Derek Atkins wrote:
> Jason,
>
> Jason Wessel <[email protected]> writes:
>
>   
>> Unless you patch in the kgdb8250 driver, you cannot use it.  If you
>> build the kernel documentation you would get a directory called
>> Documentation/DocBook/kgdb.   In there you would find information about
>> kgdboc, which is the only I/O driver merged to the mainline kernel.
>>     
>
> One of the benefits of the (very old, like pre-2.6.25) kgdb8250 driver
> was that it would both allow you to ^C from gdb to stop the running
> kernel (no need to use the SysRq-g) and also it would allow all printk's
> to be delivered to the remote gdb process.  Last time I tried the kgdboc
> driver (probably about 2.6.28) it didn't have either of these features.
> Has that changed more recently?  If so, where and when?
>
>   

I have patches to kgdboc which allow you to do this, but Alan Cox (tty
maintainer at the time) rejected them because the tty lisc and locking
infrastructure was in complete flux.  The extension to kgdboc allows
kgdb to open a simulated file handle such that the tty can be opened
before the user space init or on a tty that has not been opened by
another program.

In the later half of 2009 Alan stopped maintaining the tty layer, and
perhaps these patches might get accepted this time around.  I was
planning on resubmitting some of this work after the kdb / kgdb merge
activities are completed.

It may not be of interest, but the kgdboc with this functionality also
has the capability to declare any key you like as the kernel interrupt
character.  This was needed on archs like sparc where sysrq can be
overloaded with an exit to prom code.

Long story short:
  * The functionality you asked about is not in the mainline
  * There are patches in the kgdb dev tree for this

Jason.

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