When generating a light skeleton (bpftool gen skeleton -L), bpf_object__load() skips loading programs marked as non-autoload (e.g. SEC("?...")), so the generated loader program only records and populates file descriptors for autoloaded programs. Previously, bpftool emitted struct bpf_prog_desc fields, link fields, and attach/detach/destroy functions for all programs in the BPF object, causing the loader program to store subsequent program FDs into incorrect skeleton struct fields when non-autoload programs were present. Furthermore, bpf_object__load() can update a program's autoload status during preparation (e.g. for struct_ops programs when resolving kernel BTF members or adjusting autoload based on map autocreate settings). Move bpf_object__gen_loader() and bpf_object__load() out of gen_trace() into do_skeleton() before counting programs and emitting struct fields so that struct field declarations and attach/detach/destroy functions all observe the final post-load autoload state. Skip programs with !bpf_program__autoload(prog) when counting programs and generating progs/links struct fields as well as attach, detach, and destroy functions for light skeletons. Fixes: d510296d331a ("bpftool: Use syscall/loader program in "prog load" and "gen skeleton" command.") Signed-off-by: Thiébaud Weksteen --- v2 -> v3: - Move comment from gen_trace() to do_skeleton() - Add comment to do_skeleton() why the loader is called early v1 -> v2: - Move bpf_object__gen_loader() and bpf_object__load() out of gen_trace() .../bpf/bpftool/Documentation/bpftool-gen.rst | 4 +- tools/bpf/bpftool/gen.c | 76 ++++++++++++------- 2 files changed, 52 insertions(+), 28 deletions(-) diff --git a/tools/bpf/bpftool/Documentation/bpftool-gen.rst b/tools/bpf/bpftool/Documentation/bpftool-gen.rst index d0a36f442db7..1cdecf3e4fa5 100644 --- a/tools/bpf/bpftool/Documentation/bpftool-gen.rst +++ b/tools/bpf/bpftool/Documentation/bpftool-gen.rst @@ -184,7 +184,9 @@ OPTIONS -L, --use-loader For skeletons, generate a "light" skeleton (also known as "loader" skeleton). A light skeleton contains a loader eBPF program. It does not use - the majority of the libbpf infrastructure, and does not need libelf. + the majority of the libbpf infrastructure, and does not need libelf. BPF + programs marked as non-autoload (e.g., via **SEC("?...")**) are skipped and + not included in the generated skeleton. -S, --sign For skeletons, generate a signed skeleton. This option must be used with diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index a50540ef6521..1e55f0e67d91 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -583,6 +583,9 @@ static void codegen_attach_detach(struct bpf_object *obj, const char *obj_name) bpf_object__for_each_program(prog, obj) { const char *tp_name; + if (!bpf_program__autoload(prog)) + continue; + codegen("\ \n\ \n\ @@ -629,6 +632,8 @@ static void codegen_attach_detach(struct bpf_object *obj, const char *obj_name) ", obj_name); bpf_object__for_each_program(prog, obj) { + if (!bpf_program__autoload(prog)) + continue; codegen("\ \n\ ret = ret < 0 ? ret : %1$s__%2$s__attach(skel); \n\ @@ -646,6 +651,8 @@ static void codegen_attach_detach(struct bpf_object *obj, const char *obj_name) ", obj_name); bpf_object__for_each_program(prog, obj) { + if (!bpf_program__autoload(prog)) + continue; codegen("\ \n\ skel_closenz(skel->links.%1$s_fd); \n\ @@ -676,6 +683,8 @@ static void codegen_destroy(struct bpf_object *obj, const char *obj_name) obj_name); bpf_object__for_each_program(prog, obj) { + if (!bpf_program__autoload(prog)) + continue; codegen("\ \n\ skel_closenz(skel->progs.%1$s.prog_fd); \n\ @@ -701,9 +710,9 @@ static void codegen_destroy(struct bpf_object *obj, const char *obj_name) obj_name); } -static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *header_guard) +static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *header_guard, + const struct gen_loader_opts *opts) { - DECLARE_LIBBPF_OPTS(gen_loader_opts, opts); struct bpf_load_and_run_opts sopts = {}; char sig_buf[MAX_SIG_SIZE]; __u8 prog_sha[SHA256_DIGEST_LENGTH]; @@ -712,23 +721,6 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h char ident[256]; int err = 0; - if (sign_progs) - opts.gen_hash = true; - - err = bpf_object__gen_loader(obj, &opts); - if (err) - return err; - - err = bpf_object__load(obj); - if (err) { - p_err("failed to load object file"); - goto out; - } - - /* If there was no error during load then gen_loader_opts - * are populated with the loader program. - */ - /* finish generating 'struct skel' */ codegen("\ \n\ @@ -752,7 +744,7 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h goto cleanup; \n\ skel->ctx.sz = (char *)&skel->links - (char *)skel; \n\ ", - obj_name, opts.data_sz); + obj_name, opts->data_sz); bpf_object__for_each_map(map, obj) { const void *mmap_data = NULL; size_t mmap_size = 0; @@ -795,22 +787,22 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h static const char opts_data[] __attribute__((__aligned__(8))) = \"\\\n\ ", obj_name); - print_hex(opts.data, opts.data_sz); + print_hex(opts->data, opts->data_sz); codegen("\ \n\ \"; \n\ static const char opts_insn[] __attribute__((__aligned__(8))) = \"\\\n\ "); - print_hex(opts.insns, opts.insns_sz); + print_hex(opts->insns, opts->insns_sz); codegen("\ \n\ \";\n"); if (sign_progs) { - sopts.insns = opts.insns; - sopts.insns_sz = opts.insns_sz; - sopts.data = opts.data; - sopts.data_sz = opts.data_sz; + sopts.insns = opts->insns; + sopts.insns_sz = opts->insns_sz; + sopts.data = opts->data; + sopts.data_sz = opts->data_sz; sopts.excl_prog_hash = prog_sha; sopts.excl_prog_hash_sz = sizeof(prog_sha); sopts.signature = sig_buf; @@ -1250,6 +1242,7 @@ static int do_skeleton(int argc, char **argv) char header_guard[MAX_OBJ_NAME_LEN + sizeof("__SKEL_H__")]; size_t map_cnt = 0, prog_cnt = 0, attach_map_cnt = 0, file_sz, mmap_sz; DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts); + DECLARE_LIBBPF_OPTS(gen_loader_opts, gen_opts); char obj_name[MAX_OBJ_NAME_LEN] = "", *obj_data; struct bpf_object *obj = NULL; const char *file; @@ -1326,6 +1319,29 @@ static int do_skeleton(int argc, char **argv) goto out_obj; } + /* If we are generating a loader, load the object early (before + * counting programs and emitting skeleton struct definitions), as + * bpf_object__load() may disable (i.e., autoload=false) some programs + * if their requirements are not met. + */ + if (use_loader) { + if (sign_progs) + gen_opts.gen_hash = true; + + err = bpf_object__gen_loader(obj, &gen_opts); + if (err) + goto out; + + err = bpf_object__load(obj); + if (err) { + p_err("failed to load object file"); + goto out; + } + /* If there was no error during load, gen_opts is populated with + * the loader program. + */ + } + bpf_object__for_each_map(map, obj) { if (!get_map_ident(map, ident, sizeof(ident))) { p_err("ignoring unrecognized internal map '%s'...", @@ -1339,6 +1355,8 @@ static int do_skeleton(int argc, char **argv) map_cnt++; } bpf_object__for_each_program(prog, obj) { + if (use_loader && !bpf_program__autoload(prog)) + continue; prog_cnt++; } @@ -1402,6 +1420,8 @@ static int do_skeleton(int argc, char **argv) if (prog_cnt) { printf("\tstruct {\n"); bpf_object__for_each_program(prog, obj) { + if (use_loader && !bpf_program__autoload(prog)) + continue; if (use_loader) printf("\t\tstruct bpf_prog_desc %s;\n", bpf_program__name(prog)); @@ -1415,6 +1435,8 @@ static int do_skeleton(int argc, char **argv) if (prog_cnt + attach_map_cnt) { printf("\tstruct {\n"); bpf_object__for_each_program(prog, obj) { + if (use_loader && !bpf_program__autoload(prog)) + continue; if (use_loader) printf("\t\tint %s_fd;\n", bpf_program__name(prog)); @@ -1451,7 +1473,7 @@ static int do_skeleton(int argc, char **argv) goto out; } if (use_loader) { - err = gen_trace(obj, obj_name, header_guard); + err = gen_trace(obj, obj_name, header_guard, &gen_opts); goto out; } -- 2.55.0.1082.g2b9226bbc0-goog