From: "Thiébaud Weksteen" <tweek@google.com>
To: "Quentin Monnet" <qmo@kernel.org>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Shuah Khan" <shuah@kernel.org>,
"Thiébaud Weksteen" <tweek@google.com>,
"KP Singh" <kpsingh@kernel.org>,
"Leon Hwang" <leon.hwang@linux.dev>,
"Emil Tsalapatis" <emil@etsalapatis.com>
Cc: Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>,
Ihor Solodrai <ihor.solodrai@linux.dev>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: [PATCH bpf-next v2 2/3] bpftool: Compute light skeleton ctx.sz without relying on links
Date: Wed, 9 Sep 2026 14:24:32 +1000 [thread overview]
Message-ID: <20260909042433.1775591-2-tweek@google.com> (raw)
In-Reply-To: <20260909042433.1775591-1-tweek@google.com>
When generating a light skeleton, gen_trace() unconditionally sets
skel->ctx.sz using (char *)&skel->links - (char *)skel. However, if a
BPF object has no programs and no struct_ops maps (prog_cnt +
attach_map_cnt == 0), do_skeleton() omits the links struct, causing the
generated skeleton header to fail compilation.
Compute skel->ctx.sz from the end of progs (if prog_cnt > 0), maps (if
map_cnt > 0), or ctx instead of relying on skel->links. Also remove the
unused opts.data_sz argument passed to codegen().
Fixes: d510296d331a ("bpftool: Use syscall/loader program in "prog load" and "gen skeleton" command.")
Signed-off-by: Thiébaud Weksteen <tweek@google.com>
---
tools/bpf/bpftool/gen.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index e9a1a018f270..4a93c392857a 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -711,7 +711,7 @@ static void codegen_destroy(struct bpf_object *obj, const char *obj_name)
}
static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *header_guard,
- const struct gen_loader_opts *opts)
+ const struct gen_loader_opts *opts, size_t prog_cnt, size_t map_cnt)
{
struct bpf_load_and_run_opts sopts = {};
char sig_buf[MAX_SIG_SIZE];
@@ -746,9 +746,16 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h
skel = (struct %1$s *)skel_alloc(sizeof(*skel)); \n\
if (!skel) \n\
goto cleanup; \n\
- skel->ctx.sz = (char *)&skel->links - (char *)skel; \n\
",
- obj_name, opts->data_sz);
+ obj_name);
+ if (prog_cnt)
+ printf("\tskel->ctx.sz = (char *)&skel->progs - (char *)skel\n"
+ "\t\t + sizeof(skel->progs);\n");
+ else if (map_cnt)
+ printf("\tskel->ctx.sz = (char *)&skel->maps - (char *)skel\n"
+ "\t\t + sizeof(skel->maps);\n");
+ else
+ printf("\tskel->ctx.sz = sizeof(skel->ctx);\n");
bpf_object__for_each_map(map, obj) {
const void *mmap_data = NULL;
size_t mmap_size = 0;
@@ -1469,7 +1476,7 @@ static int do_skeleton(int argc, char **argv)
goto out;
}
if (use_loader) {
- err = gen_trace(obj, obj_name, header_guard, &gen_opts);
+ err = gen_trace(obj, obj_name, header_guard, &gen_opts, prog_cnt, map_cnt);
goto out;
}
--
2.55.0.979.g7e5102b832-goog
next prev parent reply other threads:[~2026-09-09 4:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-09 4:24 [PATCH bpf-next v2 1/3] bpftool: Skip non-autoload programs when generating light skeletons Thiébaud Weksteen
2026-09-09 4:24 ` Thiébaud Weksteen [this message]
2026-09-09 4:24 ` [PATCH bpf-next v2 3/3] selftests/bpf: Verify program FD after non-autoload programs in lskel Thiébaud Weksteen
2026-09-10 5:49 ` Leon Hwang
2026-09-09 5:02 ` [PATCH bpf-next v2 1/3] bpftool: Skip non-autoload programs when generating light skeletons bot+bpf-ci
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260909042433.1775591-2-tweek@google.com \
--to=tweek@google.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=eddyz87@gmail.com \
--cc=emil@etsalapatis.com \
--cc=ihor.solodrai@linux.dev \
--cc=jolsa@kernel.org \
--cc=kpsingh@kernel.org \
--cc=leon.hwang@linux.dev \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=martin.lau@linux.dev \
--cc=memxor@gmail.com \
--cc=qmo@kernel.org \
--cc=shuah@kernel.org \
--cc=song@kernel.org \
--cc=yonghong.song@linux.dev \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.