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 --- 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 383af9edf6f5..e14b651263b8 100644 --- a/tools/testing/selftests/bpf/exceptions_cleanup.h +++ b/tools/testing/selftests/bpf/exceptions_cleanup.h @@ -35,6 +35,9 @@ #define RAN_VAR_STACK 0x40000 #define RAN_GLOBAL_PAD 0x80000 +/* 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 2825dbb53b1c..679cf40d1707 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; @@ -458,6 +483,9 @@ 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 +#include +#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