// SPDX-License-Identifier: GPL-2.0
/* XSKMAP used for AF_XDP sockets
 * Copyright(c) 2018 Intel Corporation.
 */

#include <linux/bpf.h>
#include <linux/capability.h>
#include <net/xdp_sock.h>
#include <linux/slab.h>
#include <linux/sched.h>

#include "xsk.h"

static struct xsk_map_node *xsk_map_node_alloc(struct xsk_map *map,
                                               struct xdp_sock __rcu **map_entry)
{
        struct xsk_map_node *node;

        node = bpf_map_kzalloc(&map->map, sizeof(*node),
                               GFP_ATOMIC | __GFP_NOWARN);
        if (!node)
                return ERR_PTR(-ENOMEM);

        bpf_map_inc(&map->map);

        node->map = map;
        node->map_entry = map_entry;
        return node;
}

static void xsk_map_node_free(struct xsk_map_node *node)
{
        bpf_map_put(&node->map->map);
        kfree(node);
}

static void xsk_map_sock_add(struct xdp_sock *xs, struct xsk_map_node *node)
{
        spin_lock_bh(&xs->map_list_lock);
        list_add_tail(&node->node, &xs->map_list);
        spin_unlock_bh(&xs->map_list_lock);
}

static void xsk_map_sock_delete(struct xdp_sock *xs,
                                struct xdp_sock __rcu **map_entry)
{
        struct xsk_map_node *n, *tmp;

        spin_lock_bh(&xs->map_list_lock);
        list_for_each_entry_safe(n, tmp, &xs->map_list, node) {
                if (map_entry == n->map_entry) {
                        list_del(&n->node);
                        xsk_map_node_free(n);
                }
        }
        spin_unlock_bh(&xs->map_list_lock);
}

static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
{
        struct xsk_map *m;
        int numa_node;
        u64 size;

        if (!capable(CAP_NET_ADMIN))
                return ERR_PTR(-EPERM);

        if (attr->max_entries == 0 || attr->key_size != 4 ||
            attr->value_size != 4 ||
            attr->map_flags & ~(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY))
                return ERR_PTR(-EINVAL);

        numa_node = bpf_map_attr_numa_node(attr);
        size = struct_size(m, xsk_map, attr->max_entries);

        m = bpf_map_area_alloc(size, numa_node);
        if (!m)
                return ERR_PTR(-ENOMEM);

        bpf_map_init_from_attr(&m->map, attr);
        spin_lock_init(&m->lock);

        return &m->map;
}

static void xsk_map_free(struct bpf_map *map)
{
        struct xsk_map *m = container_of(map, struct xsk_map, map);

        synchronize_net();
        bpf_map_area_free(m);
}

static int xsk_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
{
        struct xsk_map *m = container_of(map, struct xsk_map, map);
        u32 index = key ? *(u32 *)key : U32_MAX;
        u32 *next = next_key;

        if (index >= m->map.max_entries) {
                *next = 0;
                return 0;
        }

        if (index == m->map.max_entries - 1)
                return -ENOENT;
        *next = index + 1;
        return 0;
}

static int xsk_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
{
        const int ret = BPF_REG_0, mp = BPF_REG_1, index = BPF_REG_2;
        struct bpf_insn *insn = insn_buf;

        *insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
        *insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 5);
        *insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(sizeof(struct xsk_sock *)));
        *insn++ = BPF_ALU64_IMM(BPF_ADD, mp, offsetof(struct xsk_map, xsk_map));
        *insn++ = BPF_ALU64_REG(BPF_ADD, ret, mp);
        *insn++ = BPF_LDX_MEM(BPF_SIZEOF(struct xsk_sock *), ret, ret, 0);
        *insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
        *insn++ = BPF_MOV64_IMM(ret, 0);
        return insn - insn_buf;
}

/* Elements are kept alive by RCU; either by rcu_read_lock() (from syscall) or
 * by local_bh_disable() (from XDP calls inside NAPI). The
 * rcu_read_lock_bh_held() below makes lockdep accept both.
 */
static void *__xsk_map_lookup_elem(struct bpf_map *map, u32 key)
{
        struct xsk_map *m = container_of(map, struct xsk_map, map);

        if (key >= map->max_entries)
                return NULL;

        return rcu_dereference_check(m->xsk_map[key], rcu_read_lock_bh_held());
}

static void *xsk_map_lookup_elem(struct bpf_map *map, void *key)
{
        return __xsk_map_lookup_elem(map, *(u32 *)key);
}

static void *xsk_map_lookup_elem_sys_only(struct bpf_map *map, void *key)
{
        return ERR_PTR(-EOPNOTSUPP);
}

static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
                               u64 map_flags)
{
        struct xsk_map *m = container_of(map, struct xsk_map, map);
        struct xdp_sock __rcu **map_entry;
        struct xdp_sock *xs, *old_xs;
        u32 i = *(u32 *)key, fd = *(u32 *)value;
        struct xsk_map_node *node;
        struct socket *sock;
        int err;

        if (unlikely(map_flags > BPF_EXIST))
                return -EINVAL;
        if (unlikely(i >= m->map.max_entries))
                return -E2BIG;

        sock = sockfd_lookup(fd, &err);
        if (!sock)
                return err;

        if (sock->sk->sk_family != PF_XDP) {
                sockfd_put(sock);
                return -EOPNOTSUPP;
        }

        xs = (struct xdp_sock *)sock->sk;

        map_entry = &m->xsk_map[i];
        node = xsk_map_node_alloc(m, map_entry);
        if (IS_ERR(node)) {
                sockfd_put(sock);
                return PTR_ERR(node);
        }

        spin_lock_bh(&m->lock);
        old_xs = rcu_dereference_protected(*map_entry, lockdep_is_held(&m->lock));
        if (old_xs == xs) {
                err = 0;
                goto out;
        } else if (old_xs && map_flags == BPF_NOEXIST) {
                err = -EEXIST;
                goto out;
        } else if (!old_xs && map_flags == BPF_EXIST) {
                err = -ENOENT;
                goto out;
        }
        xsk_map_sock_add(xs, node);
        rcu_assign_pointer(*map_entry, xs);
        if (old_xs)
                xsk_map_sock_delete(old_xs, map_entry);
        spin_unlock_bh(&m->lock);
        sockfd_put(sock);
        return 0;

out:
        spin_unlock_bh(&m->lock);
        sockfd_put(sock);
        xsk_map_node_free(node);
        return err;
}

static int xsk_map_delete_elem(struct bpf_map *map, void *key)
{
        struct xsk_map *m = container_of(map, struct xsk_map, map);
        struct xdp_sock __rcu **map_entry;
        struct xdp_sock *old_xs;
        int k = *(u32 *)key;

        if (k >= map->max_entries)
                return -EINVAL;

        spin_lock_bh(&m->lock);
        map_entry = &m->xsk_map[k];
        old_xs = unrcu_pointer(xchg(map_entry, NULL));
        if (old_xs)
                xsk_map_sock_delete(old_xs, map_entry);
        spin_unlock_bh(&m->lock);

        return 0;
}

static int xsk_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
{
        return __bpf_xdp_redirect_map(map, ifindex, flags, 0,
                                      __xsk_map_lookup_elem);
}

void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
                             struct xdp_sock __rcu **map_entry)
{
        spin_lock_bh(&map->lock);
        if (rcu_access_pointer(*map_entry) == xs) {
                rcu_assign_pointer(*map_entry, NULL);
                xsk_map_sock_delete(xs, map_entry);
        }
        spin_unlock_bh(&map->lock);
}

static bool xsk_map_meta_equal(const struct bpf_map *meta0,
                               const struct bpf_map *meta1)
{
        return meta0->max_entries == meta1->max_entries &&
                bpf_map_meta_equal(meta0, meta1);
}

static int xsk_map_btf_id;
const struct bpf_map_ops xsk_map_ops = {
        .map_meta_equal = xsk_map_meta_equal,
        .map_alloc = xsk_map_alloc,
        .map_free = xsk_map_free,
        .map_get_next_key = xsk_map_get_next_key,
        .map_lookup_elem = xsk_map_lookup_elem,
        .map_gen_lookup = xsk_map_gen_lookup,
        .map_lookup_elem_sys_only = xsk_map_lookup_elem_sys_only,
        .map_update_elem = xsk_map_update_elem,
        .map_delete_elem = xsk_map_delete_elem,
        .map_check_btf = map_check_no_btf,
        .map_btf_name = "xsk_map",
        .map_btf_id = &xsk_map_btf_id,
        .map_redirect = xsk_map_redirect,
};