Re: Linux/MANOS Kernel Debugger

From: Andi Kleen (ak@suse.de)
Date: Tue Sep 05 2000 - 18:34:37 EST


On Tue, Sep 05, 2000 at 05:20:53PM -0600, Jeff V. Merkey wrote:
> I think it would not be hard to put this in. My problem is time and
> "debugging the debugger" in Linux. The codes at our site and anyone who
> wants to put it in is welcome to.

I looked at the Manos code and it seems to require a functional file system
to read the source code during debugging. When the kernel is stopped
in the debugger it is definitely not safe to access anything like a file
system in Linux (e.g. due to locking issues)

Without accessing the file system the debugger couldn't
do much more than assembly level debugging like KDB, which already works
fine. Precaching source is not practical. Developing a separate independent
file system module that works safely even from a stopped kernel (and would
still be functional enough so that you can compile and edit files on it)
would also be major work. I guess Manos solved it by using DOS for that,
but this is simply not possible in Linux.

The only sane way to do source level kernel debugging IMHO is to do
it from a second machine (sane =~ without being in deadlock country), which
also already works nicely using remote gdb + kgdb stub.

-Andi

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