Debugger on top of L4

Adam Lackorzynski adam at
Mon Mar 24 18:12:41 CET 2008


On Thu Mar 20, 2008 at 08:12:13 -0700, Andrew Vadimovich wrote:
> Im totally newbie to l4, but my aim is to develop source level debugger for
> our system built on top of L4. So the procedure for source level debugger is
> common and may be presented in following steps:
> 1) Cause undef exception from user task (using undef instruction)
> 2) Catch it by undef exception handler 
> 3) Save CPU registers
> 4) Suspend running thread. Suspension must be performed by my code - not by
> l4 system code.
> 5) Continue execution with next scheduled thread
> But untill now i have no ideas how to suspend thead by my self. I even cant
> find l4 code responsible for thread suspension.
> Does anyone knows where can i find suspention procedure in l4 code?
> Probably someone has code snippets for such kind of actions?

When a thread causes an exception and the exception handler receives the
according IPC, then the thread is already suspended. No need to suspend
it yourself. The thread will resume execution upon response of the
exception handler.

Adam                 adam at

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