how to debug gdb?

[Norman Feske]

Hello,

> The same code do not show threads inside qemu -s, only show single-per-core thread.
> 
> I assume that qemu build-in gdb stub (which was recommended to me by
> Norman) do not able to see new threads for NOVA, probably it requires
> some special call from inside OS to inside qemu during creation of
> thread (may be because thread is not "native kind", native processes
> only  has separate set of TLB/etc related to virtual space, - I think
> that this could be a reason - while I did not check it).
for debugging threads, Qemu -s is indeed not very useful per se.

In many debugging situations, however, it is often possible to work
around this limitation. In [1] I have documented some life hacks that I
find useful. In particular by adding an infinite loop at a point of
interest in the code and attaching GDB once this loop is entered, one
can observe the state of the thread that is currently spinning. In many
situations that's all what's needed to prove or rule out a suspicion.

[1]
https://genode.org/documentation/articles/sel4_part_1#A_root_task_for_exercising_the_kernel_interface

Norman

-- 
Dr.-Ing. Norman Feske
Genode Labs

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