[Bug kprobes/2064] New: Support pagepoint probes

[Andi Kleen]

"jkenisto at us dot ibm dot com" <sourceware-bugzilla@sourceware.org> writes:

> It has been requested that we support "pagepoint" probes.  Such a probe is
> analogous to a watchpoint probe; but with a pagepoint probe, neither the number
> of concurrent probes nor the size of the probed area is limited by the CPU's
> debug-register architecture.
> 
> Pagepoint probes would presumably be implemented by fussing the permission bits
> on the probed page(s) and hooking the page-fault handler (or exploiting the
> existing kprobes hook).

Wouldn't that require either an x86 interpreter or SMP races when you
then replay the instruction? (when you temporarily unprotect the page)

Xen seems to have gone the first path for similar needs, but it always
looked quite bad to me (they seem to grow a new variant of x86
interpretation every month and even the original one seems to be quite
incomplete) Probably not a good idea to duplicate.

-Andi