// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
/* Copyright (c) 2020 Facebook */
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_core_read.h>
#include "exitsnoop.h"

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

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

SEC("tp/sched/sched_process_exit")
int handle_exit(struct trace_event_raw_sched_process_template* ctx)
{
	struct task_struct *task;
	struct event *e;
	pid_t pid, tid;
	u64 id, ts, *start_ts, start_time = 0;
	
	/* get PID and TID of exiting thread/process */
	id = bpf_get_current_pid_tgid();
	pid = id >> 32;
	tid = (u32)id;

	/* ignore thread exits */
	if (pid != tid)
		return 0;

	/* reserve sample from BPF ringbuf */
	e = bpf_ringbuf_reserve(&rb, sizeof(*e), 0);
	if (!e)
		return 0;

	/* fill out the sample with data */
	task = (struct task_struct *)bpf_get_current_task();
	start_time = BPF_CORE_READ(task, start_time);

	e->duration_ns = bpf_ktime_get_ns() - start_time;
	e->pid = pid;
	e->ppid = BPF_CORE_READ(task, real_parent, tgid);
	e->exit_code = (BPF_CORE_READ(task, exit_code) >> 8) & 0xff;
	bpf_get_current_comm(&e->comm, sizeof(e->comm));

	/* send data to user-space for post-processing */
	bpf_ringbuf_submit(e, 0);
	return 0;
}