Commit 341ac5ff authored by Hengqi Chen's avatar Hengqi Chen Committed by Andrii Nakryiko
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libbpf: Support static initialization of BPF_MAP_TYPE_PROG_ARRAY 

Support static initialization of BPF_MAP_TYPE_PROG_ARRAY with a
syntax similar to map-in-map initialization ([0]):

    SEC("socket")
    int tailcall_1(void *ctx)
    {
        return 0;
    }

    struct {
        __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
        __uint(max_entries, 2);
        __uint(key_size, sizeof(__u32));
        __array(values, int (void *));
    } prog_array_init SEC(".maps") = {
        .values = {
            [1] = (void *)&tailcall_1,
        },
    };

Here's the relevant part of libbpf debug log showing what's
going on with prog-array initialization:

libbpf: sec '.relsocket': collecting relocation for section(3) 'socket'
libbpf: sec '.relsocket': relo #0: insn #2 against 'prog_array_init'
libbpf: prog 'entry': found map 0 (prog_array_init, sec 4, off 0) for insn #0
libbpf: .maps relo #0: for 3 value 0 rel->r_offset 32 name 53 ('tailcall_1')
libbpf: .maps relo #0: map 'prog_array_init' slot [1] points to prog 'tailcall_1'
libbpf: map 'prog_array_init': created successfully, fd=5
libbpf: map 'prog_array_init': slot [1] set to prog 'tailcall_1' fd=6

  [0] Closes: https://github.com/libbpf/libbpf/issues/354



Signed-off-by: default avatarHengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211128141633.502339-2-hengqi.chen@gmail.com
parent e32cb12f

tools/lib/bpf/libbpf.c

+121 −33
Original line number Diff line number Diff line
@@ -2277,6 +2277,9 @@ int parse_btf_map_def(const char *map_name, struct btf *btf, 
			map_def->parts |= MAP_DEF_VALUE_SIZE | MAP_DEF_VALUE_TYPE;

		}

		else if (strcmp(name, "values") == 0) {

			bool is_map_in_map = bpf_map_type__is_map_in_map(map_def->map_type);

			bool is_prog_array = map_def->map_type == BPF_MAP_TYPE_PROG_ARRAY;

			const char *desc = is_map_in_map ? "map-in-map inner" : "prog-array value";

			char inner_map_name[128];

			int err;
@@ -2290,8 +2293,8 @@ int parse_btf_map_def(const char *map_name, struct btf *btf, 
					map_name, name);

				return -EINVAL;

			}

			if (!bpf_map_type__is_map_in_map(map_def->map_type)) {

				pr_warn("map '%s': should be map-in-map.\n",

			if (!is_map_in_map && !is_prog_array) {

				pr_warn("map '%s': should be map-in-map or prog-array.\n",

					map_name);

				return -ENOTSUP;

			}
@@ -2303,22 +2306,30 @@ int parse_btf_map_def(const char *map_name, struct btf *btf, 
			map_def->value_size = 4;

			t = btf__type_by_id(btf, m->type);

			if (!t) {

				pr_warn("map '%s': map-in-map inner type [%d] not found.\n",

					map_name, m->type);

				pr_warn("map '%s': %s type [%d] not found.\n",

					map_name, desc, m->type);

				return -EINVAL;

			}

			if (!btf_is_array(t) || btf_array(t)->nelems) {

				pr_warn("map '%s': map-in-map inner spec is not a zero-sized array.\n",

					map_name);

				pr_warn("map '%s': %s spec is not a zero-sized array.\n",

					map_name, desc);

				return -EINVAL;

			}

			t = skip_mods_and_typedefs(btf, btf_array(t)->type, NULL);

			if (!btf_is_ptr(t)) {

				pr_warn("map '%s': map-in-map inner def is of unexpected kind %s.\n",

					map_name, btf_kind_str(t));

				pr_warn("map '%s': %s def is of unexpected kind %s.\n",

					map_name, desc, btf_kind_str(t));

				return -EINVAL;

			}

			t = skip_mods_and_typedefs(btf, t->type, NULL);

			if (is_prog_array) {

				if (!btf_is_func_proto(t)) {

					pr_warn("map '%s': prog-array value def is of unexpected kind %s.\n",

						map_name, btf_kind_str(t));

					return -EINVAL;

				}

				continue;

			}

			if (!btf_is_struct(t)) {

				pr_warn("map '%s': map-in-map inner def is of unexpected kind %s.\n",

					map_name, btf_kind_str(t));
@@ -4940,7 +4951,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b 
	return err;

}



static int init_map_slots(struct bpf_object *obj, struct bpf_map *map)

static int init_map_in_map_slots(struct bpf_object *obj, struct bpf_map *map)

{

	const struct bpf_map *targ_map;

	unsigned int i;
@@ -4952,6 +4963,7 @@ static int init_map_slots(struct bpf_object *obj, struct bpf_map *map) 


		targ_map = map->init_slots[i];

		fd = bpf_map__fd(targ_map);



		if (obj->gen_loader) {

			pr_warn("// TODO map_update_elem: idx %td key %d value==map_idx %td\n",

				map - obj->maps, i, targ_map - obj->maps);
@@ -4962,8 +4974,7 @@ static int init_map_slots(struct bpf_object *obj, struct bpf_map *map) 
		if (err) {

			err = -errno;

			pr_warn("map '%s': failed to initialize slot [%d] to map '%s' fd=%d: %d\n",

				map->name, i, targ_map->name,

				fd, err);

				map->name, i, targ_map->name, fd, err);

			return err;

		}

		pr_debug("map '%s': slot [%d] set to map '%s' fd=%d\n",
@@ -4976,6 +4987,59 @@ static int init_map_slots(struct bpf_object *obj, struct bpf_map *map) 
	return 0;

}



static int init_prog_array_slots(struct bpf_object *obj, struct bpf_map *map)

{

	const struct bpf_program *targ_prog;

	unsigned int i;

	int fd, err;



	if (obj->gen_loader)

		return -ENOTSUP;



	for (i = 0; i < map->init_slots_sz; i++) {

		if (!map->init_slots[i])

			continue;



		targ_prog = map->init_slots[i];

		fd = bpf_program__fd(targ_prog);



		err = bpf_map_update_elem(map->fd, &i, &fd, 0);

		if (err) {

			err = -errno;

			pr_warn("map '%s': failed to initialize slot [%d] to prog '%s' fd=%d: %d\n",

				map->name, i, targ_prog->name, fd, err);

			return err;

		}

		pr_debug("map '%s': slot [%d] set to prog '%s' fd=%d\n",

			 map->name, i, targ_prog->name, fd);

	}



	zfree(&map->init_slots);

	map->init_slots_sz = 0;



	return 0;

}



static int bpf_object_init_prog_arrays(struct bpf_object *obj)

{

	struct bpf_map *map;

	int i, err;



	for (i = 0; i < obj->nr_maps; i++) {

		map = &obj->maps[i];



		if (!map->init_slots_sz || map->def.type != BPF_MAP_TYPE_PROG_ARRAY)

			continue;



		err = init_prog_array_slots(obj, map);

		if (err < 0) {

			zclose(map->fd);

			return err;

		}

	}

	return 0;

}



static int

bpf_object__create_maps(struct bpf_object *obj)

{
@@ -5042,8 +5106,8 @@ bpf_object__create_maps(struct bpf_object *obj) 
				}

			}



			if (map->init_slots_sz) {

				err = init_map_slots(obj, map);

			if (map->init_slots_sz && map->def.type != BPF_MAP_TYPE_PROG_ARRAY) {

				err = init_map_in_map_slots(obj, map);

				if (err < 0) {

					zclose(map->fd);

					goto err_out;
@@ -6189,9 +6253,11 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj, 
	int i, j, nrels, new_sz;

	const struct btf_var_secinfo *vi = NULL;

	const struct btf_type *sec, *var, *def;

	struct bpf_map *map = NULL, *targ_map;

	struct bpf_map *map = NULL, *targ_map = NULL;

	struct bpf_program *targ_prog = NULL;

	bool is_prog_array, is_map_in_map;

	const struct btf_member *member;

	const char *name, *mname;

	const char *name, *mname, *type;

	unsigned int moff;

	Elf64_Sym *sym;

	Elf64_Rel *rel;
@@ -6218,11 +6284,6 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj, 
			return -LIBBPF_ERRNO__FORMAT;

		}

		name = elf_sym_str(obj, sym->st_name) ?: "<?>";

		if (sym->st_shndx != obj->efile.btf_maps_shndx) {

			pr_warn(".maps relo #%d: '%s' isn't a BTF-defined map\n",

				i, name);

			return -LIBBPF_ERRNO__RELOC;

		}



		pr_debug(".maps relo #%d: for %zd value %zd rel->r_offset %zu name %d ('%s')\n",

			 i, (ssize_t)(rel->r_info >> 32), (size_t)sym->st_value,
@@ -6244,18 +6305,44 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj, 
			return -EINVAL;

		}



		if (!bpf_map_type__is_map_in_map(map->def.type))

			return -EINVAL;

		is_map_in_map = bpf_map_type__is_map_in_map(map->def.type);

		is_prog_array = map->def.type == BPF_MAP_TYPE_PROG_ARRAY;

		type = is_map_in_map ? "map" : "prog";

		if (is_map_in_map) {

			if (sym->st_shndx != obj->efile.btf_maps_shndx) {

				pr_warn(".maps relo #%d: '%s' isn't a BTF-defined map\n",

					i, name);

				return -LIBBPF_ERRNO__RELOC;

			}

			if (map->def.type == BPF_MAP_TYPE_HASH_OF_MAPS &&

			    map->def.key_size != sizeof(int)) {

				pr_warn(".maps relo #%d: hash-of-maps '%s' should have key size %zu.\n",

					i, map->name, sizeof(int));

				return -EINVAL;

			}



			targ_map = bpf_object__find_map_by_name(obj, name);

		if (!targ_map)

			if (!targ_map) {

				pr_warn(".maps relo #%d: '%s' isn't a valid map reference\n",

					i, name);

				return -ESRCH;

			}

		} else if (is_prog_array) {

			targ_prog = bpf_object__find_program_by_name(obj, name);

			if (!targ_prog) {

				pr_warn(".maps relo #%d: '%s' isn't a valid program reference\n",

					i, name);

				return -ESRCH;

			}

			if (targ_prog->sec_idx != sym->st_shndx ||

			    targ_prog->sec_insn_off * 8 != sym->st_value ||

			    prog_is_subprog(obj, targ_prog)) {

				pr_warn(".maps relo #%d: '%s' isn't an entry-point program\n",

					i, name);

				return -LIBBPF_ERRNO__RELOC;

			}

		} else {

			return -EINVAL;

		}



		var = btf__type_by_id(obj->btf, vi->type);

		def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
@@ -6287,10 +6374,10 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj, 
			       (new_sz - map->init_slots_sz) * host_ptr_sz);

			map->init_slots_sz = new_sz;

		}

		map->init_slots[moff] = targ_map;

		map->init_slots[moff] = is_map_in_map ? (void *)targ_map : (void *)targ_prog;



		pr_debug(".maps relo #%d: map '%s' slot [%d] points to map '%s'\n",

			 i, map->name, moff, name);

		pr_debug(".maps relo #%d: map '%s' slot [%d] points to %s '%s'\n",

			 i, map->name, moff, type, name);

	}



	return 0;
@@ -7304,6 +7391,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr) 
	err = err ? : bpf_object__create_maps(obj);

	err = err ? : bpf_object__relocate(obj, obj->btf_custom_path ? : attr->target_btf_path);

	err = err ? : bpf_object__load_progs(obj, attr->log_level);

	err = err ? : bpf_object_init_prog_arrays(obj);



	if (obj->gen_loader) {

		/* reset FDs */