| > What information SEGV gives you? Your clone started and segv-faulted
| > right away?
|
| The child starts by an infinite loop, so that I can attach it with gdb,
| then jump outside the loop. During the different try I made to get
| things working, I have been able to attach the child. I had a SIGSEGV on
| a stack access.

If you really want to debug this you need to debug the kernel not the
child.  Put a breakpoint in the data fault handler just before calling
trapsignal().  Then dump out the trap frames and uvmspace associated with
the child to see what's really going on there.

Eduardo