linux-kernel - Re: [RFC PATCH v4 3/3] bpf: Introduce function for outputing data to perf event

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Date:	Fri, 17 Jul 2015 12:14:47 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Alexei Starovoitov <ast@...mgrid.com>,
	He Kuang <hekuang@...wei.com>, pi3orama <pi3orama@....com>,
	Namhyung Kim <namhyung@...nel.org>
CC:	"rostedt@...dmis.org" <rostedt@...dmis.org>,
	"masami.hiramatsu.pt@...achi.com" <masami.hiramatsu.pt@...achi.com>,
	"acme@...nel.org" <acme@...nel.org>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"jolsa@...nel.org" <jolsa@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v4 3/3] bpf: Introduce function for outputing data
 to perf event



On 2015/7/17 12:11, Alexei Starovoitov wrote:
> On 7/14/15 4:54 AM, He Kuang wrote:
>>> I'm not sure llvm generates proper dwarf along with bpf code (I didn't
>>> test that part. If there are any issues they should be fixable. If you
>>> can prepapre a patch for llvm that would be even better :)
>>>
>>
>> I found objdump can't get dwarf info from bpf object file:
>>
>>    $ objdump --dwarf=info bpf.o
>>    bpf.o: file format elf64-little
>>
>>    $ readelf -a bpf.o |grep debug_info
>>    <EMPTY>
>
> yeah. looks like this part is not working.
> Interesting that when I do: clang -O2 -target bpf a.c -g -S
> there is some minimal debug info in the .s, but .o lacks
> debuginfo completely. Digging further...

Glad to see you start look at it. We are not familiar with LLVM, but I was
told that LLVM has a clean structure and very easy to introduce new 
features.
Could you please give us some hits on it so we can work together?

Thank you.

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