@@ -1510,6 +1510,37 @@ static size_t bpf_map_mmap_sz(const struct bpf_map *map)
return map_sz;
}
+static size_t __bpf_map_mmap_sz(unsigned int value_sz, unsigned int max_entries)
+{
+ const long page_sz = sysconf(_SC_PAGE_SIZE);
+ size_t map_sz;
+
+ map_sz = (size_t)roundup(value_sz, 8) * max_entries;
+ map_sz = roundup(map_sz, page_sz);
+ return map_sz;
+}
+
+static int bpf_map_mmap_resize(struct bpf_map *map, size_t old_sz, size_t new_sz)
+{
+ void *mmaped;
+
+ if (!map->mmaped)
+ return -EINVAL;
+
+ if (old_sz == new_sz)
+ return 0;
+
+ mmaped = mmap(NULL, new_sz, PROT_READ | PROT_WRITE,
+ MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+ if (mmaped == MAP_FAILED)
+ return -errno;
+
+ memcpy(mmaped, map->mmaped, min(old_sz, new_sz));
+ munmap(map->mmaped, old_sz);
+ map->mmaped = mmaped;
+ return 0;
+}
+
static char *internal_map_name(struct bpf_object *obj, const char *real_name)
{
char map_name[BPF_OBJ_NAME_LEN], *p;
@@ -9412,10 +9443,109 @@ __u32 bpf_map__value_size(const struct bpf_map *map)
return map->def.value_size;
}
+static int map_btf_datasec_resize(struct bpf_map *map, __u32 size)
+{
+ struct btf *btf;
+ struct btf_type *datasec_type, *var_type;
+ struct btf_var_secinfo *var;
+ const struct btf_type *array_type;
+ const struct btf_array *array;
+ int vlen;
+ __u32 nr_elements, new_array_id;
+ __s64 element_sz;
+
+ /* check btf existence */
+ btf = bpf_object__btf(map->obj);
+ if (!btf)
+ return -ENOENT;
+
+ /* verify map is datasec */
+ datasec_type = btf_type_by_id(btf, bpf_map__btf_value_type_id(map));
+ if (!btf_is_datasec(datasec_type)) {
+ pr_warn("map '%s': cannot be resized, map value type is not a datasec\n",
+ bpf_map__name(map));
+ return -EINVAL;
+ }
+
+ /* verify datasec has at least one var */
+ vlen = btf_vlen(datasec_type);
+ if (vlen == 0) {
+ pr_warn("map '%s': cannot be resized, map value datasec is empty\n",
+ bpf_map__name(map));
+ return -EINVAL;
+ }
+
+ /* verify last var in the datasec is an array */
+ var = &btf_var_secinfos(datasec_type)[vlen - 1];
+ var_type = btf_type_by_id(btf, var->type);
+ array_type = skip_mods_and_typedefs(btf, var_type->type, NULL);
+ if (!btf_is_array(array_type)) {
+ pr_warn("map '%s': cannot be resized, last var must be array\n",
+ bpf_map__name(map));
+ return -EINVAL;
+ }
+
+ /* verify request size aligns with array */
+ array = btf_array(array_type);
+ element_sz = btf__resolve_size(btf, array->type);
+ if (element_sz == 0)
+ return -EINVAL;
+ if ((size - var->offset) % element_sz != 0) {
+ pr_warn("map '%s': cannot be resized, requested size does not align\n",
+ bpf_map__name(map));
+ return -EINVAL;
+ }
+
+ /* create a new array based on the existing array,
+ * but with new length
+ */
+ nr_elements = (size - var->offset) / element_sz;
+ new_array_id = btf__add_array(btf, array->index_type, array->type,
+ nr_elements);
+ if (new_array_id < 0)
+ return new_array_id;
+
+ /* adding a new btf type invalidates existing pointers to btf objects,
+ * so refresh pointers before proceeding
+ */
+ datasec_type = btf_type_by_id(btf, map->btf_value_type_id);
+ var = &btf_var_secinfos(datasec_type)[vlen - 1];
+ var_type = btf_type_by_id(btf, var->type);
+
+ /* finally update btf info */
+ datasec_type->size = size;
+ var->size = size - var->offset;
+ var_type->type = new_array_id;
+
+ return 0;
+}
+
int bpf_map__set_value_size(struct bpf_map *map, __u32 size)
{
if (map->fd >= 0)
return libbpf_err(-EBUSY);
+
+ if (map->mmaped) {
+ int err;
+ size_t mmap_old_sz, mmap_new_sz;
+
+ mmap_old_sz = bpf_map_mmap_sz(map);
+ mmap_new_sz = __bpf_map_mmap_sz(size, map->def.max_entries);
+ err = bpf_map_mmap_resize(map, mmap_old_sz, mmap_new_sz);
+ if (err) {
+ pr_warn("map '%s': failed to resize memory mapped region\n",
+ bpf_map__name(map));
+ return err;
+ }
+ err = map_btf_datasec_resize(map, size);
+ if (err && err != -ENOENT) {
+ pr_warn("map '%s': failed to adjust btf for resized map, clearing btf key/value type info\n",
+ bpf_map__name(map));
+ map->btf_value_type_id = 0;
+ map->btf_key_type_id = 0;
+ }
+ }
+
map->def.value_size = size;
return 0;
}
@@ -869,8 +869,23 @@ LIBBPF_API int bpf_map__set_numa_node(struct bpf_map *map, __u32 numa_node);
/* get/set map key size */
LIBBPF_API __u32 bpf_map__key_size(const struct bpf_map *map);
LIBBPF_API int bpf_map__set_key_size(struct bpf_map *map, __u32 size);
-/* get/set map value size */
+/* get map value size */
LIBBPF_API __u32 bpf_map__value_size(const struct bpf_map *map);
+/**
+ * @brief **bpf_map__set_value_size()** sets map value size.
+ *
+ * There is a special case for maps with associated memory-mapped regions, like
+ * the global data section maps (bss, data, rodata). When this function is used
+ * on such a map, the mapped region is resized. Afterward, an attempt is made to
+ * adjust the corresponding BTF info. This attempt is best-effort and can only
+ * succeed if the last variable of the data section map is an array. The array
+ * BTF type is replaced by a new BTF array type with a different length.
+ * Because BTF info is modified to do this, pointer invalidation occurs. Any
+ * previously existing pointers returned from bpf_map__initial_value() or
+ * skeleton pointers must be reinitialized.
+ * @param map the BPF map instance
+ * @return 0, on success; negative error, otherwise
+ */
LIBBPF_API int bpf_map__set_value_size(struct bpf_map *map, __u32 size);
/* get map key/value BTF type IDs */
LIBBPF_API __u32 bpf_map__btf_key_type_id(const struct bpf_map *map);