On Thu, Feb 04, 2021 at 03:48:30PM -0800, Yonghong Song wrote:
> This patch added support for hashmap, percpu hashmap,
> lru hashmap and percpu lru hashmap.
>
> Signed-off-by: Yonghong Song <yhs@xxxxxx>
> ---
> include/linux/bpf.h | 4 +++
> kernel/bpf/hashtab.c | 57 +++++++++++++++++++++++++++++++++++++++++++
> kernel/bpf/verifier.c | 23 +++++++++++++++++
> 3 files changed, 84 insertions(+)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index c8b72ae16cc5..31e0447cadd8 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1396,6 +1396,10 @@ void bpf_iter_map_show_fdinfo(const struct bpf_iter_aux_info *aux,
> int bpf_iter_map_fill_link_info(const struct bpf_iter_aux_info *aux,
> struct bpf_link_info *info);
>
> +int map_set_for_each_callback_args(struct bpf_verifier_env *env,
> + struct bpf_func_state *caller,
> + struct bpf_func_state *callee);
> +
> int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
> int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
> int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index c1ac7f964bc9..40f5404cfb01 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -1869,6 +1869,55 @@ static const struct bpf_iter_seq_info iter_seq_info = {
> .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;
> + void __percpu *pptr;
> + struct bucket *b;
> + void *key, *val;
> + bool is_percpu;
> + long ret = 0;
> + int i;
> +
> + if (flags != 0)
> + return -EINVAL;
> +
> + is_percpu = htab_is_percpu(htab);
> +
> + roundup_key_size = round_up(map->key_size, 8);
> + 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) {
> + val = elem->key + roundup_key_size;
> + } else {
> + /* current cpu value for percpu map */
> + pptr = htab_elem_get_ptr(elem, map->key_size);
> + val = this_cpu_ptr(pptr);
> + }
> + ret = BPF_CAST_CALL(callback_fn)((u64)(long)map,
> + (u64)(long)key, (u64)(long)val,
> + (u64)(long)callback_ctx, 0);
> + if (ret) {
> + rcu_read_unlock();
> + ret = (ret == 1) ? 0 : -EINVAL;
one more thing that I should have mentioned in patch 2.
In prepare_func_exit would be good to add:
if (callee->in_callback_fn)
check that r0 is readable and in tnum_range(0, 1).
and then don't assign r0 reg_state anywhere.
> + goto out;
> + }
> + }
> + rcu_read_unlock();
Sleepable progs can do cond_resched here.
How about adding migrate_disable before for() loop
to make sure that for_each(per_cpu_map,...) is still meaningful and
if (!in_atomic())
cond_resched();
here.
Since this helper is called from bpf progs only the in_atomic check
(whether prog was sleepable or not) is accurate.
> + }
migrate_enable() here after the loop.
> +out:
> + return ret;
> +}
> +
> static int htab_map_btf_id;
> const struct bpf_map_ops htab_map_ops = {
> .map_meta_equal = bpf_map_meta_equal,
> @@ -1881,6 +1930,8 @@ const struct bpf_map_ops htab_map_ops = {
> .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,
> @@ -1900,6 +1951,8 @@ const struct bpf_map_ops htab_lru_map_ops = {
> .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,
> @@ -2019,6 +2072,8 @@ const struct bpf_map_ops htab_percpu_map_ops = {
> .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,
> @@ -2036,6 +2091,8 @@ const struct bpf_map_ops htab_lru_percpu_map_ops = {
> .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,
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 050b067a0be6..32c8dcc27da8 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -4987,6 +4987,29 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
> return 0;
> }
>
> +int map_set_for_each_callback_args(struct bpf_verifier_env *env,
> + struct bpf_func_state *caller,
> + struct bpf_func_state *callee)
> +{
> + /* pointer to map */
> + callee->regs[BPF_REG_1] = caller->regs[BPF_REG_1];
> +
> + callee->regs[BPF_REG_2].type = PTR_TO_MAP_KEY;
> + __mark_reg_known_zero(&callee->regs[BPF_REG_2]);
> + callee->regs[BPF_REG_2].map_ptr = caller->regs[BPF_REG_1].map_ptr;
> +
> + callee->regs[BPF_REG_3].type = PTR_TO_MAP_VALUE;
> + __mark_reg_known_zero(&callee->regs[BPF_REG_3]);
> + callee->regs[BPF_REG_3].map_ptr = caller->regs[BPF_REG_1].map_ptr;
> +
> + /* pointer to stack or null */
> + callee->regs[BPF_REG_4] = caller->regs[BPF_REG_3];
This hard coding of regs 1 through 4 makes sense.
May be add a comment with bpf_for_each_map_elem and callback_fn prototypes,
so it's more obvious what's going on.
> +
> + /* unused */
> + __mark_reg_unknown(env, &callee->regs[BPF_REG_5]);
I think it should be __mark_reg_not_init to make sure that callback_fn
doesn't use r5.
That will help with future extensions via new flags arg that is passed
into bpf_for_each_map_elem.
