text: /* 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>
  
  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;
  
  	if (map->map_type == BPF_MAP_TYPE_PROG_ARRAY)
  		/* prog_array stores refcnt-ed bpf_prog pointers
  		 * release them all when user space closes prog_array_fd
  		 */
  		bpf_fd_array_map_clear(map);
  
  	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 bpf_map *map;
  	void *key, *value, *ptr;
  	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;
  
  	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 bpf_map *map;
  	void *key, *value;
  	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;
  
  	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 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;
  
  	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 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_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 void __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_free(aux->prog);
  }
  
  /* version of bpf_prog_put() that is called after a grace period */
  void bpf_prog_put_rcu(struct bpf_prog *prog)
  {
  	if (atomic_dec_and_test(&prog->aux->refcnt)) {
  		prog->aux->prog = prog;
  		call_rcu(&prog->aux->rcu, __prog_put_rcu);
  	}
  }
  
  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);
  	}
  }
  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_rcu(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;
  }
  EXPORT_SYMBOL_GPL(bpf_prog_get);
  
  /* 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;
  
  	/* 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->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 */
  	err = bpf_prog_select_runtime(prog);
  	if (err < 0)
  		goto free_used_maps;
  
  	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;
  }
  