/*
 * sampleip: sample instruction pointer and frequency count in a BPF map.
 *
 * Copyright 2016 Netflix, Inc.
 *
 * 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 <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <assert.h>
#include <linux/perf_event.h>
#include <linux/ptrace.h>
#include <linux/bpf.h>
#include <sys/ioctl.h>
#include "libbpf.h"
#include "bpf_load.h"

#define DEFAULT_FREQ    99
#define DEFAULT_SECS    5
#define MAX_IPS         8192
#define PAGE_OFFSET     0xffff880000000000

static int nr_cpus;

static void usage(void)
{
        printf("USAGE: sampleip [-F freq] [duration]\n");
        printf("       -F freq    # sample frequency (Hertz), default 99\n");
        printf("       duration   # sampling duration (seconds), default 5\n");
}

static int sampling_start(int *pmu_fd, int freq)
{
        int i;

        struct perf_event_attr pe_sample_attr = {
                .type = PERF_TYPE_SOFTWARE,
                .freq = 1,
                .sample_period = freq,
                .config = PERF_COUNT_SW_CPU_CLOCK,
                .inherit = 1,
        };

        for (i = 0; i < nr_cpus; i++) {
                pmu_fd[i] = perf_event_open(&pe_sample_attr, -1 /* pid */, i,
                                            -1 /* group_fd */, 0 /* flags */);
                if (pmu_fd[i] < 0) {
                        fprintf(stderr, "ERROR: Initializing perf sampling\n");
                        return 1;
                }
                assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF,
                             prog_fd[0]) == 0);
                assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE, 0) == 0);
        }

        return 0;
}

static void sampling_end(int *pmu_fd)
{
        int i;

        for (i = 0; i < nr_cpus; i++)
                close(pmu_fd[i]);
}

struct ipcount {
        __u64 ip;
        __u32 count;
};

/* used for sorting */
struct ipcount counts[MAX_IPS];

static int count_cmp(const void *p1, const void *p2)
{
        return ((struct ipcount *)p1)->count - ((struct ipcount *)p2)->count;
}

static void print_ip_map(int fd)
{
        struct ksym *sym;
        __u64 key, next_key;
        __u32 value;
        int i, max;

        printf("%-19s %-32s %s\n", "ADDR", "KSYM", "COUNT");

        /* fetch IPs and counts */
        key = 0, i = 0;
        while (bpf_get_next_key(fd, &key, &next_key) == 0) {
                bpf_lookup_elem(fd, &next_key, &value);
                counts[i].ip = next_key;
                counts[i++].count = value;
                key = next_key;
        }
        max = i;

        /* sort and print */
        qsort(counts, max, sizeof(struct ipcount), count_cmp);
        for (i = 0; i < max; i++) {
                if (counts[i].ip > PAGE_OFFSET) {
                        sym = ksym_search(counts[i].ip);
                        printf("0x%-17llx %-32s %u\n", counts[i].ip, sym->name,
                               counts[i].count);
                } else {
                        printf("0x%-17llx %-32s %u\n", counts[i].ip, "(user)",
                               counts[i].count);
                }
        }

        if (max == MAX_IPS) {
                printf("WARNING: IP hash was full (max %d entries); ", max);
                printf("may have dropped samples\n");
        }
}

static void int_exit(int sig)
{
        printf("\n");
        print_ip_map(map_fd[0]);
        exit(0);
}

int main(int argc, char **argv)
{
        char filename[256];
        int *pmu_fd, opt, freq = DEFAULT_FREQ, secs = DEFAULT_SECS;

        /* process arguments */
        while ((opt = getopt(argc, argv, "F:h")) != -1) {
                switch (opt) {
                case 'F':
                        freq = atoi(optarg);
                        break;
                case 'h':
                default:
                        usage();
                        return 0;
                }
        }
        if (argc - optind == 1)
                secs = atoi(argv[optind]);
        if (freq == 0 || secs == 0) {
                usage();
                return 1;
        }

        /* initialize kernel symbol translation */
        if (load_kallsyms()) {
                fprintf(stderr, "ERROR: loading /proc/kallsyms\n");
                return 2;
        }

        /* create perf FDs for each CPU */
        nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
        pmu_fd = malloc(nr_cpus * sizeof(int));
        if (pmu_fd == NULL) {
                fprintf(stderr, "ERROR: malloc of pmu_fd\n");
                return 1;
        }

        /* load BPF program */
        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
        if (load_bpf_file(filename)) {
                fprintf(stderr, "ERROR: loading BPF program (errno %d):\n",
                        errno);
                if (strcmp(bpf_log_buf, "") == 0)
                        fprintf(stderr, "Try: ulimit -l unlimited\n");
                else
                        fprintf(stderr, "%s", bpf_log_buf);
                return 1;
        }
        signal(SIGINT, int_exit);

        /* do sampling */
        printf("Sampling at %d Hertz for %d seconds. Ctrl-C also ends.\n",
               freq, secs);
        if (sampling_start(pmu_fd, freq) != 0)
                return 1;
        sleep(secs);
        sampling_end(pmu_fd);
        free(pmu_fd);

        /* output sample counts */
        print_ip_map(map_fd[0]);

        return 0;
}