kernel/bpf/syscall.c - third_party/linux - Git at Google

 /* 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>

 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);
 }

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

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

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

 	bpf_map_put(map);
 	return 0;
 }

 static const struct file_operations bpf_map_fops = {
 	.release = bpf_map_release,
 };

 /* 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 max_entries
 /* 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);

 	err = anon_inode_getfd("bpf-map", &bpf_map_fops, map, O_RDWR | O_CLOEXEC);

 	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)
 {
 	struct bpf_map *map;

 	if (!f.file)
 		return ERR_PTR(-EBADF);

 	if (f.file->f_op != &bpf_map_fops) {
 		fdput(f);
 		return ERR_PTR(-EINVAL);
 	}

 	map = f.file->private_data;

 	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;
 }

 /* 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 fd f = fdget(ufd);
 	struct bpf_map *map;
 	void *key, *value, *ptr;
 	int err;

 	if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
 		return -EINVAL;

 	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;
 	value = kmalloc(map->value_size, GFP_USER);
 	if (!value)
 		goto free_key;

 	rcu_read_lock();
 	ptr = map->ops->map_lookup_elem(map, key);
 	if (ptr)
 		memcpy(value, ptr, map->value_size);
 	rcu_read_unlock();

 	err = -ENOENT;
 	if (!ptr)
 		goto free_value;

 	err = -EFAULT;
 	if (copy_to_user(uvalue, value, map->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 fd f = fdget(ufd);
 	struct bpf_map *map;
 	void *key, *value;
 	int err;

 	if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))
 		return -EINVAL;

 	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;
 	value = kmalloc(map->value_size, GFP_USER);
 	if (!value)
 		goto free_key;

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

 	/* eBPF program that use maps are running under rcu_read_lock(),
 	 * therefore all map accessors rely on this fact, so do the same here
 	 */
 	rcu_read_lock();
 	err = map->ops->map_update_elem(map, key, value, attr->flags);
 	rcu_read_unlock();

 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 fd f = fdget(ufd);
 	struct bpf_map *map;
 	void *key;
 	int err;

 	if (CHECK_ATTR(BPF_MAP_DELETE_ELEM))
 		return -EINVAL;

 	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;

 	rcu_read_lock();
 	err = map->ops->map_delete_elem(map, key);
 	rcu_read_unlock();

 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 fd f = fdget(ufd);
 	struct bpf_map *map;
 	void *key, *next_key;
 	int err;

 	if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY))
 		return -EINVAL;

 	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->aux->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);

 			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);
 }

 void bpf_prog_put(struct bpf_prog *prog)
 {
 	if (atomic_dec_and_test(&prog->aux->refcnt)) {
 		free_used_maps(prog->aux);
 		bpf_prog_free(prog);
 	}
 }

 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,
 };

 static struct bpf_prog *get_prog(struct fd f)
 {
 	struct bpf_prog *prog;

 	if (!f.file)
 		return ERR_PTR(-EBADF);

 	if (f.file->f_op != &bpf_prog_fops) {
 		fdput(f);
 		return ERR_PTR(-EINVAL);
 	}

 	prog = f.file->private_data;

 	return prog;
 }

 /* called by sockets/tracing/seccomp before attaching program to an event
  * pairs with bpf_prog_put()
  */
 struct bpf_prog *bpf_prog_get(u32 ufd)
 {
 	struct fd f = fdget(ufd);
 	struct bpf_prog *prog;

 	prog = get_prog(f);

 	if (IS_ERR(prog))
 		return prog;

 	atomic_inc(&prog->aux->refcnt);
 	fdput(f);
 	return prog;
 }

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

 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;

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

 	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 = false;

 	atomic_set(&prog->aux->refcnt, 1);
 	prog->aux->is_gpl_compatible = is_gpl;

 	/* 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 */
 	bpf_prog_select_runtime(prog);

 	err = anon_inode_getfd("bpf-prog", &bpf_prog_fops, prog, O_RDWR | O_CLOEXEC);

 	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_free(prog);
 	return err;
 }

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

 	/* the syscall is limited to root temporarily. This restriction will be
 	 * lifted when security audit is clean. Note that eBPF+tracing must have
 	 * this restriction, since it may pass kernel data to user space
 	 */
 	if (!capable(CAP_SYS_ADMIN))
 		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;
 	default:
 		err = -EINVAL;
 		break;
 	}

 	return err;
 }
	/* 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>

	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);
	}

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

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

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

	bpf_map_put(map);
	return 0;
	}

	static const struct file_operations bpf_map_fops = {
	.release = bpf_map_release,
	};

	/* 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 max_entries
	/* 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);

	err = anon_inode_getfd("bpf-map", &bpf_map_fops, map, O_RDWR \| O_CLOEXEC);

	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)
	{
	struct bpf_map *map;

	if (!f.file)
	return ERR_PTR(-EBADF);

	if (f.file->f_op != &bpf_map_fops) {
	fdput(f);
	return ERR_PTR(-EINVAL);
	}

	map = f.file->private_data;

	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;
	}

	/* 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 fd f = fdget(ufd);
	struct bpf_map *map;
	void key, value, *ptr;
	int err;

	if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
	return -EINVAL;

	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;
	value = kmalloc(map->value_size, GFP_USER);
	if (!value)
	goto free_key;

	rcu_read_lock();
	ptr = map->ops->map_lookup_elem(map, key);
	if (ptr)
	memcpy(value, ptr, map->value_size);
	rcu_read_unlock();

	err = -ENOENT;
	if (!ptr)
	goto free_value;

	err = -EFAULT;
	if (copy_to_user(uvalue, value, map->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 fd f = fdget(ufd);
	struct bpf_map *map;
	void key, value;
	int err;

	if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))
	return -EINVAL;

	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;
	value = kmalloc(map->value_size, GFP_USER);
	if (!value)
	goto free_key;

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

	/* eBPF program that use maps are running under rcu_read_lock(),
	* therefore all map accessors rely on this fact, so do the same here
	*/
	rcu_read_lock();
	err = map->ops->map_update_elem(map, key, value, attr->flags);
	rcu_read_unlock();

	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 fd f = fdget(ufd);
	struct bpf_map *map;
	void *key;
	int err;

	if (CHECK_ATTR(BPF_MAP_DELETE_ELEM))
	return -EINVAL;

	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;

	rcu_read_lock();
	err = map->ops->map_delete_elem(map, key);
	rcu_read_unlock();

	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 fd f = fdget(ufd);
	struct bpf_map *map;
	void key, next_key;
	int err;

	if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY))
	return -EINVAL;

	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->aux->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);

	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);
	}

	void bpf_prog_put(struct bpf_prog *prog)
	{
	if (atomic_dec_and_test(&prog->aux->refcnt)) {
	free_used_maps(prog->aux);
	bpf_prog_free(prog);
	}
	}

	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,
	};

	static struct bpf_prog *get_prog(struct fd f)
	{
	struct bpf_prog *prog;

	if (!f.file)
	return ERR_PTR(-EBADF);

	if (f.file->f_op != &bpf_prog_fops) {
	fdput(f);
	return ERR_PTR(-EINVAL);
	}

	prog = f.file->private_data;

	return prog;
	}

	/* called by sockets/tracing/seccomp before attaching program to an event
	* pairs with bpf_prog_put()
	*/
	struct bpf_prog *bpf_prog_get(u32 ufd)
	{
	struct fd f = fdget(ufd);
	struct bpf_prog *prog;

	prog = get_prog(f);

	if (IS_ERR(prog))
	return prog;

	atomic_inc(&prog->aux->refcnt);
	fdput(f);
	return prog;
	}

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

	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;

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

	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 = false;

	atomic_set(&prog->aux->refcnt, 1);
	prog->aux->is_gpl_compatible = is_gpl;

	/* 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 */
	bpf_prog_select_runtime(prog);

	err = anon_inode_getfd("bpf-prog", &bpf_prog_fops, prog, O_RDWR \| O_CLOEXEC);

	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_free(prog);
	return err;
	}

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

	/* the syscall is limited to root temporarily. This restriction will be
	* lifted when security audit is clean. Note that eBPF+tracing must have
	* this restriction, since it may pass kernel data to user space
	*/
	if (!capable(CAP_SYS_ADMIN))
	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;
	default:
	err = -EINVAL;
	break;
	}

	return err;
	}