Re: [PATCH 2/2] btf_encoder: Change functions check due to broken dwarf

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On Sat, Oct 31, 2020 at 11:31:31PM +0100, Jiri Olsa wrote:
> We need to generate just single BTF instance for the
> function, while DWARF data contains multiple instances
> of DW_TAG_subprogram tag.
> 
> Unfortunately we can no longer rely on DW_AT_declaration
> tag (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97060)
> 
> Instead we apply following checks:
>   - argument names are defined for the function
>   - there's symbol and address defined for the function
>   - function is generated only once
> 
> Also because we want to follow kernel's ftrace traceable
> functions, this patchset is adding extra check that the
> function is one of the ftrace's functions.
> 
> All ftrace functions addresses are stored in vmlinux
> binary within symbols:
>   __start_mcount_loc
>   __stop_mcount_loc

hum, for some reason this does not pass through bpf internal
functions like bpf_iter_bpf_map.. I learned it hard way ;-)
will check

jirka




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