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: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7ee44d8..88609dc 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -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;
@@ -808,29 +840,58 @@ 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);
 
-               if (scn)
-                       data = elf_getdata(scn, NULL);
-               if (!scn || !data) {
-                       pr_warning("failed to get Elf_Data from map section %d\n",
-                                  obj->efile.maps_shndx);
-                       return -EINVAL;
-               }
+       scn = elf_getscn(obj->efile.elf, obj->efile.maps_shndx);
+       if (scn)
+               data = elf_getdata(scn, NULL);
+       if (!scn || !data) {
+               pr_warning("failed to get Elf_Data from map section %d\n",
+                          obj->efile.maps_shndx);
+               return -EINVAL;
        }
 
        /*
@@ -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))
@@ -858,79 +911,56 @@ 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);
-
-               map_def_sz = data->d_size / nr_maps;
-               if (!data->d_size || (data->d_size % nr_maps) != 0) {
-                       pr_warning("unable to determine map definition size "
-                                  "section %s, %d maps in %zd bytes\n",
-                                  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;
+       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) {
+               pr_warning("unable to determine map definition size "
+                          "section %s, %d maps in %zd bytes\n",
+                          obj->path, nr_maps, data->d_size);
+               return -EINVAL;
        }
 
-       /*
-        * 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)
@@ -1262,14 +1285,10 @@ 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;
-       }
-       err = bpf_object__init_prog_names(obj);
+       if (!err)
+               err = bpf_object__init_prog_names(obj);
        return err;
 }