > >  	bool "Compile the kernel with frame pointers"
> > >  	depends on DEBUG_KERNEL && \
> > >  		(CRIS || M68K || M68KNOMMU || FRV || UML || S390 || \
> > > -		 AVR32 || SUPERH || BLACKFIN || MN10300) || \
> > > +		 AVR32 || SUPERH || BLACKFIN || MN10300 || PPC) || \
> > >  		ARCH_WANT_FRAME_POINTERS
> > >  	default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
> > >  	help
> > 
>