About the exception ipc reply

Adam Lackorzynski adam at os.inf.tu-dresden.de
Wed Oct 14 00:52:10 CEST 2009

On Tue Oct 13, 2009 at 13:01:46 +0800, Guanghui, Cheng wrote:
> On Monday 12 October 2009 02:03:41 Adam Lackorzynski wrote:
> > On Sun Oct 11, 2009 at 22:17:49 +0800, Guanghui, Cheng wrote:
> > > 	From the l4-x2 manual it is said the reply from the exception handler
> > > contains a label, an instruction pointer where the faulting thread is
> > > resumed. I want to know whether it is implemented in the Fiasco.
> > > 	I try to do this. Modify the utcb before send ipc resume the exception
> > > thread but it seems no any effect about the instruction pointer and stack
> > > pointer of resumed exception thread.
> >
> > My guess would be that you did not set the number of words to send in
> > the reply. Set L4_UTCB_EXCEPTION_REGS_SIZE in the msgtag-words field of
> > the reply.
> Hello Adam:
> 	Now i use L4_UTCB_EXCEPTION_REGS_SIZE and i could fix the thread with esp and 
> eip by exception handler UTCB. And the thread could start with new instruction 
> pointer and new stack pointer.  But it still has some problem when the thread 
> quit from new function. So i want to know how an thread is resumed by 
> exception reply. I mean which part of code in kernel could finish the thread 
> wakeup. I read the receive.c but i don't find it.

The function copy_utcb_to_ts copies the state from the utcb of the
exception handler over the state of the thread. The thread then resumes
with this new state. I think what you have to do is to e.g. prepare the
stack of the thread in a way that when the new function's ret is
called it resumes at the position it was intercepted. Is this possible?

Adam                 adam at os.inf.tu-dresden.de
  Lackorzynski         http://os.inf.tu-dresden.de/~adam/

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