Linux Kernel GDB tracepoint module demo release

Hui Zhu teawater@gmail.com
Sun Aug 15 06:33:00 GMT 2010


Support x86-64 now.

On Fri, Aug 13, 2010 at 01:13, Michael Snyder <msnyder@vmware.com> wrote:
> Very interesting then.  I'd like to see you continue this work.
>
>
> Hui Zhu wrote:
>>
>> KGTP use Kprobes, I think it can work with most part of kernel.
>>
>> Thanks,
>> Hui
>>
>> On Thu, Aug 12, 2010 at 05:10, Michael Snyder <msnyder@vmware.com> wrote:
>>>
>>> Actually, this is kind of interesting.
>>> Can your system set a tracepoint at any arbitrary location in the
>>> kernel?  If so, I think that makes it more powerful than existing
>>> systems such as LTTng, which can only trace statically pre-determined
>>> locations.
>>>
>>> Hui Zhu wrote:
>>>>
>>>> Hi,
>>>>
>>>> GDB Tracepoint
>>>> (http://sourceware.org/gdb/current/onlinedocs/gdb/Tracepoints.html)
>>>> is new feature that make GDB can debug real-time program.
>>>> I think this feature is very fit for debug Linux Kernel.  So I make a
>>>> lkm to make kernel support it. You can get it in
>>>> https://code.google.com/p/kgtp/
>>>>
>>>> I just release the demo for it.  It just support collect $reg in
>>>> x86_32.  I will add the other tracepoint support in the future.
>>>>
>>>> For example:
>>>> tar vxjf gtp_20100811.tar.bz2
>>>> cd gtp
>>>> make
>>>> insmod gtp.ko
>>>> gdb ./vmlinux
>>>> GNU gdb (GDB) 7.2.50.20100720-cvs
>>>> Copyright (C) 2010 Free Software Foundation, Inc.
>>>> License GPLv3+: GNU GPL version 3 or later
>>>> <http://gnu.org/licenses/gpl.html>
>>>> This is free software: you are free to change and redistribute it.
>>>> There is NO WARRANTY, to the extent permitted by law.  Type "show
>>>> copying"
>>>> and "show warranty" for details.
>>>> This GDB was configured as "i686-pc-linux-gnu".
>>>> For bug reporting instructions, please see:
>>>> <http://www.gnu.org/software/gdb/bugs/>...
>>>> Reading symbols from /vmlinux...done.
>>>> (gdb) target remote /proc/gtp
>>>> Remote debugging using /proc/gtp
>>>> 0x00000000 in ?? ()
>>>> (gdb) trace vfs_readdir
>>>> Tracepoint 1 at 0xc01a1ac0: file
>>>> /home/teawater/kernel/linux-2.6/fs/readdir.c, line 23.
>>>> (gdb) actions
>>>> Enter actions for tracepoint 1, one per line.
>>>> End with a line saying just "end".
>>>>>
>>>>> collect $reg
>>>>> end
>>>>
>>>> (gdb) tstart
>>>> (gdb) shell ls
>>>> (gdb) tstop
>>>> (gdb) tfind
>>>> Found trace frame 0, tracepoint 1
>>>> #0  0xc01a1ac1 in vfs_readdir (file=0xc5528d00, filler=0xc01a1900
>>>> <filldir64>,
>>>>   buf=0xc0d09f90) at /home/teawater/kernel/linux-2.6/fs/readdir.c:23
>>>> 23      /home/teawater/kernel/linux-2.6/fs/readdir.c: No such file or
>>>> directory.
>>>>       in /home/teawater/kernel/linux-2.6/fs/readdir.c
>>>> (gdb) info reg
>>>> eax            0xc5528d00       -984445696
>>>> ecx            0xc0d09f90       -1060069488
>>>> edx            0xc01a1900       -1072031488
>>>> ebx            0xfffffff7       -9
>>>> esp            0xc0d09f8c       0xc0d09f8c
>>>> ebp            0x0      0x0
>>>> esi            0x8061480        134616192
>>>> edi            0xc5528d00       -984445696
>>>> eip            0xc01a1ac1       0xc01a1ac1 <vfs_readdir+1>
>>>> eflags         0x286    [ PF SF IF ]
>>>> cs             0x60     96
>>>> ss             0x8061480        134616192
>>>> ds             0x7b     123
>>>> es             0x7b     123
>>>> fs             0x0      0
>>>> gs             0x0      0
>>>> (gdb) tfind
>>>> Found trace frame 1, tracepoint 1
>>>> 0xc01a1ac1      23      in /home/teawater/kernel/linux-2.6/fs/readdir.c
>>>> (gdb) info reg
>>>> eax            0xc5528d00       -984445696
>>>> ecx            0xc0d09f90       -1060069488
>>>> edx            0xc01a1900       -1072031488
>>>> ebx            0xfffffff7       -9
>>>> esp            0xc0d09f8c       0xc0d09f8c
>>>> ebp            0x0      0x0
>>>> esi            0x8061480        134616192
>>>> edi            0xc5528d00       -984445696
>>>> eip            0xc01a1ac1       0xc01a1ac1 <vfs_readdir+1>
>>>> eflags         0x286    [ PF SF IF ]
>>>> cs             0x60     96
>>>> ss             0x8061480        134616192
>>>> ds             0x7b     123
>>>> es             0x7b     123
>>>> fs             0x0      0
>>>> gs             0x0      0
>>>> (gdb) tfind
>>>> Found trace frame 2, tracepoint 1
>>>> #0  0xc01a1ac1 in vfs_readdir (file=0xc5528300, filler=0xc01a19e0
>>>> <filldir>,
>>>>   buf=0xc6c2df90) at /home/teawater/kernel/linux-2.6/fs/readdir.c:23
>>>> 23      in /home/teawater/kernel/linux-2.6/fs/readdir.c
>>>> (gdb)
>>>> Found trace frame 3, tracepoint 1
>>>> 0xc01a1ac1      23      in /home/teawater/kernel/linux-2.6/fs/readdir.c
>>>> (gdb)
>>>> Target failed to find requested trace frame.
>>>> (gdb) quit
>>>> A debugging session is active.
>>>>
>>>>       Inferior 1 [Remote target] will be killed.
>>>>
>>>> Quit anyway? (y or n) y
>>>>
>>>> Thanks,
>>>> Hui
>>>
>
>



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