[Consult] blackfin: About one building break issue for STACKTRACE

[Chen Gang]

Hello Maintainers:

I want to consult one building issue about blackfin, the related issue
is:

    CC      arch/blackfin/kernel/stacktrace.o
  arch/blackfin/kernel/stacktrace.c: In function 'save_stack_trace':
  arch/blackfin/kernel/stacktrace.c:23:6: error: frame pointer required, but reserved
   void save_stack_trace(struct stack_trace *trace)
        ^
  arch/blackfin/kernel/stacktrace.c:13:24: note: for 'current_frame_pointer'
   register unsigned long current_frame_pointer asm("FP");
                          ^

For me:

 - Originally, I treated it as gcc's issue, but after think of, for me,
   gcc is OK:

    "-fomit-frame-pointer" is needed by extern "FP" pointer.

    "-fomit-frame-pointer" is against "-pg" (they can not be together).

 - For kernel:

    STACKTRACE needs "-fomit-frame-pointer", and FUNCTION_TRACER will
    enable "-pg",

    FUNCTION_TRACER and STACKTRACE are related.

    The related commit: "1c873be Blackfin: initial support for ftrace"
    (the commit time point is Jun 9 2009).

 - After this related commit, it never can pass building by upstream
   blackfin gcc5:

    make defconfig && make menuconfig

    enable FUNCTION_TRACER (which also enable STACKTRACE)

    make (which will cause building break)

So I want to consult:

 - Is it OK to use upstream gcc5 for blackfin? (or which gcc version is
   suitable for building blackfin Linux kernel?)

 - Did the original commit pass building ? (e.g. by one of old gcc
   version).

 - How to fix this issue, next?


Welcome any members ideas, suggestions and completions.

Thanks.
-- 
Chen Gang

Open, share, and attitude like air, water, and life which God blessed
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