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

From	Mark Rutland <mark.rutland@arm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option
Date	2015-11-06 14:00 +0100
Message-ID	<qrOMx-4BZ-9@gated-at.bofh.it> (permalink)
References	<qravM-3Aq-3@gated-at.bofh.it> <qrOtb-4v4-11@gated-at.bofh.it>
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On Fri, Nov 06, 2015 at 12:30:09PM +0000, Will Deacon wrote:
> On Wed, Nov 04, 2015 at 09:37:51AM -0800, Yang Shi wrote:
> > FRAME_POINTER is defined in lib/Kconfig.debug, it is unnecessary to redefine
> > it in arch/arm64/Kconfig.debug.
> 
> It might be worth noting that this adds a dependency on DEBUG_KERNEL
> for building with frame pointers. I'm ok with that (it appears to be
> enabled in defconfig and follows the vast majority of other archs) but
> it is a change in behaviour.
> 
> With that:
> 
>   Acked-by: Will Deacon <will.deacon@arm.com>

The code in arch/arm64/kernel/stacktrace.c assumes we have frame
pointers regardless of FRAME_POINTER. Depending on what the compiler
decides to use x29 for, we could get some weird fake unwinding and/or
dodgy memory accesses.

I think we should first audit the uses of frame pointers to ensure that
they are guarded for !FRAME_POINTER.

Thanks,
Mark.
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Thread

[PATCH] arm64: remove redundant FRAME_POINTER kconfig option Yang Shi <yang.shi@linaro.org> - 2015-11-04 19:00 +0100
  Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Will Deacon <will.deacon@arm.com> - 2015-11-06 13:40 +0100
    Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Mark Rutland <mark.rutland@arm.com> - 2015-11-06 14:00 +0100
      Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Will Deacon <will.deacon@arm.com> - 2015-11-06 16:50 +0100
      Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Will Deacon <will.deacon@arm.com> - 2015-11-06 17:30 +0100
        Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option "Shi, Yang" <yang.shi@linaro.org> - 2015-11-06 18:30 +0100
          Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Catalin Marinas <catalin.marinas@arm.com> - 2015-11-06 18:40 +0100
            Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option "Shi, Yang" <yang.shi@linaro.org> - 2015-11-06 18:40 +0100
              Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Catalin Marinas <catalin.marinas@arm.com> - 2015-11-06 19:00 +0100
                Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option "Shi, Yang" <yang.shi@linaro.org> - 2015-11-06 19:00 +0100
                Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Catalin Marinas <catalin.marinas@arm.com> - 2015-11-09 17:00 +0100
      Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Catalin Marinas <catalin.marinas@arm.com> - 2015-11-06 17:30 +0100
    Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Catalin Marinas <catalin.marinas@arm.com> - 2015-11-06 17:20 +0100
      Re: [PATCH] arm64: remove redundant FRAME_POINTER kconfig option Will Deacon <will.deacon@arm.com> - 2015-11-06 17:20 +0100

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