/* 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 <linux/random.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 */
        u32 hashrnd;
};

/* 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;

        htab->hashrnd = get_random_int();
        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, u32 hashrnd)
{
        return jhash(key, key_len, hashrnd);
}

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, htab->hashrnd);

        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;

        BUILD_BUG_ON(!__same_type(&__htab_map_lookup_elem,
                     (void *(*)(struct bpf_map *map, void *key))NULL));
        *insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(__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;

        BUILD_BUG_ON(!__same_type(&__htab_map_lookup_elem,
                     (void *(*)(struct bpf_map *map, void *key))NULL));
        *insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(__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, htab->hashrnd);

        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
                                 */
                                l_new = ERR_PTR(-E2BIG);
                                goto dec_count;
                        }
                l_new = kmalloc_node(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN,
                                     htab->map.numa_node);
                if (!l_new) {
                        l_new = ERR_PTR(-ENOMEM);
                        goto dec_count;
                }
        }

        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);
                                l_new = ERR_PTR(-ENOMEM);
                                goto dec_count;
                        }
                }

                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;
dec_count:
        atomic_dec(&htab->count);
        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, htab->hashrnd);

        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, htab->hashrnd);

        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, htab->hashrnd);

        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, htab->hashrnd);

        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, htab->hashrnd);
        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, htab->hashrnd);
        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;

        BUILD_BUG_ON(!__same_type(&__htab_map_lookup_elem,
                     (void *(*)(struct bpf_map *map, void *key))NULL));
        *insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(__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,
};