Messages in this thread | | | From | Stephane Eranian <> | Date | Wed, 8 Jun 2016 00:27:33 -0700 | Subject | Re: [PATCH 1/3] perf/x86/intel: output LBR support statement after validation |
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Andi,
On Sun, Jun 5, 2016 at 6:59 PM, Andi Kleen <ak@linux.intel.com> wrote: > > > It is not because you force LBR to ring3 only that you do not capture > > kernel addresses in the FROM field. > > Keep in mind that LBR priv level filtering applies to the target of > > the branch and not the source. You might > > still get a kernel address if returning from kernel. Now, in callstack > > mode, I think the return branch is never > > actually recorded in the LBR, it just causes a pop, so theoretically > > this should not happen. I'd like to be > > 100% sure of that, though. > > Far branches shouldn't be included in call stack LBR. Don't think > there is any other situation where the ring 0 address could leak either. > Ok, so you're saying that syscall and int are not causing LBR callstack to record an entry. If that is the case, then a rfi should not cause a pop of the last LBR entry. Is that right?
> > -Andi > -- > ak@linux.intel.com -- Speaking for myself only
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