// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include <linux/bpf.h>
#include <time.h>
#include <errno.h>
#include <bpf/bpf_helpers.h>
#include "bpf_tcp_helpers.h"

char _license[] SEC("license") = "GPL";
struct hmap_elem {
        int counter;
        struct bpf_timer timer;
        struct bpf_spin_lock lock; /* unused */
};

struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __uint(max_entries, 1000);
        __type(key, int);
        __type(value, struct hmap_elem);
} hmap SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __uint(map_flags, BPF_F_NO_PREALLOC);
        __uint(max_entries, 1000);
        __type(key, int);
        __type(value, struct hmap_elem);
} hmap_malloc SEC(".maps");

struct elem {
        struct bpf_timer t;
};

struct {
        __uint(type, BPF_MAP_TYPE_ARRAY);
        __uint(max_entries, 2);
        __type(key, int);
        __type(value, struct elem);
} array SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_LRU_HASH);
        __uint(max_entries, 4);
        __type(key, int);
        __type(value, struct elem);
} lru SEC(".maps");

__u64 bss_data;
__u64 err;
__u64 ok;
__u64 callback_check = 52;
__u64 callback2_check = 52;

#define ARRAY 1
#define HTAB 2
#define HTAB_MALLOC 3
#define LRU 4

/* callback for array and lru timers */
static int timer_cb1(void *map, int *key, struct bpf_timer *timer)
{
        /* increment bss variable twice.
         * Once via array timer callback and once via lru timer callback
         */
        bss_data += 5;

        /* *key == 0 - the callback was called for array timer.
         * *key == 4 - the callback was called from lru timer.
         */
        if (*key == ARRAY) {
                struct bpf_timer *lru_timer;
                int lru_key = LRU;

                /* rearm array timer to be called again in ~35 seconds */
                if (bpf_timer_start(timer, 1ull << 35, 0) != 0)
                        err |= 1;

                lru_timer = bpf_map_lookup_elem(&lru, &lru_key);
                if (!lru_timer)
                        return 0;
                bpf_timer_set_callback(lru_timer, timer_cb1);
                if (bpf_timer_start(lru_timer, 0, 0) != 0)
                        err |= 2;
        } else if (*key == LRU) {
                int lru_key, i;

                for (i = LRU + 1;
                     i <= 100  /* for current LRU eviction algorithm this number
                                * should be larger than ~ lru->max_entries * 2
                                */;
                     i++) {
                        struct elem init = {};

                        /* lru_key cannot be used as loop induction variable
                         * otherwise the loop will be unbounded.
                         */
                        lru_key = i;

                        /* add more elements into lru map to push out current
                         * element and force deletion of this timer
                         */
                        bpf_map_update_elem(map, &lru_key, &init, 0);
                        /* look it up to bump it into active list */
                        bpf_map_lookup_elem(map, &lru_key);

                        /* keep adding until *key changes underneath,
                         * which means that key/timer memory was reused
                         */
                        if (*key != LRU)
                                break;
                }

                /* check that the timer was removed */
                if (bpf_timer_cancel(timer) != -EINVAL)
                        err |= 4;
                ok |= 1;
        }
        return 0;
}

SEC("fentry/bpf_fentry_test1")
int BPF_PROG(test1, int a)
{
        struct bpf_timer *arr_timer, *lru_timer;
        struct elem init = {};
        int lru_key = LRU;
        int array_key = ARRAY;

        arr_timer = bpf_map_lookup_elem(&array, &array_key);
        if (!arr_timer)
                return 0;
        bpf_timer_init(arr_timer, &array, CLOCK_MONOTONIC);

        bpf_map_update_elem(&lru, &lru_key, &init, 0);
        lru_timer = bpf_map_lookup_elem(&lru, &lru_key);
        if (!lru_timer)
                return 0;
        bpf_timer_init(lru_timer, &lru, CLOCK_MONOTONIC);

        bpf_timer_set_callback(arr_timer, timer_cb1);
        bpf_timer_start(arr_timer, 0 /* call timer_cb1 asap */, 0);

        /* init more timers to check that array destruction
         * doesn't leak timer memory.
         */
        array_key = 0;
        arr_timer = bpf_map_lookup_elem(&array, &array_key);
        if (!arr_timer)
                return 0;
        bpf_timer_init(arr_timer, &array, CLOCK_MONOTONIC);
        return 0;
}

/* callback for prealloc and non-prealloca hashtab timers */
static int timer_cb2(void *map, int *key, struct hmap_elem *val)
{
        if (*key == HTAB)
                callback_check--;
        else
                callback2_check--;
        if (val->counter > 0 && --val->counter) {
                /* re-arm the timer again to execute after 1 usec */
                bpf_timer_start(&val->timer, 1000, 0);
        } else if (*key == HTAB) {
                struct bpf_timer *arr_timer;
                int array_key = ARRAY;

                /* cancel arr_timer otherwise bpf_fentry_test1 prog
                 * will stay alive forever.
                 */
                arr_timer = bpf_map_lookup_elem(&array, &array_key);
                if (!arr_timer)
                        return 0;
                if (bpf_timer_cancel(arr_timer) != 1)
                        /* bpf_timer_cancel should return 1 to indicate
                         * that arr_timer was active at this time
                         */
                        err |= 8;

                /* try to cancel ourself. It shouldn't deadlock. */
                if (bpf_timer_cancel(&val->timer) != -EDEADLK)
                        err |= 16;

                /* delete this key and this timer anyway.
                 * It shouldn't deadlock either.
                 */
                bpf_map_delete_elem(map, key);

                /* in preallocated hashmap both 'key' and 'val' could have been
                 * reused to store another map element (like in LRU above),
                 * but in controlled test environment the below test works.
                 * It's not a use-after-free. The memory is owned by the map.
                 */
                if (bpf_timer_start(&val->timer, 1000, 0) != -EINVAL)
                        err |= 32;
                ok |= 2;
        } else {
                if (*key != HTAB_MALLOC)
                        err |= 64;

                /* try to cancel ourself. It shouldn't deadlock. */
                if (bpf_timer_cancel(&val->timer) != -EDEADLK)
                        err |= 128;

                /* delete this key and this timer anyway.
                 * It shouldn't deadlock either.
                 */
                bpf_map_delete_elem(map, key);

                /* in non-preallocated hashmap both 'key' and 'val' are RCU
                 * protected and still valid though this element was deleted
                 * from the map. Arm this timer for ~35 seconds. When callback
                 * finishes the call_rcu will invoke:
                 * htab_elem_free_rcu
                 *   check_and_free_timer
                 *     bpf_timer_cancel_and_free
                 * to cancel this 35 second sleep and delete the timer for real.
                 */
                if (bpf_timer_start(&val->timer, 1ull << 35, 0) != 0)
                        err |= 256;
                ok |= 4;
        }
        return 0;
}

int bpf_timer_test(void)
{
        struct hmap_elem *val;
        int key = HTAB, key_malloc = HTAB_MALLOC;

        val = bpf_map_lookup_elem(&hmap, &key);
        if (val) {
                if (bpf_timer_init(&val->timer, &hmap, CLOCK_BOOTTIME) != 0)
                        err |= 512;
                bpf_timer_set_callback(&val->timer, timer_cb2);
                bpf_timer_start(&val->timer, 1000, 0);
        }
        val = bpf_map_lookup_elem(&hmap_malloc, &key_malloc);
        if (val) {
                if (bpf_timer_init(&val->timer, &hmap_malloc, CLOCK_BOOTTIME) != 0)
                        err |= 1024;
                bpf_timer_set_callback(&val->timer, timer_cb2);
                bpf_timer_start(&val->timer, 1000, 0);
        }
        return 0;
}

SEC("fentry/bpf_fentry_test2")
int BPF_PROG(test2, int a, int b)
{
        struct hmap_elem init = {}, *val;
        int key = HTAB, key_malloc = HTAB_MALLOC;

        init.counter = 10; /* number of times to trigger timer_cb2 */
        bpf_map_update_elem(&hmap, &key, &init, 0);
        val = bpf_map_lookup_elem(&hmap, &key);
        if (val)
                bpf_timer_init(&val->timer, &hmap, CLOCK_BOOTTIME);
        /* update the same key to free the timer */
        bpf_map_update_elem(&hmap, &key, &init, 0);

        bpf_map_update_elem(&hmap_malloc, &key_malloc, &init, 0);
        val = bpf_map_lookup_elem(&hmap_malloc, &key_malloc);
        if (val)
                bpf_timer_init(&val->timer, &hmap_malloc, CLOCK_BOOTTIME);
        /* update the same key to free the timer */
        bpf_map_update_elem(&hmap_malloc, &key_malloc, &init, 0);

        /* init more timers to check that htab operations
         * don't leak timer memory.
         */
        key = 0;
        bpf_map_update_elem(&hmap, &key, &init, 0);
        val = bpf_map_lookup_elem(&hmap, &key);
        if (val)
                bpf_timer_init(&val->timer, &hmap, CLOCK_BOOTTIME);
        bpf_map_delete_elem(&hmap, &key);
        bpf_map_update_elem(&hmap, &key, &init, 0);
        val = bpf_map_lookup_elem(&hmap, &key);
        if (val)
                bpf_timer_init(&val->timer, &hmap, CLOCK_BOOTTIME);

        /* and with non-prealloc htab */
        key_malloc = 0;
        bpf_map_update_elem(&hmap_malloc, &key_malloc, &init, 0);
        val = bpf_map_lookup_elem(&hmap_malloc, &key_malloc);
        if (val)
                bpf_timer_init(&val->timer, &hmap_malloc, CLOCK_BOOTTIME);
        bpf_map_delete_elem(&hmap_malloc, &key_malloc);
        bpf_map_update_elem(&hmap_malloc, &key_malloc, &init, 0);
        val = bpf_map_lookup_elem(&hmap_malloc, &key_malloc);
        if (val)
                bpf_timer_init(&val->timer, &hmap_malloc, CLOCK_BOOTTIME);

        return bpf_timer_test();
}