Recovery kernel and application crashes how?

Hi All,
I am interested to know the behaviour of L4Ka in the following conditions.

1. Thread (or task) trying to access unmapped memory (null pointer
dereference)
2. Kernel/driver trying to access unmapped memory (null pointer dereference)
3. Thread (or task) trying to access memory mapped to other process (may not
holds good for l4 since each thread has its own address space).

And how the recover from such exceptions(errors) are done.

Thanks
Prem