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Message-ID: <4d0aafe9-75c7-43fe-d9eb-62bb2053b53e@iogearbox.net>
Date: Tue, 7 Jan 2020 17:00:37 +0100
From: Daniel Borkmann <daniel@...earbox.net>
To: Martin KaFai Lau <kafai@...com>, bpf@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
David Miller <davem@...emloft.net>, kernel-team@...com,
netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 06/11] bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
On 12/31/19 7:20 AM, Martin KaFai Lau wrote:
[...]
> +static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
> + void *value, u64 flags)
> +{
> + struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
> + const struct bpf_struct_ops *st_ops = st_map->st_ops;
> + struct bpf_struct_ops_value *uvalue, *kvalue;
> + const struct btf_member *member;
> + const struct btf_type *t = st_ops->type;
> + void *udata, *kdata;
> + int prog_fd, err = 0;
> + void *image;
> + u32 i;
> +
> + if (flags)
> + return -EINVAL;
> +
> + if (*(u32 *)key != 0)
> + return -E2BIG;
> +
> + err = check_zero_holes(st_ops->value_type, value);
> + if (err)
> + return err;
> +
> + uvalue = (struct bpf_struct_ops_value *)value;
> + err = check_zero_holes(t, uvalue->data);
> + if (err)
> + return err;
> +
> + if (uvalue->state || refcount_read(&uvalue->refcnt))
> + return -EINVAL;
> +
> + uvalue = (struct bpf_struct_ops_value *)st_map->uvalue;
> + kvalue = (struct bpf_struct_ops_value *)&st_map->kvalue;
> +
> + spin_lock(&st_map->lock);
> +
> + if (kvalue->state != BPF_STRUCT_OPS_STATE_INIT) {
> + err = -EBUSY;
> + goto unlock;
> + }
> +
> + memcpy(uvalue, value, map->value_size);
> +
> + udata = &uvalue->data;
> + kdata = &kvalue->data;
> + image = st_map->image;
> +
> + for_each_member(i, t, member) {
> + const struct btf_type *mtype, *ptype;
> + struct bpf_prog *prog;
> + u32 moff;
> +
> + moff = btf_member_bit_offset(t, member) / 8;
> + ptype = btf_type_resolve_ptr(btf_vmlinux, member->type, NULL);
> + if (ptype == module_type) {
> + if (*(void **)(udata + moff))
> + goto reset_unlock;
> + *(void **)(kdata + moff) = BPF_MODULE_OWNER;
> + continue;
> + }
> +
> + err = st_ops->init_member(t, member, kdata, udata);
> + if (err < 0)
> + goto reset_unlock;
> +
> + /* The ->init_member() has handled this member */
> + if (err > 0)
> + continue;
> +
> + /* If st_ops->init_member does not handle it,
> + * we will only handle func ptrs and zero-ed members
> + * here. Reject everything else.
> + */
> +
> + /* All non func ptr member must be 0 */
> + if (!ptype || !btf_type_is_func_proto(ptype)) {
> + u32 msize;
> +
> + mtype = btf_type_by_id(btf_vmlinux, member->type);
> + mtype = btf_resolve_size(btf_vmlinux, mtype, &msize,
> + NULL, NULL);
> + if (IS_ERR(mtype)) {
> + err = PTR_ERR(mtype);
> + goto reset_unlock;
> + }
> +
> + if (memchr_inv(udata + moff, 0, msize)) {
> + err = -EINVAL;
> + goto reset_unlock;
> + }
> +
> + continue;
> + }
> +
> + prog_fd = (int)(*(unsigned long *)(udata + moff));
> + /* Similar check as the attr->attach_prog_fd */
> + if (!prog_fd)
> + continue;
> +
> + prog = bpf_prog_get(prog_fd);
> + if (IS_ERR(prog)) {
> + err = PTR_ERR(prog);
> + goto reset_unlock;
> + }
> + st_map->progs[i] = prog;
> +
> + if (prog->type != BPF_PROG_TYPE_STRUCT_OPS ||
> + prog->aux->attach_btf_id != st_ops->type_id ||
> + prog->expected_attach_type != i) {
> + err = -EINVAL;
> + goto reset_unlock;
> + }
> +
> + err = arch_prepare_bpf_trampoline(image,
> + st_map->image + PAGE_SIZE,
> + &st_ops->func_models[i], 0,
> + &prog, 1, NULL, 0, NULL);
> + if (err < 0)
> + goto reset_unlock;
> +
> + *(void **)(kdata + moff) = image;
> + image += err;
> +
> + /* put prog_id to udata */
> + *(unsigned long *)(udata + moff) = prog->aux->id;
> + }
> +
> + refcount_set(&kvalue->refcnt, 1);
> + bpf_map_inc(map);
> +
> + err = st_ops->reg(kdata);
> + if (!err) {
> + /* Pair with smp_load_acquire() during lookup */
> + smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_INUSE);
Is there a reason using READ_ONCE/WRITE_ONCE pair is not enough?
> + goto unlock;
> + }
> +
> + /* Error during st_ops->reg() */
> + bpf_map_put(map);
> +
> +reset_unlock:
> + bpf_struct_ops_map_put_progs(st_map);
> + memset(uvalue, 0, map->value_size);
> + memset(kvalue, 0, map->value_size);
> +
> +unlock:
> + spin_unlock(&st_map->lock);
> + return err;
> +}
[...]
> +static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
> +{
> + const struct bpf_struct_ops *st_ops;
> + size_t map_total_size, st_map_size;
> + struct bpf_struct_ops_map *st_map;
> + const struct btf_type *t, *vt;
> + struct bpf_map_memory mem;
> + struct bpf_map *map;
> + int err;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return ERR_PTR(-EPERM);
> +
> + st_ops = bpf_struct_ops_find_value(attr->btf_vmlinux_value_type_id);
> + if (!st_ops)
> + return ERR_PTR(-ENOTSUPP);
> +
> + vt = st_ops->value_type;
> + if (attr->value_size != vt->size)
> + return ERR_PTR(-EINVAL);
> +
> + t = st_ops->type;
> +
> + st_map_size = sizeof(*st_map) +
> + /* kvalue stores the
> + * struct bpf_struct_ops_tcp_congestions_ops
> + */
> + (vt->size - sizeof(struct bpf_struct_ops_value));
> + map_total_size = st_map_size +
> + /* uvalue */
> + sizeof(vt->size) +
> + /* struct bpf_progs **progs */
> + btf_type_vlen(t) * sizeof(struct bpf_prog *);
> + err = bpf_map_charge_init(&mem, map_total_size);
> + if (err < 0)
> + return ERR_PTR(err);
> +
> + st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);
> + if (!st_map) {
> + bpf_map_charge_finish(&mem);
> + return ERR_PTR(-ENOMEM);
> + }
> + st_map->st_ops = st_ops;
> + map = &st_map->map;
> +
> + st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);
> + st_map->progs =
> + bpf_map_area_alloc(btf_type_vlen(t) * sizeof(struct bpf_prog *),
> + NUMA_NO_NODE);
> + st_map->image = bpf_jit_alloc_exec(PAGE_SIZE);
> + if (!st_map->uvalue || !st_map->progs || !st_map->image) {
> + bpf_struct_ops_map_free(map);
> + bpf_map_charge_finish(&mem);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + spin_lock_init(&st_map->lock);
> + set_vm_flush_reset_perms(st_map->image);
> + set_memory_x((long)st_map->image, 1);
Shouldn't this be using text poke as well once you write the image later on,
otherwise we create yet another instance of W+X memory ... :/
> + bpf_map_init_from_attr(map, attr);
> + bpf_map_charge_move(&map->memory, &mem);
> +
> + return map;
> +}
> +
> +const struct bpf_map_ops bpf_struct_ops_map_ops = {
> + .map_alloc_check = bpf_struct_ops_map_alloc_check,
> + .map_alloc = bpf_struct_ops_map_alloc,
> + .map_free = bpf_struct_ops_map_free,
> + .map_get_next_key = bpf_struct_ops_map_get_next_key,
> + .map_lookup_elem = bpf_struct_ops_map_lookup_elem,
> + .map_delete_elem = bpf_struct_ops_map_delete_elem,
> + .map_update_elem = bpf_struct_ops_map_update_elem,
> + .map_seq_show_elem = bpf_struct_ops_map_seq_show_elem,
> +};
[...]
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