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

Hui Zhu
2010-09-04T16:35:25Z

Hi Frank,

I try systemtrap but got some error:

On Fri, Sep 3, 2010 at 22:05, Frank Ch. Eigler <fche@redhat.com> wrote:
>
> Steven <mqyoung@gmail.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("*@fs/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