On Fri, Sep 10, 2021 at 11:33:50AM -0700, Song Liu wrote: > The typical way to access branch record (e.g. Intel LBR) is via hardware > perf_event. For CPUs with FREEZE_LBRS_ON_PMI support, PMI could capture > reliable LBR. On the other hand, LBR could also be useful in non-PMI > scenario. For example, in kretprobe or bpf fexit program, LBR could > provide a lot of information on what happened with the function. Add API > to use branch record for software use. > > Note that, when the software event triggers, it is necessary to stop the > branch record hardware asap. Therefore, static_call is used to remove some > branch instructions in this process. > > Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Acked-by: John Fastabend <john.fastabend@xxxxxxxxx> > Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > Signed-off-by: Song Liu <songliubraving@xxxxxx> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
