δΊ 2015/7/23 10:22, Alexei Starovoitov ει: > On 7/22/15 7:12 PM, xiakaixu wrote: >> So you mean like this? >> >> u64 bpf_perf_event_read(u64 r1, u64 index,...) >> { >> struct bpf_perf_event_array *array = (void *) (long) r1; >> struct perf_event *event; >> ... >> event = array->events[index]; >> ... >> } > > yes. the only thing needed is to add: > if (index >= array->map.max_entries) > return -E2BIG; > before accessing array->events[index]; > >>> > >>>> >>+const struct bpf_func_proto bpf_perf_event_read_proto = { >>>> >>+ .func = bpf_perf_event_read, >>>> >>+ .gpl_only = false, >>>> >>+ .ret_type = RET_INTEGER, >>>> >>+ .arg1_type = ARG_CONST_MAP_PTR, >>>> >>+ .arg2_type = ARG_PTR_TO_MAP_KEY, >>> > >>> >make it arg2_type = ARG_ANYTHING then you'll just index >>> >into array the way prog_array does and similar to bpf_tail_call. > >> ARG_ANYTHING means any (initialized) argument is ok, but we here > > correct. > >> really want is map key. So I'm not sure ARG_ANYTHING is suitable. >> You know ARG_ANYTHING is not checked enough in verifier. > > why? during perf_event_array creation time we check that key_size == u32 > so we can accept any integer. > ARG_PTR_TO_MAP_KEY forces program author to use stack instead of > passing index directly. Direct index is obviously faster.
Copy that. We will follow them in V3. > > > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/