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 <[email protected]>
---
Changes since v1:
- 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 | 64 ++++++++++++-------
2 files changed, 44 insertions(+), 24 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..e9a1a018f270 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];
@@ -712,19 +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.
*/
@@ -752,7 +748,7 @@ 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 +791,22 @@ 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 +1246,7 @@ 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 +1323,21 @@ static int do_skeleton(int argc, char **argv)
goto out_obj;
}
+ 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;
+ }
+ }
+
bpf_object__for_each_map(map, obj) {
if (!get_map_ident(map, ident, sizeof(ident))) {
p_err("ignoring unrecognized internal map '%s'...",
@@ -1339,6 +1351,8 @@ 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 +1416,8 @@ 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 +1431,8 @@ 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 +1469,7 @@ 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;
}
--
2.55.0.979.g7e5102b832-goog
