// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
 * Copyright (c) 2016 Facebook
 */
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/jhash.h>
#include <linux/filter.h>
#include <linux/rculist_nulls.h>
#include <linux/random.h>
#include <uapi/linux/btf.h>
#include <linux/rcupdate_trace.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_ACCESS_MASK | BPF_F_ZERO_SEED)

#define BATCH_OPS(_name)                        \
        .map_lookup_batch =                     \
        _name##_map_lookup_batch,               \
        .map_lookup_and_delete_batch =          \
        _name##_map_lookup_and_delete_batch,    \
        .map_update_batch =                     \
        generic_map_update_batch,               \
        .map_delete_batch =                     \
        generic_map_delete_batch

/*
 * The bucket lock has two protection scopes:
 *
 * 1) Serializing concurrent operations from BPF programs on different
 *    CPUs
 *
 * 2) Serializing concurrent operations from BPF programs and sys_bpf()
 *
 * BPF programs can execute in any context including perf, kprobes and
 * tracing. As there are almost no limits where perf, kprobes and tracing
 * can be invoked from the lock operations need to be protected against
 * deadlocks. Deadlocks can be caused by recursion and by an invocation in
 * the lock held section when functions which acquire this lock are invoked
 * from sys_bpf(). BPF recursion is prevented by incrementing the per CPU
 * variable bpf_prog_active, which prevents BPF programs attached to perf
 * events, kprobes and tracing to be invoked before the prior invocation
 * from one of these contexts completed. sys_bpf() uses the same mechanism
 * by pinning the task to the current CPU and incrementing the recursion
 * protection across the map operation.
 *
 * This has subtle implications on PREEMPT_RT. PREEMPT_RT forbids certain
 * operations like memory allocations (even with GFP_ATOMIC) from atomic
 * contexts. This is required because even with GFP_ATOMIC the memory
 * allocator calls into code paths which acquire locks with long held lock
 * sections. To ensure the deterministic behaviour these locks are regular
 * spinlocks, which are converted to 'sleepable' spinlocks on RT. The only
 * true atomic contexts on an RT kernel are the low level hardware
 * handling, scheduling, low level interrupt handling, NMIs etc. None of
 * these contexts should ever do memory allocations.
 *
 * As regular device interrupt handlers and soft interrupts are forced into
 * thread context, the existing code which does
 *   spin_lock*(); alloc(GPF_ATOMIC); spin_unlock*();
 * just works.
 *
 * In theory the BPF locks could be converted to regular spinlocks as well,
 * but the bucket locks and percpu_freelist locks can be taken from
 * arbitrary contexts (perf, kprobes, tracepoints) which are required to be
 * atomic contexts even on RT. These mechanisms require preallocated maps,
 * so there is no need to invoke memory allocations within the lock held
 * sections.
 *
 * BPF maps which need dynamic allocation are only used from (forced)
 * thread context on RT and can therefore use regular spinlocks which in
 * turn allows to invoke memory allocations from the lock held section.
 *
 * On a non RT kernel this distinction is neither possible nor required.
 * spinlock maps to raw_spinlock and the extra code is optimized out by the
 * compiler.
 */
struct bucket {
        struct hlist_nulls_head head;
        union {
                raw_spinlock_t raw_lock;
                spinlock_t     lock;
        };
};

#define HASHTAB_MAP_LOCK_COUNT 8
#define HASHTAB_MAP_LOCK_MASK (HASHTAB_MAP_LOCK_COUNT - 1)

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;
        struct lock_class_key lockdep_key;
        int __percpu *map_locked[HASHTAB_MAP_LOCK_COUNT];
};

/* 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;
                                struct htab_elem *batch_flink;
                        };
                };
        };
        union {
                struct rcu_head rcu;
                struct bpf_lru_node lru_node;
        };
        u32 hash;
        char key[] __aligned(8);
};

static inline bool htab_is_prealloc(const struct bpf_htab *htab)
{
        return !(htab->map.map_flags & BPF_F_NO_PREALLOC);
}

static inline bool htab_use_raw_lock(const struct bpf_htab *htab)
{
        return (!IS_ENABLED(CONFIG_PREEMPT_RT) || htab_is_prealloc(htab));
}

static void htab_init_buckets(struct bpf_htab *htab)
{
        unsigned i;

        for (i = 0; i < htab->n_buckets; i++) {
                INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
                if (htab_use_raw_lock(htab)) {
                        raw_spin_lock_init(&htab->buckets[i].raw_lock);
                        lockdep_set_class(&htab->buckets[i].raw_lock,
                                          &htab->lockdep_key);
                } else {
                        spin_lock_init(&htab->buckets[i].lock);
                        lockdep_set_class(&htab->buckets[i].lock,
                                          &htab->lockdep_key);
                }
                cond_resched();
        }
}

static inline int htab_lock_bucket(const struct bpf_htab *htab,
                                   struct bucket *b, u32 hash,
                                   unsigned long *pflags)
{
        unsigned long flags;

        hash = hash & HASHTAB_MAP_LOCK_MASK;

        migrate_disable();
        if (unlikely(__this_cpu_inc_return(*(htab->map_locked[hash])) != 1)) {
                __this_cpu_dec(*(htab->map_locked[hash]));
                migrate_enable();
                return -EBUSY;
        }

        if (htab_use_raw_lock(htab))
                raw_spin_lock_irqsave(&b->raw_lock, flags);
        else
                spin_lock_irqsave(&b->lock, flags);
        *pflags = flags;

        return 0;
}

static inline void htab_unlock_bucket(const struct bpf_htab *htab,
                                      struct bucket *b, u32 hash,
                                      unsigned long flags)
{
        hash = hash & HASHTAB_MAP_LOCK_MASK;
        if (htab_use_raw_lock(htab))
                raw_spin_unlock_irqrestore(&b->raw_lock, flags);
        else
                spin_unlock_irqrestore(&b->lock, flags);
        __this_cpu_dec(*(htab->map_locked[hash]));
        migrate_enable();
}

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 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 * (u64)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);
}

/* The LRU list has a lock (lru_lock). Each htab bucket has a lock
 * (bucket_lock). If both locks need to be acquired together, the lock
 * order is always lru_lock -> bucket_lock and this only happens in
 * bpf_lru_list.c logic. For example, certain code path of
 * bpf_lru_pop_free(), which is called by function prealloc_lru_pop(),
 * will acquire lru_lock first followed by acquiring bucket_lock.
 *
 * In hashtab.c, to avoid deadlock, lock acquisition of
 * bucket_lock followed by lru_lock is not allowed. In such cases,
 * bucket_lock needs to be released first before acquiring lru_lock.
 */
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((u64)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 = bpf_map_alloc_percpu(&htab->map, 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 = bpf_map_alloc_percpu(&htab->map, 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);
        bool zero_seed = (attr->map_flags & BPF_F_ZERO_SEED);
        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 && !bpf_capable())
                /* LRU implementation is much complicated than other
                 * maps.  Hence, limit to CAP_BPF.
                 */
                return -EPERM;

        if (zero_seed && !capable(CAP_SYS_ADMIN))
                /* Guard against local DoS, and discourage production use. */
                return -EPERM;

        if (attr->map_flags & ~HTAB_CREATE_FLAG_MASK ||
            !bpf_map_flags_access_ok(attr->map_flags))
                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 ((u64)attr->key_size + attr->value_size >= KMALLOC_MAX_SIZE -
           sizeof(struct htab_elem))
                /* if key_size + 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;

        htab = kzalloc(sizeof(*htab), GFP_USER | __GFP_ACCOUNT);
        if (!htab)
                return ERR_PTR(-ENOMEM);

        lockdep_register_key(&htab->lockdep_key);

        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;

        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 < HASHTAB_MAP_LOCK_COUNT; i++) {
                htab->map_locked[i] = bpf_map_alloc_percpu(&htab->map,
                                                           sizeof(int),
                                                           sizeof(int),
                                                           GFP_USER);
                if (!htab->map_locked[i])
                        goto free_map_locked;
        }

        if (htab->map.map_flags & BPF_F_ZERO_SEED)
                htab->hashrnd = 0;
        else
                htab->hashrnd = get_random_int();

        htab_init_buckets(htab);

        if (prealloc) {
                err = prealloc_init(htab);
                if (err)
                        goto free_map_locked;

                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_map_locked:
        for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++)
                free_percpu(htab->map_locked[i]);
        bpf_map_area_free(htab->buckets);
free_htab:
        lockdep_unregister_key(&htab->lockdep_key);
        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;

        WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() &&
                     !rcu_read_lock_bh_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 int 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 __always_inline void *__htab_lru_map_lookup_elem(struct bpf_map *map,
                                                        void *key, const bool mark)
{
        struct htab_elem *l = __htab_map_lookup_elem(map, key);

        if (l) {
                if (mark)
                        bpf_lru_node_set_ref(&l->lru_node);
                return l->key + round_up(map->key_size, 8);
        }

        return NULL;
}

static void *htab_lru_map_lookup_elem(struct bpf_map *map, void *key)
{
        return __htab_lru_map_lookup_elem(map, key, true);
}

static void *htab_lru_map_lookup_elem_sys(struct bpf_map *map, void *key)
{
        return __htab_lru_map_lookup_elem(map, key, false);
}

static int 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;
        int ret;

        tgt_l = container_of(node, struct htab_elem, lru_node);
        b = __select_bucket(htab, tgt_l->hash);
        head = &b->head;

        ret = htab_lock_bucket(htab, b, tgt_l->hash, &flags);
        if (ret)
                return false;

        hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
                if (l == tgt_l) {
                        hlist_nulls_del_rcu(&l->hash_node);
                        break;
                }

        htab_unlock_bucket(htab, b, tgt_l->hash, 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;

        htab_elem_free(htab, l);
}

static void htab_put_fd_value(struct bpf_htab *htab, struct htab_elem *l)
{
        struct bpf_map *map = &htab->map;
        void *ptr;

        if (map->ops->map_fd_put_ptr) {
                ptr = fd_htab_map_get_ptr(map, l);
                map->ops->map_fd_put_ptr(ptr);
        }
}

static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
{
        htab_put_fd_value(htab, l);

        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 void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
                            void *value, bool onallcpus)
{
        /* When using prealloc and not setting the initial value on all cpus,
         * zero-fill element values for other cpus (just as what happens when
         * not using prealloc). Otherwise, bpf program has no way to ensure
         * known initial values for cpus other than current one
         * (onallcpus=false always when coming from bpf prog).
         */
        if (htab_is_prealloc(htab) && !onallcpus) {
                u32 size = round_up(htab->map.value_size, 8);
                int current_cpu = raw_smp_processor_id();
                int cpu;

                for_each_possible_cpu(cpu) {
                        if (cpu == current_cpu)
                                bpf_long_memcpy(per_cpu_ptr(pptr, cpu), value,
                                                size);
                        else
                                memset(per_cpu_ptr(pptr, cpu), 0, size);
                }
        } else {
                pcpu_copy_value(htab, pptr, value, onallcpus);
        }
}

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 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->map.value_size;
        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;
                        htab_put_fd_value(htab, old_elem);
                        *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 = bpf_map_kmalloc_node(&htab->map, htab->elem_size,
                                             GFP_ATOMIC | __GFP_NOWARN,
                                             htab->map.numa_node);
                if (!l_new) {
                        l_new = ERR_PTR(-ENOMEM);
                        goto dec_count;
                }
                check_and_init_map_lock(&htab->map,
                                        l_new->key + round_up(key_size, 8));
        }

        memcpy(l_new->key, key, key_size);
        if (percpu) {
                size = round_up(size, 8);
                if (prealloc) {
                        pptr = htab_elem_get_ptr(l_new, key_size);
                } else {
                        /* alloc_percpu zero-fills */
                        pptr = bpf_map_alloc_percpu(&htab->map, size, 8,
                                                    GFP_ATOMIC | __GFP_NOWARN);
                        if (!pptr) {
                                kfree(l_new);
                                l_new = ERR_PTR(-ENOMEM);
                                goto dec_count;
                        }
                }

                pcpu_init_value(htab, pptr, value, onallcpus);

                if (!prealloc)
                        htab_elem_set_ptr(l_new, key_size, pptr);
        } else if (fd_htab_map_needs_adjust(htab)) {
                size = round_up(size, 8);
                memcpy(l_new->key + round_up(key_size, 8), value, size);
        } else {
                copy_map_value(&htab->map,
                               l_new->key + round_up(key_size, 8),
                               value);
        }

        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_F_LOCK) == BPF_NOEXIST)
                /* elem already exists */
                return -EEXIST;

        if (!l_old && (map_flags & ~BPF_F_LOCK) == 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_F_LOCK) > BPF_EXIST))
                /* unknown flags */
                return -EINVAL;

        WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() &&
                     !rcu_read_lock_bh_held());

        key_size = map->key_size;

        hash = htab_map_hash(key, key_size, htab->hashrnd);

        b = __select_bucket(htab, hash);

        head = &b->head;

        if (unlikely(map_flags & BPF_F_LOCK)) {
                if (unlikely(!map_value_has_spin_lock(map)))
                        return -EINVAL;
                /* find an element without taking the bucket lock */
                l_old = lookup_nulls_elem_raw(head, hash, key, key_size,
                                              htab->n_buckets);
                ret = check_flags(htab, l_old, map_flags);
                if (ret)
                        return ret;
                if (l_old) {
                        /* grab the element lock and update value in place */
                        copy_map_value_locked(map,
                                              l_old->key + round_up(key_size, 8),
                                              value, false);
                        return 0;
                }
                /* fall through, grab the bucket lock and lookup again.
                 * 99.9% chance that the element won't be found,
                 * but second lookup under lock has to be done.
                 */
        }

        ret = htab_lock_bucket(htab, b, hash, &flags);
        if (ret)
                return ret;

        l_old = lookup_elem_raw(head, hash, key, key_size);

        ret = check_flags(htab, l_old, map_flags);
        if (ret)
                goto err;

        if (unlikely(l_old && (map_flags & BPF_F_LOCK))) {
                /* first lookup without the bucket lock didn't find the element,
                 * but second lookup with the bucket lock found it.
                 * This case is highly unlikely, but has to be dealt with:
                 * grab the element lock in addition to the bucket lock
                 * and update element in place
                 */
                copy_map_value_locked(map,
                                      l_old->key + round_up(key_size, 8),
                                      value, false);
                ret = 0;
                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:
        htab_unlock_bucket(htab, b, hash, 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() && !rcu_read_lock_trace_held() &&
                     !rcu_read_lock_bh_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);

        ret = htab_lock_bucket(htab, b, hash, &flags);
        if (ret)
                return ret;

        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:
        htab_unlock_bucket(htab, b, hash, 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() && !rcu_read_lock_trace_held() &&
                     !rcu_read_lock_bh_held());

        key_size = map->key_size;

        hash = htab_map_hash(key, key_size, htab->hashrnd);

        b = __select_bucket(htab, hash);
        head = &b->head;

        ret = htab_lock_bucket(htab, b, hash, &flags);
        if (ret)
                return ret;

        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:
        htab_unlock_bucket(htab, b, hash, 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() && !rcu_read_lock_trace_held() &&
                     !rcu_read_lock_bh_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;
        }

        ret = htab_lock_bucket(htab, b, hash, &flags);
        if (ret)
                return ret;

        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_init_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:
        htab_unlock_bucket(htab, b, hash, 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;

        WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() &&
                     !rcu_read_lock_bh_held());

        key_size = map->key_size;

        hash = htab_map_hash(key, key_size, htab->hashrnd);
        b = __select_bucket(htab, hash);
        head = &b->head;

        ret = htab_lock_bucket(htab, b, hash, &flags);
        if (ret)
                return ret;

        l = lookup_elem_raw(head, hash, key, key_size);

        if (l) {
                hlist_nulls_del_rcu(&l->hash_node);
                free_htab_elem(htab, l);
        } else {
                ret = -ENOENT;
        }

        htab_unlock_bucket(htab, b, hash, 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;

        WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() &&
                     !rcu_read_lock_bh_held());

        key_size = map->key_size;

        hash = htab_map_hash(key, key_size, htab->hashrnd);
        b = __select_bucket(htab, hash);
        head = &b->head;

        ret = htab_lock_bucket(htab, b, hash, &flags);
        if (ret)
                return ret;

        l = lookup_elem_raw(head, hash, key, key_size);

        if (l)
                hlist_nulls_del_rcu(&l->hash_node);
        else
                ret = -ENOENT;

        htab_unlock_bucket(htab, b, hash, 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);
        int i;

        /* bpf_free_used_maps() or close(map_fd) will trigger this map_free callback.
         * bpf_free_used_maps() is called after bpf prog is no longer executing.
         * There is no need to synchronize_rcu() here to protect map elements.
         */

        /* 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);
        for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++)
                free_percpu(htab->map_locked[i]);
        lockdep_unregister_key(&htab->lockdep_key);
        kfree(htab);
}

static void htab_map_seq_show_elem(struct bpf_map *map, void *key,
                                   struct seq_file *m)
{
        void *value;

        rcu_read_lock();

        value = htab_map_lookup_elem(map, key);
        if (!value) {
                rcu_read_unlock();
                return;
        }

        btf_type_seq_show(map->btf, map->btf_key_type_id, key, m);
        seq_puts(m, ": ");
        btf_type_seq_show(map->btf, map->btf_value_type_id, value, m);
        seq_puts(m, "\n");

        rcu_read_unlock();
}

static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
                                             void *value, bool is_lru_map,
                                             bool is_percpu, u64 flags)
{
        struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
        struct hlist_nulls_head *head;
        unsigned long bflags;
        struct htab_elem *l;
        u32 hash, key_size;
        struct bucket *b;
        int ret;

        key_size = map->key_size;

        hash = htab_map_hash(key, key_size, htab->hashrnd);
        b = __select_bucket(htab, hash);
        head = &b->head;

        ret = htab_lock_bucket(htab, b, hash, &bflags);
        if (ret)
                return ret;

        l = lookup_elem_raw(head, hash, key, key_size);
        if (!l) {
                ret = -ENOENT;
        } else {
                if (is_percpu) {
                        u32 roundup_value_size = round_up(map->value_size, 8);
                        void __percpu *pptr;
                        int off = 0, cpu;

                        pptr = htab_elem_get_ptr(l, key_size);
                        for_each_possible_cpu(cpu) {
                                bpf_long_memcpy(value + off,
                                                per_cpu_ptr(pptr, cpu),
                                                roundup_value_size);
                                off += roundup_value_size;
                        }
                } else {
                        u32 roundup_key_size = round_up(map->key_size, 8);

                        if (flags & BPF_F_LOCK)
                                copy_map_value_locked(map, value, l->key +
                                                      roundup_key_size,
                                                      true);
                        else
                                copy_map_value(map, value, l->key +
                                               roundup_key_size);
                        check_and_init_map_lock(map, value);
                }

                hlist_nulls_del_rcu(&l->hash_node);
                if (!is_lru_map)
                        free_htab_elem(htab, l);
        }

        htab_unlock_bucket(htab, b, hash, bflags);

        if (is_lru_map && l)
                bpf_lru_push_free(&htab->lru, &l->lru_node);

        return ret;
}

static int htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
                                           void *value, u64 flags)
{
        return __htab_map_lookup_and_delete_elem(map, key, value, false, false,
                                                 flags);
}

static int htab_percpu_map_lookup_and_delete_elem(struct bpf_map *map,
                                                  void *key, void *value,
                                                  u64 flags)
{
        return __htab_map_lookup_and_delete_elem(map, key, value, false, true,
                                                 flags);
}

static int htab_lru_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
                                               void *value, u64 flags)
{
        return __htab_map_lookup_and_delete_elem(map, key, value, true, false,
                                                 flags);
}

static int htab_lru_percpu_map_lookup_and_delete_elem(struct bpf_map *map,
                                                      void *key, void *value,
                                                      u64 flags)
{
        return __htab_map_lookup_and_delete_elem(map, key, value, true, true,
                                                 flags);
}

static int
__htab_map_lookup_and_delete_batch(struct bpf_map *map,
                                   const union bpf_attr *attr,
                                   union bpf_attr __user *uattr,
                                   bool do_delete, bool is_lru_map,
                                   bool is_percpu)
{
        struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
        u32 bucket_cnt, total, key_size, value_size, roundup_key_size;
        void *keys = NULL, *values = NULL, *value, *dst_key, *dst_val;
        void __user *uvalues = u64_to_user_ptr(attr->batch.values);
        void __user *ukeys = u64_to_user_ptr(attr->batch.keys);
        void __user *ubatch = u64_to_user_ptr(attr->batch.in_batch);
        u32 batch, max_count, size, bucket_size;
        struct htab_elem *node_to_free = NULL;
        u64 elem_map_flags, map_flags;
        struct hlist_nulls_head *head;
        struct hlist_nulls_node *n;
        unsigned long flags = 0;
        bool locked = false;
        struct htab_elem *l;
        struct bucket *b;
        int ret = 0;

        elem_map_flags = attr->batch.elem_flags;
        if ((elem_map_flags & ~BPF_F_LOCK) ||
            ((elem_map_flags & BPF_F_LOCK) && !map_value_has_spin_lock(map)))
                return -EINVAL;

        map_flags = attr->batch.flags;
        if (map_flags)
                return -EINVAL;

        max_count = attr->batch.count;
        if (!max_count)
                return 0;

        if (put_user(0, &uattr->batch.count))
                return -EFAULT;

        batch = 0;
        if (ubatch && copy_from_user(&batch, ubatch, sizeof(batch)))
                return -EFAULT;

        if (batch >= htab->n_buckets)
                return -ENOENT;

        key_size = htab->map.key_size;
        roundup_key_size = round_up(htab->map.key_size, 8);
        value_size = htab->map.value_size;
        size = round_up(value_size, 8);
        if (is_percpu)
                value_size = size * num_possible_cpus();
        total = 0;
        /* while experimenting with hash tables with sizes ranging from 10 to
         * 1000, it was observed that a bucket can have upto 5 entries.
         */
        bucket_size = 5;

alloc:
        /* We cannot do copy_from_user or copy_to_user inside
         * the rcu_read_lock. Allocate enough space here.
         */
        keys = kvmalloc_array(key_size, bucket_size, GFP_USER | __GFP_NOWARN);
        values = kvmalloc_array(value_size, bucket_size, GFP_USER | __GFP_NOWARN);
        if (!keys || !values) {
                ret = -ENOMEM;
                goto after_loop;
        }

again:
        bpf_disable_instrumentation();
        rcu_read_lock();
again_nocopy:
        dst_key = keys;
        dst_val = values;
        b = &htab->buckets[batch];
        head = &b->head;
        /* do not grab the lock unless need it (bucket_cnt > 0). */
        if (locked) {
                ret = htab_lock_bucket(htab, b, batch, &flags);
                if (ret)
                        goto next_batch;
        }

        bucket_cnt = 0;
        hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
                bucket_cnt++;

        if (bucket_cnt && !locked) {
                locked = true;
                goto again_nocopy;
        }

        if (bucket_cnt > (max_count - total)) {
                if (total == 0)
                        ret = -ENOSPC;
                /* Note that since bucket_cnt > 0 here, it is implicit
                 * that the locked was grabbed, so release it.
                 */
                htab_unlock_bucket(htab, b, batch, flags);
                rcu_read_unlock();
                bpf_enable_instrumentation();
                goto after_loop;
        }

        if (bucket_cnt > bucket_size) {
                bucket_size = bucket_cnt;
                /* Note that since bucket_cnt > 0 here, it is implicit
                 * that the locked was grabbed, so release it.
                 */
                htab_unlock_bucket(htab, b, batch, flags);
                rcu_read_unlock();
                bpf_enable_instrumentation();
                kvfree(keys);
                kvfree(values);
                goto alloc;
        }

        /* Next block is only safe to run if you have grabbed the lock */
        if (!locked)
                goto next_batch;

        hlist_nulls_for_each_entry_safe(l, n, head, hash_node) {
                memcpy(dst_key, l->key, key_size);

                if (is_percpu) {
                        int off = 0, cpu;
                        void __percpu *pptr;

                        pptr = htab_elem_get_ptr(l, map->key_size);
                        for_each_possible_cpu(cpu) {
                                bpf_long_memcpy(dst_val + off,
                                                per_cpu_ptr(pptr, cpu), size);
                                off += size;
                        }
                } else {
                        value = l->key + roundup_key_size;
                        if (elem_map_flags & BPF_F_LOCK)
                                copy_map_value_locked(map, dst_val, value,
                                                      true);
                        else
                                copy_map_value(map, dst_val, value);
                        check_and_init_map_lock(map, dst_val);
                }
                if (do_delete) {
                        hlist_nulls_del_rcu(&l->hash_node);

                        /* bpf_lru_push_free() will acquire lru_lock, which
                         * may cause deadlock. See comments in function
                         * prealloc_lru_pop(). Let us do bpf_lru_push_free()
                         * after releasing the bucket lock.
                         */
                        if (is_lru_map) {
                                l->batch_flink = node_to_free;
                                node_to_free = l;
                        } else {
                                free_htab_elem(htab, l);
                        }
                }
                dst_key += key_size;
                dst_val += value_size;
        }

        htab_unlock_bucket(htab, b, batch, flags);
        locked = false;

        while (node_to_free) {
                l = node_to_free;
                node_to_free = node_to_free->batch_flink;
                bpf_lru_push_free(&htab->lru, &l->lru_node);
        }

next_batch:
        /* If we are not copying data, we can go to next bucket and avoid
         * unlocking the rcu.
         */
        if (!bucket_cnt && (batch + 1 < htab->n_buckets)) {
                batch++;
                goto again_nocopy;
        }

        rcu_read_unlock();
        bpf_enable_instrumentation();
        if (bucket_cnt && (copy_to_user(ukeys + total * key_size, keys,
            key_size * bucket_cnt) ||
            copy_to_user(uvalues + total * value_size, values,
            value_size * bucket_cnt))) {
                ret = -EFAULT;
                goto after_loop;
        }

        total += bucket_cnt;
        batch++;
        if (batch >= htab->n_buckets) {
                ret = -ENOENT;
                goto after_loop;
        }
        goto again;

after_loop:
        if (ret == -EFAULT)
                goto out;

        /* copy # of entries and next batch */
        ubatch = u64_to_user_ptr(attr->batch.out_batch);
        if (copy_to_user(ubatch, &batch, sizeof(batch)) ||
            put_user(total, &uattr->batch.count))
                ret = -EFAULT;

out:
        kvfree(keys);
        kvfree(values);
        return ret;
}

static int
htab_percpu_map_lookup_batch(struct bpf_map *map, const union bpf_attr *attr,
                             union bpf_attr __user *uattr)
{
        return __htab_map_lookup_and_delete_batch(map, attr, uattr, false,
                                                  false, true);
}

static int
htab_percpu_map_lookup_and_delete_batch(struct bpf_map *map,
                                        const union bpf_attr *attr,
                                        union bpf_attr __user *uattr)
{
        return __htab_map_lookup_and_delete_batch(map, attr, uattr, true,
                                                  false, true);
}

static int
htab_map_lookup_batch(struct bpf_map *map, const union bpf_attr *attr,
                      union bpf_attr __user *uattr)
{
        return __htab_map_lookup_and_delete_batch(map, attr, uattr, false,
                                                  false, false);
}

static int
htab_map_lookup_and_delete_batch(struct bpf_map *map,
                                 const union bpf_attr *attr,
                                 union bpf_attr __user *uattr)
{
        return __htab_map_lookup_and_delete_batch(map, attr, uattr, true,
                                                  false, false);
}

static int
htab_lru_percpu_map_lookup_batch(struct bpf_map *map,
                                 const union bpf_attr *attr,
                                 union bpf_attr __user *uattr)
{
        return __htab_map_lookup_and_delete_batch(map, attr, uattr, false,
                                                  true, true);
}

static int
htab_lru_percpu_map_lookup_and_delete_batch(struct bpf_map *map,
                                            const union bpf_attr *attr,
                                            union bpf_attr __user *uattr)
{
        return __htab_map_lookup_and_delete_batch(map, attr, uattr, true,
                                                  true, true);
}

static int
htab_lru_map_lookup_batch(struct bpf_map *map, const union bpf_attr *attr,
                          union bpf_attr __user *uattr)
{
        return __htab_map_lookup_and_delete_batch(map, attr, uattr, false,
                                                  true, false);
}

static int
htab_lru_map_lookup_and_delete_batch(struct bpf_map *map,
                                     const union bpf_attr *attr,
                                     union bpf_attr __user *uattr)
{
        return __htab_map_lookup_and_delete_batch(map, attr, uattr, true,
                                                  true, false);
}

struct bpf_iter_seq_hash_map_info {
        struct bpf_map *map;
        struct bpf_htab *htab;
        void *percpu_value_buf; // non-zero means percpu hash
        u32 bucket_id;
        u32 skip_elems;
};

static struct htab_elem *
bpf_hash_map_seq_find_next(struct bpf_iter_seq_hash_map_info *info,
                           struct htab_elem *prev_elem)
{
        const struct bpf_htab *htab = info->htab;
        u32 skip_elems = info->skip_elems;
        u32 bucket_id = info->bucket_id;
        struct hlist_nulls_head *head;
        struct hlist_nulls_node *n;
        struct htab_elem *elem;
        struct bucket *b;
        u32 i, count;

        if (bucket_id >= htab->n_buckets)
                return NULL;

        /* try to find next elem in the same bucket */
        if (prev_elem) {
                /* no update/deletion on this bucket, prev_elem should be still valid
                 * and we won't skip elements.
                 */
                n = rcu_dereference_raw(hlist_nulls_next_rcu(&prev_elem->hash_node));
                elem = hlist_nulls_entry_safe(n, struct htab_elem, hash_node);
                if (elem)
                        return elem;

                /* not found, unlock and go to the next bucket */
                b = &htab->buckets[bucket_id++];
                rcu_read_unlock();
                skip_elems = 0;
        }

        for (i = bucket_id; i < htab->n_buckets; i++) {
                b = &htab->buckets[i];
                rcu_read_lock();

                count = 0;
                head = &b->head;
                hlist_nulls_for_each_entry_rcu(elem, n, head, hash_node) {
                        if (count >= skip_elems) {
                                info->bucket_id = i;
                                info->skip_elems = count;
                                return elem;
                        }
                        count++;
                }

                rcu_read_unlock();
                skip_elems = 0;
        }

        info->bucket_id = i;
        info->skip_elems = 0;
        return NULL;
}

static void *bpf_hash_map_seq_start(struct seq_file *seq, loff_t *pos)
{
        struct bpf_iter_seq_hash_map_info *info = seq->private;
        struct htab_elem *elem;

        elem = bpf_hash_map_seq_find_next(info, NULL);
        if (!elem)
                return NULL;

        if (*pos == 0)
                ++*pos;
        return elem;
}

static void *bpf_hash_map_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct bpf_iter_seq_hash_map_info *info = seq->private;

        ++*pos;
        ++info->skip_elems;
        return bpf_hash_map_seq_find_next(info, v);
}

static int __bpf_hash_map_seq_show(struct seq_file *seq, struct htab_elem *elem)
{
        struct bpf_iter_seq_hash_map_info *info = seq->private;
        u32 roundup_key_size, roundup_value_size;
        struct bpf_iter__bpf_map_elem ctx = {};
        struct bpf_map *map = info->map;
        struct bpf_iter_meta meta;
        int ret = 0, off = 0, cpu;
        struct bpf_prog *prog;
        void __percpu *pptr;

        meta.seq = seq;
        prog = bpf_iter_get_info(&meta, elem == NULL);
        if (prog) {
                ctx.meta = &meta;
                ctx.map = info->map;
                if (elem) {
                        roundup_key_size = round_up(map->key_size, 8);
                        ctx.key = elem->key;
                        if (!info->percpu_value_buf) {
                                ctx.value = elem->key + roundup_key_size;
                        } else {
                                roundup_value_size = round_up(map->value_size, 8);
                                pptr = htab_elem_get_ptr(elem, map->key_size);
                                for_each_possible_cpu(cpu) {
                                        bpf_long_memcpy(info->percpu_value_buf + off,
                                                        per_cpu_ptr(pptr, cpu),
                                                        roundup_value_size);
                                        off += roundup_value_size;
                                }
                                ctx.value = info->percpu_value_buf;
                        }
                }
                ret = bpf_iter_run_prog(prog, &ctx);
        }

        return ret;
}

static int bpf_hash_map_seq_show(struct seq_file *seq, void *v)
{
        return __bpf_hash_map_seq_show(seq, v);
}

static void bpf_hash_map_seq_stop(struct seq_file *seq, void *v)
{
        if (!v)
                (void)__bpf_hash_map_seq_show(seq, NULL);
        else
                rcu_read_unlock();
}

static int bpf_iter_init_hash_map(void *priv_data,
                                  struct bpf_iter_aux_info *aux)
{
        struct bpf_iter_seq_hash_map_info *seq_info = priv_data;
        struct bpf_map *map = aux->map;
        void *value_buf;
        u32 buf_size;

        if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
            map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) {
                buf_size = round_up(map->value_size, 8) * num_possible_cpus();
                value_buf = kmalloc(buf_size, GFP_USER | __GFP_NOWARN);
                if (!value_buf)
                        return -ENOMEM;

                seq_info->percpu_value_buf = value_buf;
        }

        seq_info->map = map;
        seq_info->htab = container_of(map, struct bpf_htab, map);
        return 0;
}

static void bpf_iter_fini_hash_map(void *priv_data)
{
        struct bpf_iter_seq_hash_map_info *seq_info = priv_data;

        kfree(seq_info->percpu_value_buf);
}

static const struct seq_operations bpf_hash_map_seq_ops = {
        .start  = bpf_hash_map_seq_start,
        .next   = bpf_hash_map_seq_next,
        .stop   = bpf_hash_map_seq_stop,
        .show   = bpf_hash_map_seq_show,
};

static const struct bpf_iter_seq_info iter_seq_info = {
        .seq_ops                = &bpf_hash_map_seq_ops,
        .init_seq_private       = bpf_iter_init_hash_map,
        .fini_seq_private       = bpf_iter_fini_hash_map,
        .seq_priv_size          = sizeof(struct bpf_iter_seq_hash_map_info),
};

static int bpf_for_each_hash_elem(struct bpf_map *map, void *callback_fn,
                                  void *callback_ctx, u64 flags)
{
        struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
        struct hlist_nulls_head *head;
        struct hlist_nulls_node *n;
        struct htab_elem *elem;
        u32 roundup_key_size;
        int i, num_elems = 0;
        void __percpu *pptr;
        struct bucket *b;
        void *key, *val;
        bool is_percpu;
        u64 ret = 0;

        if (flags != 0)
                return -EINVAL;

        is_percpu = htab_is_percpu(htab);

        roundup_key_size = round_up(map->key_size, 8);
        /* disable migration so percpu value prepared here will be the
         * same as the one seen by the bpf program with bpf_map_lookup_elem().
         */
        if (is_percpu)
                migrate_disable();
        for (i = 0; i < htab->n_buckets; i++) {
                b = &htab->buckets[i];

                rcu_read_lock();
                head = &b->head;
                hlist_nulls_for_each_entry_rcu(elem, n, head, hash_node) {
                        key = elem->key;
                        if (is_percpu) {
                                /* current cpu value for percpu map */
                                pptr = htab_elem_get_ptr(elem, map->key_size);
                                val = this_cpu_ptr(pptr);
                        } else {
                                val = elem->key + roundup_key_size;
                        }
                        num_elems++;
                        ret = BPF_CAST_CALL(callback_fn)((u64)(long)map,
                                        (u64)(long)key, (u64)(long)val,
                                        (u64)(long)callback_ctx, 0);
                        /* return value: 0 - continue, 1 - stop and return */
                        if (ret) {
                                rcu_read_unlock();
                                goto out;
                        }
                }
                rcu_read_unlock();
        }
out:
        if (is_percpu)
                migrate_enable();
        return num_elems;
}

static int htab_map_btf_id;
const struct bpf_map_ops htab_map_ops = {
        .map_meta_equal = bpf_map_meta_equal,
        .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_lookup_and_delete_elem = htab_map_lookup_and_delete_elem,
        .map_update_elem = htab_map_update_elem,
        .map_delete_elem = htab_map_delete_elem,
        .map_gen_lookup = htab_map_gen_lookup,
        .map_seq_show_elem = htab_map_seq_show_elem,
        .map_set_for_each_callback_args = map_set_for_each_callback_args,
        .map_for_each_callback = bpf_for_each_hash_elem,
        BATCH_OPS(htab),
        .map_btf_name = "bpf_htab",
        .map_btf_id = &htab_map_btf_id,
        .iter_seq_info = &iter_seq_info,
};

static int htab_lru_map_btf_id;
const struct bpf_map_ops htab_lru_map_ops = {
        .map_meta_equal = bpf_map_meta_equal,
        .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_lookup_and_delete_elem = htab_lru_map_lookup_and_delete_elem,
        .map_lookup_elem_sys_only = htab_lru_map_lookup_elem_sys,
        .map_update_elem = htab_lru_map_update_elem,
        .map_delete_elem = htab_lru_map_delete_elem,
        .map_gen_lookup = htab_lru_map_gen_lookup,
        .map_seq_show_elem = htab_map_seq_show_elem,
        .map_set_for_each_callback_args = map_set_for_each_callback_args,
        .map_for_each_callback = bpf_for_each_hash_elem,
        BATCH_OPS(htab_lru),
        .map_btf_name = "bpf_htab",
        .map_btf_id = &htab_lru_map_btf_id,
        .iter_seq_info = &iter_seq_info,
};

/* 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 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;
        /* We do not mark LRU map element here in order to not mess up
         * eviction heuristics when user space does a map walk.
         */
        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;
}

static void htab_percpu_map_seq_show_elem(struct bpf_map *map, void *key,
                                          struct seq_file *m)
{
        struct htab_elem *l;
        void __percpu *pptr;
        int cpu;

        rcu_read_lock();

        l = __htab_map_lookup_elem(map, key);
        if (!l) {
                rcu_read_unlock();
                return;
        }

        btf_type_seq_show(map->btf, map->btf_key_type_id, key, m);
        seq_puts(m, ": {\n");
        pptr = htab_elem_get_ptr(l, map->key_size);
        for_each_possible_cpu(cpu) {
                seq_printf(m, "\tcpu%d: ", cpu);
                btf_type_seq_show(map->btf, map->btf_value_type_id,
                                  per_cpu_ptr(pptr, cpu), m);
                seq_puts(m, "\n");
        }
        seq_puts(m, "}\n");

        rcu_read_unlock();
}

static int htab_percpu_map_btf_id;
const struct bpf_map_ops htab_percpu_map_ops = {
        .map_meta_equal = bpf_map_meta_equal,
        .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_lookup_and_delete_elem = htab_percpu_map_lookup_and_delete_elem,
        .map_update_elem = htab_percpu_map_update_elem,
        .map_delete_elem = htab_map_delete_elem,
        .map_seq_show_elem = htab_percpu_map_seq_show_elem,
        .map_set_for_each_callback_args = map_set_for_each_callback_args,
        .map_for_each_callback = bpf_for_each_hash_elem,
        BATCH_OPS(htab_percpu),
        .map_btf_name = "bpf_htab",
        .map_btf_id = &htab_percpu_map_btf_id,
        .iter_seq_info = &iter_seq_info,
};

static int htab_lru_percpu_map_btf_id;
const struct bpf_map_ops htab_lru_percpu_map_ops = {
        .map_meta_equal = bpf_map_meta_equal,
        .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_lookup_and_delete_elem = htab_lru_percpu_map_lookup_and_delete_elem,
        .map_update_elem = htab_lru_percpu_map_update_elem,
        .map_delete_elem = htab_lru_map_delete_elem,
        .map_seq_show_elem = htab_percpu_map_seq_show_elem,
        .map_set_for_each_callback_args = map_set_for_each_callback_args,
        .map_for_each_callback = bpf_for_each_hash_elem,
        BATCH_OPS(htab_lru_percpu),
        .map_btf_name = "bpf_htab",
        .map_btf_id = &htab_lru_percpu_map_btf_id,
        .iter_seq_info = &iter_seq_info,
};

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 int 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);
}

static int htab_of_maps_map_btf_id;
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,
        .map_check_btf = map_check_no_btf,
        .map_btf_name = "bpf_htab",
        .map_btf_id = &htab_of_maps_map_btf_id,
};