On Fri, Jun 15, 2018 at 01:31:34PM +0000, Liang, Kan wrote: > > On Thu, Jun 14, 2018 at 11:02:53PM -0700, Stephane Eranian wrote: > > > On Thu, Jun 14, 2018 at 7:10 PM Jin Yao <yao....@linux.intel.com> wrote: > > > > + /* > > > > + * Due to interrupt latency (AKA "skid"), we may enter the > > > > + * kernel before taking an overflow, even if the PMU is only > > > > + * counting user events. > > > > + * To avoid leaking information to userspace, we must always > > > > + * reject kernel samples when exclude_kernel is set. > > > > + */ > > > > + if (event->attr.exclude_kernel && !user_mode(regs)) > > > > + return false; > > > > + > > > And how does that filter PEBS or LBR records? > > > > I suspect the user_mode() thing actually covers PEBS, but yes LBR might need > > additional filtering. > > I think the large PEBS still need to be specially handled.
large pebs should be fine too, all pebs stuff eventually calls perf_event_output() with a synthesized register set.
