Re: kgdb for mainline kernel: core-lite [patch 1/3]

George Anzinger
2004-03-08T22:19:34Z

Amit S. Kale wrote:
> On Monday 08 Mar 2004 4:50 pm, Amit S. Kale wrote:
>
>>On Monday 08 Mar 2004 4:37 pm, Andrew Morton wrote:
>>
>>>"Amit S. Kale" <amitkale@emsyssoft.com> wrote:
>>>
>>>>On Monday 08 Mar 2004 3:56 pm, Andrew Morton wrote:
>>>> > "Amit S. Kale" <amitkale@emsyssoft.com> wrote:
>>>> > > Here are features that are present only in full kgdb:
>>>> > > 1. Thread support (aka info threads)
>>>> >
>>>> > argh, disaster. I discussed this with Tom a week or so ago when it
>>>> > looked like this it was being chopped out and I recall being told
>>>> > that the discussion was referring to something else.
>>>> >
>>>> > Ho-hum, sorry. Can we please put this back in?
>>>>
>>>> Err., well this is one of the particularly dirty parts of kgdb. That's
>>>>why it's been kept away. It takes care of correct thread backtraces in
>>>>some rare cases.
>>>
>>>Let me just make sure we're taking about the same thing here. Are you
>>>saying that with kgdb-lite, `info threads' is completely missing, or does
>>>it just not work correctly with threads (as opposed to heavyweight
>>>processes)?
>>
>>info threads shows a list of threads. Heavy/light weight processes doesn't
>>matter. Thread frame shown is incorrect.
>>
>>I looked at i386 dependent code again. Following code in it is incorrect. I
>>never noticed it because this code is rarely used in full version of kgdb:
>>
>>+void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct
>>task_struct *p)
>>....
>>+ gdb_regs[_EBP] = *(int *)p->thread.esp;
>>
>>We can't guss ebp this way. This line should be removed.
>>
>>+ gdb_regs[_DS] = __KERNEL_DS;
>>+ gdb_regs[_ES] = __KERNEL_DS;
>>+ gdb_regs[_PS] = 0;
>>+ gdb_regs[_CS] = __KERNEL_CS;
>>+ gdb_regs[_PC] = p->thread.eip;
>>+ gdb_regs[_ESP] = p->thread.esp;
>>
>>This should be gdb_regs[_ESP] = &p->thread.esp
>
>
> That's not correct it. It should be gdb_regs[_ESP] = p->thread.esp;
> Even with these changes I can't get thread listing correctly.
>
> Here is the intrusive piece of code that helps get thread state correctly. Any
> ideas on cleaning it?

I wonder what version of gdb you are using. What is it that you see?

You really do need a gdb that handles the dwarft2 frames. This is a rather new
gdb (I use the CVS version).

-g
~

--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml