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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: fb.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SJ0PR15MB5154.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3081ff61-6d0b-4795-64cf-08d9fbf73097 X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Mar 2022 02:48:53.9561 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: JRdILaFzXG7Th2OMIirM25BXSKe6mjoSw7JrL8iB21FmSe7Yi5XNui6eDUDn7CDT X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR15MB4441 X-Proofpoint-GUID: BPorzhRkqrfeH3TR34TTx8-RWnqmrvFH X-Proofpoint-ORIG-GUID: BPorzhRkqrfeH3TR34TTx8-RWnqmrvFH X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.64.514 definitions=2022-03-02_01,2022-02-26_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=fb_outbound_notspam policy=fb_outbound score=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 priorityscore=1501 mlxscore=0 spamscore=0 suspectscore=0 mlxlogscore=999 phishscore=0 adultscore=0 bulkscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2203020010 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Subskeletons are headers which require an already loaded program to operate. For example, when a BPF library is linked into a larger BPF object file, the library userspace needs a way to access its own global variables without requiring knowledge about the larger program at build time. As a result, subskeletons require a loaded bpf_object to open(). Further, they find their own symbols in the larger program by walking BTF type data at run time. At this time, only globals are supported, though non-owning references to links, programs, and other objects may be added as the needs arise. Signed-off-by: Delyan Kratunov --- tools/bpf/bpftool/gen.c | 322 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 313 insertions(+), 9 deletions(-) diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index 145734b4fe41..ea292e09c17b 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -125,14 +125,14 @@ static int codegen_datasec_def(struct bpf_object *obj= , struct btf *btf, struct btf_dump *d, const struct btf_type *sec, - const char *obj_name) + const char *obj_name, + bool subskel) { const char *sec_name =3D btf__name_by_offset(btf, sec->name_off); const struct btf_var_secinfo *sec_var =3D btf_var_secinfos(sec); int i, err, off =3D 0, pad_cnt =3D 0, vlen =3D btf_vlen(sec); char var_ident[256], sec_ident[256]; bool strip_mods =3D false; - if (!get_datasec_ident(sec_name, sec_ident, sizeof(sec_ident))) return 0; =20 @@ -183,7 +183,7 @@ static int codegen_datasec_def(struct bpf_object *obj, align =3D 4; =20 align_off =3D (off + align - 1) / align * align; - if (align_off !=3D need_off) { + if (align_off !=3D need_off && !subskel) { printf("\t\tchar __pad%d[%d];\n", pad_cnt, need_off - off); pad_cnt++; @@ -197,6 +197,15 @@ static int codegen_datasec_def(struct bpf_object *obj, strncat(var_ident, var_name, sizeof(var_ident) - 1); sanitize_identifier(var_ident); =20 + /* to emit a pointer to the type in the map, we need to + * make sure our btf has that pointer type first. + */ + if (subskel) { + var_type_id =3D btf__add_ptr(btf, var_type_id); + if (var_type_id < 0) + return var_type_id; + } + printf("\t\t"); err =3D btf_dump__emit_type_decl(d, var_type_id, &opts); if (err) @@ -205,7 +214,10 @@ static int codegen_datasec_def(struct bpf_object *obj, =20 off =3D sec_var->offset + sec_var->size; } - printf(" } *%s;\n", sec_ident); + if (subskel) + printf(" } %s;\n", sec_ident); + else + printf(" } *%s;\n", sec_ident); return 0; } =20 @@ -231,7 +243,7 @@ static const struct btf_type *find_type_for_map(struct = btf *btf, const char *map return NULL; } =20 -static int codegen_datasecs(struct bpf_object *obj, const char *obj_name) +static int codegen_datasecs(struct bpf_object *obj, const char *obj_name, = bool subskel) { struct btf *btf =3D bpf_object__btf(obj); struct btf_dump *d; @@ -240,6 +252,13 @@ static int codegen_datasecs(struct bpf_object *obj, co= nst char *obj_name) char map_ident[256]; int err =3D 0; =20 + /* When generating a subskeleton, we need to emit _pointers_ + * to the types in the maps. Use a new btf object as storage for these + * new types as they're not guaranteed to already exist. + */ + if (subskel) + btf =3D btf__new_empty_split(btf); + d =3D btf_dump__new(btf, codegen_btf_dump_printf, NULL, NULL); err =3D libbpf_get_error(d); if (err) @@ -264,11 +283,11 @@ static int codegen_datasecs(struct bpf_object *obj, c= onst char *obj_name) * map. It will still be memory-mapped and its contents * accessible from user-space through BPF skeleton. */ - if (!sec) { + if (!sec && !subskel) { printf(" struct %s__%s {\n", obj_name, map_ident); printf(" } *%s;\n", map_ident); - } else { - err =3D codegen_datasec_def(obj, btf, d, sec, obj_name); + } else if (sec) { + err =3D codegen_datasec_def(obj, btf, d, sec, obj_name, subskel); if (err) goto out; } @@ -276,6 +295,8 @@ static int codegen_datasecs(struct bpf_object *obj, con= st char *obj_name) =20 =20 out: + if (subskel) + btf__free(btf); btf_dump__free(d); return err; } @@ -896,7 +917,7 @@ static int do_skeleton(int argc, char **argv) =20 btf =3D bpf_object__btf(obj); if (btf) { - err =3D codegen_datasecs(obj, obj_name); + err =3D codegen_datasecs(obj, obj_name, false); if (err) goto out; } @@ -1141,6 +1162,287 @@ static int do_skeleton(int argc, char **argv) return err; } =20 +/* Subskeletons are like skeletons, except they don't own the bpf_object, + * associated maps, links, etc. Instead, they know about the existence of + * a certain number of datasec fields and are able to find their locations + * _at runtime_ from an already loaded bpf_object. + * + * This allows for library-like BPF objects to have userspace counterparts + * with access to their globals without having to know anything about the + * final BPF object that the library was linked into. + */ +static int do_subskeleton(int argc, char **argv) +{ + char header_guard[MAX_OBJ_NAME_LEN + sizeof("__SKEL_H__")]; + size_t i, len, file_sz, mmap_sz, sym_sz =3D 0, sym_idx =3D 0; + DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts); + char obj_name[MAX_OBJ_NAME_LEN] =3D "", *obj_data; + struct bpf_object *obj =3D NULL; + const char *file, *var_name; + char ident[256], var_ident[256]; + int fd, err =3D -1, map_type_id; + const struct bpf_map *map; + struct btf *btf; + const struct btf_type *map_type, *var_type; + const struct btf_var_secinfo *var; + struct stat st; + + if (!REQ_ARGS(1)) { + usage(); + return -1; + } + file =3D GET_ARG(); + + while (argc) { + if (!REQ_ARGS(2)) + return -1; + + if (is_prefix(*argv, "name")) { + NEXT_ARG(); + + if (obj_name[0] !=3D '\0') { + p_err("object name already specified"); + return -1; + } + + strncpy(obj_name, *argv, MAX_OBJ_NAME_LEN - 1); + obj_name[MAX_OBJ_NAME_LEN - 1] =3D '\0'; + } else { + p_err("unknown arg %s", *argv); + return -1; + } + + NEXT_ARG(); + } + + if (argc) { + p_err("extra unknown arguments"); + return -1; + } + + if (use_loader) { + p_err("cannot use loader for subskeletons"); + return -1; + } + + if (stat(file, &st)) { + p_err("failed to stat() %s: %s", file, strerror(errno)); + return -1; + } + file_sz =3D st.st_size; + mmap_sz =3D roundup(file_sz, sysconf(_SC_PAGE_SIZE)); + fd =3D open(file, O_RDONLY); + if (fd < 0) { + p_err("failed to open() %s: %s", file, strerror(errno)); + return -1; + } + obj_data =3D mmap(NULL, mmap_sz, PROT_READ, MAP_PRIVATE, fd, 0); + if (obj_data =3D=3D MAP_FAILED) { + obj_data =3D NULL; + p_err("failed to mmap() %s: %s", file, strerror(errno)); + goto out; + } + if (obj_name[0] =3D=3D '\0') + get_obj_name(obj_name, file); + opts.object_name =3D obj_name; + if (verifier_logs) + /* log_level1 + log_level2 + stats, but not stable UAPI */ + opts.kernel_log_level =3D 1 + 2 + 4; + obj =3D bpf_object__open_mem(obj_data, file_sz, &opts); + err =3D libbpf_get_error(obj); + if (err) { + char err_buf[256]; + + libbpf_strerror(err, err_buf, sizeof(err_buf)); + p_err("failed to open BPF object file: %s", err_buf); + obj =3D NULL; + goto out; + } + + btf =3D bpf_object__btf(obj); + err =3D libbpf_get_error(btf); + if (err) { + err =3D -1; + p_err("need btf type information for %s", obj_name); + goto out; + } + + /* First, count how many symbols we have to link. */ + bpf_object__for_each_map(map, obj) { + if (!bpf_map__is_internal(map)) + continue; + + if (!(bpf_map__map_flags(map) & BPF_F_MMAPABLE)) + continue; + + if (!get_map_ident(map, ident, sizeof(ident))) + continue; + + map_type_id =3D btf__find_by_name_kind(btf, bpf_map__section_name(map), = BTF_KIND_DATASEC); + if (map_type_id < 0) { + err =3D map_type_id; + goto out; + } + map_type =3D btf__type_by_id(btf, map_type_id); + + for (i =3D 0, var =3D btf_var_secinfos(map_type), len =3D btf_vlen(map_t= ype); + i < len; + i++, var++) { + sym_sz++; + } + } + + get_header_guard(header_guard, obj_name); + codegen("\ + \n\ + /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ \n\ + \n\ + /* THIS FILE IS AUTOGENERATED! */ \n\ + #ifndef %2$s \n\ + #define %2$s \n\ + \n\ + #include \n\ + #include \n\ + #include \n\ + \n\ + struct %1$s { \n\ + struct bpf_object *obj; \n\ + struct bpf_object_subskeleton *subskel; \n\ + ", obj_name, header_guard); + + err =3D codegen_datasecs(obj, obj_name, true); + if (err) + goto out; + + /* emit code that will allocate enough storage for all symbols */ + codegen("\ + \n\ + \n\ + #ifdef __cplusplus \n\ + static inline struct %1$s *open(const struct bpf_object *src);\n\ + static inline void %1$s::destroy(struct %1$s *skel);\n\ + #endif /* __cplusplus */ \n\ + }; \n\ + \n\ + static inline void \n\ + %1$s__destroy(struct %1$s *skel) \n\ + { \n\ + if (!skel) \n\ + return; \n\ + if (skel->subskel) \n\ + bpf_object__destroy_subskeleton(skel->subskel);\n\ + free(skel); \n\ + } \n\ + \n\ + static inline struct %1$s * \n\ + %1$s__open(const struct bpf_object *src) \n\ + { \n\ + struct %1$s *obj; \n\ + struct bpf_object_subskeleton *subskel; \n\ + struct bpf_sym_skeleton *syms; \n\ + int err; \n\ + \n\ + obj =3D (struct %1$s *)calloc(1, sizeof(*obj)); \n\ + if (!obj) { \n\ + errno =3D ENOMEM; \n\ + return NULL; \n\ + } \n\ + subskel =3D (struct bpf_object_subskeleton *)calloc(1, sizeof(*subskel)= );\n\ + if (!subskel) { \n\ + errno =3D ENOMEM; \n\ + return NULL; \n\ + } \n\ + subskel->sz =3D sizeof(*subskel); \n\ + subskel->obj =3D src; \n\ + subskel->sym_skel_sz =3D sizeof(struct bpf_sym_skeleton); \n\ + subskel->sym_cnt =3D %2$d; \n\ + obj->subskel =3D subskel; \n\ + \n\ + syms =3D (struct bpf_sym_skeleton *)calloc(%2$d, sizeof(*syms));\n\ + if (!syms) { \n\ + free(subskel); \n\ + errno =3D ENOMEM; \n\ + return NULL; \n\ + } \n\ + subskel->syms =3D syms; \n\ + \n\ + ", + obj_name, sym_sz + ); + + /* walk through each symbol and emit the runtime representation + */ + bpf_object__for_each_map(map, obj) { + if (!bpf_map__is_internal(map)) + continue; + + if (!(bpf_map__map_flags(map) & BPF_F_MMAPABLE)) + continue; + + if (!get_map_ident(map, ident, sizeof(ident))) + continue; + + map_type_id =3D btf__find_by_name_kind(btf, bpf_map__section_name(map), = BTF_KIND_DATASEC); + if (map_type_id < 0) { + err =3D map_type_id; + goto out; + } + map_type =3D btf__type_by_id(btf, map_type_id); + + for (i =3D 0, var =3D btf_var_secinfos(map_type), len =3D btf_vlen(map_t= ype); + i < len; + i++, var++, sym_idx++) { + var_type =3D btf__type_by_id(btf, var->type); + var_name =3D btf__name_by_offset(btf, var_type->name_off); + + var_ident[0] =3D '\0'; + strncat(var_ident, var_name, sizeof(var_ident) - 1); + sanitize_identifier(var_ident); + + codegen("\ + \n\ + syms[%4$d].name =3D \"%1$s\"; \n\ + syms[%4$d].section =3D \"%3$s\"; \n\ + syms[%4$d].addr =3D (void**) &obj->%2$s.%1$s; \n\ + ", var_ident, ident, bpf_map__section_name(map), sym_idx); + } + } + + codegen("\ + \n\ + \n\ + err =3D bpf_object__open_subskeleton(subskel); \n\ + if (err) { \n\ + %1$s__destroy(obj); \n\ + errno =3D err; \n\ + return NULL; \n\ + } \n\ + \n\ + return obj; \n\ + } \n\ + ", + obj_name); + + codegen("\ + \n\ + \n\ + #ifdef __cplusplus \n\ + struct %1$s *%1$s::open(const struct bpf_object *src) { return %1$s__ope= n(src); }\n\ + void %1$s::destroy(struct %1$s *skel) { %1$s__destroy(skel); }\n\ + #endif /* __cplusplus */ \n\ + \n\ + #endif /* %2$s */ \n\ + ", + obj_name, header_guard); + err =3D 0; +out: + bpf_object__close(obj); + if (obj_data) + munmap(obj_data, mmap_sz); + close(fd); + return err; +} + static int do_object(int argc, char **argv) { struct bpf_linker *linker; @@ -1192,6 +1494,7 @@ static int do_help(int argc, char **argv) fprintf(stderr, "Usage: %1$s %2$s object OUTPUT_FILE INPUT_FILE [INPUT_FILE...]\n" " %1$s %2$s skeleton FILE [name OBJECT_NAME]\n" + " %1$s %2$s subskeleton FILE [name OBJECT_NAME]\n" " %1$s %2$s min_core_btf INPUT OUTPUT OBJECT [OBJECT...]\n" " %1$s %2$s help\n" "\n" @@ -1788,6 +2091,7 @@ static int do_min_core_btf(int argc, char **argv) static const struct cmd cmds[] =3D { { "object", do_object }, { "skeleton", do_skeleton }, + { "subskeleton", do_subskeleton }, { "min_core_btf", do_min_core_btf}, { "help", do_help }, { 0 } --=20 2.34.1