Vince reported the perf_fuzzer giving various unwinder warnings and Josh reported: > Deja vu. Most of these are related to perf PEBS, similar to the > following issue: > > b8000586c90b ("perf/x86/intel: Cure bogus unwind from PEBS entries") > > This is basically the ORC version of that. setup_pebs_sample_data() is > assembling a franken-pt_regs which ORC isn't happy about. RIP is > inconsistent with some of the other registers (like RSP and RBP). And where the previous unwinder only needed BP,SP ORC also requires IP. But we cannot spoof IP because then the sample will get displaced, entirely negating the point of PEBS. So cure the whole thing differently by doing the unwind early; this does however require a means to communicate we did the unwind early. We (ab)use an unused sample_type bit for this, which we set on events that fill out the data->callchain before the normal perf_prepare_sample().
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| @@ -143,6 +143,8 @@ enum perf_event_sample_format { · 142 unmodified lines | |||
| 143 | PERF_SAMPLE_PHYS_ADDR = 1U << 19, | 143 | PERF_SAMPLE_PHYS_ADDR = 1U << 19, |
| 144 | 144 | ||
| 145 | PERF_SAMPLE_MAX = 1U << 20, /* non-ABI */ | 145 | PERF_SAMPLE_MAX = 1U << 20, /* non-ABI */ |
| 146 | |||
| 147 | __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63, | ||
| 146 | }; | 148 | }; |
| 147 | 149 | ||
| 148 | /* | 150 | /* |