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;
+}