From: Yonghong Song <yonghong.song@linux.dev>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Eduard Zingerman <eddyz87@gmail.com>,
kernel-team@fb.com
Subject: [PATCH bpf-next v5 21/21] selftests/bpf: Load an exception cleanup program from a light skeleton
Date: Tue, 22 Sep 2026 22:00:34 -0700 [thread overview]
Message-ID: <20260923050034.2427959-1-yonghong.song@linux.dev> (raw)
In-Reply-To: <20260923045846.2414643-1-yonghong.song@linux.dev>
For a light skeleton, libbpf hands the records to bpf_gen__prog_load(),
which writes them into a blob and emits a loader program that issues
BPF_PROG_LOAD from inside the kernel. Nothing about that is shared with the
ordinary path: the attr is built field by field, and the kfunc names are
resolved by the loader program when it runs.
exceptions_cleanup_light.c is the smallest program that can tell whether a
table survives that trip: one record covering the bpf_throw() call itself,
one pad that sets a bit and resumes. If the table arrives, the pad runs and
the cookie comes back; if it does not, the program does not load at all.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
tools/testing/selftests/bpf/Makefile.skel | 2 +-
.../selftests/bpf/exceptions_cleanup.h | 3 ++
.../bpf/prog_tests/exceptions_cleanup.c | 28 +++++++++++++
.../bpf/progs/exceptions_cleanup_light.c | 39 +++++++++++++++++++
4 files changed, 71 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/bpf/progs/exceptions_cleanup_light.c
diff --git a/tools/testing/selftests/bpf/Makefile.skel b/tools/testing/selftests/bpf/Makefile.skel
index 580d1d82c186..6d7518fa4018 100644
--- a/tools/testing/selftests/bpf/Makefile.skel
+++ b/tools/testing/selftests/bpf/Makefile.skel
@@ -33,7 +33,7 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h \
LSKELS := fexit_sleep.c trace_printk.c trace_vprintk.c map_ptr_kern.c \
core_kern.c core_kern_overflow.c test_ringbuf.c \
test_ringbuf_n.c test_ringbuf_map_key.c test_ringbuf_write.c \
- test_ringbuf_overwrite.c
+ test_ringbuf_overwrite.c exceptions_cleanup_light.c
LSKELS_SIGNED := fentry_test.c fexit_test.c atomics.c
diff --git a/tools/testing/selftests/bpf/exceptions_cleanup.h b/tools/testing/selftests/bpf/exceptions_cleanup.h
index d6f63f147c4a..68f2d61a694b 100644
--- a/tools/testing/selftests/bpf/exceptions_cleanup.h
+++ b/tools/testing/selftests/bpf/exceptions_cleanup.h
@@ -36,6 +36,9 @@
#define RAN_GLOBAL_PAD 0x80000
#define RAN_PAD_R0 0x100000
+/* progs/exceptions_cleanup_light.c: the one pad it has. */
+#define RAN_LIGHT 0x1
+
#define CLEANUP_REC(begin, end, landing_pad) \
".pushsection .bpf_cleanup,\"a\",@progbits;" \
".long " begin ";" \
diff --git a/tools/testing/selftests/bpf/prog_tests/exceptions_cleanup.c b/tools/testing/selftests/bpf/prog_tests/exceptions_cleanup.c
index dbdb78b791e0..323ee8d72c91 100644
--- a/tools/testing/selftests/bpf/prog_tests/exceptions_cleanup.c
+++ b/tools/testing/selftests/bpf/prog_tests/exceptions_cleanup.c
@@ -8,6 +8,7 @@
#include "exceptions_cleanup_freplace.skel.h"
#include "exceptions_cleanup_pad_freplace.skel.h"
#include "exceptions_cleanup_ext_table.skel.h"
+#include "exceptions_cleanup_light.lskel.h"
/* foo3 threw: every frame that has a pad ran it. */
#define PADS_FOO3_THREW \
@@ -171,6 +172,30 @@ static void test_ext_table(struct exceptions_cleanup_shapes *skel)
exceptions_cleanup_ext_table__destroy(fr);
}
+static void test_light_skeleton(void)
+{
+ struct exceptions_cleanup_light_lskel *skel;
+ __u64 ctx = 0;
+ int err;
+
+ LIBBPF_OPTS(bpf_test_run_opts, topts,
+ .ctx_in = &ctx,
+ .ctx_size_in = sizeof(ctx),
+ );
+
+ skel = exceptions_cleanup_light_lskel__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "light open_and_load"))
+ return;
+
+ err = bpf_prog_test_run_opts(skel->progs.entry_light.prog_fd, &topts);
+ if (!ASSERT_OK(err, "run"))
+ goto out;
+ ASSERT_EQ(topts.retval, THROW_COOKIE, "retval");
+ ASSERT_EQ(skel->bss->pads_ran, RAN_LIGHT, "pads_ran");
+out:
+ exceptions_cleanup_light_lskel__destroy(skel);
+}
+
static void test_shapes(void)
{
struct exceptions_cleanup_shapes *skel;
@@ -487,6 +512,9 @@ void test_exceptions_cleanup(void)
exceptions_cleanup__destroy(skel);
+ if (test__start_subtest("light_skeleton"))
+ test_light_skeleton();
+
test_shapes();
RUN_TESTS(exceptions_cleanup_fail);
diff --git a/tools/testing/selftests/bpf/progs/exceptions_cleanup_light.c b/tools/testing/selftests/bpf/progs/exceptions_cleanup_light.c
new file mode 100644
index 000000000000..de7ae478d67f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/exceptions_cleanup_light.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+#include "exceptions_cleanup.h"
+
+static __used __noinline void __kfunc_btf_anchor(void)
+{
+ bpf_throw(0);
+ bpf_preempt_disable();
+ bpf_preempt_enable();
+ bpf_unwind_resume();
+}
+
+__u64 pads_ran = 0;
+
+SEC("syscall")
+__naked int entry_light(void)
+{
+ asm volatile (
+ "call bpf_preempt_disable;"
+ "r1 = %[cookie];"
+"1:" "call bpf_throw;" /* cleanup region */
+"2:"
+ "exit;"
+"3:" /* landing pad */
+ "call bpf_preempt_enable;"
+ PAD_RAN("%[ran]")
+ "call bpf_unwind_resume;"
+ "exit;"
+ CLEANUP_REC("1b", "2b", "3b")
+ :
+ : [cookie]"i"(THROW_COOKIE), [ran]"i"(RAN_LIGHT),
+ __imm_addr(pads_ran)
+ : __clobber_all);
+}
+
+char _license[] SEC("license") = "GPL";
--
2.53.0-Meta
prev parent reply other threads:[~2026-09-23 5:00 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-23 4:58 [PATCH bpf-next v5 00/21] bpf: Run exception cleanup landing pads when bpf_throw() unwinds Yonghong Song
2026-09-23 4:58 ` [PATCH bpf-next v5 01/21] bpf: Pack bpf_insn_aux_data flags into bit fields Yonghong Song
2026-09-23 5:40 ` bot+bpf-ci
2026-09-23 19:16 ` Eduard Zingerman
2026-09-23 4:58 ` [PATCH bpf-next v5 02/21] bpf: Accept the compiler's exception cleanup table at program load Yonghong Song
2026-09-23 4:59 ` [PATCH bpf-next v5 03/21] bpf: Add the bpf_unwind_resume() kfunc Yonghong Song
2026-09-23 6:13 ` Kumar Kartikeya Dwivedi
2026-09-23 4:59 ` [PATCH bpf-next v5 04/21] bpf: Add lookups for exception cleanup resumes and landing pads Yonghong Song
2026-09-23 4:59 ` [PATCH bpf-next v5 05/21] bpf: Prepare for an exception cleanup table before the CFG walk Yonghong Song
2026-09-23 5:40 ` bot+bpf-ci
2026-09-23 4:59 ` [PATCH bpf-next v5 06/21] bpf: Make exception landing pads reachable in the CFG Yonghong Song
2026-09-23 5:51 ` bot+bpf-ci
2026-09-23 19:25 ` Eduard Zingerman
2026-09-23 4:59 ` [PATCH bpf-next v5 07/21] bpf: Explore the landing pads no call site reaches Yonghong Song
2026-09-23 16:26 ` Eduard Zingerman
2026-09-23 17:27 ` Yonghong Song
2026-09-23 18:06 ` Eduard Zingerman
2026-09-23 18:09 ` Yonghong Song
2026-09-23 21:28 ` Alexei Starovoitov
2026-09-23 22:19 ` Eduard Zingerman
2026-09-23 23:20 ` Alexei Starovoitov
2026-09-24 0:13 ` Kumar Kartikeya Dwivedi
2026-09-24 1:53 ` Alexei Starovoitov
2026-09-24 6:12 ` Kumar Kartikeya Dwivedi
2026-09-23 23:09 ` Yonghong Song
2026-09-23 4:59 ` [PATCH bpf-next v5 08/21] bpf: Walk the exception unwind in the verifier Yonghong Song
2026-09-23 16:34 ` Eduard Zingerman
2026-09-23 18:01 ` Yonghong Song
2026-09-23 4:59 ` [PATCH bpf-next v5 09/21] bpf: Refuse exception cleanup shapes bpf_throw() cannot dispatch Yonghong Song
2026-09-23 4:59 ` [PATCH bpf-next v5 10/21] bpf: Refuse a private stack for a program with an exception cleanup table Yonghong Song
2026-09-23 4:59 ` [PATCH bpf-next v5 11/21] bpf: Dispatch exception cleanup pads from bpf_throw() Yonghong Song
2026-09-23 4:59 ` [PATCH bpf-next v5 12/21] bpf, x86: Dispatch exception cleanup pads at run time Yonghong Song
2026-09-23 6:45 ` Eduard Zingerman
2026-09-23 20:45 ` Yonghong Song
2026-09-23 4:59 ` [PATCH bpf-next v5 13/21] bpf, arm64: " Yonghong Song
2026-09-23 4:59 ` [PATCH bpf-next v5 14/21] libbpf: Resolve the compiler's _Unwind_Resume to the kernel's kfunc Yonghong Song
2026-09-23 8:36 ` Kumar Kartikeya Dwivedi
2026-09-23 5:00 ` [PATCH bpf-next v5 15/21] libbpf: Add cleanup_info to bpf_prog_load_opts Yonghong Song
2026-09-23 5:00 ` [PATCH bpf-next v5 16/21] libbpf: Collect .bpf_cleanup records and pass them to the kernel Yonghong Song
2026-09-23 5:52 ` Kumar Kartikeya Dwivedi
2026-09-23 5:00 ` [PATCH bpf-next v5 17/21] libbpf: Carry the exception cleanup table through the light skeleton Yonghong Song
2026-09-23 5:00 ` [PATCH bpf-next v5 18/21] libbpf: Let the static linker carry .bpf_cleanup relocations Yonghong Song
2026-09-23 5:40 ` bot+bpf-ci
2026-09-23 5:00 ` [PATCH bpf-next v5 19/21] selftests/bpf: Add an end-to-end .bpf_cleanup exception test Yonghong Song
2026-09-23 5:51 ` bot+bpf-ci
2026-09-23 5:00 ` [PATCH bpf-next v5 20/21] selftests/bpf: Cover the exception cleanup shapes the chain does not reach Yonghong Song
2026-09-23 5:51 ` bot+bpf-ci
2026-09-23 7:50 ` Eduard Zingerman
2026-09-23 5:00 ` Yonghong Song [this message]
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