// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2019 Facebook
 * Copyright 2020 Google LLC.
 */

#include <linux/rculist.h>
#include <linux/list.h>
#include <linux/hash.h>
#include <linux/types.h>
#include <linux/spinlock.h>
#include <linux/bpf.h>
#include <linux/bpf_local_storage.h>
#include <net/sock.h>
#include <uapi/linux/sock_diag.h>
#include <uapi/linux/btf.h>
#include <linux/bpf_lsm.h>
#include <linux/btf_ids.h>
#include <linux/fdtable.h>

DEFINE_BPF_STORAGE_CACHE(inode_cache);

static struct bpf_local_storage __rcu **
inode_storage_ptr(void *owner)
{
        struct inode *inode = owner;
        struct bpf_storage_blob *bsb;

        bsb = bpf_inode(inode);
        if (!bsb)
                return NULL;
        return &bsb->storage;
}

static struct bpf_local_storage_data *inode_storage_lookup(struct inode *inode,
                                                           struct bpf_map *map,
                                                           bool cacheit_lockit)
{
        struct bpf_local_storage *inode_storage;
        struct bpf_local_storage_map *smap;
        struct bpf_storage_blob *bsb;

        bsb = bpf_inode(inode);
        if (!bsb)
                return NULL;

        inode_storage = rcu_dereference(bsb->storage);
        if (!inode_storage)
                return NULL;

        smap = (struct bpf_local_storage_map *)map;
        return bpf_local_storage_lookup(inode_storage, smap, cacheit_lockit);
}

void bpf_inode_storage_free(struct inode *inode)
{
        struct bpf_local_storage_elem *selem;
        struct bpf_local_storage *local_storage;
        bool free_inode_storage = false;
        struct bpf_storage_blob *bsb;
        struct hlist_node *n;

        bsb = bpf_inode(inode);
        if (!bsb)
                return;

        rcu_read_lock();

        local_storage = rcu_dereference(bsb->storage);
        if (!local_storage) {
                rcu_read_unlock();
                return;
        }

        /* Neither the bpf_prog nor the bpf-map's syscall
         * could be modifying the local_storage->list now.
         * Thus, no elem can be added-to or deleted-from the
         * local_storage->list by the bpf_prog or by the bpf-map's syscall.
         *
         * It is racing with bpf_local_storage_map_free() alone
         * when unlinking elem from the local_storage->list and
         * the map's bucket->list.
         */
        raw_spin_lock_bh(&local_storage->lock);
        hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
                /* Always unlink from map before unlinking from
                 * local_storage.
                 */
                bpf_selem_unlink_map(selem);
                free_inode_storage = bpf_selem_unlink_storage_nolock(
                        local_storage, selem, false);
        }
        raw_spin_unlock_bh(&local_storage->lock);
        rcu_read_unlock();

        /* free_inoode_storage should always be true as long as
         * local_storage->list was non-empty.
         */
        if (free_inode_storage)
                kfree_rcu(local_storage, rcu);
}

static void *bpf_fd_inode_storage_lookup_elem(struct bpf_map *map, void *key)
{
        struct bpf_local_storage_data *sdata;
        struct file *f;
        int fd;

        fd = *(int *)key;
        f = fget_raw(fd);
        if (!f)
                return ERR_PTR(-EBADF);

        sdata = inode_storage_lookup(f->f_inode, map, true);
        fput(f);
        return sdata ? sdata->data : NULL;
}

static int bpf_fd_inode_storage_update_elem(struct bpf_map *map, void *key,
                                         void *value, u64 map_flags)
{
        struct bpf_local_storage_data *sdata;
        struct file *f;
        int fd;

        fd = *(int *)key;
        f = fget_raw(fd);
        if (!f)
                return -EBADF;
        if (!inode_storage_ptr(f->f_inode)) {
                fput(f);
                return -EBADF;
        }

        sdata = bpf_local_storage_update(f->f_inode,
                                         (struct bpf_local_storage_map *)map,
                                         value, map_flags);
        fput(f);
        return PTR_ERR_OR_ZERO(sdata);
}

static int inode_storage_delete(struct inode *inode, struct bpf_map *map)
{
        struct bpf_local_storage_data *sdata;

        sdata = inode_storage_lookup(inode, map, false);
        if (!sdata)
                return -ENOENT;

        bpf_selem_unlink(SELEM(sdata));

        return 0;
}

static int bpf_fd_inode_storage_delete_elem(struct bpf_map *map, void *key)
{
        struct file *f;
        int fd, err;

        fd = *(int *)key;
        f = fget_raw(fd);
        if (!f)
                return -EBADF;

        err = inode_storage_delete(f->f_inode, map);
        fput(f);
        return err;
}

BPF_CALL_4(bpf_inode_storage_get, struct bpf_map *, map, struct inode *, inode,
           void *, value, u64, flags)
{
        struct bpf_local_storage_data *sdata;

        if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
                return (unsigned long)NULL;

        /* explicitly check that the inode_storage_ptr is not
         * NULL as inode_storage_lookup returns NULL in this case and
         * bpf_local_storage_update expects the owner to have a
         * valid storage pointer.
         */
        if (!inode || !inode_storage_ptr(inode))
                return (unsigned long)NULL;

        sdata = inode_storage_lookup(inode, map, true);
        if (sdata)
                return (unsigned long)sdata->data;

        /* This helper must only called from where the inode is guaranteed
         * to have a refcount and cannot be freed.
         */
        if (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) {
                sdata = bpf_local_storage_update(
                        inode, (struct bpf_local_storage_map *)map, value,
                        BPF_NOEXIST);
                return IS_ERR(sdata) ? (unsigned long)NULL :
                                             (unsigned long)sdata->data;
        }

        return (unsigned long)NULL;
}

BPF_CALL_2(bpf_inode_storage_delete,
           struct bpf_map *, map, struct inode *, inode)
{
        if (!inode)
                return -EINVAL;

        /* This helper must only called from where the inode is guaranteed
         * to have a refcount and cannot be freed.
         */
        return inode_storage_delete(inode, map);
}

static int notsupp_get_next_key(struct bpf_map *map, void *key,
                                void *next_key)
{
        return -ENOTSUPP;
}

static struct bpf_map *inode_storage_map_alloc(union bpf_attr *attr)
{
        struct bpf_local_storage_map *smap;

        smap = bpf_local_storage_map_alloc(attr);
        if (IS_ERR(smap))
                return ERR_CAST(smap);

        smap->cache_idx = bpf_local_storage_cache_idx_get(&inode_cache);
        return &smap->map;
}

static void inode_storage_map_free(struct bpf_map *map)
{
        struct bpf_local_storage_map *smap;

        smap = (struct bpf_local_storage_map *)map;
        bpf_local_storage_cache_idx_free(&inode_cache, smap->cache_idx);
        bpf_local_storage_map_free(smap, NULL);
}

static int inode_storage_map_btf_id;
const struct bpf_map_ops inode_storage_map_ops = {
        .map_meta_equal = bpf_map_meta_equal,
        .map_alloc_check = bpf_local_storage_map_alloc_check,
        .map_alloc = inode_storage_map_alloc,
        .map_free = inode_storage_map_free,
        .map_get_next_key = notsupp_get_next_key,
        .map_lookup_elem = bpf_fd_inode_storage_lookup_elem,
        .map_update_elem = bpf_fd_inode_storage_update_elem,
        .map_delete_elem = bpf_fd_inode_storage_delete_elem,
        .map_check_btf = bpf_local_storage_map_check_btf,
        .map_btf_name = "bpf_local_storage_map",
        .map_btf_id = &inode_storage_map_btf_id,
        .map_owner_storage_ptr = inode_storage_ptr,
};

BTF_ID_LIST_SINGLE(bpf_inode_storage_btf_ids, struct, inode)

const struct bpf_func_proto bpf_inode_storage_get_proto = {
        .func           = bpf_inode_storage_get,
        .gpl_only       = false,
        .ret_type       = RET_PTR_TO_MAP_VALUE_OR_NULL,
        .arg1_type      = ARG_CONST_MAP_PTR,
        .arg2_type      = ARG_PTR_TO_BTF_ID,
        .arg2_btf_id    = &bpf_inode_storage_btf_ids[0],
        .arg3_type      = ARG_PTR_TO_MAP_VALUE_OR_NULL,
        .arg4_type      = ARG_ANYTHING,
};

const struct bpf_func_proto bpf_inode_storage_delete_proto = {
        .func           = bpf_inode_storage_delete,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_CONST_MAP_PTR,
        .arg2_type      = ARG_PTR_TO_BTF_ID,
        .arg2_btf_id    = &bpf_inode_storage_btf_ids[0],
};