linux-kernel - Re: [PATCH 14/31] perf tools: Add BPF_PROLOGUE config options for further patches

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Message-ID: <20151029224538.GN2923@kernel.org>
Date:	Thu, 29 Oct 2015 19:45:38 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	ast@...mgrid.com, brendan.d.gregg@...il.com,
	a.p.zijlstra@...llo.nl, daniel@...earbox.net, dsahern@...il.com,
	hekuang@...wei.com, jolsa@...nel.org, lizefan@...wei.com,
	masami.hiramatsu.pt@...achi.com, namhyung@...nel.org,
	paulus@...ba.org, linux-kernel@...r.kernel.org, pi3orama@....com,
	xiakaixu@...wei.com
Subject: Re: [PATCH 14/31] perf tools: Add BPF_PROLOGUE config options for
 further patches

Em Wed, Oct 14, 2015 at 12:41:25PM +0000, Wang Nan escreveu:
> If both LIBBPF and DWARF are detected, it is possible to create prologue
> for eBPF programs to help them accessing kernel data. HAVE_BPF_PROLOGUE

                                       what kernel data? you mean to be
able to map from variable/function argument name to where they are in
memory/registers?

> and CONFIG_BPF_PROLOGUE is added as flags for this feature.
> 
> PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET indicates an architecture
> supports converting name of a register to its offset in
> 'struct pt_regs'. Without this support, BPF_PROLOGUE should be turned off.
> 
> HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET is introduced as the corresponding
> CFLAGS of PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET.
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Alexei Starovoitov <ast@...mgrid.com>
> Cc: Brendan Gregg <brendan.d.gregg@...il.com>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: David Ahern <dsahern@...il.com>
> Cc: He Kuang <hekuang@...wei.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Kaixu Xia <xiakaixu@...wei.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Link: http://lkml.kernel.org/n/ebpf-6yw9eg0ej3l4jnqhinngkw86@git.kernel.org
> ---
>  tools/perf/config/Makefile | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
> index de89ec5..6eb9a95 100644
> --- a/tools/perf/config/Makefile
> +++ b/tools/perf/config/Makefile
> @@ -318,6 +318,18 @@ ifndef NO_LIBELF
>        CFLAGS += -DHAVE_LIBBPF_SUPPORT
>        $(call detected,CONFIG_LIBBPF)
>      endif
> +
> +    ifndef NO_DWARF
> +      ifdef PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET
> +        CFLAGS += -DHAVE_BPF_PROLOGUE
> +        $(call detected,CONFIG_BPF_PROLOGUE)
> +      else
> +        msg := $(warning BPF prologue is not supported by architecture $(ARCH), missing regs_query_register_offset());
> +      endif
> +    else
> +      msg := $(warning DWARF support is off, BPF prologue is disabled);
> +    endif
> +
>    endif # NO_LIBBPF
>  endif # NO_LIBELF
>  
> -- 
> 1.8.3.4
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