Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option

Catalin Marinas
2015-11-06T17:51:25Z

On Fri, Nov 06, 2015 at 09:39:07AM -0800, Shi, Yang wrote:
> On 11/6/2015 9:35 AM, Catalin Marinas wrote:
> >On Fri, Nov 06, 2015 at 09:23:38AM -0800, Shi, Yang wrote:
> >>On 11/6/2015 8:25 AM, Will Deacon wrote:
> >>>However, the patch would allow one to
> >>>disable FRAME_POINTERS (not sure it has any effect on the aarch64 gcc
> >>>though).
> >>
> >>No, it doesn't. Actually, FRAME_POINTER could be disabled regardless of the
> >>patch.
> >
> >In which case I suggest that we always select it just as a clearer
> >statement that the feature cannot be disabled (and you never know what
> >the compiler people decide to do in the future).
>
> Do you mean select FRAME_POINTER in ARCH_WANT_FRAME_POINTERS?
>
> Yes, we could, but this may cause other architectures which select
> ARCH_WANT_FRAME_POINTERS to have FRAME_POINTER selected too.

This would have been the ideal option, something like:

--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -322,7 +322,7 @@ config ARCH_WANT_FRAME_POINTERS
help

config FRAME_POINTER
- bool "Compile the kernel with frame pointers"
+ bool "Compile the kernel with frame pointers" if !ARCH_WANT_FRAME_POINTERS
depends on DEBUG_KERNEL && \
(CRIS || M68K || FRV || UML || \
AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \

But, as you said, we would need to check the other architectures
selecting ARCH_WANT_FRAME_POINTERS.

In the meantime:

--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -27,6 +27,7 @@ config ARM64
select CPU_PM if (SUSPEND || CPU_IDLE)
select DCACHE_WORD_ACCESS
select EDAC_SUPPORT
+ select FRAME_POINTER
select GENERIC_ALLOCATOR
select GENERIC_CLOCKEVENTS
select GENERIC_CLOCKEVENTS_BROADCAST

--
Catalin