Messages in this thread | | | From | Arnd Bergmann <> | Date | Mon, 15 Apr 2019 14:28:59 +0200 | Subject | Re: Kconfig dependency issue on function-graph tracer and frame pointer on arm |
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On Sun, Apr 14, 2019 at 3:35 PM Russell King - ARM Linux admin <linux@armlinux.org.uk> wrote:
> The subsequent hunks remove the defaulting of the choice according to > the function graph tracer - this is not a "hint" where the user can > still choose either option irrespective of the state of the function > graph tracer. They should only be able to select the frame pointer > option in that case. > > Another way forward would be for someone to put the work in to making > the function graph tracer work without frame pointers.
I think Stefan was already looking into making CONFIG_FUNCTION_TRACER work with clang. I don't know what the status of that work is, but I think getting FUNCTION_GRAPH_TRACER working at the same time would be best.
I never noticed the Kconfig issue here, because I was using a patch to turn off FUNCTION_TRACER on ARM with clang to make it build, and that turns off FUNCTION_GRAPH_TRACER in the process.
> So, how about this: > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 850b4805e2d1..9aed25a6019b 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -73,7 +73,7 @@ config ARM > select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU > select HAVE_EXIT_THREAD > select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL > - select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL > + select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG > select HAVE_FUNCTION_TRACER if !XIP_KERNEL > select HAVE_GCC_PLUGINS > select HAVE_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7) > diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug > index 6d6e0330930b..e388af4594a6 100644 > --- a/arch/arm/Kconfig.debug > +++ b/arch/arm/Kconfig.debug > @@ -47,8 +47,8 @@ config DEBUG_WX > > choice > prompt "Choose kernel unwinder" > - default UNWINDER_ARM if AEABI && !FUNCTION_GRAPH_TRACER > - default UNWINDER_FRAME_POINTER if !AEABI || FUNCTION_GRAPH_TRACER > + default UNWINDER_ARM if AEABI > + default UNWINDER_FRAME_POINTER if !AEABI > help > This determines which method will be used for unwinding kernel stack > traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack, > @@ -65,7 +65,7 @@ config UNWINDER_FRAME_POINTER > > config UNWINDER_ARM > bool "ARM EABI stack unwinder" > - depends on AEABI > + depends on AEABI && !FUNCTION_GRAPH_TRACER > select ARM_UNWIND > help > This option enables stack unwinding support in the kernel
This looks good to me in the meantime, at least if there is any way to get the non-graph FUNCTION_TRACER to build with clang.
Arnd
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