Re: [PATCH PATCH v2 v2 2/6] bpf: Add bpf_perf_event_aux_pause kfunc

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2025-07-18 at 16:25 +0100, Leo Yan wrote:

[...]

> +__bpf_kfunc int bpf_perf_event_aux_pause(void *p__map, u64 flags, u32 pause)
> +{
> +	struct bpf_map *map = p__map;
> +	struct bpf_array *array = container_of(map, struct bpf_array, map);

Verifier makes sure that p__map is a not null pointer to an object of
type bpf_map, but it does not guarantee that the object is an instance
of bpf_array.
You need to check map->type, same way bpf_arena_alloc_pages() does.

> +	unsigned int cpu = smp_processor_id();
> +	u64 index = flags & BPF_F_INDEX_MASK;
> +	struct bpf_event_entry *ee;
> +	int ret = 0;
> +
> +	/* Disabling IRQ avoids race condition with perf event flows. */
> +	guard(irqsave)();
> +
> +	if (unlikely(flags & ~(BPF_F_INDEX_MASK))) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	if (index == BPF_F_CURRENT_CPU)
> +		index = cpu;
> +
> +	if (unlikely(index >= array->map.max_entries)) {
> +		ret = -E2BIG;
> +		goto out;
> +	}
> +
> +	ee = READ_ONCE(array->ptrs[index]);
> +	if (!ee) {
> +		ret = -ENOENT;
> +		goto out;
> +	}
> +
> +	if (!has_aux(ee->event))
> +		ret = -EINVAL;
> +
> +	perf_event_aux_pause(ee->event, pause);
> +out:
> +	return ret;
> +}

[...]