[ktap] Re: [PATCH] add new symbol module to search symbols in DSO (for uprobes)
- From: Jovi Zhangwei <jovi.zhangwei@xxxxxxxxx>
- To: ktap@xxxxxxxxxxxxx
- Date: Thu, 7 Nov 2013 13:46:28 +0800
On Thu, Nov 7, 2013 at 1:38 PM, Azat Khuzhin <a3at.mail@xxxxxxxxx> wrote:
>
> On 7 Nov 2013 09:06, "Jovi Zhangwei" <jovi.zhangwei@xxxxxxxxx> wrote:
>>
>> On Thu, Nov 7, 2013 at 11:55 AM, Azat Khuzhin <a3at.mail@xxxxxxxxx> wrote:
>> >
>> > On 7 Nov 2013 07:29, "Jovi Zhangwei" <jovi.zhangwei@xxxxxxxxx> wrote:
>> >>
>> >> On Wed, Nov 6, 2013 at 5:51 PM, Azat Khuzhin <a3at.mail@xxxxxxxxx>
>> >> wrote:
>> >> > This will allow to don't hardcoding addresses of functions in ktap
>> >> > scripts, that use uprobes, but instead, use normal function names.
>> >> >
>> >> > Before this patch:
>> >> > $ ktap -e 'trace probe:/path/to/bin:0xDEADBEAF' # instead some real
>> >> > address
>> >> >
>> >> > After this path:
>> >> > $ ktap -e 'trace probe:/path/to/bin:foo'
>> >> >
>> >> > Works also for ret probes (%return)
>> >> > Requires libelf.
>> >> >
>> >> > Have NO_LIBELF option for makefile, for cross-builds.
>> >> >
>> >> > Signed-off-by: Azat Khuzhin <a3at.mail@xxxxxxxxx>
>> >> > ---
>> >> > v2: make it more pretty
>> >> > v3: make it faster (thanks to Yicheng)
>> >> > v4: add NO_LIBELF option into Makefile, and more common parsing
>> >> > v5: fix leaking of "tail"
>> >> > v6: coding styles fixes
>> >> >
>> >> Applied, thank you.
>> >>
>> >> Now we can use symbol(like malloc and free) in ktap uprobe scripts, a
>> >> big
>> >> step.
>> >
>> > Nice!
>> > I see you also changed examples, thanks.
>> >
>> Btw, you have opened the gate for elf debugging info resolving, actually
>> there
>> still have a big feature missed in ktap uprobe: SDT markers
>>
>> In my machine, there have many built-in sdt in glibc, see below:
>>
>> # readelf -n /lib64/libc.so.6
>> setjmp, longjmp, longjmp_target, lll_futex_wake, lll_lock_wait_private
>>
>> There also have many other program with compiled sdt, like JVM, Erlang,
>> MySQL,
>> NodeJS, etc. so SDT marker parsing would be a useful feature for dynamic
>> tracing
>> tool (already supported in Systemtap/Dtrace).
>>
>> They also plan to support SDT markers in perf. (ongoing work)
>> (https://lkml.org/lkml/2013/10/23/10)
>>
>> How about SDT markers support in ktap? I thought about this a little
>> before.
>>
>> trace sdt:libc:setjmp {
>> print(execname(), argevent)
>> }
>>
>> So, if anyone interest on implement this, that's would be great.
>> (the implementation wouldn't be hard to start because we have some minimal
>> elf
>> reading code in there now, and there also have perf-sdt patch demo.)
>
> Yeah, I agree, it wouldn't be hard.
> I can implement this on weekends I hope.
> (I also need to make symbol module more common and simple)
>
I appreciate on this, Thank you very much.
Jovi
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