linux-kernel - Re: [PATCH 27/31] perf record: Support custom vmlinux path

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Date:	Tue, 1 Sep 2015 17:19:17 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	mingo@...nel.org, ast@...mgrid.com, linux-kernel@...r.kernel.org,
	lizefan@...wei.com, pi3orama@....com,
	He Kuang <hekuang@...wei.com>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
	Kaixu Xia <xiakaixu@...wei.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 27/31] perf record: Support custom vmlinux path

Em Sat, Aug 29, 2015 at 04:22:01AM +0000, Wang Nan escreveu:
> From: He Kuang <hekuang@...wei.com>
> 
> Make perf-record command support --vmlinux option if BPF_PROLOGUE is on.

Ok, this should be supported, i.e. letting the user specify a vmlinux
path to use.

But it shouldn't be _required_, i.e. we have things like vmlinux_path to
try to find it in well known places.

Right now it will search for it in the process of trying to load its
symtab, but I think we should have a function that tries to find a
vmlinux that matches the build-id of the running kernel, for things that
want to have access directly to the ELF file with debuginfo without
having to load the symtab in a struct dso, etc.

I'll look at the next patches to check how you make use of this info...

- Arnaldo

> 'perf record' needs vmlinux as the source of DWARF info to generate
> prologue for BPF programs, so path of vmlinux should be specified.
> 
> Short name 'k' has been taken by 'clockid'. This patch skips the short
> option name and use '--vmlinux' for vmlinux path.
> 
> Signed-off-by: He Kuang <hekuang@...wei.com>
> 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/1436445342-1402-38-git-send-email-wangnan0@huawei.com
> ---
>  tools/perf/builtin-record.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 212718c..8eb39d5 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1100,6 +1100,10 @@ struct option __record_options[] = {
>  		   "clang binary to use for compiling BPF scriptlets"),
>  	OPT_STRING(0, "clang-opt", &llvm_param.clang_opt, "clang options",
>  		   "options passed to clang when compiling BPF scriptlets"),
> +#ifdef HAVE_BPF_PROLOGUE
> +	OPT_STRING(0, "vmlinux", &symbol_conf.vmlinux_name,
> +		   "file", "vmlinux pathname"),
> +#endif
>  #endif
>  	OPT_END()
>  };
> -- 
> 2.1.0
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