[Qemu-devel] [DEBUG] how to use GDB to debug qemu?

[Qemu-devel] [DEBUG] how to use GDB to debug qemu?

[robert song]

Hello, everyone.
Now I am trying to read the QEMU source code.
And sometimes it's helpful to use GDB to do the debug for me to
understand the code.

For example, in the qemu environment,
I use gdb to attach to the qemu process.

Then I just run "info cpus" as following.
(QEMU) info cpus

But now how can I get into the rountine of "info cpus" ?
Of course, set trace point to the function can do the work, but if I
don't know where the routine is, is there any way to step into the
rountine?
Maybe it's sometimes about the usage of gdb, but I will be very
thankful if anyone can tell me some debug tips during the QEMU
development.

Best Regards,
  robert

[Qemu-devel] Re: [DEBUG] how to use GDB to debug qemu?

[robert song]

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> Then I just run "info cpus" as following.
> (QEMU) info cpus
>
> But now how can I get into the rountine of "info cpus" ?
> Of course, set trace point to the function can do the work, but if I
> don't know where the routine is, is there any way to step into the
> rountine?
>

Regarding to the question,
I found one tool named as tracef.
http://binary.nahi.to/hogetrace/#dl
It's in Japanese.
The tool can trace the functions called by qemu while recompling
qemu with exra options like -finstrument-functions.
It's just like strace and ltrace, but used to trace userland function.

Attach it to qemu, and the result can be got.

For exmaple:
[pid 26180] do_info_cpus() at 0x08056870

so do_info_cpus is used while you call "info cpus".
Currently tracef only supports x86 arch.

Hope this will help someone.

Best Regards,
  robert

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[Qemu-devel] Re: [DEBUG] how to use GDB to debug qemu?

[robert song]

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> The tool can trace the functions called by qemu while recompling
> qemu with exra options like -finstrument-functions.
> It's just like strace and ltrace, but used to trace userland function.
>

Sorry, a mistake.
The tool can trace the functions directly without any exra options.

Regards,
  robert

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