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RE: [microblaze-uclinux] GDB with uClinux
Hi John,
Finally got past the particularly nasty strain of versionitis.
Our kernel is now updated to 2.4.29, so I've been able to
setup gdbserver and get the mb-gdb-user application to connect
to the remote gdbserver.
This is great and will be very helpful. However, I'd really
like to be able to raise the bar just a little and be able to
use DDD or some similar graphical debugger for application
development. I keep getting authentication errors when trying
to connect DDD to the remote target. Since there were some
custom modifications required of the mb-gdb (i.e. mb-gdb-user),
I'm wondering if DDD or similar graphical debugger would also
need to be modified to work with gdbserver on the microblaze.
Is it possible to use DDD for remote debug on the microblaze?
Thanks,
Walt
-----Original Message-----
From: owner-microblaze-uclinux@itee.uq.edu.au
[mailto:owner-microblaze-uclinux@itee.uq.edu.au]On Behalf Of John
Williams
Sent: Thursday, March 24, 2005 5:06 PM
To: microblaze-uclinux@itee.uq.edu.au
Subject: Re: [microblaze-uclinux] GDB with uClinux
Hi Walt,
White, Walt J (GE Infrastructure) wrote:
> I expanded the tarball in the user/gdbserver dir, updated entry.S and ptrace.c from CVS and put the mb-gdb-user next to mb-gdb.
>
> I rebuilt everything and loaded the ./images/pImage.romfs onto the target as usual and booted it. It comes up like this:
>
[snip]
> Linux version 2.4.26-uc0-GEIS (root@WaltsLinuxBox) (gcc version 2.95.3-4 Xilinx
> EDK 6.2.1 Build EDK_Gm.12.3) #4 Thu Mar 24 12:54:35 PST 2005
[snip]
> I don't know why I'm getting the kernel BUG. I enabled full symbolic debugging from the menuconfig->kernel hacking area, assuming it would be useful for gdb. However, I then built and ran it without the symbolic debugging enabled and get this:
>
[snip]
> Looks like it hit the kernel bug and performed a reset. Any ideas on what could be wrong?
I'm almost certain this is versionitis, and a particularly nasty strain
which I will call intra-kernel version skew! Your kernel is reporting
2.4.26, the CVS sources are now up at 2.4.29. I guess you've made a
snapshot of an earlier kernel, and are working on this?
What's happened is that the new version of entry.S that you've updated,
is mismatched with the rest of your kernel - thus major wierdness that
you have witnessed.
There was a subtle but important architectural change made to the system
call interface (e.g. entry.S) back in November, where we migrated to use
the brki instruction (break), rather than bralid (branch). This was
necessary for reasons of stability and cleanness. You've now updated to
the new entry.S, but not the rest of the kernel.
Your options here are several:
1. roll forward (in a quarantined test area) to the latest kernel
sources. Depending on how much work you've been doing in your private
kernel you may have a little work to do in forward-porting your changes.
I suspect you will have very little work to do.
You will also need to get fresh versions of the files in
uClibc/libc/sysdeps/linux/microblaze directory. This is uClibc's
version of the system call interface - it must match the kernel's or
nothing will work.
I strongly recommend that you choose this approach. If you don't, you
will remain cut-off from ongoing improvements in the kernel.
2. do some forensic diffing between your previous (e.g. pre this-week)
pre-gdb versions of entry.S and ptrace.c (ptrace shouldn't matter,
entry.S is crucial), and the current CVS head. Then manually back-port
the ptrace/gdb specific changes in entry.S, into your older version.
Actually, it looks like the version of entry.S revision 1.12 should
probably work. You could try "cvs update -C -r 1.12 entry.S", and see
how that goes.
You need to decide and resolve you kernel versionitis before anything
else will make sense. It's just bad luck that you chose to snapshot
before the BRK/BRANCH change in the syscall interface. This was the
most fundamental architectural restructure since the microblaze port
began, and you've just ended up with one foot on either side of the
divide.
Regards,
John
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