Re: [PATCH] kprobes for s390 architecture

Heiko Carstens
2006-06-26T11:20:23Z

On Mon, Jun 26, 2006 at 03:49:45AM -0700, Mike Grundy wrote:
> On Mon, Jun 26, 2006 at 10:09:10AM +0200, Heiko Carstens wrote:
> > > After reading your notes it's probably overkill doing the cs on each cpu, since
> > > the interrupt will discard the prefetched instructions.
> >
> > Indeed. Another thing that should not be forgotten: it could be that the
> > whole kernel text segment resides in a shared read only segment. So it can
> > be shared by multiple z/VM guests.
> > In that case the cs instruction will fail. Looks like you need to write the
> > part that replaces the instruction in assembly and supply a fixup section
> > which in turn makes sure that -EFAULT is returned.
>
> If it fails, won't it will generate a program interrupt, 5 (access exception)?

Yes, that's why you need a fixup section :)