/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 */
#include <linux/bpf.h>
#include <linux/err.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/filter.h>
#include <linux/perf_event.h>

/* Called from syscall */
static struct bpf_map *array_map_alloc(union bpf_attr *attr)
{
        struct bpf_array *array;
        u32 elem_size, array_size;

        /* check sanity of attributes */
        if (attr->max_entries == 0 || attr->key_size != 4 ||
            attr->value_size == 0)
                return ERR_PTR(-EINVAL);

        if (attr->value_size >= 1 << (KMALLOC_SHIFT_MAX - 1))
                /* if value_size is bigger, the user space won't be able to
                 * access the elements.
                 */
                return ERR_PTR(-E2BIG);

        elem_size = round_up(attr->value_size, 8);

        /* check round_up into zero and u32 overflow */
        if (elem_size == 0 ||
            attr->max_entries > (U32_MAX - PAGE_SIZE - sizeof(*array)) / elem_size)
                return ERR_PTR(-ENOMEM);

        array_size = sizeof(*array) + attr->max_entries * elem_size;

        /* allocate all map elements and zero-initialize them */
        array = kzalloc(array_size, GFP_USER | __GFP_NOWARN);
        if (!array) {
                array = vzalloc(array_size);
                if (!array)
                        return ERR_PTR(-ENOMEM);
        }

        /* copy mandatory map attributes */
        array->map.key_size = attr->key_size;
        array->map.value_size = attr->value_size;
        array->map.max_entries = attr->max_entries;
        array->map.pages = round_up(array_size, PAGE_SIZE) >> PAGE_SHIFT;
        array->elem_size = elem_size;

        return &array->map;
}

/* Called from syscall or from eBPF program */
static void *array_map_lookup_elem(struct bpf_map *map, void *key)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        u32 index = *(u32 *)key;

        if (index >= array->map.max_entries)
                return NULL;

        return array->value + array->elem_size * index;
}

/* Called from syscall */
static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        u32 index = *(u32 *)key;
        u32 *next = (u32 *)next_key;

        if (index >= array->map.max_entries) {
                *next = 0;
                return 0;
        }

        if (index == array->map.max_entries - 1)
                return -ENOENT;

        *next = index + 1;
        return 0;
}

/* Called from syscall or from eBPF program */
static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
                                 u64 map_flags)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        u32 index = *(u32 *)key;

        if (map_flags > BPF_EXIST)
                /* unknown flags */
                return -EINVAL;

        if (index >= array->map.max_entries)
                /* all elements were pre-allocated, cannot insert a new one */
                return -E2BIG;

        if (map_flags == BPF_NOEXIST)
                /* all elements already exist */
                return -EEXIST;

        memcpy(array->value + array->elem_size * index, value, map->value_size);
        return 0;
}

/* Called from syscall or from eBPF program */
static int array_map_delete_elem(struct bpf_map *map, void *key)
{
        return -EINVAL;
}

/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
static void array_map_free(struct bpf_map *map)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);

        /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
         * so the programs (can be more than one that used this map) were
         * disconnected from events. Wait for outstanding programs to complete
         * and free the array
         */
        synchronize_rcu();

        kvfree(array);
}

static const struct bpf_map_ops array_ops = {
        .map_alloc = array_map_alloc,
        .map_free = array_map_free,
        .map_get_next_key = array_map_get_next_key,
        .map_lookup_elem = array_map_lookup_elem,
        .map_update_elem = array_map_update_elem,
        .map_delete_elem = array_map_delete_elem,
};

static struct bpf_map_type_list array_type __read_mostly = {
        .ops = &array_ops,
        .type = BPF_MAP_TYPE_ARRAY,
};

static int __init register_array_map(void)
{
        bpf_register_map_type(&array_type);
        return 0;
}
late_initcall(register_array_map);

static struct bpf_map *fd_array_map_alloc(union bpf_attr *attr)
{
        /* only file descriptors can be stored in this type of map */
        if (attr->value_size != sizeof(u32))
                return ERR_PTR(-EINVAL);
        return array_map_alloc(attr);
}

static void fd_array_map_free(struct bpf_map *map)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        int i;

        synchronize_rcu();

        /* make sure it's empty */
        for (i = 0; i < array->map.max_entries; i++)
                BUG_ON(array->ptrs[i] != NULL);
        kvfree(array);
}

static void *fd_array_map_lookup_elem(struct bpf_map *map, void *key)
{
        return NULL;
}

/* only called from syscall */
static int fd_array_map_update_elem(struct bpf_map *map, void *key,
                                    void *value, u64 map_flags)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        void *new_ptr, *old_ptr;
        u32 index = *(u32 *)key, ufd;

        if (map_flags != BPF_ANY)
                return -EINVAL;

        if (index >= array->map.max_entries)
                return -E2BIG;

        ufd = *(u32 *)value;
        new_ptr = map->ops->map_fd_get_ptr(map, ufd);
        if (IS_ERR(new_ptr))
                return PTR_ERR(new_ptr);

        old_ptr = xchg(array->ptrs + index, new_ptr);
        if (old_ptr)
                map->ops->map_fd_put_ptr(old_ptr);

        return 0;
}

static int fd_array_map_delete_elem(struct bpf_map *map, void *key)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        void *old_ptr;
        u32 index = *(u32 *)key;

        if (index >= array->map.max_entries)
                return -E2BIG;

        old_ptr = xchg(array->ptrs + index, NULL);
        if (old_ptr) {
                map->ops->map_fd_put_ptr(old_ptr);
                return 0;
        } else {
                return -ENOENT;
        }
}

static void *prog_fd_array_get_ptr(struct bpf_map *map, int fd)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        struct bpf_prog *prog = bpf_prog_get(fd);
        if (IS_ERR(prog))
                return prog;

        if (!bpf_prog_array_compatible(array, prog)) {
                bpf_prog_put(prog);
                return ERR_PTR(-EINVAL);
        }
        return prog;
}

static void prog_fd_array_put_ptr(void *ptr)
{
        struct bpf_prog *prog = ptr;

        bpf_prog_put_rcu(prog);
}

/* decrement refcnt of all bpf_progs that are stored in this map */
void bpf_fd_array_map_clear(struct bpf_map *map)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        int i;

        for (i = 0; i < array->map.max_entries; i++)
                fd_array_map_delete_elem(map, &i);
}

static const struct bpf_map_ops prog_array_ops = {
        .map_alloc = fd_array_map_alloc,
        .map_free = fd_array_map_free,
        .map_get_next_key = array_map_get_next_key,
        .map_lookup_elem = fd_array_map_lookup_elem,
        .map_update_elem = fd_array_map_update_elem,
        .map_delete_elem = fd_array_map_delete_elem,
        .map_fd_get_ptr = prog_fd_array_get_ptr,
        .map_fd_put_ptr = prog_fd_array_put_ptr,
};

static struct bpf_map_type_list prog_array_type __read_mostly = {
        .ops = &prog_array_ops,
        .type = BPF_MAP_TYPE_PROG_ARRAY,
};

static int __init register_prog_array_map(void)
{
        bpf_register_map_type(&prog_array_type);
        return 0;
}
late_initcall(register_prog_array_map);

static void perf_event_array_map_free(struct bpf_map *map)
{
        bpf_fd_array_map_clear(map);
        fd_array_map_free(map);
}

static void *perf_event_fd_array_get_ptr(struct bpf_map *map, int fd)
{
        struct perf_event *event;
        const struct perf_event_attr *attr;

        event = perf_event_get(fd);
        if (IS_ERR(event))
                return event;

        attr = perf_event_attrs(event);
        if (IS_ERR(attr))
                goto err;

        if (attr->inherit)
                goto err;

        if (attr->type == PERF_TYPE_RAW)
                return event;

        if (attr->type == PERF_TYPE_HARDWARE)
                return event;

        if (attr->type == PERF_TYPE_SOFTWARE &&
            attr->config == PERF_COUNT_SW_BPF_OUTPUT)
                return event;
err:
        perf_event_release_kernel(event);
        return ERR_PTR(-EINVAL);
}

static void perf_event_fd_array_put_ptr(void *ptr)
{
        struct perf_event *event = ptr;

        perf_event_release_kernel(event);
}

static const struct bpf_map_ops perf_event_array_ops = {
        .map_alloc = fd_array_map_alloc,
        .map_free = perf_event_array_map_free,
        .map_get_next_key = array_map_get_next_key,
        .map_lookup_elem = fd_array_map_lookup_elem,
        .map_update_elem = fd_array_map_update_elem,
        .map_delete_elem = fd_array_map_delete_elem,
        .map_fd_get_ptr = perf_event_fd_array_get_ptr,
        .map_fd_put_ptr = perf_event_fd_array_put_ptr,
};

static struct bpf_map_type_list perf_event_array_type __read_mostly = {
        .ops = &perf_event_array_ops,
        .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
};

static int __init register_perf_event_array_map(void)
{
        bpf_register_map_type(&perf_event_array_type);
        return 0;
}
late_initcall(register_perf_event_array_map);