/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
/* Copyright (c) 2021 Hengqi Chen */
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_core_read.h>
#include "exitsnoop.h"

const volatile pid_t target_pid = 0;
const volatile bool trace_failed_only = false;
const volatile bool trace_by_process = true;

struct {
	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
	__uint(key_size, sizeof(__u32));
	__uint(value_size, sizeof(__u32));
} events SEC(".maps");

SEC("tracepoint/sched/sched_process_exit")
int sched_process_exit(void *ctx)
{
	__u64 pid_tgid = bpf_get_current_pid_tgid();
	__u32 pid = pid_tgid >> 32;
	__u32 tid = (__u32)pid_tgid;
	int exit_code;
	struct task_struct *task;
	struct event event = {};

	if (target_pid && target_pid != pid)
		return 0;

	if (trace_by_process && pid != tid)
		return 0;

	task = (struct task_struct *)bpf_get_current_task();
	exit_code = BPF_CORE_READ(task, exit_code);
	if (trace_failed_only && exit_code == 0)
		return 0;

	event.start_time = BPF_CORE_READ(task, start_time);
	event.exit_time = bpf_ktime_get_ns();
	event.pid = pid;
	event.tid = tid;
	event.ppid = BPF_CORE_READ(task, real_parent, tgid);
	event.sig = exit_code & 0xff;
	event.exit_code = exit_code >> 8;
	bpf_get_current_comm(event.comm, sizeof(event.comm));
	bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU, &event, sizeof(event));
	return 0;
}

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