Re: [RFC PATCH v5 4/9] Add basic Linux kernel support

Philipp Rudo
2018-03-14T09:48:36Z

Hi Kamil,

On Tue, 13 Mar 2018 15:08:32 +0100
Kamil Rytarowski <n54@gmx.com> wrote:

> On 12.03.2018 16:31, Philipp Rudo wrote:
> > Implement the basic infrastructure and functionality to allow Linux kernel
> > debugging with GDB. This contains handling of kernel symbols and data
> > structures as well as a simple target_ops to hook into GDB. For the code
> > to work architectures must provide an implementation for the virtual
> > methods in linux_kernel_ops.
> >
> > For simplicity this patch only supports static targets, i.e. core dumps.
> > Support for live debugging will be provided in a separate patch.
> >
>
>
> What's wrong with kgdb? It works well on NetBSD for alive and dead
> kernels since 90ties.

I don't know kgdb well. We at IBM mostly work with dumps and the crash tool,
which is based on an old version of gdb and has some drawbacks. For example it
doesn't have a dwarf unwinder. That's why we wanted to see if the logic needed
for kernel debugging can be added directly to gdb, instead of having a hack
working on top of it.

Furthermore, I don't see a conflict between kgdb and this work. The way I see
it, kgdb is a technique to retrieve information from the kernel. This work
however, teaches gdb how to interpret the data from the kernel in order to make
it easier to find the information you need.

Thanks
Philipp