Re: mpc8xx-2.2.13 kernel hangs during boot.

Alan Mimms wrote:

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We use a serial connection to debug our applications with GDB all the time
using stubs that are part of our "OS".  It certainly is possible.  We put the
devices on the end of a 24 port Livingston Portmaster terminal server and then
setup the ports as raw data ports to which we connect with GDB running on our
main build/debug box.  That way the user can debug something in another room or
across the planet very easily through the network.

Cool.  A little overkill never hurt anybody :)
I'll assume one build/debug box connected directly to the target via a serial cable
or ethernet for now.

I see what you mean, but I still think it's a necessity.  It's not overkill if
it means I don't have to wander across the hall every 5 minutes to dink with the
platform or sit in a room full of LOUD fans to work and debug.

I was being a bit sarchy.  It is not overkill.  Infact I will probably setup some kind of
server for compile and debug too so some other engineers can work on linux from there
MS-Win machines (poor buggers).  I have cross-compiled Insight to work with the cygwin
environment so that might be an option with gdbserver.  I may even compile the entire
tool chain for cygwin and see if I can compile the kernel and apps from the MS-Win
machines (I'm just asking for trouble aren't I).  If it works I will ask Dan to put the
tools on the ftp server.

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I debugged my initial port of the linux kernel to our platform using just this
kind of interface.  You have to commandeer the serial hardware away from the
driver - I simply didn't tell the kernel there was a device there and
configured it "manually" from the GDB nub initialization function which I
called early in main.c.  This works fine for KERNEL debugging.

When you say configured manually what exactly do you mean.
Is this in the kernel itself ?
When you say main.c do you mean init/main.c in the linux kernel source tree ?
Has this got anything to do with the kgdb option in the "make config" process ?
Can ethernet be used to debug the kernel or is a serial port the only or best way to
go ?

I DO mean init/main.c.  I mean "manually" in the sense that the low level
driver I used in my gdb nub has an "init" call made from init/main.c to
setup the UART registers properly (baud rate, etc.).  The nub UART driver simply
polls the UART and does simple one byte read/write operations to it.  The nub
has the necessary (simple) hex/unhex conversion routines for the GDB serial
protocol.  Doesn't use anything else so you can theoretically debug the
kernel's version of printf with breakpoints and everything without screwing up
the debugger by debugging code it depends upon.

What is "nub" ?
Have you have written the code to interpret the gdb serial protocol or are you using code
from gdb itself ?
Are your suggestions taken from the gdb howto or documentation ?

Thanks,
Brendan Simon.


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