Re: kgdb support in vanilla 2.6.2

[George Anzinger <george@mvista.com>]

Piet Delaney wrote:
> On Tue, 2004-02-10 at 13:56, George Anzinger wrote:
> 
> I thought I'd poke around an AMD64 with etherbased kgdb on 2.6.*.
> I just picked up a used AMD64 K8D Master-F MS-9131 and thought I'd
> install Fedora Core 1 test1 and the latest kernel from kernel.org.
> 
> It Might be interesting to try out a SuSE release also, I was wondering
> if 9.0 from linuxiso.org might be best.
> 
> Last I worked with your kgdb patch for 2.6 Andrew's mm patch had the
> latest code; Is that still the case?

I think so.  I haven't look lately.  I did send out an additional patch that 
only put in dwarft2 records in some of the asm code to allow better "bt" through 
the interrupt/exception frames.  I don't know if he picked this up or not, but 
it does require using the cvs version of gdb.

-g
> 
> -piet
> 
> 
>>Andi Kleen wrote:
>>
>>>On Thu, 5 Feb 2004 23:20:04 +0530
>>>"Amit S. Kale" <amitkale@emsyssoft.com> wrote:
>>>
>>>
>>>
>>>>On Thursday 05 Feb 2004 8:41 am, Andi Kleen wrote:
>>>>
>>>>
>>>>>Andrew Morton <akpm@osdl.org> writes:
>>>>>
>>>>>
>>>>>>need to take a look at such things and really convice ourselves that
>>>>>>they're worthwhile.  Personally, I'd only be interested in the basic
>>>>>>stub.
>>>>>
>>>>>What I found always extremly ugly in the i386 stub was that it uses
>>>>>magic globals to talk to the page fault handler. For the x86-64
>>>>>version I replaced that by just using __get/__put_user in the memory
>>>>>accesses, which is much cleaner. I would suggest doing that for i386
>>>>>too.
>>>>
>>>>May be I am missing something obvious. When debugging a page fault handler if 
>>>>kgdb accesses an swapped-out user page doesn't it deadlock when trying to 
>>>>hold mm semaphore?
>>>
>>>
>>>Modern i386 kernels don't grab the mm semaphore when the access is >= TASK_SIZE
>>>and the access came from kernel space (actually I see x86-64 still does, but that's 
>>>a bug, will fix). You could only see a deadlock when using user addresses
>>>and you already hold the mm semaphore for writing (normal read lock is ok). 
>>>Just don't do that. 
>>>
>>>
>>>
>>>
>>>>George has coded cfi directives i386 too. He can use them to backtrace past 
>>>>irqs stack.
>>>
>>>
>>>Problem is that he did it without binutils support. I don't think that's a good
>>>idea because it makes the code basically unmaintainable for normal souls
>>>(it's like writing assembly code directly in hex) 
>>
>>Well, bin utils, at this time, makes it even worse in that it does not support 
>>the expression syntax.  Also, it is not asm but dwarf2 and it is written in, 
>>IMHO, useful macros (not hex :)
>>
>>
>>
>>-- 
>>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
>>
>>-
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-- 
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