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

From: Steven Rostedt <[email-masked]>
Date: Fri, 20 Mar 2009 23:49:29 -0400

Ben,

Can you ACK this patch? Or even take it in your tree?

Thanks,

-- Steve

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 <[email-masked]>
> ---
>  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