[PATCH 2/5] powerpc/kprobes: Do not suppress instruction emulation if a single run failed

[Naveen N. Rao]

On 2017/09/13 04:53PM, Masami Hiramatsu wrote:
> On Thu, 14 Sep 2017 02:50:33 +0530
> "Naveen N. Rao" <naveen.n.rao at linux.vnet.ibm.com> wrote:
> 
> > Currently, we disable instruction emulation if emulate_step() fails for
> > any reason. However, such failures could be transient and specific to a
> > particular run. Instead, only disable instruction emulation if we have
> > never been able to emulate this. If we had emulated this instruction
> > successfully at least once, then we single step only this probe hit and
> > continue to try emulating the instruction in subsequent probe hits.
> 
> Hmm, would this mean that the instruction is emulatable or not depends
> on context? What kind of situation is considerable?

Yes, as an example, a load/store instruction can cause exceptions 
depending on the address. In some of those cases, we will have to single 
step the instruction, but we will be able to emulate in most scenarios.

Thanks for the review!
- Naveen