linux-kernel - Re: Linux Kernel GDB tracepoint module 2010-8-30 release

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Date:	Sun, 5 Sep 2010 00:34:22 +0800
From:	Hui Zhu <teawater@...il.com>
To:	"Frank Ch. Eigler" <fche@...hat.com>
Cc:	Steven <mqyoung@...il.com>,
	"gdb@...rceware.org" <gdb@...rceware.org>,
	linux-kernel@...r.kernel.org, Michael Snyder <msnyder@...are.com>,
	Marc Khouzam <marc.khouzam@...csson.com>,
	Thiago Jung Bauermann <thiago.bauermann@...il.com>
Subject: Re: Linux Kernel GDB tracepoint module 2010-8-30 release

Hi Frank,

I try systemtrap but got some error:

On Fri, Sep 3, 2010 at 22:05, Frank Ch. Eigler <fche@...hat.com> wrote:
>
> Steven <mqyoung@...il.com> writes:
>
>> [...]
>>         (gdb) trace vfs_readdir
>>         Tracepoint 3 at 0xc1175690: file fs/readdir.c, line 23.
>>         (gdb) actions
>>         Enter actions for tracepoint 3, one per line.
>>         End with a line saying just "end".
>>         > collect jiffies_64
>>         > collect *file
>>         > end
>
> By the way, the systemtap equivalent would be:
>
> #! /usr/bin/stap -g
> probe kernel.function("vfs_readdir") {
>      println(%{ jiffies_64 %})
>      println($file$)
> }

parse error: expected literal string or number
	saw: embedded-code at ./1.sh:3:14
     source:      println(%{ jiffies_64 %})
                          ^
parse error: expected statement
	saw: ./1.sh EOF
2 parse error(s).
Pass 1: parse failed.  Try again with another '--vp 1' option.


>
>
>> 2) I can not collect local variable, despite I rebuild the kernel with
>> -O0 optimization option. what is the problem? Many thanks
>>         -------------------------------------------------------------------
>>         (gdb) trace fs/readdir.c:29
>>         Tracepoint 2 at 0xc11756ca: file fs/readdir.c, line 29.
>>         (gdb) actions
>>         Enter actions for tracepoint 2, one per line.
>>         End with a line saying just "end".
>>         > collect res
>>         > end
>
>
> #! /usr/bin/stap
> probe kernel.statement("*@...readdir.c:29") {
>      println($res)
> }
>

semantic error: not accessible at this address: identifier '$res' at ./1.sh:3:14
        source:      println($res)
                             ^
Pass 2: analysis failed.  Try again with another '--vp 01' option.
[1]+  Done                    gedit 1.sh


Could you help me with it?

Thanks,
Hui
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