Re: [PATCH bpf-next v2 2/5] verifier: parse BTF type tags for function arguments

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2026-05-29 at 20:22 -0400, Emil Tsalapatis wrote:
> The BTF parsing logic for function arguments goes through
> the arguments' decl tags, but does not go into their type
> tags. Add type tag parsing for function arguments.
> 
> Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>

[...]

> +static int btf_scan_type_tags(struct bpf_verifier_env *env,
> +			      const struct btf *btf, u32 type_id,
> +			      u32 *tags)
> +{
> +	const struct btf_type *t;
> +
> +	/* Find the first pointer type in the chain. */
> +	t = btf_type_skip_modifiers(btf, type_id, NULL);
> +	if (!t || !btf_type_is_ptr(t))
> +		return 0;

Nit: do we want to report -EOPNOTSUPP if type tag is attached to a non-pointer type?

> +
> +	/* We got a pointer, get all associated type tags. */
> +	t = btf_type_by_id(btf, t->type);
> +	while (t && btf_type_is_type_tag(t)) {
> +		const char *tag = __btf_name_by_offset(btf, t->name_off);
> +
> +		if (strcmp(tag, "arena") == 0) {
> +			*tags |= ARG_TAG_ARENA;
> +		} else {
> +			bpf_log(&env->log, "function signature member has unsupported type tag '%s'\n",
> +				tag);
> +			return -EOPNOTSUPP;
> +		}
> +
> +		t = btf_type_by_id(btf, t->type);
> +	}
> +
> +	return 0;
> +}
> +

[...]