kernel serial debugging question

kernel serial debugging question

[Stephane Charette]

Background:
-----------

In the past, I have had to use the kernel serial debugger with the
2.2.14 kernel.

The steps I followed (if my notes are correct) were:

- in "make menuconfig", within "<Kernel Hacking>", select "<Kernel
support for GDB>"
- pass the additional options "gdb gdbttyS=1 gdbbaud=115200" to loadlin
- wait for the message "Waiting for connection from remote gdb on
ttyS1"


My question:
------------

Has any of this changed with the 2.4.x kernel?  I'm currently playing
with 2.4.19-pre9.  Is there a "serial debugger" patch that has to be
applied first, or is this support normally built-in?

The reason I ask is because I don't see the option "Kernel support for
GDB", which leads me to think that maybe this functionality actually
came from a patch that was applied on top of 2.2.14.

While I'm at it:  is there a "better", or perhaps a "more popular"
method of debugging the kernel?

Thanks,

Stephane Charette

Re: kernel serial debugging question

[Andrew Morton]

Stephane Charette wrote:
> 
> Background:
> -----------
> 
> In the past, I have had to use the kernel serial debugger with the
> 2.2.14 kernel.
> 

It's an external patch.  From http://kgdb.sourceforge.net/
I have kgdb patches for all kernels back to 2.4.0-test.
Some of those can be found by poking around in
http://www.zip.com.au/~akpm/linux/patches/.

Re: kernel serial debugging question

[Frank Schaefer]

On Sat, 2002-06-08 at 01:18, Stephane Charette wrote:
> My question:
> ------------
> 
> Has any of this changed with the 2.4.x kernel?  I'm currently playing
> with 2.4.19-pre9.  Is there a "serial debugger" patch that has to be
> applied first, or is this support normally built-in?

I've set up kernel remote debugging for 2.4.18 not so far ago. The
procedure is the same as for the 2.2.* series. You should simply use the
patch for the kernel version you use.

> The reason I ask is because I don't see the option "Kernel support for
> GDB", which leads me to think that maybe this functionality actually
> came from a patch that was applied on top of 2.2.14.
> 
> While I'm at it:  is there a "better", or perhaps a "more popular"
> method of debugging the kernel?

On my development machine I've set up one kernel with the kgdb internal
debugger, one kernel with the gdb-patch and one unpatched kernel with
the usual debugging stuff enabled ( all kernels of the same version - of
course ). Which kernel to run depends on the kind of problem to solve,
and is IMHO more a question of personal taste.

Regards
Frank