Re: KGDB 2..26 fails to wait while booting

Previous thread: [git pull] Input updates for 2.6.27-rc0 (round 2) by Dmitry Torokhov on Thursday, August 14, 2008 - 7:28 pm. (2 messages)

Next thread: [PATCH 0/3] ftrace: handle kernel code remove by Steven Rostedt on Thursday, August 14, 2008 - 7:47 pm. (7 messages)
From: amruth
Date: Thursday, August 14, 2008 - 7:46 pm

Hi
I have created 2.6.26 kernel with KGDB enabled but the system fails to wait. Can anybody provide me detailed info on how to setup the grub configuration to wait until gdb connects from development machine. 
Thanks
Amruth p.v


      

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From: Jason Wessel
Date: Monday, August 18, 2008 - 7:05 am

wait. Can anybody provide me detailed info on how to setup the grub

What parameters did you use in grub?

Generally speaking you have to setup the boot parameters to be something
like:

kgdboc=ttyS0,115200 kgdbwait

Jason.

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From: amruth
Date: Monday, August 18, 2008 - 8:36 am

Thanks Jason. I got it working, but is it possible to enable kdb with kgdb. 
How can I debug the kernel early. In kdb we have option called as kdb=early, can we do the same in kgdb. I tried to set breakpoint in kgdb at start_kernel, it looks like kgdb executed past the start_kernel code.Hence break point does not work.
Please let me know how to enable debug early kernel option in KGDB. 

Thanks
Amruth p.v




      

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From: Jason Wessel
Date: Monday, August 18, 2008 - 8:51 am

This is a limitation of the kgdb which in the mainline sources.  The
kgdb core itself can support early debugging.

The kgdboc I/O module does not support early debugging however because
it waits for the tty driver to get setup.  There is an 8250_kgdb kernel
module which supports debugging from an ealier point than the kgdboc
driver but this is not in the main line sources.  You can get it from
the kgdb branch.

IE:

http://git.kernel.org/?p=linux/kernel/git/jwessel/linux-2.6-kgdb.git;a=commitdiff_plai...

and

http://git.kernel.org/?p=linux/kernel/git/jwessel/linux-2.6-kgdb.git;a=commitdiff_plai...

Jason.

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Previous thread: [git pull] Input updates for 2.6.27-rc0 (round 2) by Dmitry Torokhov on Thursday, August 14, 2008 - 7:28 pm. (2 messages)

Next thread: [PATCH 0/3] ftrace: handle kernel code remove by Steven Rostedt on Thursday, August 14, 2008 - 7:47 pm. (7 messages)