#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_core_read.h>
#include <linux/uio.h>
//#include <linux/sched.h>
#include "common.h"

struct {
    __uint(type, BPF_MAP_TYPE_RINGBUF);
    __uint(max_entries, 256 * 1024 /* 256kb */);
} data SEC(".maps");

struct {
    __uint(type, BPF_MAP_TYPE_ARRAY);
    __uint(max_entries, 4194304); /* /proc/sys/kernel/pid_max */
    __type(key, __u32);
    __type(value, __u32);
} m_pid SEC(".maps");

// https://lwn.net/Articles/605828/

// https://lwn.net/Articles/625077/
// cat /proc/kallsyms | grep get_random_bytes
SEC("kprobe/get_random_bytes_user")
int get_random_user(){
    struct random *s_random = 0;
    __u32 pid = bpf_get_current_pid_tgid() >> 32;

    __u32 *n_pid = bpf_map_lookup_elem(&m_pid, &pid);
    if (!n_pid)
        return 0;
    // bpf_printk("pid: %d", pid);

    /*
     * To avoid to "burst" the user-space
     * We add the pid in a map. If doesn't exist, we send data to the ring buffer
     */
    if (*n_pid == 0){
        // bpf_printk("value: %d %d", pid, *n_pid);
        /* TODO: get the procname */
        /*struct task_struct *task = (struct task_struct *)bpf_get_current_task();
        if (!task)
            return 0;
        struct mm_struct *mm = task->mm;*/

        if (bpf_map_update_elem(&m_pid, &pid, &pid, BPF_ANY) < 0){
            bpf_printk("Failed to update map");
            return 0;
        }
        
        s_random = bpf_ringbuf_reserve(&data, sizeof(struct random *), 0);
        if (!s_random)
            return 0;

        s_random->pid = pid;
        bpf_ringbuf_submit(s_random, 0);
    }

    return 0;
}
char LICENSE[] SEC("license") = "Dual BSD/GPL";