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

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

#include "../bpf_experimental.h"
#include "task_kfunc_common.h"

char _license[] SEC("license") = "GPL";

int err, pid;

/* Prototype for all of the program trace events below:
 *
 * TRACE_EVENT(task_newtask,
 *         TP_PROTO(struct task_struct *p, u64 clone_flags)
 */

struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym __weak;

struct task_struct *bpf_task_acquire___one(struct task_struct *task) __ksym __weak;
/* The two-param bpf_task_acquire doesn't exist */
struct task_struct *bpf_task_acquire___two(struct task_struct *p, void *ctx) __ksym __weak;
/* Incorrect type for first param */
struct task_struct *bpf_task_acquire___three(void *ctx) __ksym __weak;

void invalid_kfunc(void) __ksym __weak;
void bpf_testmod_test_mod_kfunc(int i) __ksym __weak;

static bool is_test_kfunc_task(void)
{
        int cur_pid = bpf_get_current_pid_tgid() >> 32;

        return pid == cur_pid;
}

static int test_acquire_release(struct task_struct *task)
{
        struct task_struct *acquired = NULL;

        if (!bpf_ksym_exists(bpf_task_acquire)) {
                err = 3;
                return 0;
        }
        if (!bpf_ksym_exists(bpf_testmod_test_mod_kfunc)) {
                err = 4;
                return 0;
        }
        if (bpf_ksym_exists(invalid_kfunc)) {
                /* the verifier's dead code elimination should remove this */
                err = 5;
                asm volatile ("goto -1"); /* for (;;); */
        }

        acquired = bpf_task_acquire(task);
        if (acquired)
                bpf_task_release(acquired);
        else
                err = 6;

        return 0;
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_kfunc_flavor_relo, struct task_struct *task, u64 clone_flags)
{
        struct task_struct *acquired = NULL;
        int fake_ctx = 42;

        if (bpf_ksym_exists(bpf_task_acquire___one)) {
                acquired = bpf_task_acquire___one(task);
        } else if (bpf_ksym_exists(bpf_task_acquire___two)) {
                /* Here, bpf_object__resolve_ksym_func_btf_id's find_ksym_btf_id
                 * call will find vmlinux's bpf_task_acquire, but subsequent
                 * bpf_core_types_are_compat will fail
                 */
                acquired = bpf_task_acquire___two(task, &fake_ctx);
                err = 3;
                return 0;
        } else if (bpf_ksym_exists(bpf_task_acquire___three)) {
                /* bpf_core_types_are_compat will fail similarly to above case */
                acquired = bpf_task_acquire___three(&fake_ctx);
                err = 4;
                return 0;
        }

        if (acquired)
                bpf_task_release(acquired);
        else
                err = 5;
        return 0;
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_kfunc_flavor_relo_not_found, struct task_struct *task, u64 clone_flags)
{
        /* Neither symbol should successfully resolve.
         * Success or failure of one ___flavor should not affect others
         */
        if (bpf_ksym_exists(bpf_task_acquire___two))
                err = 1;
        else if (bpf_ksym_exists(bpf_task_acquire___three))
                err = 2;

        return 0;
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_acquire_release_argument, struct task_struct *task, u64 clone_flags)
{
        if (!is_test_kfunc_task())
                return 0;

        return test_acquire_release(task);
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_acquire_release_current, struct task_struct *task, u64 clone_flags)
{
        if (!is_test_kfunc_task())
                return 0;

        return test_acquire_release(bpf_get_current_task_btf());
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_acquire_leave_in_map, struct task_struct *task, u64 clone_flags)
{
        long status;

        if (!is_test_kfunc_task())
                return 0;

        status = tasks_kfunc_map_insert(task);
        if (status)
                err = 1;

        return 0;
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_xchg_release, struct task_struct *task, u64 clone_flags)
{
        struct task_struct *kptr, *acquired;
        struct __tasks_kfunc_map_value *v, *local;
        int refcnt, refcnt_after_drop;
        long status;

        if (!is_test_kfunc_task())
                return 0;

        status = tasks_kfunc_map_insert(task);
        if (status) {
                err = 1;
                return 0;
        }

        v = tasks_kfunc_map_value_lookup(task);
        if (!v) {
                err = 2;
                return 0;
        }

        kptr = bpf_kptr_xchg(&v->task, NULL);
        if (!kptr) {
                err = 3;
                return 0;
        }

        local = bpf_obj_new(typeof(*local));
        if (!local) {
                err = 4;
                bpf_task_release(kptr);
                return 0;
        }

        kptr = bpf_kptr_xchg(&local->task, kptr);
        if (kptr) {
                err = 5;
                bpf_obj_drop(local);
                bpf_task_release(kptr);
                return 0;
        }

        kptr = bpf_kptr_xchg(&local->task, NULL);
        if (!kptr) {
                err = 6;
                bpf_obj_drop(local);
                return 0;
        }

        /* Stash a copy into local kptr and check if it is released recursively */
        acquired = bpf_task_acquire(kptr);
        if (!acquired) {
                err = 7;
                bpf_obj_drop(local);
                bpf_task_release(kptr);
                return 0;
        }
        bpf_probe_read_kernel(&refcnt, sizeof(refcnt), &acquired->rcu_users);

        acquired = bpf_kptr_xchg(&local->task, acquired);
        if (acquired) {
                err = 8;
                bpf_obj_drop(local);
                bpf_task_release(kptr);
                bpf_task_release(acquired);
                return 0;
        }

        bpf_obj_drop(local);

        bpf_probe_read_kernel(&refcnt_after_drop, sizeof(refcnt_after_drop), &kptr->rcu_users);
        if (refcnt != refcnt_after_drop + 1) {
                err = 9;
                bpf_task_release(kptr);
                return 0;
        }

        bpf_task_release(kptr);

        return 0;
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_map_acquire_release, struct task_struct *task, u64 clone_flags)
{
        struct task_struct *kptr;
        struct __tasks_kfunc_map_value *v;
        long status;

        if (!is_test_kfunc_task())
                return 0;

        status = tasks_kfunc_map_insert(task);
        if (status) {
                err = 1;
                return 0;
        }

        v = tasks_kfunc_map_value_lookup(task);
        if (!v) {
                err = 2;
                return 0;
        }

        bpf_rcu_read_lock();
        kptr = v->task;
        if (!kptr) {
                err = 3;
        } else {
                kptr = bpf_task_acquire(kptr);
                if (!kptr)
                        err = 4;
                else
                        bpf_task_release(kptr);
        }
        bpf_rcu_read_unlock();

        return 0;
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_current_acquire_release, struct task_struct *task, u64 clone_flags)
{
        struct task_struct *current, *acquired;

        if (!is_test_kfunc_task())
                return 0;

        current = bpf_get_current_task_btf();
        acquired = bpf_task_acquire(current);
        if (acquired)
                bpf_task_release(acquired);
        else
                err = 1;

        return 0;
}

static void lookup_compare_pid(const struct task_struct *p)
{
        struct task_struct *acquired;

        acquired = bpf_task_from_pid(p->pid);
        if (!acquired) {
                err = 1;
                return;
        }

        if (acquired->pid != p->pid)
                err = 2;
        bpf_task_release(acquired);
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_from_pid_arg, struct task_struct *task, u64 clone_flags)
{
        if (!is_test_kfunc_task())
                return 0;

        lookup_compare_pid(task);
        return 0;
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_from_pid_current, struct task_struct *task, u64 clone_flags)
{
        if (!is_test_kfunc_task())
                return 0;

        lookup_compare_pid(bpf_get_current_task_btf());
        return 0;
}

static int is_pid_lookup_valid(s32 pid)
{
        struct task_struct *acquired;

        acquired = bpf_task_from_pid(pid);
        if (acquired) {
                bpf_task_release(acquired);
                return 1;
        }

        return 0;
}

SEC("tp_btf/task_newtask")
int BPF_PROG(test_task_from_pid_invalid, struct task_struct *task, u64 clone_flags)
{
        if (!is_test_kfunc_task())
                return 0;

        bpf_strncmp(task->comm, 12, "foo");
        bpf_strncmp(task->comm, 16, "foo");
        bpf_strncmp(&task->comm[8], 4, "foo");

        if (is_pid_lookup_valid(-1)) {
                err = 1;
                return 0;
        }

        if (is_pid_lookup_valid(0xcafef00d)) {
                err = 2;
                return 0;
        }

        return 0;
}

SEC("tp_btf/task_newtask")
int BPF_PROG(task_kfunc_acquire_trusted_walked, struct task_struct *task, u64 clone_flags)
{
        struct task_struct *acquired;

        /* task->group_leader is listed as a trusted, non-NULL field of task struct. */
        acquired = bpf_task_acquire(task->group_leader);
        if (acquired)
                bpf_task_release(acquired);
        else
                err = 1;


        return 0;
}

SEC("syscall")
int test_task_from_vpid_current(const void *ctx)
{
        struct task_struct *current, *v_task;

        v_task = bpf_task_from_vpid(1);
        if (!v_task) {
                err = 1;
                return 0;
        }

        current = bpf_get_current_task_btf();

        /* The current process should be the init process (pid 1) in the new pid namespace. */
        if (current != v_task)
                err = 2;

        bpf_task_release(v_task);
        return 0;
}

SEC("syscall")
int test_task_from_vpid_invalid(const void *ctx)
{
        struct task_struct *v_task;

        v_task = bpf_task_from_vpid(-1);
        if (v_task) {
                err = 1;
                goto err;
        }

        /* There should be only one process (current process) in the new pid namespace. */
        v_task = bpf_task_from_vpid(2);
        if (v_task) {
                err = 2;
                goto err;
        }

        v_task = bpf_task_from_vpid(9999);
        if (v_task) {
                err = 3;
                goto err;
        }

        return 0;
err:
        bpf_task_release(v_task);
        return 0;
}