/* This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <fcntl.h>
#include <poll.h>
#include <linux/perf_event.h>
#include <linux/bpf.h>
#include <errno.h>
#include <assert.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <time.h>
#include <signal.h>
#include "libbpf.h"
#include "bpf_load.h"
#include "perf-sys.h"

static int pmu_fd;

int page_size;
int page_cnt = 8;
volatile struct perf_event_mmap_page *header;

typedef void (*print_fn)(void *data, int size);

static int perf_event_mmap(int fd)
{
        void *base;
        int mmap_size;

        page_size = getpagesize();
        mmap_size = page_size * (page_cnt + 1);

        base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
        if (base == MAP_FAILED) {
                printf("mmap err\n");
                return -1;
        }

        header = base;
        return 0;
}

static int perf_event_poll(int fd)
{
        struct pollfd pfd = { .fd = fd, .events = POLLIN };

        return poll(&pfd, 1, 1000);
}

struct perf_event_sample {
        struct perf_event_header header;
        __u32 size;
        char data[];
};

static void perf_event_read(print_fn fn)
{
        __u64 data_tail = header->data_tail;
        __u64 data_head = header->data_head;
        __u64 buffer_size = page_cnt * page_size;
        void *base, *begin, *end;
        char buf[256];

        asm volatile("" ::: "memory"); /* in real code it should be smp_rmb() */
        if (data_head == data_tail)
                return;

        base = ((char *)header) + page_size;

        begin = base + data_tail % buffer_size;
        end = base + data_head % buffer_size;

        while (begin != end) {
                struct perf_event_sample *e;

                e = begin;
                if (begin + e->header.size > base + buffer_size) {
                        long len = base + buffer_size - begin;

                        assert(len < e->header.size);
                        memcpy(buf, begin, len);
                        memcpy(buf + len, base, e->header.size - len);
                        e = (void *) buf;
                        begin = base + e->header.size - len;
                } else if (begin + e->header.size == base + buffer_size) {
                        begin = base;
                } else {
                        begin += e->header.size;
                }

                if (e->header.type == PERF_RECORD_SAMPLE) {
                        fn(e->data, e->size);
                } else if (e->header.type == PERF_RECORD_LOST) {
                        struct {
                                struct perf_event_header header;
                                __u64 id;
                                __u64 lost;
                        } *lost = (void *) e;
                        printf("lost %lld events\n", lost->lost);
                } else {
                        printf("unknown event type=%d size=%d\n",
                               e->header.type, e->header.size);
                }
        }

        __sync_synchronize(); /* smp_mb() */
        header->data_tail = data_head;
}

static __u64 time_get_ns(void)
{
        struct timespec ts;

        clock_gettime(CLOCK_MONOTONIC, &ts);
        return ts.tv_sec * 1000000000ull + ts.tv_nsec;
}

static __u64 start_time;

#define MAX_CNT 100000ll

static void print_bpf_output(void *data, int size)
{
        static __u64 cnt;
        struct {
                __u64 pid;
                __u64 cookie;
        } *e = data;

        if (e->cookie != 0x12345678) {
                printf("BUG pid %llx cookie %llx sized %d\n",
                       e->pid, e->cookie, size);
                kill(0, SIGINT);
        }

        cnt++;

        if (cnt == MAX_CNT) {
                printf("recv %lld events per sec\n",
                       MAX_CNT * 1000000000ll / (time_get_ns() - start_time));
                kill(0, SIGINT);
        }
}

static void test_bpf_perf_event(void)
{
        struct perf_event_attr attr = {
                .sample_type = PERF_SAMPLE_RAW,
                .type = PERF_TYPE_SOFTWARE,
                .config = PERF_COUNT_SW_BPF_OUTPUT,
        };
        int key = 0;

        pmu_fd = sys_perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);

        assert(pmu_fd >= 0);
        assert(bpf_map_update_elem(map_fd[0], &key, &pmu_fd, BPF_ANY) == 0);
        ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
}

int main(int argc, char **argv)
{
        char filename[256];
        FILE *f;

        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);

        if (load_bpf_file(filename)) {
                printf("%s", bpf_log_buf);
                return 1;
        }

        test_bpf_perf_event();

        if (perf_event_mmap(pmu_fd) < 0)
                return 1;

        f = popen("taskset 1 dd if=/dev/zero of=/dev/null", "r");
        (void) f;

        start_time = time_get_ns();
        for (;;) {
                perf_event_poll(pmu_fd);
                perf_event_read(print_bpf_output);
        }

        return 0;
}