text: /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
   * Copyright (c) 2016 Facebook
   *
   * 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/jhash.h>
  #include <linux/filter.h>
  #include <linux/rculist_nulls.h>
  #include "percpu_freelist.h"
  #include "bpf_lru_list.h"
  #include "map_in_map.h"
  
  #define HTAB_CREATE_FLAG_MASK						\
  	(BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU | BPF_F_NUMA_NODE |	\
  	 BPF_F_RDONLY | BPF_F_WRONLY)
  
  struct bucket {
  	struct hlist_nulls_head head;
  	raw_spinlock_t lock;
  };
  
  struct bpf_htab {
  	struct bpf_map map;
  	struct bucket *buckets;
  	void *elems;
  	union {
  		struct pcpu_freelist freelist;
  		struct bpf_lru lru;
  	};
  	struct htab_elem *__percpu *extra_elems;
  	atomic_t count;	/* number of elements in this hashtable */
  	u32 n_buckets;	/* number of hash buckets */
  	u32 elem_size;	/* size of each element in bytes */
  };
  
  /* each htab element is struct htab_elem + key + value */
  struct htab_elem {
  	union {
  		struct hlist_nulls_node hash_node;
  		struct {
  			void *padding;
  			union {
  				struct bpf_htab *htab;
  				struct pcpu_freelist_node fnode;
  			};
  		};
  	};
  	union {
  		struct rcu_head rcu;
  		struct bpf_lru_node lru_node;
  	};
  	u32 hash;
  	char key[0] __aligned(8);
  };
  
  static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node);
  
  static bool htab_is_lru(const struct bpf_htab *htab)
  {
  	return htab->map.map_type == BPF_MAP_TYPE_LRU_HASH ||
  		htab->map.map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH;
  }
  
  static bool htab_is_percpu(const struct bpf_htab *htab)
  {
  	return htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH ||
  		htab->map.map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH;
  }
  
  static bool htab_is_prealloc(const struct bpf_htab *htab)
  {
  	return !(htab->map.map_flags & BPF_F_NO_PREALLOC);
  }
  
  static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
  				     void __percpu *pptr)
  {
  	*(void __percpu **)(l->key + key_size) = pptr;
  }
  
  static inline void __percpu *htab_elem_get_ptr(struct htab_elem *l, u32 key_size)
  {
  	return *(void __percpu **)(l->key + key_size);
  }
  
  static void *fd_htab_map_get_ptr(const struct bpf_map *map, struct htab_elem *l)
  {
  	return *(void **)(l->key + roundup(map->key_size, 8));
  }
  
  static struct htab_elem *get_htab_elem(struct bpf_htab *htab, int i)
  {
  	return (struct htab_elem *) (htab->elems + i * htab->elem_size);
  }
  
  static void htab_free_elems(struct bpf_htab *htab)
  {
  	int i;
  
  	if (!htab_is_percpu(htab))
  		goto free_elems;
  
  	for (i = 0; i < htab->map.max_entries; i++) {
  		void __percpu *pptr;
  
  		pptr = htab_elem_get_ptr(get_htab_elem(htab, i),
  					 htab->map.key_size);
  		free_percpu(pptr);
  		cond_resched();
  	}
  free_elems:
  	bpf_map_area_free(htab->elems);
  }
  
  static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key,
  					  u32 hash)
  {
  	struct bpf_lru_node *node = bpf_lru_pop_free(&htab->lru, hash);
  	struct htab_elem *l;
  
  	if (node) {
  		l = container_of(node, struct htab_elem, lru_node);
  		memcpy(l->key, key, htab->map.key_size);
  		return l;
  	}
  
  	return NULL;
  }
  
  static int prealloc_init(struct bpf_htab *htab)
  {
  	u32 num_entries = htab->map.max_entries;
  	int err = -ENOMEM, i;
  
  	if (!htab_is_percpu(htab) && !htab_is_lru(htab))
  		num_entries += num_possible_cpus();
  
  	htab->elems = bpf_map_area_alloc(htab->elem_size * num_entries,
  					 htab->map.numa_node);
  	if (!htab->elems)
  		return -ENOMEM;
  
  	if (!htab_is_percpu(htab))
  		goto skip_percpu_elems;
  
  	for (i = 0; i < num_entries; i++) {
  		u32 size = round_up(htab->map.value_size, 8);
  		void __percpu *pptr;
  
  		pptr = __alloc_percpu_gfp(size, 8, GFP_USER | __GFP_NOWARN);
  		if (!pptr)
  			goto free_elems;
  		htab_elem_set_ptr(get_htab_elem(htab, i), htab->map.key_size,
  				  pptr);
  		cond_resched();
  	}
  
  skip_percpu_elems:
  	if (htab_is_lru(htab))
  		err = bpf_lru_init(&htab->lru,
  				   htab->map.map_flags & BPF_F_NO_COMMON_LRU,
  				   offsetof(struct htab_elem, hash) -
  				   offsetof(struct htab_elem, lru_node),
  				   htab_lru_map_delete_node,
  				   htab);
  	else
  		err = pcpu_freelist_init(&htab->freelist);
  
  	if (err)
  		goto free_elems;
  
  	if (htab_is_lru(htab))
  		bpf_lru_populate(&htab->lru, htab->elems,
  				 offsetof(struct htab_elem, lru_node),
  				 htab->elem_size, num_entries);
  	else
  		pcpu_freelist_populate(&htab->freelist,
  				       htab->elems + offsetof(struct htab_elem, fnode),
  				       htab->elem_size, num_entries);
  
  	return 0;
  
  free_elems:
  	htab_free_elems(htab);
  	return err;
  }
  
  static void prealloc_destroy(struct bpf_htab *htab)
  {
  	htab_free_elems(htab);
  
  	if (htab_is_lru(htab))
  		bpf_lru_destroy(&htab->lru);
  	else
  		pcpu_freelist_destroy(&htab->freelist);
  }
  
  static int alloc_extra_elems(struct bpf_htab *htab)
  {
  	struct htab_elem *__percpu *pptr, *l_new;
  	struct pcpu_freelist_node *l;
  	int cpu;
  
  	pptr = __alloc_percpu_gfp(sizeof(struct htab_elem *), 8,
  				  GFP_USER | __GFP_NOWARN);
  	if (!pptr)
  		return -ENOMEM;
  
  	for_each_possible_cpu(cpu) {
  		l = pcpu_freelist_pop(&htab->freelist);
  		/* pop will succeed, since prealloc_init()
  		 * preallocated extra num_possible_cpus elements
  		 */
  		l_new = container_of(l, struct htab_elem, fnode);
  		*per_cpu_ptr(pptr, cpu) = l_new;
  	}
  	htab->extra_elems = pptr;
  	return 0;
  }
  
  /* Called from syscall */
  static int htab_map_alloc_check(union bpf_attr *attr)
  {
  	bool percpu = (attr->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
  		       attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
  	bool lru = (attr->map_type == BPF_MAP_TYPE_LRU_HASH ||
  		    attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
  	/* percpu_lru means each cpu has its own LRU list.
  	 * it is different from BPF_MAP_TYPE_PERCPU_HASH where
  	 * the map's value itself is percpu.  percpu_lru has
  	 * nothing to do with the map's value.
  	 */
  	bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
  	bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
  	int numa_node = bpf_map_attr_numa_node(attr);
  
  	BUILD_BUG_ON(offsetof(struct htab_elem, htab) !=
  		     offsetof(struct htab_elem, hash_node.pprev));
  	BUILD_BUG_ON(offsetof(struct htab_elem, fnode.next) !=
  		     offsetof(struct htab_elem, hash_node.pprev));
  
  	if (lru && !capable(CAP_SYS_ADMIN))
  		/* LRU implementation is much complicated than other
  		 * maps.  Hence, limit to CAP_SYS_ADMIN for now.
  		 */
  		return -EPERM;
  
  	if (attr->map_flags & ~HTAB_CREATE_FLAG_MASK)
  		/* reserved bits should not be used */
  		return -EINVAL;
  
  	if (!lru && percpu_lru)
  		return -EINVAL;
  
  	if (lru && !prealloc)
  		return -ENOTSUPP;
  
  	if (numa_node != NUMA_NO_NODE && (percpu || percpu_lru))
  		return -EINVAL;
  
  	/* check sanity of attributes.
  	 * value_size == 0 may be allowed in the future to use map as a set
  	 */
  	if (attr->max_entries == 0 || attr->key_size == 0 ||
  	    attr->value_size == 0)
  		return -EINVAL;
  
  	if (attr->key_size > MAX_BPF_STACK)
  		/* eBPF programs initialize keys on stack, so they cannot be
  		 * larger than max stack size
  		 */
  		return -E2BIG;
  
  	if (attr->value_size >= KMALLOC_MAX_SIZE -
  	    MAX_BPF_STACK - sizeof(struct htab_elem))
  		/* if value_size is bigger, the user space won't be able to
  		 * access the elements via bpf syscall. This check also makes
  		 * sure that the elem_size doesn't overflow and it's
  		 * kmalloc-able later in htab_map_update_elem()
  		 */
  		return -E2BIG;
  
  	return 0;
  }
  
  static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
  {
  	bool percpu = (attr->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
  		       attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
  	bool lru = (attr->map_type == BPF_MAP_TYPE_LRU_HASH ||
  		    attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
  	/* percpu_lru means each cpu has its own LRU list.
  	 * it is different from BPF_MAP_TYPE_PERCPU_HASH where
  	 * the map's value itself is percpu.  percpu_lru has
  	 * nothing to do with the map's value.
  	 */
  	bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
  	bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
  	struct bpf_htab *htab;
  	int err, i;
  	u64 cost;
  
  	htab = kzalloc(sizeof(*htab), GFP_USER);
  	if (!htab)
  		return ERR_PTR(-ENOMEM);
  
  	bpf_map_init_from_attr(&htab->map, attr);
  
  	if (percpu_lru) {
  		/* ensure each CPU's lru list has >=1 elements.
  		 * since we are at it, make each lru list has the same
  		 * number of elements.
  		 */
  		htab->map.max_entries = roundup(attr->max_entries,
  						num_possible_cpus());
  		if (htab->map.max_entries < attr->max_entries)
  			htab->map.max_entries = rounddown(attr->max_entries,
  							  num_possible_cpus());
  	}
  
  	/* hash table size must be power of 2 */
  	htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);
  
  	htab->elem_size = sizeof(struct htab_elem) +
  			  round_up(htab->map.key_size, 8);
  	if (percpu)
  		htab->elem_size += sizeof(void *);
  	else
  		htab->elem_size += round_up(htab->map.value_size, 8);
  
  	err = -E2BIG;
  	/* prevent zero size kmalloc and check for u32 overflow */
  	if (htab->n_buckets == 0 ||
  	    htab->n_buckets > U32_MAX / sizeof(struct bucket))
  		goto free_htab;
  
  	cost = (u64) htab->n_buckets * sizeof(struct bucket) +
  	       (u64) htab->elem_size * htab->map.max_entries;
  
  	if (percpu)
  		cost += (u64) round_up(htab->map.value_size, 8) *
  			num_possible_cpus() * htab->map.max_entries;
  	else
  	       cost += (u64) htab->elem_size * num_possible_cpus();
  
  	if (cost >= U32_MAX - PAGE_SIZE)
  		/* make sure page count doesn't overflow */
  		goto free_htab;
  
  	htab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
  
  	/* if map size is larger than memlock limit, reject it early */
  	err = bpf_map_precharge_memlock(htab->map.pages);
  	if (err)
  		goto free_htab;
  
  	err = -ENOMEM;
  	htab->buckets = bpf_map_area_alloc(htab->n_buckets *
  					   sizeof(struct bucket),
  					   htab->map.numa_node);
  	if (!htab->buckets)
  		goto free_htab;
  
  	for (i = 0; i < htab->n_buckets; i++) {
  		INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
  		raw_spin_lock_init(&htab->buckets[i].lock);
  	}
  
  	if (prealloc) {
  		err = prealloc_init(htab);
  		if (err)
  			goto free_buckets;
  
  		if (!percpu && !lru) {
  			/* lru itself can remove the least used element, so
  			 * there is no need for an extra elem during map_update.
  			 */
  			err = alloc_extra_elems(htab);
  			if (err)
  				goto free_prealloc;
  		}
  	}
  
  	return &htab->map;
  
  free_prealloc:
  	prealloc_destroy(htab);
  free_buckets:
  	bpf_map_area_free(htab->buckets);
  free_htab:
  	kfree(htab);
  	return ERR_PTR(err);
  }
  
  static inline u32 htab_map_hash(const void *key, u32 key_len)
  {
  	return jhash(key, key_len, 0);
  }
  
  static inline struct bucket *__select_bucket(struct bpf_htab *htab, u32 hash)
  {
  	return &htab->buckets[hash & (htab->n_buckets - 1)];
  }
  
  static inline struct hlist_nulls_head *select_bucket(struct bpf_htab *htab, u32 hash)
  {
  	return &__select_bucket(htab, hash)->head;
  }
  
  /* this lookup function can only be called with bucket lock taken */
  static struct htab_elem *lookup_elem_raw(struct hlist_nulls_head *head, u32 hash,
  					 void *key, u32 key_size)
  {
  	struct hlist_nulls_node *n;
  	struct htab_elem *l;
  
  	hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
  		if (l->hash == hash && !memcmp(&l->key, key, key_size))
  			return l;
  
  	return NULL;
  }
  
  /* can be called without bucket lock. it will repeat the loop in
   * the unlikely event when elements moved from one bucket into another
   * while link list is being walked
   */
  static struct htab_elem *lookup_nulls_elem_raw(struct hlist_nulls_head *head,
  					       u32 hash, void *key,
  					       u32 key_size, u32 n_buckets)
  {
  	struct hlist_nulls_node *n;
  	struct htab_elem *l;
  
  again:
  	hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
  		if (l->hash == hash && !memcmp(&l->key, key, key_size))
  			return l;
  
  	if (unlikely(get_nulls_value(n) != (hash & (n_buckets - 1))))
  		goto again;
  
  	return NULL;
  }
  
  /* Called from syscall or from eBPF program directly, so
   * arguments have to match bpf_map_lookup_elem() exactly.
   * The return value is adjusted by BPF instructions
   * in htab_map_gen_lookup().
   */
  static void *__htab_map_lookup_elem(struct bpf_map *map, void *key)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct hlist_nulls_head *head;
  	struct htab_elem *l;
  	u32 hash, key_size;
  
  	/* Must be called with rcu_read_lock. */
  	WARN_ON_ONCE(!rcu_read_lock_held());
  
  	key_size = map->key_size;
  
  	hash = htab_map_hash(key, key_size);
  
  	head = select_bucket(htab, hash);
  
  	l = lookup_nulls_elem_raw(head, hash, key, key_size, htab->n_buckets);
  
  	return l;
  }
  
  static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
  {
  	struct htab_elem *l = __htab_map_lookup_elem(map, key);
  
  	if (l)
  		return l->key + round_up(map->key_size, 8);
  
  	return NULL;
  }
  
  /* inline bpf_map_lookup_elem() call.
   * Instead of:
   * bpf_prog
   *   bpf_map_lookup_elem
   *     map->ops->map_lookup_elem
   *       htab_map_lookup_elem
   *         __htab_map_lookup_elem
   * do:
   * bpf_prog
   *   __htab_map_lookup_elem
   */
  static u32 htab_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
  {
  	struct bpf_insn *insn = insn_buf;
  	const int ret = BPF_REG_0;
  
  	*insn++ = BPF_EMIT_CALL((u64 (*)(u64, u64, u64, u64, u64))__htab_map_lookup_elem);
  	*insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 1);
  	*insn++ = BPF_ALU64_IMM(BPF_ADD, ret,
  				offsetof(struct htab_elem, key) +
  				round_up(map->key_size, 8));
  	return insn - insn_buf;
  }
  
  static void *htab_lru_map_lookup_elem(struct bpf_map *map, void *key)
  {
  	struct htab_elem *l = __htab_map_lookup_elem(map, key);
  
  	if (l) {
  		bpf_lru_node_set_ref(&l->lru_node);
  		return l->key + round_up(map->key_size, 8);
  	}
  
  	return NULL;
  }
  
  static u32 htab_lru_map_gen_lookup(struct bpf_map *map,
  				   struct bpf_insn *insn_buf)
  {
  	struct bpf_insn *insn = insn_buf;
  	const int ret = BPF_REG_0;
  	const int ref_reg = BPF_REG_1;
  
  	*insn++ = BPF_EMIT_CALL((u64 (*)(u64, u64, u64, u64, u64))__htab_map_lookup_elem);
  	*insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 4);
  	*insn++ = BPF_LDX_MEM(BPF_B, ref_reg, ret,
  			      offsetof(struct htab_elem, lru_node) +
  			      offsetof(struct bpf_lru_node, ref));
  	*insn++ = BPF_JMP_IMM(BPF_JNE, ref_reg, 0, 1);
  	*insn++ = BPF_ST_MEM(BPF_B, ret,
  			     offsetof(struct htab_elem, lru_node) +
  			     offsetof(struct bpf_lru_node, ref),
  			     1);
  	*insn++ = BPF_ALU64_IMM(BPF_ADD, ret,
  				offsetof(struct htab_elem, key) +
  				round_up(map->key_size, 8));
  	return insn - insn_buf;
  }
  
  /* It is called from the bpf_lru_list when the LRU needs to delete
   * older elements from the htab.
   */
  static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
  {
  	struct bpf_htab *htab = (struct bpf_htab *)arg;
  	struct htab_elem *l = NULL, *tgt_l;
  	struct hlist_nulls_head *head;
  	struct hlist_nulls_node *n;
  	unsigned long flags;
  	struct bucket *b;
  
  	tgt_l = container_of(node, struct htab_elem, lru_node);
  	b = __select_bucket(htab, tgt_l->hash);
  	head = &b->head;
  
  	raw_spin_lock_irqsave(&b->lock, flags);
  
  	hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
  		if (l == tgt_l) {
  			hlist_nulls_del_rcu(&l->hash_node);
  			break;
  		}
  
  	raw_spin_unlock_irqrestore(&b->lock, flags);
  
  	return l == tgt_l;
  }
  
  /* Called from syscall */
  static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct hlist_nulls_head *head;
  	struct htab_elem *l, *next_l;
  	u32 hash, key_size;
  	int i = 0;
  
  	WARN_ON_ONCE(!rcu_read_lock_held());
  
  	key_size = map->key_size;
  
  	if (!key)
  		goto find_first_elem;
  
  	hash = htab_map_hash(key, key_size);
  
  	head = select_bucket(htab, hash);
  
  	/* lookup the key */
  	l = lookup_nulls_elem_raw(head, hash, key, key_size, htab->n_buckets);
  
  	if (!l)
  		goto find_first_elem;
  
  	/* key was found, get next key in the same bucket */
  	next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_next_rcu(&l->hash_node)),
  				  struct htab_elem, hash_node);
  
  	if (next_l) {
  		/* if next elem in this hash list is non-zero, just return it */
  		memcpy(next_key, next_l->key, key_size);
  		return 0;
  	}
  
  	/* no more elements in this hash list, go to the next bucket */
  	i = hash & (htab->n_buckets - 1);
  	i++;
  
  find_first_elem:
  	/* iterate over buckets */
  	for (; i < htab->n_buckets; i++) {
  		head = select_bucket(htab, i);
  
  		/* pick first element in the bucket */
  		next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_first_rcu(head)),
  					  struct htab_elem, hash_node);
  		if (next_l) {
  			/* if it's not empty, just return it */
  			memcpy(next_key, next_l->key, key_size);
  			return 0;
  		}
  	}
  
  	/* iterated over all buckets and all elements */
  	return -ENOENT;
  }
  
  static void htab_elem_free(struct bpf_htab *htab, struct htab_elem *l)
  {
  	if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH)
  		free_percpu(htab_elem_get_ptr(l, htab->map.key_size));
  	kfree(l);
  }
  
  static void htab_elem_free_rcu(struct rcu_head *head)
  {
  	struct htab_elem *l = container_of(head, struct htab_elem, rcu);
  	struct bpf_htab *htab = l->htab;
  
  	/* must increment bpf_prog_active to avoid kprobe+bpf triggering while
  	 * we're calling kfree, otherwise deadlock is possible if kprobes
  	 * are placed somewhere inside of slub
  	 */
  	preempt_disable();
  	__this_cpu_inc(bpf_prog_active);
  	htab_elem_free(htab, l);
  	__this_cpu_dec(bpf_prog_active);
  	preempt_enable();
  }
  
  static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
  {
  	struct bpf_map *map = &htab->map;
  
  	if (map->ops->map_fd_put_ptr) {
  		void *ptr = fd_htab_map_get_ptr(map, l);
  
  		map->ops->map_fd_put_ptr(ptr);
  	}
  
  	if (htab_is_prealloc(htab)) {
  		pcpu_freelist_push(&htab->freelist, &l->fnode);
  	} else {
  		atomic_dec(&htab->count);
  		l->htab = htab;
  		call_rcu(&l->rcu, htab_elem_free_rcu);
  	}
  }
  
  static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
  			    void *value, bool onallcpus)
  {
  	if (!onallcpus) {
  		/* copy true value_size bytes */
  		memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
  	} else {
  		u32 size = round_up(htab->map.value_size, 8);
  		int off = 0, cpu;
  
  		for_each_possible_cpu(cpu) {
  			bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
  					value + off, size);
  			off += size;
  		}
  	}
  }
  
  static bool fd_htab_map_needs_adjust(const struct bpf_htab *htab)
  {
  	return htab->map.map_type == BPF_MAP_TYPE_HASH_OF_MAPS &&
  	       BITS_PER_LONG == 64;
  }
  
  static u32 htab_size_value(const struct bpf_htab *htab, bool percpu)
  {
  	u32 size = htab->map.value_size;
  
  	if (percpu || fd_htab_map_needs_adjust(htab))
  		size = round_up(size, 8);
  	return size;
  }
  
  static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
  					 void *value, u32 key_size, u32 hash,
  					 bool percpu, bool onallcpus,
  					 struct htab_elem *old_elem)
  {
  	u32 size = htab_size_value(htab, percpu);
  	bool prealloc = htab_is_prealloc(htab);
  	struct htab_elem *l_new, **pl_new;
  	void __percpu *pptr;
  
  	if (prealloc) {
  		if (old_elem) {
  			/* if we're updating the existing element,
  			 * use per-cpu extra elems to avoid freelist_pop/push
  			 */
  			pl_new = this_cpu_ptr(htab->extra_elems);
  			l_new = *pl_new;
  			*pl_new = old_elem;
  		} else {
  			struct pcpu_freelist_node *l;
  
  			l = pcpu_freelist_pop(&htab->freelist);
  			if (!l)
  				return ERR_PTR(-E2BIG);
  			l_new = container_of(l, struct htab_elem, fnode);
  		}
  	} else {
  		if (atomic_inc_return(&htab->count) > htab->map.max_entries)
  			if (!old_elem) {
  				/* when map is full and update() is replacing
  				 * old element, it's ok to allocate, since
  				 * old element will be freed immediately.
  				 * Otherwise return an error
  				 */
  				atomic_dec(&htab->count);
  				return ERR_PTR(-E2BIG);
  			}
  		l_new = kmalloc_node(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN,
  				     htab->map.numa_node);
  		if (!l_new)
  			return ERR_PTR(-ENOMEM);
  	}
  
  	memcpy(l_new->key, key, key_size);
  	if (percpu) {
  		if (prealloc) {
  			pptr = htab_elem_get_ptr(l_new, key_size);
  		} else {
  			/* alloc_percpu zero-fills */
  			pptr = __alloc_percpu_gfp(size, 8,
  						  GFP_ATOMIC | __GFP_NOWARN);
  			if (!pptr) {
  				kfree(l_new);
  				return ERR_PTR(-ENOMEM);
  			}
  		}
  
  		pcpu_copy_value(htab, pptr, value, onallcpus);
  
  		if (!prealloc)
  			htab_elem_set_ptr(l_new, key_size, pptr);
  	} else {
  		memcpy(l_new->key + round_up(key_size, 8), value, size);
  	}
  
  	l_new->hash = hash;
  	return l_new;
  }
  
  static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
  		       u64 map_flags)
  {
  	if (l_old && map_flags == BPF_NOEXIST)
  		/* elem already exists */
  		return -EEXIST;
  
  	if (!l_old && map_flags == BPF_EXIST)
  		/* elem doesn't exist, cannot update it */
  		return -ENOENT;
  
  	return 0;
  }
  
  /* Called from syscall or from eBPF program */
  static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
  				u64 map_flags)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct htab_elem *l_new = NULL, *l_old;
  	struct hlist_nulls_head *head;
  	unsigned long flags;
  	struct bucket *b;
  	u32 key_size, hash;
  	int ret;
  
  	if (unlikely(map_flags > BPF_EXIST))
  		/* unknown flags */
  		return -EINVAL;
  
  	WARN_ON_ONCE(!rcu_read_lock_held());
  
  	key_size = map->key_size;
  
  	hash = htab_map_hash(key, key_size);
  
  	b = __select_bucket(htab, hash);
  	head = &b->head;
  
  	/* bpf_map_update_elem() can be called in_irq() */
  	raw_spin_lock_irqsave(&b->lock, flags);
  
  	l_old = lookup_elem_raw(head, hash, key, key_size);
  
  	ret = check_flags(htab, l_old, map_flags);
  	if (ret)
  		goto err;
  
  	l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false,
  				l_old);
  	if (IS_ERR(l_new)) {
  		/* all pre-allocated elements are in use or memory exhausted */
  		ret = PTR_ERR(l_new);
  		goto err;
  	}
  
  	/* add new element to the head of the list, so that
  	 * concurrent search will find it before old elem
  	 */
  	hlist_nulls_add_head_rcu(&l_new->hash_node, head);
  	if (l_old) {
  		hlist_nulls_del_rcu(&l_old->hash_node);
  		if (!htab_is_prealloc(htab))
  			free_htab_elem(htab, l_old);
  	}
  	ret = 0;
  err:
  	raw_spin_unlock_irqrestore(&b->lock, flags);
  	return ret;
  }
  
  static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
  				    u64 map_flags)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct htab_elem *l_new, *l_old = NULL;
  	struct hlist_nulls_head *head;
  	unsigned long flags;
  	struct bucket *b;
  	u32 key_size, hash;
  	int ret;
  
  	if (unlikely(map_flags > BPF_EXIST))
  		/* unknown flags */
  		return -EINVAL;
  
  	WARN_ON_ONCE(!rcu_read_lock_held());
  
  	key_size = map->key_size;
  
  	hash = htab_map_hash(key, key_size);
  
  	b = __select_bucket(htab, hash);
  	head = &b->head;
  
  	/* For LRU, we need to alloc before taking bucket's
  	 * spinlock because getting free nodes from LRU may need
  	 * to remove older elements from htab and this removal
  	 * operation will need a bucket lock.
  	 */
  	l_new = prealloc_lru_pop(htab, key, hash);
  	if (!l_new)
  		return -ENOMEM;
  	memcpy(l_new->key + round_up(map->key_size, 8), value, map->value_size);
  
  	/* bpf_map_update_elem() can be called in_irq() */
  	raw_spin_lock_irqsave(&b->lock, flags);
  
  	l_old = lookup_elem_raw(head, hash, key, key_size);
  
  	ret = check_flags(htab, l_old, map_flags);
  	if (ret)
  		goto err;
  
  	/* add new element to the head of the list, so that
  	 * concurrent search will find it before old elem
  	 */
  	hlist_nulls_add_head_rcu(&l_new->hash_node, head);
  	if (l_old) {
  		bpf_lru_node_set_ref(&l_new->lru_node);
  		hlist_nulls_del_rcu(&l_old->hash_node);
  	}
  	ret = 0;
  
  err:
  	raw_spin_unlock_irqrestore(&b->lock, flags);
  
  	if (ret)
  		bpf_lru_push_free(&htab->lru, &l_new->lru_node);
  	else if (l_old)
  		bpf_lru_push_free(&htab->lru, &l_old->lru_node);
  
  	return ret;
  }
  
  static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
  					 void *value, u64 map_flags,
  					 bool onallcpus)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct htab_elem *l_new = NULL, *l_old;
  	struct hlist_nulls_head *head;
  	unsigned long flags;
  	struct bucket *b;
  	u32 key_size, hash;
  	int ret;
  
  	if (unlikely(map_flags > BPF_EXIST))
  		/* unknown flags */
  		return -EINVAL;
  
  	WARN_ON_ONCE(!rcu_read_lock_held());
  
  	key_size = map->key_size;
  
  	hash = htab_map_hash(key, key_size);
  
  	b = __select_bucket(htab, hash);
  	head = &b->head;
  
  	/* bpf_map_update_elem() can be called in_irq() */
  	raw_spin_lock_irqsave(&b->lock, flags);
  
  	l_old = lookup_elem_raw(head, hash, key, key_size);
  
  	ret = check_flags(htab, l_old, map_flags);
  	if (ret)
  		goto err;
  
  	if (l_old) {
  		/* per-cpu hash map can update value in-place */
  		pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
  				value, onallcpus);
  	} else {
  		l_new = alloc_htab_elem(htab, key, value, key_size,
  					hash, true, onallcpus, NULL);
  		if (IS_ERR(l_new)) {
  			ret = PTR_ERR(l_new);
  			goto err;
  		}
  		hlist_nulls_add_head_rcu(&l_new->hash_node, head);
  	}
  	ret = 0;
  err:
  	raw_spin_unlock_irqrestore(&b->lock, flags);
  	return ret;
  }
  
  static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
  					     void *value, u64 map_flags,
  					     bool onallcpus)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct htab_elem *l_new = NULL, *l_old;
  	struct hlist_nulls_head *head;
  	unsigned long flags;
  	struct bucket *b;
  	u32 key_size, hash;
  	int ret;
  
  	if (unlikely(map_flags > BPF_EXIST))
  		/* unknown flags */
  		return -EINVAL;
  
  	WARN_ON_ONCE(!rcu_read_lock_held());
  
  	key_size = map->key_size;
  
  	hash = htab_map_hash(key, key_size);
  
  	b = __select_bucket(htab, hash);
  	head = &b->head;
  
  	/* For LRU, we need to alloc before taking bucket's
  	 * spinlock because LRU's elem alloc may need
  	 * to remove older elem from htab and this removal
  	 * operation will need a bucket lock.
  	 */
  	if (map_flags != BPF_EXIST) {
  		l_new = prealloc_lru_pop(htab, key, hash);
  		if (!l_new)
  			return -ENOMEM;
  	}
  
  	/* bpf_map_update_elem() can be called in_irq() */
  	raw_spin_lock_irqsave(&b->lock, flags);
  
  	l_old = lookup_elem_raw(head, hash, key, key_size);
  
  	ret = check_flags(htab, l_old, map_flags);
  	if (ret)
  		goto err;
  
  	if (l_old) {
  		bpf_lru_node_set_ref(&l_old->lru_node);
  
  		/* per-cpu hash map can update value in-place */
  		pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
  				value, onallcpus);
  	} else {
  		pcpu_copy_value(htab, htab_elem_get_ptr(l_new, key_size),
  				value, onallcpus);
  		hlist_nulls_add_head_rcu(&l_new->hash_node, head);
  		l_new = NULL;
  	}
  	ret = 0;
  err:
  	raw_spin_unlock_irqrestore(&b->lock, flags);
  	if (l_new)
  		bpf_lru_push_free(&htab->lru, &l_new->lru_node);
  	return ret;
  }
  
  static int htab_percpu_map_update_elem(struct bpf_map *map, void *key,
  				       void *value, u64 map_flags)
  {
  	return __htab_percpu_map_update_elem(map, key, value, map_flags, false);
  }
  
  static int htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
  					   void *value, u64 map_flags)
  {
  	return __htab_lru_percpu_map_update_elem(map, key, value, map_flags,
  						 false);
  }
  
  /* Called from syscall or from eBPF program */
  static int htab_map_delete_elem(struct bpf_map *map, void *key)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct hlist_nulls_head *head;
  	struct bucket *b;
  	struct htab_elem *l;
  	unsigned long flags;
  	u32 hash, key_size;
  	int ret = -ENOENT;
  
  	WARN_ON_ONCE(!rcu_read_lock_held());
  
  	key_size = map->key_size;
  
  	hash = htab_map_hash(key, key_size);
  	b = __select_bucket(htab, hash);
  	head = &b->head;
  
  	raw_spin_lock_irqsave(&b->lock, flags);
  
  	l = lookup_elem_raw(head, hash, key, key_size);
  
  	if (l) {
  		hlist_nulls_del_rcu(&l->hash_node);
  		free_htab_elem(htab, l);
  		ret = 0;
  	}
  
  	raw_spin_unlock_irqrestore(&b->lock, flags);
  	return ret;
  }
  
  static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct hlist_nulls_head *head;
  	struct bucket *b;
  	struct htab_elem *l;
  	unsigned long flags;
  	u32 hash, key_size;
  	int ret = -ENOENT;
  
  	WARN_ON_ONCE(!rcu_read_lock_held());
  
  	key_size = map->key_size;
  
  	hash = htab_map_hash(key, key_size);
  	b = __select_bucket(htab, hash);
  	head = &b->head;
  
  	raw_spin_lock_irqsave(&b->lock, flags);
  
  	l = lookup_elem_raw(head, hash, key, key_size);
  
  	if (l) {
  		hlist_nulls_del_rcu(&l->hash_node);
  		ret = 0;
  	}
  
  	raw_spin_unlock_irqrestore(&b->lock, flags);
  	if (l)
  		bpf_lru_push_free(&htab->lru, &l->lru_node);
  	return ret;
  }
  
  static void delete_all_elements(struct bpf_htab *htab)
  {
  	int i;
  
  	for (i = 0; i < htab->n_buckets; i++) {
  		struct hlist_nulls_head *head = select_bucket(htab, i);
  		struct hlist_nulls_node *n;
  		struct htab_elem *l;
  
  		hlist_nulls_for_each_entry_safe(l, n, head, hash_node) {
  			hlist_nulls_del_rcu(&l->hash_node);
  			htab_elem_free(htab, l);
  		}
  	}
  }
  
  /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
  static void htab_map_free(struct bpf_map *map)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, 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 critical sections in
  	 * these programs to complete
  	 */
  	synchronize_rcu();
  
  	/* some of free_htab_elem() callbacks for elements of this map may
  	 * not have executed. Wait for them.
  	 */
  	rcu_barrier();
  	if (!htab_is_prealloc(htab))
  		delete_all_elements(htab);
  	else
  		prealloc_destroy(htab);
  
  	free_percpu(htab->extra_elems);
  	bpf_map_area_free(htab->buckets);
  	kfree(htab);
  }
  
  const struct bpf_map_ops htab_map_ops = {
  	.map_alloc_check = htab_map_alloc_check,
  	.map_alloc = htab_map_alloc,
  	.map_free = htab_map_free,
  	.map_get_next_key = htab_map_get_next_key,
  	.map_lookup_elem = htab_map_lookup_elem,
  	.map_update_elem = htab_map_update_elem,
  	.map_delete_elem = htab_map_delete_elem,
  	.map_gen_lookup = htab_map_gen_lookup,
  };
  
  const struct bpf_map_ops htab_lru_map_ops = {
  	.map_alloc_check = htab_map_alloc_check,
  	.map_alloc = htab_map_alloc,
  	.map_free = htab_map_free,
  	.map_get_next_key = htab_map_get_next_key,
  	.map_lookup_elem = htab_lru_map_lookup_elem,
  	.map_update_elem = htab_lru_map_update_elem,
  	.map_delete_elem = htab_lru_map_delete_elem,
  	.map_gen_lookup = htab_lru_map_gen_lookup,
  };
  
  /* Called from eBPF program */
  static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
  {
  	struct htab_elem *l = __htab_map_lookup_elem(map, key);
  
  	if (l)
  		return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
  	else
  		return NULL;
  }
  
  static void *htab_lru_percpu_map_lookup_elem(struct bpf_map *map, void *key)
  {
  	struct htab_elem *l = __htab_map_lookup_elem(map, key);
  
  	if (l) {
  		bpf_lru_node_set_ref(&l->lru_node);
  		return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
  	}
  
  	return NULL;
  }
  
  int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct htab_elem *l;
  	void __percpu *pptr;
  	int ret = -ENOENT;
  	int cpu, off = 0;
  	u32 size;
  
  	/* per_cpu areas are zero-filled and bpf programs can only
  	 * access 'value_size' of them, so copying rounded areas
  	 * will not leak any kernel data
  	 */
  	size = round_up(map->value_size, 8);
  	rcu_read_lock();
  	l = __htab_map_lookup_elem(map, key);
  	if (!l)
  		goto out;
  	if (htab_is_lru(htab))
  		bpf_lru_node_set_ref(&l->lru_node);
  	pptr = htab_elem_get_ptr(l, map->key_size);
  	for_each_possible_cpu(cpu) {
  		bpf_long_memcpy(value + off,
  				per_cpu_ptr(pptr, cpu), size);
  		off += size;
  	}
  	ret = 0;
  out:
  	rcu_read_unlock();
  	return ret;
  }
  
  int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
  			   u64 map_flags)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	int ret;
  
  	rcu_read_lock();
  	if (htab_is_lru(htab))
  		ret = __htab_lru_percpu_map_update_elem(map, key, value,
  							map_flags, true);
  	else
  		ret = __htab_percpu_map_update_elem(map, key, value, map_flags,
  						    true);
  	rcu_read_unlock();
  
  	return ret;
  }
  
  const struct bpf_map_ops htab_percpu_map_ops = {
  	.map_alloc_check = htab_map_alloc_check,
  	.map_alloc = htab_map_alloc,
  	.map_free = htab_map_free,
  	.map_get_next_key = htab_map_get_next_key,
  	.map_lookup_elem = htab_percpu_map_lookup_elem,
  	.map_update_elem = htab_percpu_map_update_elem,
  	.map_delete_elem = htab_map_delete_elem,
  };
  
  const struct bpf_map_ops htab_lru_percpu_map_ops = {
  	.map_alloc_check = htab_map_alloc_check,
  	.map_alloc = htab_map_alloc,
  	.map_free = htab_map_free,
  	.map_get_next_key = htab_map_get_next_key,
  	.map_lookup_elem = htab_lru_percpu_map_lookup_elem,
  	.map_update_elem = htab_lru_percpu_map_update_elem,
  	.map_delete_elem = htab_lru_map_delete_elem,
  };
  
  static int fd_htab_map_alloc_check(union bpf_attr *attr)
  {
  	if (attr->value_size != sizeof(u32))
  		return -EINVAL;
  	return htab_map_alloc_check(attr);
  }
  
  static void fd_htab_map_free(struct bpf_map *map)
  {
  	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
  	struct hlist_nulls_node *n;
  	struct hlist_nulls_head *head;
  	struct htab_elem *l;
  	int i;
  
  	for (i = 0; i < htab->n_buckets; i++) {
  		head = select_bucket(htab, i);
  
  		hlist_nulls_for_each_entry_safe(l, n, head, hash_node) {
  			void *ptr = fd_htab_map_get_ptr(map, l);
  
  			map->ops->map_fd_put_ptr(ptr);
  		}
  	}
  
  	htab_map_free(map);
  }
  
  /* only called from syscall */
  int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value)
  {
  	void **ptr;
  	int ret = 0;
  
  	if (!map->ops->map_fd_sys_lookup_elem)
  		return -ENOTSUPP;
  
  	rcu_read_lock();
  	ptr = htab_map_lookup_elem(map, key);
  	if (ptr)
  		*value = map->ops->map_fd_sys_lookup_elem(READ_ONCE(*ptr));
  	else
  		ret = -ENOENT;
  	rcu_read_unlock();
  
  	return ret;
  }
  
  /* only called from syscall */
  int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,
  				void *key, void *value, u64 map_flags)
  {
  	void *ptr;
  	int ret;
  	u32 ufd = *(u32 *)value;
  
  	ptr = map->ops->map_fd_get_ptr(map, map_file, ufd);
  	if (IS_ERR(ptr))
  		return PTR_ERR(ptr);
  
  	ret = htab_map_update_elem(map, key, &ptr, map_flags);
  	if (ret)
  		map->ops->map_fd_put_ptr(ptr);
  
  	return ret;
  }
  
  static struct bpf_map *htab_of_map_alloc(union bpf_attr *attr)
  {
  	struct bpf_map *map, *inner_map_meta;
  
  	inner_map_meta = bpf_map_meta_alloc(attr->inner_map_fd);
  	if (IS_ERR(inner_map_meta))
  		return inner_map_meta;
  
  	map = htab_map_alloc(attr);
  	if (IS_ERR(map)) {
  		bpf_map_meta_free(inner_map_meta);
  		return map;
  	}
  
  	map->inner_map_meta = inner_map_meta;
  
  	return map;
  }
  
  static void *htab_of_map_lookup_elem(struct bpf_map *map, void *key)
  {
  	struct bpf_map **inner_map  = htab_map_lookup_elem(map, key);
  
  	if (!inner_map)
  		return NULL;
  
  	return READ_ONCE(*inner_map);
  }
  
  static u32 htab_of_map_gen_lookup(struct bpf_map *map,
  				  struct bpf_insn *insn_buf)
  {
  	struct bpf_insn *insn = insn_buf;
  	const int ret = BPF_REG_0;
  
  	*insn++ = BPF_EMIT_CALL((u64 (*)(u64, u64, u64, u64, u64))__htab_map_lookup_elem);
  	*insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 2);
  	*insn++ = BPF_ALU64_IMM(BPF_ADD, ret,
  				offsetof(struct htab_elem, key) +
  				round_up(map->key_size, 8));
  	*insn++ = BPF_LDX_MEM(BPF_DW, ret, ret, 0);
  
  	return insn - insn_buf;
  }
  
  static void htab_of_map_free(struct bpf_map *map)
  {
  	bpf_map_meta_free(map->inner_map_meta);
  	fd_htab_map_free(map);
  }
  
  const struct bpf_map_ops htab_of_maps_map_ops = {
  	.map_alloc_check = fd_htab_map_alloc_check,
  	.map_alloc = htab_of_map_alloc,
  	.map_free = htab_of_map_free,
  	.map_get_next_key = htab_map_get_next_key,
  	.map_lookup_elem = htab_of_map_lookup_elem,
  	.map_delete_elem = htab_map_delete_elem,
  	.map_fd_get_ptr = bpf_map_fd_get_ptr,
  	.map_fd_put_ptr = bpf_map_fd_put_ptr,
  	.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
  	.map_gen_lookup = htab_of_map_gen_lookup,
  };
  