On Wed, 6 Aug 2025 at 16:46, Mykyta Yatsenko <mykyta.yatsenko5@xxxxxxxxx> wrote:
>
> From: Mykyta Yatsenko <yatsenko@xxxxxxxx>
>
> Calculation of the BPF map key, given the pointer to a value is
> duplicated in a couple of places in helpers already, in the next patch
> another use case is introduced as well.
> This patch extracts that functionality into a separate function.
>
> Signed-off-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
> ---
Acked-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> kernel/bpf/helpers.c | 31 ++++++++++++++-----------------
> 1 file changed, 14 insertions(+), 17 deletions(-)
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 322ffcaedc38..516286f67f0d 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -1084,6 +1084,18 @@ const struct bpf_func_proto bpf_snprintf_proto = {
> .arg5_type = ARG_CONST_SIZE_OR_ZERO,
> };
>
> +static void *map_key_from_value(struct bpf_map *map, void *value, u32 *arr_idx)
> +{
> + if (map->map_type == BPF_MAP_TYPE_ARRAY) {
> + struct bpf_array *array =
> + container_of(map, struct bpf_array, map);
nit: Can we keep it on the same line?
> +
> + *arr_idx = ((char *)value - array->value) / array->elem_size;
> + return arr_idx;
> + }
> + return (void *)value - round_up(map->key_size, 8);
> +}
> +
> struct bpf_async_cb {
> struct bpf_map *map;
> struct bpf_prog *prog;
> @@ -1166,15 +1178,8 @@ static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer)
> * bpf_map_delete_elem() on the same timer.
> */
> this_cpu_write(hrtimer_running, t);
> - if (map->map_type == BPF_MAP_TYPE_ARRAY) {
> - struct bpf_array *array = container_of(map, struct bpf_array, map);
>
> - /* compute the key */
> - idx = ((char *)value - array->value) / array->elem_size;
> - key = &idx;
> - } else { /* hash or lru */
> - key = value - round_up(map->key_size, 8);
> - }
> + key = map_key_from_value(map, value, &idx);
>
> callback_fn((u64)(long)map, (u64)(long)key, (u64)(long)value, 0, 0);
> /* The verifier checked that return value is zero. */
> @@ -1200,15 +1205,7 @@ static void bpf_wq_work(struct work_struct *work)
> if (!callback_fn)
> return;
>
> - if (map->map_type == BPF_MAP_TYPE_ARRAY) {
> - struct bpf_array *array = container_of(map, struct bpf_array, map);
> -
> - /* compute the key */
> - idx = ((char *)value - array->value) / array->elem_size;
> - key = &idx;
> - } else { /* hash or lru */
> - key = value - round_up(map->key_size, 8);
> - }
> + key = map_key_from_value(map, value, &idx);
>
> rcu_read_lock_trace();
> migrate_disable();
> --
> 2.50.1
>
>
