// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <sys/resource.h>

#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include "bpf_util.h"

#define MAX_INDEX       64
#define MAX_STARS       38

/* my_map, my_hist_map */
static int map_fd[2];

static void stars(char *str, long val, long max, int width)
{
        int i;

        for (i = 0; i < (width * val / max) - 1 && i < width - 1; i++)
                str[i] = '*';
        if (val > max)
                str[i - 1] = '+';
        str[i] = '\0';
}

struct task {
        char comm[16];
        __u64 pid_tgid;
        __u64 uid_gid;
};

struct hist_key {
        struct task t;
        __u32 index;
};

#define SIZE sizeof(struct task)

static void print_hist_for_pid(int fd, void *task)
{
        unsigned int nr_cpus = bpf_num_possible_cpus();
        struct hist_key key = {}, next_key;
        long values[nr_cpus];
        char starstr[MAX_STARS];
        long value;
        long data[MAX_INDEX] = {};
        int max_ind = -1;
        long max_value = 0;
        int i, ind;

        while (bpf_map_get_next_key(fd, &key, &next_key) == 0) {
                if (memcmp(&next_key, task, SIZE)) {
                        key = next_key;
                        continue;
                }
                bpf_map_lookup_elem(fd, &next_key, values);
                value = 0;
                for (i = 0; i < nr_cpus; i++)
                        value += values[i];
                ind = next_key.index;
                data[ind] = value;
                if (value && ind > max_ind)
                        max_ind = ind;
                if (value > max_value)
                        max_value = value;
                key = next_key;
        }

        printf("           syscall write() stats\n");
        printf("     byte_size       : count     distribution\n");
        for (i = 1; i <= max_ind + 1; i++) {
                stars(starstr, data[i - 1], max_value, MAX_STARS);
                printf("%8ld -> %-8ld : %-8ld |%-*s|\n",
                       (1l << i) >> 1, (1l << i) - 1, data[i - 1],
                       MAX_STARS, starstr);
        }
}

static void print_hist(int fd)
{
        struct hist_key key = {}, next_key;
        static struct task tasks[1024];
        int task_cnt = 0;
        int i;

        while (bpf_map_get_next_key(fd, &key, &next_key) == 0) {
                int found = 0;

                for (i = 0; i < task_cnt; i++)
                        if (memcmp(&tasks[i], &next_key, SIZE) == 0)
                                found = 1;
                if (!found)
                        memcpy(&tasks[task_cnt++], &next_key, SIZE);
                key = next_key;
        }

        for (i = 0; i < task_cnt; i++) {
                printf("\npid %d cmd %s uid %d\n",
                       (__u32) tasks[i].pid_tgid,
                       tasks[i].comm,
                       (__u32) tasks[i].uid_gid);
                print_hist_for_pid(fd, &tasks[i]);
        }

}

static void int_exit(int sig)
{
        print_hist(map_fd[1]);
        exit(0);
}

int main(int ac, char **argv)
{
        long key, next_key, value;
        struct bpf_link *links[2];
        struct bpf_program *prog;
        struct bpf_object *obj;
        char filename[256];
        int i, j = 0;
        FILE *f;

        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
        obj = bpf_object__open_file(filename, NULL);
        if (libbpf_get_error(obj)) {
                fprintf(stderr, "ERROR: opening BPF object file failed\n");
                return 0;
        }

        /* load BPF program */
        if (bpf_object__load(obj)) {
                fprintf(stderr, "ERROR: loading BPF object file failed\n");
                goto cleanup;
        }

        map_fd[0] = bpf_object__find_map_fd_by_name(obj, "my_map");
        map_fd[1] = bpf_object__find_map_fd_by_name(obj, "my_hist_map");
        if (map_fd[0] < 0 || map_fd[1] < 0) {
                fprintf(stderr, "ERROR: finding a map in obj file failed\n");
                goto cleanup;
        }

        signal(SIGINT, int_exit);
        signal(SIGTERM, int_exit);

        /* start 'ping' in the background to have some kfree_skb events */
        f = popen("ping -4 -c5 localhost", "r");
        (void) f;

        /* start 'dd' in the background to have plenty of 'write' syscalls */
        f = popen("dd if=/dev/zero of=/dev/null count=5000000", "r");
        (void) f;

        bpf_object__for_each_program(prog, obj) {
                links[j] = bpf_program__attach(prog);
                if (libbpf_get_error(links[j])) {
                        fprintf(stderr, "ERROR: bpf_program__attach failed\n");
                        links[j] = NULL;
                        goto cleanup;
                }
                j++;
        }

        for (i = 0; i < 5; i++) {
                key = 0;
                while (bpf_map_get_next_key(map_fd[0], &key, &next_key) == 0) {
                        bpf_map_lookup_elem(map_fd[0], &next_key, &value);
                        printf("location 0x%lx count %ld\n", next_key, value);
                        key = next_key;
                }
                if (key)
                        printf("\n");
                sleep(1);
        }
        print_hist(map_fd[1]);

cleanup:
        for (j--; j >= 0; j--)
                bpf_link__destroy(links[j]);

        bpf_object__close(obj);
        return 0;
}