Re: [Qemu-devel] Re: About QEMU debugging console

[Zhiyuan Shao]

On Thu, 2010-10-28 at 14:36 +0200, Jan Kiszka wrote:
> Am 26.10.2010 14:22, Zhiyuan Shao wrote:
> > Hi team,
> > 
> > I am a Qemu User, and using Qemu 0.13.0 to debugging the linux kernel
> > code (Qemu+GDB). 
> > 
> > During the usage, I found the Qemu debugging console (i.e., entered by
> > pressing Ctl+Alt+2 in Qemu SDL window or by passing "-monitor stdio" to
> > Qemu in the command line) is rather difficult to use. 
> 
> Regarding usability in this scenario: You know that there is QEMU
> monitor pass-through via gdb "monitor" command?
> 
Yes, Just learned to use that. By gdb "monitor" command, the output of
QEMU debugging console is redirected to gdb. 

> > It can not show
> > some important information, e.g., on i386 platform, which is my major
> > interest, it can not show IDT, GDT information. Regarding the page
> > mapping information, "info tlb" actually do a really bad job. 
> > 
> > On this side, I think Bochs is good. Unfortunately, it seems do not
> > support gdb-stub debugging and general purpose debugging at the same
> > time.
> > 
> > I do not know if the Qemu team had made any plans to improve this? such
> > as embedding the bochs debugging alike functionalities in future Qemu
> > releases?
> 
> The most important lacking feature is proper system-level debugging
> support for gdb (via gdbstub). Once gdb has full access to all CPU
> states of the x86 targets, you can pretty-print whatever you want inside
> gdb via some nice Python scripts etc.
> 
Are you mean that it is the responsibility of gdb to parse the output
data of qemu built-in commands and generate user-friend output? Or grant
gdb full access to the target machine, which is emulated by Qemu, and it
is the responsibility of gdb again to generate easy-to-read output for
the users?

I think the first solution sounds more feasible, however, we still need
more helpful built-in commands in Qemu. 
And it is hard to implement the second solution: By doing this, we may
need to have full support from GDB community. 

Maybe, I am wrong. If possible, please give us more advices.

Thanks!

> Jan
> 

Zhiyuan