[ktap] Re: [PATCH] add new symbol module to search symbols in DSO (for uprobes)
- From: Azat Khuzhin <a3at.mail@xxxxxxxxx>
- To: ktap <ktap@xxxxxxxxxxxxx>
- Date: Thu, 7 Nov 2013 09:38:32 +0400
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)
Azat.
>
> Jovi
>
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