kernel debugging question

[Sascha Wildner]

Matthew Dillon wrote:

    You can actually run gdb on a live kernel like this:

    gdb -k /dev/mem /path/to/kernel.debug
It's the other way round here:

gdb -k /path/to/kernel.debug /dev/mem

:)


    You can then use the 'proc' command to switch to a process (give it a
    pid), and do a stack backtrace.  That part only really works if the
    process is blocked on something (i.e. not running).
    But you can also dig around kernel globals and various data structures
    and that can be quite useful on a live system.
My problem is that I want to take a look at what's happening during 
console initialization, i.e. when init386() calls cninit() in machdep.c.

I started with putting printfs into syscons code. Then it dawned upon me 
that printf() is probably not yet working at the stage I was interested 
in (values that should've been 0 were already initialized in my printf 
output and so on).

So I thought serial debugging would be the way to go until I found that 
console initialization is done before the debugger comes into play 
(well, of course it is). D'oh! :)

The only way I can think of now is to create global data that I can look 
at after Debugger() has been called (in fact, this is what I'm going to 
do next). Question was, is there a better/more elegant way?

But it was interesting so far, I learned a few things, set up serial gdb...

Regards,
Sascha
--
http://yoyodyne.ath.cx