Commit c1cccec9 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
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libbpf: Reject static maps 



Static maps never really worked with libbpf, because all such maps were always
silently resolved to the very first map. Detect static maps (both legacy and
BTF-defined) and report user-friendly error.

Tested locally by switching few maps (legacy and BTF-defined) in selftests to
static ones and verifying that now libbpf rejects them loudly.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210513233643.194711-2-andrii@kernel.org
parent 9e9b4515

tools/lib/bpf/libbpf.c

+19 −5
Original line number Diff line number Diff line
@@ -1795,7 +1795,6 @@ static int bpf_object__init_user_maps(struct bpf_object *obj, bool strict) 
	if (!symbols)

		return -EINVAL;





	scn = elf_sec_by_idx(obj, obj->efile.maps_shndx);

	data = elf_sec_data(obj, scn);

	if (!scn || !data) {
@@ -1855,6 +1854,12 @@ static int bpf_object__init_user_maps(struct bpf_object *obj, bool strict) 
			return -LIBBPF_ERRNO__FORMAT;

		}



		if (GELF_ST_TYPE(sym.st_info) == STT_SECTION

		    || GELF_ST_BIND(sym.st_info) == STB_LOCAL) {

			pr_warn("map '%s' (legacy): static maps are not supported\n", map_name);

			return -ENOTSUP;

		}



		map->libbpf_type = LIBBPF_MAP_UNSPEC;

		map->sec_idx = sym.st_shndx;

		map->sec_offset = sym.st_value;
@@ -2262,6 +2267,16 @@ static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def 
		pr_debug("map '%s': found inner map definition.\n", map->name);

}



static const char *btf_var_linkage_str(__u32 linkage)

{

	switch (linkage) {

	case BTF_VAR_STATIC: return "static";

	case BTF_VAR_GLOBAL_ALLOCATED: return "global";

	case BTF_VAR_GLOBAL_EXTERN: return "extern";

	default: return "unknown";

	}

}



static int bpf_object__init_user_btf_map(struct bpf_object *obj,

					 const struct btf_type *sec,

					 int var_idx, int sec_idx,
@@ -2294,10 +2309,9 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj, 
			map_name, btf_kind_str(var));

		return -EINVAL;

	}

	if (var_extra->linkage != BTF_VAR_GLOBAL_ALLOCATED &&

	    var_extra->linkage != BTF_VAR_STATIC) {

		pr_warn("map '%s': unsupported var linkage %u.\n",

			map_name, var_extra->linkage);

	if (var_extra->linkage != BTF_VAR_GLOBAL_ALLOCATED) {

		pr_warn("map '%s': unsupported map linkage %s.\n",

			map_name, btf_var_linkage_str(var_extra->linkage));

		return -EOPNOTSUPP;

	}