How to enable GDB for l4linux

[Christian Prochaska]

Hi 정복득,

> I'd like to use gdb_monitor to monitor l4linux and processes running on the l4linux.
>

unfortunately, l4linux and processes running on l4linux cannot be
debugged using GDB monitor. Let me explain:

GDB monitor monitors an application by virtualizing the CPU, RAM and RM
services used by the application. But because the l4linux kernel uses
the VCPU feature of Fiasco.OC instead of Genode services for its kernel
threads, GDB monitor doesn't know about them. Also, the l4linux kernel
needs to be configured by an XML<config> node in the 'config' file,
which GDB monitor currently doesn't provide to the target application
(this could be easily fixed, though).

Further, GDB monitor currently cannot monitor child processes created by
the target application. We're thinking about a good way to support this
in the future, but even if it were supported, it would not work for
processes running on l4linux, since these use the VCPU feature, too.

Regards
Christian