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bpf: extract map key pointer calculation

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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@meta.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250923112404.668720-7-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Mykyta Yatsenko
2025-09-23 12:24:01 +01:00
committed by Alexei Starovoitov
parent 5c8fd7e2b5
commit 5e8134f50d
1 changed files with 13 additions and 17 deletions
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30
kernel/bpf/helpers.c
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@@ -1082,6 +1082,17 @@ 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);
*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;
@@ -1164,15 +1175,8 @@ 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. */
@@ -1198,15 +1202,7 @@ 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();