int bpf_core_parse_spec()

in contrib/libbpf/src/relo_core.c [263:393]

• 104 lines of code
• 29 McCabe index (conditional complexity)

int bpf_core_parse_spec(const char *prog_name, const struct btf *btf,
			const struct bpf_core_relo *relo,
			struct bpf_core_spec *spec)
{
	int access_idx, parsed_len, i;
	struct bpf_core_accessor *acc;
	const struct btf_type *t;
	const char *name, *spec_str;
	__u32 id, name_off;
	__s64 sz;

	spec_str = btf__name_by_offset(btf, relo->access_str_off);
	if (str_is_empty(spec_str) || *spec_str == ':')
		return -EINVAL;

	memset(spec, 0, sizeof(*spec));
	spec->btf = btf;
	spec->root_type_id = relo->type_id;
	spec->relo_kind = relo->kind;

	/* type-based relocations don't have a field access string */
	if (core_relo_is_type_based(relo->kind)) {
		if (strcmp(spec_str, "0"))
			return -EINVAL;
		return 0;
	}

	/* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */
	while (*spec_str) {
		if (*spec_str == ':')
			++spec_str;
		if (sscanf(spec_str, "%d%n", &access_idx, &parsed_len) != 1)
			return -EINVAL;
		if (spec->raw_len == BPF_CORE_SPEC_MAX_LEN)
			return -E2BIG;
		spec_str += parsed_len;
		spec->raw_spec[spec->raw_len++] = access_idx;
	}

	if (spec->raw_len == 0)
		return -EINVAL;

	t = skip_mods_and_typedefs(btf, relo->type_id, &id);
	if (!t)
		return -EINVAL;

	access_idx = spec->raw_spec[0];
	acc = &spec->spec[0];
	acc->type_id = id;
	acc->idx = access_idx;
	spec->len++;

	if (core_relo_is_enumval_based(relo->kind)) {
		if (!btf_is_any_enum(t) || spec->raw_len > 1 || access_idx >= btf_vlen(t))
			return -EINVAL;

		/* record enumerator name in a first accessor */
		name_off = btf_is_enum(t) ? btf_enum(t)[access_idx].name_off
					  : btf_enum64(t)[access_idx].name_off;
		acc->name = btf__name_by_offset(btf, name_off);
		return 0;
	}

	if (!core_relo_is_field_based(relo->kind))
		return -EINVAL;

	sz = btf__resolve_size(btf, id);
	if (sz < 0)
		return sz;
	spec->bit_offset = access_idx * sz * 8;

	for (i = 1; i < spec->raw_len; i++) {
		t = skip_mods_and_typedefs(btf, id, &id);
		if (!t)
			return -EINVAL;

		access_idx = spec->raw_spec[i];
		acc = &spec->spec[spec->len];

		if (btf_is_composite(t)) {
			const struct btf_member *m;
			__u32 bit_offset;

			if (access_idx >= btf_vlen(t))
				return -EINVAL;

			bit_offset = btf_member_bit_offset(t, access_idx);
			spec->bit_offset += bit_offset;

			m = btf_members(t) + access_idx;
			if (m->name_off) {
				name = btf__name_by_offset(btf, m->name_off);
				if (str_is_empty(name))
					return -EINVAL;

				acc->type_id = id;
				acc->idx = access_idx;
				acc->name = name;
				spec->len++;
			}

			id = m->type;
		} else if (btf_is_array(t)) {
			const struct btf_array *a = btf_array(t);
			bool flex;

			t = skip_mods_and_typedefs(btf, a->type, &id);
			if (!t)
				return -EINVAL;

			flex = is_flex_arr(btf, acc - 1, a);
			if (!flex && access_idx >= a->nelems)
				return -EINVAL;

			spec->spec[spec->len].type_id = id;
			spec->spec[spec->len].idx = access_idx;
			spec->len++;

			sz = btf__resolve_size(btf, id);
			if (sz < 0)
				return sz;
			spec->bit_offset += access_idx * sz * 8;
		} else {
			pr_warn("prog '%s': relo for [%u] %s (at idx %d) captures type [%d] of unexpected kind %s\n",
				prog_name, relo->type_id, spec_str, i, id, btf_kind_str(t));
			return -EINVAL;
		}
	}

	return 0;
}