// SPDX-License-Identifier: GPL-2.0
#include <sys/mman.h>
#include <inttypes.h>
#include <asm/bug.h>
#include <errno.h>
#include <string.h>
#include <linux/ring_buffer.h>
#include <linux/perf_event.h>
#include <perf/mmap.h>
#include <perf/event.h>
#include <perf/evsel.h>
#include <internal/mmap.h>
#include <internal/lib.h>
#include <linux/kernel.h>
#include <linux/math64.h>
#include "internal.h"

void perf_mmap__init(struct perf_mmap *map, struct perf_mmap *prev,
                     bool overwrite, libperf_unmap_cb_t unmap_cb)
{
        map->fd = -1;
        map->overwrite = overwrite;
        map->unmap_cb  = unmap_cb;
        refcount_set(&map->refcnt, 0);
        if (prev)
                prev->next = map;
}

size_t perf_mmap__mmap_len(struct perf_mmap *map)
{
        return map->mask + 1 + page_size;
}

int perf_mmap__mmap(struct perf_mmap *map, struct perf_mmap_param *mp,
                    int fd, int cpu)
{
        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) {
                map->base = NULL;
                return -1;
        }

        map->fd  = fd;
        map->cpu = cpu;
        return 0;
}

void perf_mmap__munmap(struct perf_mmap *map)
{
        if (map && map->base != NULL) {
                munmap(map->base, perf_mmap__mmap_len(map));
                map->base = NULL;
                map->fd = -1;
                refcount_set(&map->refcnt, 0);
        }
        if (map && map->unmap_cb)
                map->unmap_cb(map);
}

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);
}

static inline void perf_mmap__write_tail(struct perf_mmap *md, u64 tail)
{
        ring_buffer_write_tail(md->base, tail);
}

u64 perf_mmap__read_head(struct perf_mmap *map)
{
        return ring_buffer_read_head(map->base);
}

static bool perf_mmap__empty(struct perf_mmap *map)
{
        struct perf_event_mmap_page *pc = map->base;

        return perf_mmap__read_head(map) == map->prev && !pc->aux_size;
}

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);
}

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->end - md->start) < md->flush)
                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);
}

/*
 * Mandatory for overwrite mode
 * The direction of overwrite mode is backward.
 * The last perf_mmap__read() will set tail to map->core.prev.
 * Need to correct the map->core.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);
}

/* 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;
}

#if defined(__i386__) || defined(__x86_64__)
static u64 read_perf_counter(unsigned int counter)
{
        unsigned int low, high;

        asm volatile("rdpmc" : "=a" (low), "=d" (high) : "c" (counter));

        return low | ((u64)high) << 32;
}

static u64 read_timestamp(void)
{
        unsigned int low, high;

        asm volatile("rdtsc" : "=a" (low), "=d" (high));

        return low | ((u64)high) << 32;
}
#else
static u64 read_perf_counter(unsigned int counter __maybe_unused) { return 0; }
static u64 read_timestamp(void) { return 0; }
#endif

int perf_mmap__read_self(struct perf_mmap *map, struct perf_counts_values *count)
{
        struct perf_event_mmap_page *pc = map->base;
        u32 seq, idx, time_mult = 0, time_shift = 0;
        u64 cnt, cyc = 0, time_offset = 0, time_cycles = 0, time_mask = ~0ULL;

        if (!pc || !pc->cap_user_rdpmc)
                return -1;

        do {
                seq = READ_ONCE(pc->lock);
                barrier();

                count->ena = READ_ONCE(pc->time_enabled);
                count->run = READ_ONCE(pc->time_running);

                if (pc->cap_user_time && count->ena != count->run) {
                        cyc = read_timestamp();
                        time_mult = READ_ONCE(pc->time_mult);
                        time_shift = READ_ONCE(pc->time_shift);
                        time_offset = READ_ONCE(pc->time_offset);

                        if (pc->cap_user_time_short) {
                                time_cycles = READ_ONCE(pc->time_cycles);
                                time_mask = READ_ONCE(pc->time_mask);
                        }
                }

                idx = READ_ONCE(pc->index);
                cnt = READ_ONCE(pc->offset);
                if (pc->cap_user_rdpmc && idx) {
                        s64 evcnt = read_perf_counter(idx - 1);
                        u16 width = READ_ONCE(pc->pmc_width);

                        evcnt <<= 64 - width;
                        evcnt >>= 64 - width;
                        cnt += evcnt;
                } else
                        return -1;

                barrier();
        } while (READ_ONCE(pc->lock) != seq);

        if (count->ena != count->run) {
                u64 delta;

                /* Adjust for cap_usr_time_short, a nop if not */
                cyc = time_cycles + ((cyc - time_cycles) & time_mask);

                delta = time_offset + mul_u64_u32_shr(cyc, time_mult, time_shift);

                count->ena += delta;
                if (idx)
                        count->run += delta;

                cnt = mul_u64_u64_div64(cnt, count->ena, count->run);
        }

        count->val = cnt;

        return 0;
}