Commit bf829271 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

libbpf: refactor map initialization 



User and global data maps initialization has gotten pretty complicated
and unnecessarily convoluted. This patch splits out the logic for global
data map and user-defined map initialization. It also removes the
restriction of pre-calculating how many maps will be initialized,
instead allowing to keep adding new maps as they are discovered, which
will be used later for BTF-defined map definitions.

Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 01b29d1d

tools/lib/bpf/libbpf.c

+133 −114
Original line number Diff line number Diff line
@@ -234,6 +234,7 @@ struct bpf_object { 
	size_t nr_programs;

	struct bpf_map *maps;

	size_t nr_maps;

	size_t maps_cap;

	struct bpf_secdata sections;



	bool loaded;
@@ -763,21 +764,51 @@ int bpf_object__variable_offset(const struct bpf_object *obj, const char *name, 
	return -ENOENT;

}



static bool bpf_object__has_maps(const struct bpf_object *obj)

static struct bpf_map *bpf_object__add_map(struct bpf_object *obj)

{

	return obj->efile.maps_shndx >= 0 ||

	       obj->efile.data_shndx >= 0 ||

	       obj->efile.rodata_shndx >= 0 ||

	       obj->efile.bss_shndx >= 0;

	struct bpf_map *new_maps;

	size_t new_cap;

	int i;



	if (obj->nr_maps < obj->maps_cap)

		return &obj->maps[obj->nr_maps++];



	new_cap = max(4ul, obj->maps_cap * 3 / 2);

	new_maps = realloc(obj->maps, new_cap * sizeof(*obj->maps));

	if (!new_maps) {

		pr_warning("alloc maps for object failed\n");

		return ERR_PTR(-ENOMEM);

	}



	obj->maps_cap = new_cap;

	obj->maps = new_maps;



	/* zero out new maps */

	memset(obj->maps + obj->nr_maps, 0,

	       (obj->maps_cap - obj->nr_maps) * sizeof(*obj->maps));

	/*

	 * fill all fd with -1 so won't close incorrect fd (fd=0 is stdin)

	 * when failure (zclose won't close negative fd)).

	 */

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

		obj->maps[i].fd = -1;

		obj->maps[i].inner_map_fd = -1;

	}



	return &obj->maps[obj->nr_maps++];

}



static int

bpf_object__init_internal_map(struct bpf_object *obj, struct bpf_map *map,

			      enum libbpf_map_type type, Elf_Data *data,

			      void **data_buff)

bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,

			      Elf_Data *data, void **data_buff)

{

	struct bpf_map_def *def = &map->def;

	char map_name[BPF_OBJ_NAME_LEN];

	struct bpf_map_def *def;

	struct bpf_map *map;



	map = bpf_object__add_map(obj);

	if (IS_ERR(map))

		return PTR_ERR(map);



	map->libbpf_type = type;

	map->offset = ~(typeof(map->offset))0;
@@ -789,6 +820,7 @@ bpf_object__init_internal_map(struct bpf_object *obj, struct bpf_map *map, 
		return -ENOMEM;

	}



	def = &map->def;

	def->type = BPF_MAP_TYPE_ARRAY;

	def->key_size = sizeof(int);

	def->value_size = data->d_size;
@@ -808,22 +840,52 @@ bpf_object__init_internal_map(struct bpf_object *obj, struct bpf_map *map, 
	return 0;

}



static int bpf_object__init_maps(struct bpf_object *obj, int flags)

static int bpf_object__init_global_data_maps(struct bpf_object *obj)

{

	int err;



	if (!obj->caps.global_data)

		return 0;

	/*

	 * Populate obj->maps with libbpf internal maps.

	 */

	if (obj->efile.data_shndx >= 0) {

		err = bpf_object__init_internal_map(obj, LIBBPF_MAP_DATA,

						    obj->efile.data,

						    &obj->sections.data);

		if (err)

			return err;

	}

	if (obj->efile.rodata_shndx >= 0) {

		err = bpf_object__init_internal_map(obj, LIBBPF_MAP_RODATA,

						    obj->efile.rodata,

						    &obj->sections.rodata);

		if (err)

			return err;

	}

	if (obj->efile.bss_shndx >= 0) {

		err = bpf_object__init_internal_map(obj, LIBBPF_MAP_BSS,

						    obj->efile.bss, NULL);

		if (err)

			return err;

	}

	return 0;

}



static int bpf_object__init_user_maps(struct bpf_object *obj, bool strict)

{

	int i, map_idx, map_def_sz = 0, nr_syms, nr_maps = 0, nr_maps_glob = 0;

	bool strict = !(flags & MAPS_RELAX_COMPAT);

	Elf_Data *symbols = obj->efile.symbols;

	int i, map_def_sz = 0, nr_maps = 0, nr_syms;

	Elf_Data *data = NULL;

	int ret = 0;

	Elf_Scn *scn;



	if (obj->efile.maps_shndx < 0)

		return 0;



	if (!symbols)

		return -EINVAL;

	nr_syms = symbols->d_size / sizeof(GElf_Sym);



	if (obj->efile.maps_shndx >= 0) {

		Elf_Scn *scn = elf_getscn(obj->efile.elf,

					  obj->efile.maps_shndx);



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

	if (scn)

		data = elf_getdata(scn, NULL);

	if (!scn || !data) {
@@ -831,7 +893,6 @@ static int bpf_object__init_maps(struct bpf_object *obj, int flags) 
			   obj->efile.maps_shndx);

		return -EINVAL;

	}

	}



	/*

	 * Count number of maps. Each map has a name.
@@ -840,16 +901,8 @@ static int bpf_object__init_maps(struct bpf_object *obj, int flags) 
	 *

	 * TODO: Detect array of map and report error.

	 */

	if (obj->caps.global_data) {

		if (obj->efile.data_shndx >= 0)

			nr_maps_glob++;

		if (obj->efile.rodata_shndx >= 0)

			nr_maps_glob++;

		if (obj->efile.bss_shndx >= 0)

			nr_maps_glob++;

	}



	for (i = 0; data && i < nr_syms; i++) {

	nr_syms = symbols->d_size / sizeof(GElf_Sym);

	for (i = 0; i < nr_syms; i++) {

		GElf_Sym sym;



		if (!gelf_getsym(symbols, i, &sym))
@@ -858,14 +911,9 @@ static int bpf_object__init_maps(struct bpf_object *obj, int flags) 
			continue;

		nr_maps++;

	}



	if (!nr_maps && !nr_maps_glob)

		return 0;



	/* Assume equally sized map definitions */

	if (data) {

		pr_debug("maps in %s: %d maps in %zd bytes\n", obj->path,

			 nr_maps, data->d_size);

	pr_debug("maps in %s: %d maps in %zd bytes\n",

		 obj->path, nr_maps, data->d_size);



	map_def_sz = data->d_size / nr_maps;

	if (!data->d_size || (data->d_size % nr_maps) != 0) {
@@ -874,63 +922,45 @@ static int bpf_object__init_maps(struct bpf_object *obj, int flags) 
			   obj->path, nr_maps, data->d_size);

		return -EINVAL;

	}

	}



	nr_maps += nr_maps_glob;

	obj->maps = calloc(nr_maps, sizeof(obj->maps[0]));

	if (!obj->maps) {

		pr_warning("alloc maps for object failed\n");

		return -ENOMEM;

	}

	obj->nr_maps = nr_maps;



	for (i = 0; i < nr_maps; i++) {

		/*

		 * fill all fd with -1 so won't close incorrect

		 * fd (fd=0 is stdin) when failure (zclose won't close

		 * negative fd)).

		 */

		obj->maps[i].fd = -1;

		obj->maps[i].inner_map_fd = -1;

	}



	/*

	 * Fill obj->maps using data in "maps" section.

	 */

	for (i = 0, map_idx = 0; data && i < nr_syms; i++) {

	/* Fill obj->maps using data in "maps" section.  */

	for (i = 0; i < nr_syms; i++) {

		GElf_Sym sym;

		const char *map_name;

		struct bpf_map_def *def;

		struct bpf_map *map;



		if (!gelf_getsym(symbols, i, &sym))

			continue;

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

			continue;



		map_name = elf_strptr(obj->efile.elf,

				      obj->efile.strtabidx,

		map = bpf_object__add_map(obj);

		if (IS_ERR(map))

			return PTR_ERR(map);



		map_name = elf_strptr(obj->efile.elf, obj->efile.strtabidx,

				      sym.st_name);

		if (!map_name) {

			pr_warning("failed to get map #%d name sym string for obj %s\n",

				   map_idx, obj->path);

				   i, obj->path);

			return -LIBBPF_ERRNO__FORMAT;

		}



		obj->maps[map_idx].libbpf_type = LIBBPF_MAP_UNSPEC;

		obj->maps[map_idx].offset = sym.st_value;

		map->libbpf_type = LIBBPF_MAP_UNSPEC;

		map->offset = sym.st_value;

		if (sym.st_value + map_def_sz > data->d_size) {

			pr_warning("corrupted maps section in %s: last map \"%s\" too small\n",

				   obj->path, map_name);

			return -EINVAL;

		}



		obj->maps[map_idx].name = strdup(map_name);

		if (!obj->maps[map_idx].name) {

		map->name = strdup(map_name);

		if (!map->name) {

			pr_warning("failed to alloc map name\n");

			return -ENOMEM;

		}

		pr_debug("map %d is \"%s\"\n", map_idx,

			 obj->maps[map_idx].name);

		pr_debug("map %d is \"%s\"\n", i, map->name);

		def = (struct bpf_map_def *)(data->d_buf + sym.st_value);

		/*

		 * If the definition of the map in the object file fits in
@@ -939,7 +969,7 @@ static int bpf_object__init_maps(struct bpf_object *obj, int flags) 
		 * calloc above.

		 */

		if (map_def_sz <= sizeof(struct bpf_map_def)) {

			memcpy(&obj->maps[map_idx].def, def, map_def_sz);

			memcpy(&map->def, def, map_def_sz);

		} else {

			/*

			 * Here the map structure being read is bigger than what
@@ -959,37 +989,30 @@ static int bpf_object__init_maps(struct bpf_object *obj, int flags) 
						return -EINVAL;

				}

			}

			memcpy(&obj->maps[map_idx].def, def,

			       sizeof(struct bpf_map_def));

			memcpy(&map->def, def, sizeof(struct bpf_map_def));

		}

		map_idx++;

	}

	return 0;

}



	if (!obj->caps.global_data)

		goto finalize;

static int bpf_object__init_maps(struct bpf_object *obj, int flags)

{

	bool strict = !(flags & MAPS_RELAX_COMPAT);

	int err;



	/*

	 * Populate rest of obj->maps with libbpf internal maps.

	 */

	if (obj->efile.data_shndx >= 0)

		ret = bpf_object__init_internal_map(obj, &obj->maps[map_idx++],

						    LIBBPF_MAP_DATA,

						    obj->efile.data,

						    &obj->sections.data);

	if (!ret && obj->efile.rodata_shndx >= 0)

		ret = bpf_object__init_internal_map(obj, &obj->maps[map_idx++],

						    LIBBPF_MAP_RODATA,

						    obj->efile.rodata,

						    &obj->sections.rodata);

	if (!ret && obj->efile.bss_shndx >= 0)

		ret = bpf_object__init_internal_map(obj, &obj->maps[map_idx++],

						    LIBBPF_MAP_BSS,

						    obj->efile.bss, NULL);

finalize:

	if (!ret)

	err = bpf_object__init_user_maps(obj, strict);

	if (err)

		return err;



	err = bpf_object__init_global_data_maps(obj);

	if (err)

		return err;



	if (obj->nr_maps) {

		qsort(obj->maps, obj->nr_maps, sizeof(obj->maps[0]),

		      compare_bpf_map);

	return ret;

	}

	return 0;

}



static bool section_have_execinstr(struct bpf_object *obj, int idx)
@@ -1262,13 +1285,9 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags) 
		return -LIBBPF_ERRNO__FORMAT;

	}

	err = bpf_object__load_btf(obj, btf_data, btf_ext_data);

	if (err)

		return err;

	if (bpf_object__has_maps(obj)) {

	if (!err)

		err = bpf_object__init_maps(obj, flags);

		if (err)

			return err;

	}

	if (!err)

		err = bpf_object__init_prog_names(obj);

	return err;

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE