/* 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/syscalls.h>
#include <linux/slab.h>
#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/license.h>
#include <linux/filter.h>
#include <linux/version.h>

DEFINE_PER_CPU(int, bpf_prog_active);

int sysctl_unprivileged_bpf_disabled __read_mostly;

static LIST_HEAD(bpf_map_types);

static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
{
        struct bpf_map_type_list *tl;
        struct bpf_map *map;

        list_for_each_entry(tl, &bpf_map_types, list_node) {
                if (tl->type == attr->map_type) {
                        map = tl->ops->map_alloc(attr);
                        if (IS_ERR(map))
                                return map;
                        map->ops = tl->ops;
                        map->map_type = attr->map_type;
                        return map;
                }
        }
        return ERR_PTR(-EINVAL);
}

/* boot time registration of different map implementations */
void bpf_register_map_type(struct bpf_map_type_list *tl)
{
        list_add(&tl->list_node, &bpf_map_types);
}

int bpf_map_precharge_memlock(u32 pages)
{
        struct user_struct *user = get_current_user();
        unsigned long memlock_limit, cur;

        memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
        cur = atomic_long_read(&user->locked_vm);
        free_uid(user);
        if (cur + pages > memlock_limit)
                return -EPERM;
        return 0;
}

static int bpf_map_charge_memlock(struct bpf_map *map)
{
        struct user_struct *user = get_current_user();
        unsigned long memlock_limit;

        memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

        atomic_long_add(map->pages, &user->locked_vm);

        if (atomic_long_read(&user->locked_vm) > memlock_limit) {
                atomic_long_sub(map->pages, &user->locked_vm);
                free_uid(user);
                return -EPERM;
        }
        map->user = user;
        return 0;
}

static void bpf_map_uncharge_memlock(struct bpf_map *map)
{
        struct user_struct *user = map->user;

        atomic_long_sub(map->pages, &user->locked_vm);
        free_uid(user);
}

/* called from workqueue */
static void bpf_map_free_deferred(struct work_struct *work)
{
        struct bpf_map *map = container_of(work, struct bpf_map, work);

        bpf_map_uncharge_memlock(map);
        /* implementation dependent freeing */
        map->ops->map_free(map);
}

static void bpf_map_put_uref(struct bpf_map *map)
{
        if (atomic_dec_and_test(&map->usercnt)) {
                if (map->map_type == BPF_MAP_TYPE_PROG_ARRAY)
                        bpf_fd_array_map_clear(map);
        }
}

/* decrement map refcnt and schedule it for freeing via workqueue
 * (unrelying map implementation ops->map_free() might sleep)
 */
void bpf_map_put(struct bpf_map *map)
{
        if (atomic_dec_and_test(&map->refcnt)) {
                INIT_WORK(&map->work, bpf_map_free_deferred);
                schedule_work(&map->work);
        }
}

void bpf_map_put_with_uref(struct bpf_map *map)
{
        bpf_map_put_uref(map);
        bpf_map_put(map);
}

static int bpf_map_release(struct inode *inode, struct file *filp)
{
        struct bpf_map *map = filp->private_data;

        if (map->ops->map_release)
                map->ops->map_release(map, filp);

        bpf_map_put_with_uref(map);
        return 0;
}

#ifdef CONFIG_PROC_FS
static void bpf_map_show_fdinfo(struct seq_file *m, struct file *filp)
{
        const struct bpf_map *map = filp->private_data;

        seq_printf(m,
                   "map_type:\t%u\n"
                   "key_size:\t%u\n"
                   "value_size:\t%u\n"
                   "max_entries:\t%u\n"
                   "map_flags:\t%#x\n",
                   map->map_type,
                   map->key_size,
                   map->value_size,
                   map->max_entries,
                   map->map_flags);
}
#endif

static const struct file_operations bpf_map_fops = {
#ifdef CONFIG_PROC_FS
        .show_fdinfo    = bpf_map_show_fdinfo,
#endif
        .release        = bpf_map_release,
};

int bpf_map_new_fd(struct bpf_map *map)
{
        return anon_inode_getfd("bpf-map", &bpf_map_fops, map,
                                O_RDWR | O_CLOEXEC);
}

/* helper macro to check that unused fields 'union bpf_attr' are zero */
#define CHECK_ATTR(CMD) \
        memchr_inv((void *) &attr->CMD##_LAST_FIELD + \
                   sizeof(attr->CMD##_LAST_FIELD), 0, \
                   sizeof(*attr) - \
                   offsetof(union bpf_attr, CMD##_LAST_FIELD) - \
                   sizeof(attr->CMD##_LAST_FIELD)) != NULL

#define BPF_MAP_CREATE_LAST_FIELD map_flags
/* called via syscall */
static int map_create(union bpf_attr *attr)
{
        struct bpf_map *map;
        int err;

        err = CHECK_ATTR(BPF_MAP_CREATE);
        if (err)
                return -EINVAL;

        /* find map type and init map: hashtable vs rbtree vs bloom vs ... */
        map = find_and_alloc_map(attr);
        if (IS_ERR(map))
                return PTR_ERR(map);

        atomic_set(&map->refcnt, 1);
        atomic_set(&map->usercnt, 1);

        err = bpf_map_charge_memlock(map);
        if (err)
                goto free_map;

        err = bpf_map_new_fd(map);
        if (err < 0)
                /* failed to allocate fd */
                goto free_map;

        return err;

free_map:
        map->ops->map_free(map);
        return err;
}

/* if error is returned, fd is released.
 * On success caller should complete fd access with matching fdput()
 */
struct bpf_map *__bpf_map_get(struct fd f)
{
        if (!f.file)
                return ERR_PTR(-EBADF);
        if (f.file->f_op != &bpf_map_fops) {
                fdput(f);
                return ERR_PTR(-EINVAL);
        }

        return f.file->private_data;
}

/* prog's and map's refcnt limit */
#define BPF_MAX_REFCNT 32768

struct bpf_map *bpf_map_inc(struct bpf_map *map, bool uref)
{
        if (atomic_inc_return(&map->refcnt) > BPF_MAX_REFCNT) {
                atomic_dec(&map->refcnt);
                return ERR_PTR(-EBUSY);
        }
        if (uref)
                atomic_inc(&map->usercnt);
        return map;
}

struct bpf_map *bpf_map_get_with_uref(u32 ufd)
{
        struct fd f = fdget(ufd);
        struct bpf_map *map;

        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return map;

        map = bpf_map_inc(map, true);
        fdput(f);

        return map;
}

/* helper to convert user pointers passed inside __aligned_u64 fields */
static void __user *u64_to_ptr(__u64 val)
{
        return (void __user *) (unsigned long) val;
}

int __weak bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
{
        return -ENOTSUPP;
}

/* last field in 'union bpf_attr' used by this command */
#define BPF_MAP_LOOKUP_ELEM_LAST_FIELD value

static int map_lookup_elem(union bpf_attr *attr)
{
        void __user *ukey = u64_to_ptr(attr->key);
        void __user *uvalue = u64_to_ptr(attr->value);
        int ufd = attr->map_fd;
        struct bpf_map *map;
        void *key, *value, *ptr;
        u32 value_size;
        struct fd f;
        int err;

        if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
                return -EINVAL;

        f = fdget(ufd);
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);

        err = -ENOMEM;
        key = kmalloc(map->key_size, GFP_USER);
        if (!key)
                goto err_put;

        err = -EFAULT;
        if (copy_from_user(key, ukey, map->key_size) != 0)
                goto free_key;

        if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
            map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
                value_size = round_up(map->value_size, 8) * num_possible_cpus();
        else
                value_size = map->value_size;

        err = -ENOMEM;
        value = kmalloc(value_size, GFP_USER | __GFP_NOWARN);
        if (!value)
                goto free_key;

        if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH) {
                err = bpf_percpu_hash_copy(map, key, value);
        } else if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
                err = bpf_percpu_array_copy(map, key, value);
        } else if (map->map_type == BPF_MAP_TYPE_STACK_TRACE) {
                err = bpf_stackmap_copy(map, key, value);
        } else {
                rcu_read_lock();
                ptr = map->ops->map_lookup_elem(map, key);
                if (ptr)
                        memcpy(value, ptr, value_size);
                rcu_read_unlock();
                err = ptr ? 0 : -ENOENT;
        }

        if (err)
                goto free_value;

        err = -EFAULT;
        if (copy_to_user(uvalue, value, value_size) != 0)
                goto free_value;

        err = 0;

free_value:
        kfree(value);
free_key:
        kfree(key);
err_put:
        fdput(f);
        return err;
}

#define BPF_MAP_UPDATE_ELEM_LAST_FIELD flags

static int map_update_elem(union bpf_attr *attr)
{
        void __user *ukey = u64_to_ptr(attr->key);
        void __user *uvalue = u64_to_ptr(attr->value);
        int ufd = attr->map_fd;
        struct bpf_map *map;
        void *key, *value;
        u32 value_size;
        struct fd f;
        int err;

        if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))
                return -EINVAL;

        f = fdget(ufd);
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);

        err = -ENOMEM;
        key = kmalloc(map->key_size, GFP_USER);
        if (!key)
                goto err_put;

        err = -EFAULT;
        if (copy_from_user(key, ukey, map->key_size) != 0)
                goto free_key;

        if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
            map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
                value_size = round_up(map->value_size, 8) * num_possible_cpus();
        else
                value_size = map->value_size;

        err = -ENOMEM;
        value = kmalloc(value_size, GFP_USER | __GFP_NOWARN);
        if (!value)
                goto free_key;

        err = -EFAULT;
        if (copy_from_user(value, uvalue, value_size) != 0)
                goto free_value;

        /* must increment bpf_prog_active to avoid kprobe+bpf triggering from
         * inside bpf map update or delete otherwise deadlocks are possible
         */
        preempt_disable();
        __this_cpu_inc(bpf_prog_active);
        if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH) {
                err = bpf_percpu_hash_update(map, key, value, attr->flags);
        } else if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
                err = bpf_percpu_array_update(map, key, value, attr->flags);
        } else if (map->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY ||
                   map->map_type == BPF_MAP_TYPE_PROG_ARRAY ||
                   map->map_type == BPF_MAP_TYPE_CGROUP_ARRAY) {
                rcu_read_lock();
                err = bpf_fd_array_map_update_elem(map, f.file, key, value,
                                                   attr->flags);
                rcu_read_unlock();
        } else {
                rcu_read_lock();
                err = map->ops->map_update_elem(map, key, value, attr->flags);
                rcu_read_unlock();
        }
        __this_cpu_dec(bpf_prog_active);
        preempt_enable();

free_value:
        kfree(value);
free_key:
        kfree(key);
err_put:
        fdput(f);
        return err;
}

#define BPF_MAP_DELETE_ELEM_LAST_FIELD key

static int map_delete_elem(union bpf_attr *attr)
{
        void __user *ukey = u64_to_ptr(attr->key);
        int ufd = attr->map_fd;
        struct bpf_map *map;
        struct fd f;
        void *key;
        int err;

        if (CHECK_ATTR(BPF_MAP_DELETE_ELEM))
                return -EINVAL;

        f = fdget(ufd);
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);

        err = -ENOMEM;
        key = kmalloc(map->key_size, GFP_USER);
        if (!key)
                goto err_put;

        err = -EFAULT;
        if (copy_from_user(key, ukey, map->key_size) != 0)
                goto free_key;

        preempt_disable();
        __this_cpu_inc(bpf_prog_active);
        rcu_read_lock();
        err = map->ops->map_delete_elem(map, key);
        rcu_read_unlock();
        __this_cpu_dec(bpf_prog_active);
        preempt_enable();

free_key:
        kfree(key);
err_put:
        fdput(f);
        return err;
}

/* last field in 'union bpf_attr' used by this command */
#define BPF_MAP_GET_NEXT_KEY_LAST_FIELD next_key

static int map_get_next_key(union bpf_attr *attr)
{
        void __user *ukey = u64_to_ptr(attr->key);
        void __user *unext_key = u64_to_ptr(attr->next_key);
        int ufd = attr->map_fd;
        struct bpf_map *map;
        void *key, *next_key;
        struct fd f;
        int err;

        if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY))
                return -EINVAL;

        f = fdget(ufd);
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);

        err = -ENOMEM;
        key = kmalloc(map->key_size, GFP_USER);
        if (!key)
                goto err_put;

        err = -EFAULT;
        if (copy_from_user(key, ukey, map->key_size) != 0)
                goto free_key;

        err = -ENOMEM;
        next_key = kmalloc(map->key_size, GFP_USER);
        if (!next_key)
                goto free_key;

        rcu_read_lock();
        err = map->ops->map_get_next_key(map, key, next_key);
        rcu_read_unlock();
        if (err)
                goto free_next_key;

        err = -EFAULT;
        if (copy_to_user(unext_key, next_key, map->key_size) != 0)
                goto free_next_key;

        err = 0;

free_next_key:
        kfree(next_key);
free_key:
        kfree(key);
err_put:
        fdput(f);
        return err;
}

static LIST_HEAD(bpf_prog_types);

static int find_prog_type(enum bpf_prog_type type, struct bpf_prog *prog)
{
        struct bpf_prog_type_list *tl;

        list_for_each_entry(tl, &bpf_prog_types, list_node) {
                if (tl->type == type) {
                        prog->aux->ops = tl->ops;
                        prog->type = type;
                        return 0;
                }
        }

        return -EINVAL;
}

void bpf_register_prog_type(struct bpf_prog_type_list *tl)
{
        list_add(&tl->list_node, &bpf_prog_types);
}

/* fixup insn->imm field of bpf_call instructions:
 * if (insn->imm == BPF_FUNC_map_lookup_elem)
 *      insn->imm = bpf_map_lookup_elem - __bpf_call_base;
 * else if (insn->imm == BPF_FUNC_map_update_elem)
 *      insn->imm = bpf_map_update_elem - __bpf_call_base;
 * else ...
 *
 * this function is called after eBPF program passed verification
 */
static void fixup_bpf_calls(struct bpf_prog *prog)
{
        const struct bpf_func_proto *fn;
        int i;

        for (i = 0; i < prog->len; i++) {
                struct bpf_insn *insn = &prog->insnsi[i];

                if (insn->code == (BPF_JMP | BPF_CALL)) {
                        /* we reach here when program has bpf_call instructions
                         * and it passed bpf_check(), means that
                         * ops->get_func_proto must have been supplied, check it
                         */
                        BUG_ON(!prog->aux->ops->get_func_proto);

                        if (insn->imm == BPF_FUNC_get_route_realm)
                                prog->dst_needed = 1;
                        if (insn->imm == BPF_FUNC_get_prandom_u32)
                                bpf_user_rnd_init_once();
                        if (insn->imm == BPF_FUNC_tail_call) {
                                /* mark bpf_tail_call as different opcode
                                 * to avoid conditional branch in
                                 * interpeter for every normal call
                                 * and to prevent accidental JITing by
                                 * JIT compiler that doesn't support
                                 * bpf_tail_call yet
                                 */
                                insn->imm = 0;
                                insn->code |= BPF_X;
                                continue;
                        }

                        fn = prog->aux->ops->get_func_proto(insn->imm);
                        /* all functions that have prototype and verifier allowed
                         * programs to call them, must be real in-kernel functions
                         */
                        BUG_ON(!fn->func);
                        insn->imm = fn->func - __bpf_call_base;
                }
        }
}

/* drop refcnt on maps used by eBPF program and free auxilary data */
static void free_used_maps(struct bpf_prog_aux *aux)
{
        int i;

        for (i = 0; i < aux->used_map_cnt; i++)
                bpf_map_put(aux->used_maps[i]);

        kfree(aux->used_maps);
}

static int bpf_prog_charge_memlock(struct bpf_prog *prog)
{
        struct user_struct *user = get_current_user();
        unsigned long memlock_limit;

        memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

        atomic_long_add(prog->pages, &user->locked_vm);
        if (atomic_long_read(&user->locked_vm) > memlock_limit) {
                atomic_long_sub(prog->pages, &user->locked_vm);
                free_uid(user);
                return -EPERM;
        }
        prog->aux->user = user;
        return 0;
}

static void bpf_prog_uncharge_memlock(struct bpf_prog *prog)
{
        struct user_struct *user = prog->aux->user;

        atomic_long_sub(prog->pages, &user->locked_vm);
        free_uid(user);
}

static void __bpf_prog_put_rcu(struct rcu_head *rcu)
{
        struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);

        free_used_maps(aux);
        bpf_prog_uncharge_memlock(aux->prog);
        bpf_prog_free(aux->prog);
}

void bpf_prog_put(struct bpf_prog *prog)
{
        if (atomic_dec_and_test(&prog->aux->refcnt))
                call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu);
}
EXPORT_SYMBOL_GPL(bpf_prog_put);

static int bpf_prog_release(struct inode *inode, struct file *filp)
{
        struct bpf_prog *prog = filp->private_data;

        bpf_prog_put(prog);
        return 0;
}

static const struct file_operations bpf_prog_fops = {
        .release = bpf_prog_release,
};

int bpf_prog_new_fd(struct bpf_prog *prog)
{
        return anon_inode_getfd("bpf-prog", &bpf_prog_fops, prog,
                                O_RDWR | O_CLOEXEC);
}

static struct bpf_prog *____bpf_prog_get(struct fd f)
{
        if (!f.file)
                return ERR_PTR(-EBADF);
        if (f.file->f_op != &bpf_prog_fops) {
                fdput(f);
                return ERR_PTR(-EINVAL);
        }

        return f.file->private_data;
}

struct bpf_prog *bpf_prog_add(struct bpf_prog *prog, int i)
{
        if (atomic_add_return(i, &prog->aux->refcnt) > BPF_MAX_REFCNT) {
                atomic_sub(i, &prog->aux->refcnt);
                return ERR_PTR(-EBUSY);
        }
        return prog;
}
EXPORT_SYMBOL_GPL(bpf_prog_add);

struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog)
{
        return bpf_prog_add(prog, 1);
}

static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type *type)
{
        struct fd f = fdget(ufd);
        struct bpf_prog *prog;

        prog = ____bpf_prog_get(f);
        if (IS_ERR(prog))
                return prog;
        if (type && prog->type != *type) {
                prog = ERR_PTR(-EINVAL);
                goto out;
        }

        prog = bpf_prog_inc(prog);
out:
        fdput(f);
        return prog;
}

struct bpf_prog *bpf_prog_get(u32 ufd)
{
        return __bpf_prog_get(ufd, NULL);
}

struct bpf_prog *bpf_prog_get_type(u32 ufd, enum bpf_prog_type type)
{
        return __bpf_prog_get(ufd, &type);
}
EXPORT_SYMBOL_GPL(bpf_prog_get_type);

/* last field in 'union bpf_attr' used by this command */
#define BPF_PROG_LOAD_LAST_FIELD kern_version

static int bpf_prog_load(union bpf_attr *attr)
{
        enum bpf_prog_type type = attr->prog_type;
        struct bpf_prog *prog;
        int err;
        char license[128];
        bool is_gpl;

        if (CHECK_ATTR(BPF_PROG_LOAD))
                return -EINVAL;

        /* copy eBPF program license from user space */
        if (strncpy_from_user(license, u64_to_ptr(attr->license),
                              sizeof(license) - 1) < 0)
                return -EFAULT;
        license[sizeof(license) - 1] = 0;

        /* eBPF programs must be GPL compatible to use GPL-ed functions */
        is_gpl = license_is_gpl_compatible(license);

        if (attr->insn_cnt >= BPF_MAXINSNS)
                return -EINVAL;

        if (type == BPF_PROG_TYPE_KPROBE &&
            attr->kern_version != LINUX_VERSION_CODE)
                return -EINVAL;

        if (type != BPF_PROG_TYPE_SOCKET_FILTER && !capable(CAP_SYS_ADMIN))
                return -EPERM;

        /* plain bpf_prog allocation */
        prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);
        if (!prog)
                return -ENOMEM;

        err = bpf_prog_charge_memlock(prog);
        if (err)
                goto free_prog_nouncharge;

        prog->len = attr->insn_cnt;

        err = -EFAULT;
        if (copy_from_user(prog->insns, u64_to_ptr(attr->insns),
                           prog->len * sizeof(struct bpf_insn)) != 0)
                goto free_prog;

        prog->orig_prog = NULL;
        prog->jited = 0;

        atomic_set(&prog->aux->refcnt, 1);
        prog->gpl_compatible = is_gpl ? 1 : 0;

        /* find program type: socket_filter vs tracing_filter */
        err = find_prog_type(type, prog);
        if (err < 0)
                goto free_prog;

        /* run eBPF verifier */
        err = bpf_check(&prog, attr);
        if (err < 0)
                goto free_used_maps;

        /* fixup BPF_CALL->imm field */
        fixup_bpf_calls(prog);

        /* eBPF program is ready to be JITed */
        prog = bpf_prog_select_runtime(prog, &err);
        if (err < 0)
                goto free_used_maps;

        err = bpf_prog_new_fd(prog);
        if (err < 0)
                /* failed to allocate fd */
                goto free_used_maps;

        return err;

free_used_maps:
        free_used_maps(prog->aux);
free_prog:
        bpf_prog_uncharge_memlock(prog);
free_prog_nouncharge:
        bpf_prog_free(prog);
        return err;
}

#define BPF_OBJ_LAST_FIELD bpf_fd

static int bpf_obj_pin(const union bpf_attr *attr)
{
        if (CHECK_ATTR(BPF_OBJ))
                return -EINVAL;

        return bpf_obj_pin_user(attr->bpf_fd, u64_to_ptr(attr->pathname));
}

static int bpf_obj_get(const union bpf_attr *attr)
{
        if (CHECK_ATTR(BPF_OBJ) || attr->bpf_fd != 0)
                return -EINVAL;

        return bpf_obj_get_user(u64_to_ptr(attr->pathname));
}

SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
{
        union bpf_attr attr = {};
        int err;

        if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled)
                return -EPERM;

        if (!access_ok(VERIFY_READ, uattr, 1))
                return -EFAULT;

        if (size > PAGE_SIZE)   /* silly large */
                return -E2BIG;

        /* If we're handed a bigger struct than we know of,
         * ensure all the unknown bits are 0 - i.e. new
         * user-space does not rely on any kernel feature
         * extensions we dont know about yet.
         */
        if (size > sizeof(attr)) {
                unsigned char __user *addr;
                unsigned char __user *end;
                unsigned char val;

                addr = (void __user *)uattr + sizeof(attr);
                end  = (void __user *)uattr + size;

                for (; addr < end; addr++) {
                        err = get_user(val, addr);
                        if (err)
                                return err;
                        if (val)
                                return -E2BIG;
                }
                size = sizeof(attr);
        }

        /* copy attributes from user space, may be less than sizeof(bpf_attr) */
        if (copy_from_user(&attr, uattr, size) != 0)
                return -EFAULT;

        switch (cmd) {
        case BPF_MAP_CREATE:
                err = map_create(&attr);
                break;
        case BPF_MAP_LOOKUP_ELEM:
                err = map_lookup_elem(&attr);
                break;
        case BPF_MAP_UPDATE_ELEM:
                err = map_update_elem(&attr);
                break;
        case BPF_MAP_DELETE_ELEM:
                err = map_delete_elem(&attr);
                break;
        case BPF_MAP_GET_NEXT_KEY:
                err = map_get_next_key(&attr);
                break;
        case BPF_PROG_LOAD:
                err = bpf_prog_load(&attr);
                break;
        case BPF_OBJ_PIN:
                err = bpf_obj_pin(&attr);
                break;
        case BPF_OBJ_GET:
                err = bpf_obj_get(&attr);
                break;
        default:
                err = -EINVAL;
                break;
        }

        return err;
}