diff options
Diffstat (limited to 'tools/perf/util/mmap.c')
| -rw-r--r-- | tools/perf/util/mmap.c | 352 |
1 files changed, 352 insertions, 0 deletions
diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c new file mode 100644 index 000000000000..9fe5f9c7d577 --- /dev/null +++ b/tools/perf/util/mmap.c @@ -0,0 +1,352 @@ +/* + * Copyright (C) 2011-2017, Red Hat Inc, Arnaldo Carvalho de Melo <acme@redhat.com> + * + * Parts came from evlist.c builtin-{top,stat,record}.c, see those files for further + * copyright notes. + * + * Released under the GPL v2. (and only v2, not any later version) + */ + +#include <sys/mman.h> +#include <inttypes.h> +#include <asm/bug.h> +#include "debug.h" +#include "event.h" +#include "mmap.h" +#include "util.h" /* page_size */ + +size_t perf_mmap__mmap_len(struct perf_mmap *map) +{ + return map->mask + 1 + page_size; +} + +/* When check_messup is true, 'end' must points to a good entry */ +static union perf_event *perf_mmap__read(struct perf_mmap *map, bool check_messup, + u64 start, u64 end, u64 *prev) +{ + unsigned char *data = map->base + page_size; + union perf_event *event = NULL; + int diff = end - start; + + if (check_messup) { + /* + * If we're further behind than half the buffer, there's a chance + * the writer will bite our tail and mess up the samples under us. + * + * If we somehow ended up ahead of the 'end', we got messed up. + * + * In either case, truncate and restart at 'end'. + */ + if (diff > map->mask / 2 || diff < 0) { + fprintf(stderr, "WARNING: failed to keep up with mmap data.\n"); + + /* + * 'end' points to a known good entry, start there. + */ + start = end; + diff = 0; + } + } + + if (diff >= (int)sizeof(event->header)) { + size_t size; + + event = (union perf_event *)&data[start & map->mask]; + size = event->header.size; + + if (size < sizeof(event->header) || diff < (int)size) { + event = NULL; + goto broken_event; + } + + /* + * Event straddles the mmap boundary -- header should always + * be inside due to u64 alignment of output. + */ + if ((start & map->mask) + size != ((start + size) & map->mask)) { + unsigned int offset = start; + unsigned int len = min(sizeof(*event), size), cpy; + void *dst = map->event_copy; + + do { + cpy = min(map->mask + 1 - (offset & map->mask), len); + memcpy(dst, &data[offset & map->mask], cpy); + offset += cpy; + dst += cpy; + len -= cpy; + } while (len); + + event = (union perf_event *)map->event_copy; + } + + start += size; + } + +broken_event: + if (prev) + *prev = start; + + return event; +} + +union perf_event *perf_mmap__read_forward(struct perf_mmap *map, bool check_messup) +{ + u64 head; + u64 old = map->prev; + + /* + * Check if event was unmapped due to a POLLHUP/POLLERR. + */ + if (!refcount_read(&map->refcnt)) + return NULL; + + head = perf_mmap__read_head(map); + + return perf_mmap__read(map, check_messup, old, head, &map->prev); +} + +union perf_event *perf_mmap__read_backward(struct perf_mmap *map) +{ + u64 head, end; + u64 start = map->prev; + + /* + * Check if event was unmapped due to a POLLHUP/POLLERR. + */ + if (!refcount_read(&map->refcnt)) + return NULL; + + head = perf_mmap__read_head(map); + if (!head) + return NULL; + + /* + * 'head' pointer starts from 0. Kernel minus sizeof(record) form + * it each time when kernel writes to it, so in fact 'head' is + * negative. 'end' pointer is made manually by adding the size of + * the ring buffer to 'head' pointer, means the validate data can + * read is the whole ring buffer. If 'end' is positive, the ring + * buffer has not fully filled, so we must adjust 'end' to 0. + * + * However, since both 'head' and 'end' is unsigned, we can't + * simply compare 'end' against 0. Here we compare '-head' and + * the size of the ring buffer, where -head is the number of bytes + * kernel write to the ring buffer. + */ + if (-head < (u64)(map->mask + 1)) + end = 0; + else + end = head + map->mask + 1; + + return perf_mmap__read(map, false, start, end, &map->prev); +} + +void perf_mmap__read_catchup(struct perf_mmap *map) +{ + u64 head; + + if (!refcount_read(&map->refcnt)) + return; + + head = perf_mmap__read_head(map); + map->prev = head; +} + +static bool perf_mmap__empty(struct perf_mmap *map) +{ + return perf_mmap__read_head(map) == map->prev && !map->auxtrace_mmap.base; +} + +void perf_mmap__get(struct perf_mmap *map) +{ + refcount_inc(&map->refcnt); +} + +void perf_mmap__put(struct perf_mmap *map) +{ + BUG_ON(map->base && refcount_read(&map->refcnt) == 0); + + if (refcount_dec_and_test(&map->refcnt)) + perf_mmap__munmap(map); +} + +void perf_mmap__consume(struct perf_mmap *map, bool overwrite) +{ + if (!overwrite) { + u64 old = map->prev; + + perf_mmap__write_tail(map, old); + } + + if (refcount_read(&map->refcnt) == 1 && perf_mmap__empty(map)) + perf_mmap__put(map); +} + +int __weak auxtrace_mmap__mmap(struct auxtrace_mmap *mm __maybe_unused, + struct auxtrace_mmap_params *mp __maybe_unused, + void *userpg __maybe_unused, + int fd __maybe_unused) +{ + return 0; +} + +void __weak auxtrace_mmap__munmap(struct auxtrace_mmap *mm __maybe_unused) +{ +} + +void __weak auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp __maybe_unused, + off_t auxtrace_offset __maybe_unused, + unsigned int auxtrace_pages __maybe_unused, + bool auxtrace_overwrite __maybe_unused) +{ +} + +void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __maybe_unused, + struct perf_evlist *evlist __maybe_unused, + int idx __maybe_unused, + bool per_cpu __maybe_unused) +{ +} + +void perf_mmap__munmap(struct perf_mmap *map) +{ + if (map->base != NULL) { + munmap(map->base, perf_mmap__mmap_len(map)); + map->base = NULL; + map->fd = -1; + refcount_set(&map->refcnt, 0); + } + auxtrace_mmap__munmap(&map->auxtrace_mmap); +} + +int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd) +{ + /* + * The last one will be done at perf_evlist__mmap_consume(), so that we + * make sure we don't prevent tools from consuming every last event in + * the ring buffer. + * + * I.e. we can get the POLLHUP meaning that the fd doesn't exist + * anymore, but the last events for it are still in the ring buffer, + * waiting to be consumed. + * + * Tools can chose to ignore this at their own discretion, but the + * evlist layer can't just drop it when filtering events in + * perf_evlist__filter_pollfd(). + */ + refcount_set(&map->refcnt, 2); + map->prev = 0; + map->mask = mp->mask; + map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot, + MAP_SHARED, fd, 0); + if (map->base == MAP_FAILED) { + pr_debug2("failed to mmap perf event ring buffer, error %d\n", + errno); + map->base = NULL; + return -1; + } + map->fd = fd; + + if (auxtrace_mmap__mmap(&map->auxtrace_mmap, + &mp->auxtrace_mp, map->base, fd)) + return -1; + + return 0; +} + +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("Finished 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("Finished 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(void *data, int mask, u64 head, u64 old, + u64 *start, u64 *end, bool backward) +{ + if (!backward) { + *start = old; + *end = head; + return 0; + } + + return backward_rb_find_range(data, mask, head, start, end); +} + +int perf_mmap__push(struct perf_mmap *md, bool overwrite, bool backward, + void *to, int push(void *to, void *buf, size_t size)) +{ + u64 head = perf_mmap__read_head(md); + u64 old = md->prev; + u64 end = head, start = old; + unsigned char *data = md->base + page_size; + unsigned long size; + void *buf; + int rc = 0; + + if (rb_find_range(data, md->mask, head, old, &start, &end, backward)) + return -1; + + if (start == end) + return 0; + + size = end - start; + if (size > (unsigned long)(md->mask) + 1) { + WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n"); + + md->prev = head; + perf_mmap__consume(md, overwrite || backward); + return 0; + } + + if ((start & md->mask) + size != (end & md->mask)) { + buf = &data[start & md->mask]; + size = md->mask + 1 - (start & md->mask); + start += size; + + if (push(to, buf, size) < 0) { + rc = -1; + goto out; + } + } + + buf = &data[start & md->mask]; + size = end - start; + start += size; + + if (push(to, buf, size) < 0) { + rc = -1; + goto out; + } + + md->prev = head; + perf_mmap__consume(md, overwrite || backward); +out: + return rc; +} |