353 lines
8.4 KiB
C
353 lines
8.4 KiB
C
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/*
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* Copyright (C) 2011-2017, Red Hat Inc, Arnaldo Carvalho de Melo <acme@redhat.com>
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*
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* Parts came from evlist.c builtin-{top,stat,record}.c, see those files for further
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* copyright notes.
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*
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* Released under the GPL v2. (and only v2, not any later version)
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*/
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#include <sys/mman.h>
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#include <inttypes.h>
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#include <asm/bug.h>
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#include "debug.h"
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#include "event.h"
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#include "mmap.h"
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#include "util.h" /* page_size */
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size_t perf_mmap__mmap_len(struct perf_mmap *map)
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{
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return map->mask + 1 + page_size;
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}
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/* When check_messup is true, 'end' must points to a good entry */
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static union perf_event *perf_mmap__read(struct perf_mmap *map, bool check_messup,
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u64 start, u64 end, u64 *prev)
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{
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unsigned char *data = map->base + page_size;
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union perf_event *event = NULL;
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int diff = end - start;
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if (check_messup) {
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/*
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* If we're further behind than half the buffer, there's a chance
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* the writer will bite our tail and mess up the samples under us.
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*
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* If we somehow ended up ahead of the 'end', we got messed up.
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*
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* In either case, truncate and restart at 'end'.
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*/
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if (diff > map->mask / 2 || diff < 0) {
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fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
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/*
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* 'end' points to a known good entry, start there.
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*/
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start = end;
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diff = 0;
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}
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}
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if (diff >= (int)sizeof(event->header)) {
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size_t size;
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event = (union perf_event *)&data[start & map->mask];
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size = event->header.size;
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if (size < sizeof(event->header) || diff < (int)size) {
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event = NULL;
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goto broken_event;
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}
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/*
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* Event straddles the mmap boundary -- header should always
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* be inside due to u64 alignment of output.
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*/
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if ((start & map->mask) + size != ((start + size) & map->mask)) {
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unsigned int offset = start;
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unsigned int len = min(sizeof(*event), size), cpy;
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void *dst = map->event_copy;
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do {
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cpy = min(map->mask + 1 - (offset & map->mask), len);
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memcpy(dst, &data[offset & map->mask], cpy);
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offset += cpy;
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dst += cpy;
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len -= cpy;
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} while (len);
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event = (union perf_event *)map->event_copy;
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}
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start += size;
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}
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broken_event:
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if (prev)
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*prev = start;
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return event;
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}
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union perf_event *perf_mmap__read_forward(struct perf_mmap *map, bool check_messup)
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{
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u64 head;
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u64 old = map->prev;
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/*
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* Check if event was unmapped due to a POLLHUP/POLLERR.
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*/
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if (!refcount_read(&map->refcnt))
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return NULL;
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head = perf_mmap__read_head(map);
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return perf_mmap__read(map, check_messup, old, head, &map->prev);
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}
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union perf_event *perf_mmap__read_backward(struct perf_mmap *map)
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{
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u64 head, end;
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u64 start = map->prev;
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/*
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* Check if event was unmapped due to a POLLHUP/POLLERR.
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*/
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if (!refcount_read(&map->refcnt))
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return NULL;
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head = perf_mmap__read_head(map);
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if (!head)
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return NULL;
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/*
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* 'head' pointer starts from 0. Kernel minus sizeof(record) form
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* it each time when kernel writes to it, so in fact 'head' is
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* negative. 'end' pointer is made manually by adding the size of
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* the ring buffer to 'head' pointer, means the validate data can
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* read is the whole ring buffer. If 'end' is positive, the ring
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* buffer has not fully filled, so we must adjust 'end' to 0.
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*
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* However, since both 'head' and 'end' is unsigned, we can't
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* simply compare 'end' against 0. Here we compare '-head' and
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* the size of the ring buffer, where -head is the number of bytes
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* kernel write to the ring buffer.
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*/
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if (-head < (u64)(map->mask + 1))
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end = 0;
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else
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end = head + map->mask + 1;
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return perf_mmap__read(map, false, start, end, &map->prev);
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}
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void perf_mmap__read_catchup(struct perf_mmap *map)
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{
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u64 head;
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if (!refcount_read(&map->refcnt))
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return;
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head = perf_mmap__read_head(map);
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map->prev = head;
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}
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static bool perf_mmap__empty(struct perf_mmap *map)
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{
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return perf_mmap__read_head(map) == map->prev && !map->auxtrace_mmap.base;
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}
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void perf_mmap__get(struct perf_mmap *map)
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{
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refcount_inc(&map->refcnt);
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}
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void perf_mmap__put(struct perf_mmap *map)
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{
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BUG_ON(map->base && refcount_read(&map->refcnt) == 0);
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if (refcount_dec_and_test(&map->refcnt))
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perf_mmap__munmap(map);
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}
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void perf_mmap__consume(struct perf_mmap *map, bool overwrite)
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{
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if (!overwrite) {
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u64 old = map->prev;
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perf_mmap__write_tail(map, old);
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}
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if (refcount_read(&map->refcnt) == 1 && perf_mmap__empty(map))
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perf_mmap__put(map);
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}
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int __weak auxtrace_mmap__mmap(struct auxtrace_mmap *mm __maybe_unused,
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struct auxtrace_mmap_params *mp __maybe_unused,
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void *userpg __maybe_unused,
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int fd __maybe_unused)
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{
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return 0;
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}
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void __weak auxtrace_mmap__munmap(struct auxtrace_mmap *mm __maybe_unused)
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{
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}
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void __weak auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp __maybe_unused,
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off_t auxtrace_offset __maybe_unused,
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unsigned int auxtrace_pages __maybe_unused,
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bool auxtrace_overwrite __maybe_unused)
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{
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}
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void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __maybe_unused,
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struct perf_evlist *evlist __maybe_unused,
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int idx __maybe_unused,
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bool per_cpu __maybe_unused)
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{
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}
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void perf_mmap__munmap(struct perf_mmap *map)
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{
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if (map->base != NULL) {
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munmap(map->base, perf_mmap__mmap_len(map));
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map->base = NULL;
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map->fd = -1;
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refcount_set(&map->refcnt, 0);
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}
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auxtrace_mmap__munmap(&map->auxtrace_mmap);
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}
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int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd)
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{
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/*
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* The last one will be done at perf_evlist__mmap_consume(), so that we
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* make sure we don't prevent tools from consuming every last event in
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* the ring buffer.
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*
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* I.e. we can get the POLLHUP meaning that the fd doesn't exist
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* anymore, but the last events for it are still in the ring buffer,
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* waiting to be consumed.
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*
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* Tools can chose to ignore this at their own discretion, but the
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* evlist layer can't just drop it when filtering events in
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* perf_evlist__filter_pollfd().
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*/
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refcount_set(&map->refcnt, 2);
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map->prev = 0;
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map->mask = mp->mask;
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map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot,
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MAP_SHARED, fd, 0);
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if (map->base == MAP_FAILED) {
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pr_debug2("failed to mmap perf event ring buffer, error %d\n",
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errno);
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map->base = NULL;
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return -1;
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}
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map->fd = fd;
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if (auxtrace_mmap__mmap(&map->auxtrace_mmap,
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&mp->auxtrace_mp, map->base, fd))
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return -1;
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return 0;
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}
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static int backward_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end)
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{
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struct perf_event_header *pheader;
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u64 evt_head = head;
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int size = mask + 1;
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pr_debug2("backward_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head);
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pheader = (struct perf_event_header *)(buf + (head & mask));
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*start = head;
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while (true) {
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if (evt_head - head >= (unsigned int)size) {
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pr_debug("Finished reading backward ring buffer: rewind\n");
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if (evt_head - head > (unsigned int)size)
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evt_head -= pheader->size;
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*end = evt_head;
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return 0;
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}
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pheader = (struct perf_event_header *)(buf + (evt_head & mask));
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if (pheader->size == 0) {
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pr_debug("Finished reading backward ring buffer: get start\n");
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*end = evt_head;
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return 0;
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}
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evt_head += pheader->size;
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pr_debug3("move evt_head: %"PRIx64"\n", evt_head);
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}
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WARN_ONCE(1, "Shouldn't get here\n");
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return -1;
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}
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static int rb_find_range(void *data, int mask, u64 head, u64 old,
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u64 *start, u64 *end, bool backward)
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{
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if (!backward) {
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*start = old;
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*end = head;
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return 0;
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}
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return backward_rb_find_range(data, mask, head, start, end);
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}
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int perf_mmap__push(struct perf_mmap *md, bool overwrite, bool backward,
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void *to, int push(void *to, void *buf, size_t size))
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{
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u64 head = perf_mmap__read_head(md);
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u64 old = md->prev;
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u64 end = head, start = old;
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unsigned char *data = md->base + page_size;
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unsigned long size;
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void *buf;
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int rc = 0;
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if (rb_find_range(data, md->mask, head, old, &start, &end, backward))
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return -1;
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if (start == end)
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return 0;
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size = end - start;
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if (size > (unsigned long)(md->mask) + 1) {
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WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
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md->prev = head;
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perf_mmap__consume(md, overwrite || backward);
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return 0;
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}
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if ((start & md->mask) + size != (end & md->mask)) {
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buf = &data[start & md->mask];
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size = md->mask + 1 - (start & md->mask);
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start += size;
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if (push(to, buf, size) < 0) {
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rc = -1;
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goto out;
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}
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}
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buf = &data[start & md->mask];
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size = end - start;
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start += size;
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if (push(to, buf, size) < 0) {
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rc = -1;
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goto out;
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}
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md->prev = head;
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perf_mmap__consume(md, overwrite || backward);
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out:
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return rc;
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}
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