/*
 * 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,
                                         u64 *startp, u64 end)
{
        unsigned char *data = map->base + page_size;
        union perf_event *event = NULL;
        int diff = end - *startp;

        if (diff >= (int)sizeof(event->header)) {
                size_t size;

                event = (union perf_event *)&data[*startp & map->mask];
                size = event->header.size;

                if (size < sizeof(event->header) || diff < (int)size)
                        return NULL;

                /*
                 * Event straddles the mmap boundary -- header should always
                 * be inside due to u64 alignment of output.
                 */
                if ((*startp & map->mask) + size != ((*startp + size) & map->mask)) {
                        unsigned int offset = *startp;
                        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;
                }

                *startp += size;
        }

        return event;
}

/*
 * Read event from ring buffer one by one.
 * Return one event for each call.
 *
 * Usage:
 * perf_mmap__read_init()
 * while(event = perf_mmap__read_event()) {
 *      //process the event
 *      perf_mmap__consume()
 * }
 * perf_mmap__read_done()
 */
union perf_event *perf_mmap__read_event(struct perf_mmap *map)
{
        union perf_event *event;

        /*
         * Check if event was unmapped due to a POLLHUP/POLLERR.
         */
        if (!refcount_read(&map->refcnt))
                return NULL;

        /* non-overwirte doesn't pause the ringbuffer */
        if (!map->overwrite)
                map->end = perf_mmap__read_head(map);

        event = perf_mmap__read(map, &map->start, map->end);

        if (!map->overwrite)
                map->prev = map->start;

        return event;
}

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)
{
        if (!map->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_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 overwrite_rb_find_range(void *buf, int mask, u64 *start, u64 *end)
{
        struct perf_event_header *pheader;
        u64 evt_head = *start;
        int size = mask + 1;

        pr_debug2("%s: buf=%p, start=%"PRIx64"\n", __func__, buf, *start);
        pheader = (struct perf_event_header *)(buf + (*start & mask));
        while (true) {
                if (evt_head - *start >= (unsigned int)size) {
                        pr_debug("Finished reading overwrite ring buffer: rewind\n");
                        if (evt_head - *start > (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 overwrite 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;
}

/*
 * Report the start and end of the available data in ringbuffer
 */
static int __perf_mmap__read_init(struct perf_mmap *md)
{
        u64 head = perf_mmap__read_head(md);
        u64 old = md->prev;
        unsigned char *data = md->base + page_size;
        unsigned long size;

        md->start = md->overwrite ? head : old;
        md->end = md->overwrite ? old : head;

        if (md->start == md->end)
                return -EAGAIN;

        size = md->end - md->start;
        if (size > (unsigned long)(md->mask) + 1) {
                if (!md->overwrite) {
                        WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");

                        md->prev = head;
                        perf_mmap__consume(md);
                        return -EAGAIN;
                }

                /*
                 * Backward ring buffer is full. We still have a chance to read
                 * most of data from it.
                 */
                if (overwrite_rb_find_range(data, md->mask, &md->start, &md->end))
                        return -EINVAL;
        }

        return 0;
}

int perf_mmap__read_init(struct perf_mmap *map)
{
        /*
         * Check if event was unmapped due to a POLLHUP/POLLERR.
         */
        if (!refcount_read(&map->refcnt))
                return -ENOENT;

        return __perf_mmap__read_init(map);
}

int perf_mmap__push(struct perf_mmap *md, void *to,
                    int push(void *to, void *buf, size_t size))
{
        u64 head = perf_mmap__read_head(md);
        unsigned char *data = md->base + page_size;
        unsigned long size;
        void *buf;
        int rc = 0;

        rc = perf_mmap__read_init(md);
        if (rc < 0)
                return (rc == -EAGAIN) ? 0 : -1;

        size = md->end - md->start;

        if ((md->start & md->mask) + size != (md->end & md->mask)) {
                buf = &data[md->start & md->mask];
                size = md->mask + 1 - (md->start & md->mask);
                md->start += size;

                if (push(to, buf, size) < 0) {
                        rc = -1;
                        goto out;
                }
        }

        buf = &data[md->start & md->mask];
        size = md->end - md->start;
        md->start += size;

        if (push(to, buf, size) < 0) {
                rc = -1;
                goto out;
        }

        md->prev = head;
        perf_mmap__consume(md);
out:
        return rc;
}

/*
 * Mandatory for overwrite mode
 * The direction of overwrite mode is backward.
 * The last perf_mmap__read() will set tail to map->prev.
 * Need to correct the map->prev to head which is the end of next read.
 */
void perf_mmap__read_done(struct perf_mmap *map)
{
        /*
         * Check if event was unmapped due to a POLLHUP/POLLERR.
         */
        if (!refcount_read(&map->refcnt))
                return;

        map->prev = perf_mmap__read_head(map);
}