diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 73ce651c84f678cbbf8c8aaf2236b651738c6390..dc3fcb597e4c10cf091dcad73a53776387baab16 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -83,6 +83,54 @@ static int process_synthesized_event(struct perf_tool *tool, return record__write(rec, event, event->header.size); } +static int +backward_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end) +{ + struct perf_event_header *pheader; + u64 evt_head = head; + int size = mask + 1; + + pr_debug2("backward_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head); + pheader = (struct perf_event_header *)(buf + (head & mask)); + *start = head; + while (true) { + if (evt_head - head >= (unsigned int)size) { + pr_debug("Finshed reading backward ring buffer: rewind\n"); + if (evt_head - head > (unsigned int)size) + evt_head -= pheader->size; + *end = evt_head; + return 0; + } + + pheader = (struct perf_event_header *)(buf + (evt_head & mask)); + + if (pheader->size == 0) { + pr_debug("Finshed reading backward ring buffer: get start\n"); + *end = evt_head; + return 0; + } + + evt_head += pheader->size; + pr_debug3("move evt_head: %"PRIx64"\n", evt_head); + } + WARN_ONCE(1, "Shouldn't get here\n"); + return -1; +} + +static int +rb_find_range(struct perf_evlist *evlist, + void *data, int mask, u64 head, u64 old, + u64 *start, u64 *end) +{ + if (!evlist->backward) { + *start = old; + *end = head; + return 0; + } + + return backward_rb_find_range(data, mask, head, start, end); +} + static int record__mmap_read(struct record *rec, int idx) { struct perf_mmap *md = &rec->evlist->mmap[idx]; @@ -94,6 +142,10 @@ static int record__mmap_read(struct record *rec, int idx) void *buf; int rc = 0; + if (rb_find_range(rec->evlist, data, md->mask, head, + old, &start, &end)) + return -1; + if (start == end) return 0; diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 904523a2be9086d289c17f7ac431639c7055e368..e82ba90cc96997b03042c79c180e2de34bec231f 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -44,6 +44,7 @@ void perf_evlist__init(struct perf_evlist *evlist, struct cpu_map *cpus, perf_evlist__set_maps(evlist, cpus, threads); fdarray__init(&evlist->pollfd, 64); evlist->workload.pid = -1; + evlist->backward = false; } struct perf_evlist *perf_evlist__new(void) diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h index 97090b70976dfa5a5eeafd7ba7e8d947a0bc35e5..d740fb877ab6f22ac912c9fdc972fc39f1bedc6a 100644 --- a/tools/perf/util/evlist.h +++ b/tools/perf/util/evlist.h @@ -44,6 +44,7 @@ struct perf_evlist { bool overwrite; bool enabled; bool has_user_cpus; + bool backward; size_t mmap_len; int id_pos; int is_pos;