/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */

#ifndef _TASK_KFUNC_COMMON_H
#define _TASK_KFUNC_COMMON_H

#include <errno.h>
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>

struct __tasks_kfunc_map_value {
        struct task_struct __kptr * task;
};

struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __type(key, int);
        __type(value, struct __tasks_kfunc_map_value);
        __uint(max_entries, 1);
} __tasks_kfunc_map SEC(".maps");

struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
void bpf_task_release(struct task_struct *p) __ksym;
struct task_struct *bpf_task_from_pid(s32 pid) __ksym;
struct task_struct *bpf_task_from_vpid(s32 vpid) __ksym;
void bpf_rcu_read_lock(void) __ksym;
void bpf_rcu_read_unlock(void) __ksym;

static inline struct __tasks_kfunc_map_value *tasks_kfunc_map_value_lookup(struct task_struct *p)
{
        s32 pid;
        long status;

        status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
        if (status)
                return NULL;

        return bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
}

static inline int tasks_kfunc_map_insert(struct task_struct *p)
{
        struct __tasks_kfunc_map_value local, *v;
        long status;
        struct task_struct *acquired, *old;
        s32 pid;

        status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
        if (status)
                return status;

        local.task = NULL;
        status = bpf_map_update_elem(&__tasks_kfunc_map, &pid, &local, BPF_NOEXIST);
        if (status)
                return status;

        v = bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
        if (!v) {
                bpf_map_delete_elem(&__tasks_kfunc_map, &pid);
                return -ENOENT;
        }

        acquired = bpf_task_acquire(p);
        if (!acquired)
                return -ENOENT;

        old = bpf_kptr_xchg(&v->task, acquired);
        if (old) {
                bpf_task_release(old);
                return -EEXIST;
        }

        return 0;
}

#endif /* _TASK_KFUNC_COMMON_H */