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

[Hui Zhu <teawater at gmail dot com>]

On Sat, Sep 4, 2010 at 17:26, Steven <mqyoung@gmail.com> wrote:
> On Sat, 2010-09-04 at 17:17 +0800, Hui Zhu wrote:
>> On Sat, Sep 4, 2010 at 16:56, Steven <mqyoung@gmail.com> wrote:
>> > On Sat, 2010-09-04 at 11:41 +0800, Hui Zhu wrote:
>> >> BTW, looks GCC and GDB don't want handle the optimization debug
>> >> trouble (all they want is rewrite the GCC in C++ :P).
>> >> So I think make linux kernel can close optimization is better idea, do
>> >> you know some way or some patch to do it?
>> >>
>> >
>> > Just disable CONFIG_CC_OPTIMIZE_FOR_SIZE and modify the Makefile of
>> > kernel:
>> > KBUILD_CFLAGS ? += -O2
>> > to
>> > KBUILD_CFLAGS ? += -O0
>>
>> Cool, ?:)
>>
>> I try just change the compile option of readdir.c to without -O2, it
>> works OK. ?I think maybe it's a GDB bug too.
>> Could you try the second issue with gdb 7.2?
>
> I have covered the two issues in the previous mail that I could collect
> both global variables and locals(-O0 kernel + gdb7.2):
>
> ? ? ? ?--------
> ? ? ? ?(gdb) trace vfs_readdir
> ? ? ? ?Tracepoint 3 at 0xc11756a0: file fs/readdir.c, line 24.
> ? ? ? ?(gdb) actions
> ? ? ? ?Enter actions for tracepoint 3, one per line.
> ? ? ? ?End with a line saying just "end".
> ? ? ? ?>collect *file
> ? ? ? ?>end
> ? ? ? ?(gdb) trace fs/readdir.c:29
> ? ? ? ?Tracepoint 4 at 0xc11756ca: file fs/readdir.c, line 29.
> ? ? ? ?(gdb) actions
> ? ? ? ?Enter actions for tracepoint 4, one per line.
> ? ? ? ?End with a line saying just "end".
> ? ? ? ?>collect res
> ? ? ? ?>end
> ? ? ? ?(gdb) tstart
> ? ? ? ?(gdb) tstop
> ? ? ? ?(gdb) tfind
> ? ? ? ?Found trace frame 0, tracepoint 3
> ? ? ? ?#0 ?0xc11756a1 in vfs_readdir (file=0xc7b2cf00, filler=0,
> ? ? ? ?buf=0x0)
> ? ? ? ? ? ?at fs/readdir.c:24
> ? ? ? ?24 ? ? ? ? ? ? ?struct inode *inode =
> ? ? ? ?file->f_path.dentry->d_inode;
> ? ? ? ?(gdb) p *file
> ? ? ? ?$4 = {f_u = {fu_list = {next = 0xc6dca500, prev = 0xc7ade480},
> ? ? ? ?fu_rcuhead = {
> ? ? ? ? ? ? ?next = 0xc6dca500, func = 0xc7ade480}}, f_path = {mnt =
> ? ? ? ?0xc6c05300,
> ? ? ? ? ? ?dentry = 0xc761d440}, f_op = 0xc1709a20, f_lock = {{rlock =
> ? ? ? ?{raw_lock = {
> ? ? ? ? ? ? ? ? ?slock = 0}}}}, f_count = {counter = 2}, f_flags =
> ? ? ? ?624640,
> ? ? ? ? ?f_mode = 29, f_pos = 0, f_owner = {lock = {raw_lock = {lock =
> ? ? ? ?16777216}},
> ? ? ? ? ? = 0start = 0, size = 0, async_size = 0,
> ? ? ? ? ? ?ra_pages = 32, mmap_miss = 0, prev_pos = -1}, f_version =
> ? ? ? ?0,
> ? ? ? ? ?f_security = 0xc7b30120, private_data = 0x0, f_ep_links = {
> ? ? ? ? ? ?next = 0xc7b2cf74, prev = 0xc7b2cf74}, f_mapping =
> ? ? ? ?0xc761c74c}
> ? ? ? ?(gdb) p res
> ? ? ? ?$5 = 0
> ? ? ? ?(gdb) tfind
> ? ? ? ?Found trace frame 1, tracepoint 4
> ? ? ? ?0xc11756cb ? ? ?29 ? ? ? ? ? ? ?res =
> ? ? ? ?security_file_permission(file, MAY_READ);
> ? ? ? ?(gdb) p res
> ? ? ? ?$6 = -20
> ? ? ? ?--------
>
>
>

Great.  :)

Hui