From 25bb05dd06ccffd209c26465f84851f1fd344c8c Mon Sep 17 00:00:00 2001 From: Ihor Solodrai Date: Fri, 8 May 2026 17:57:30 -0700 Subject: [PATCH] selftests/bpf: Use both hrtimer enqueue helpers in vmlinux test The vmlinux selftest triggers nanosleep and checks that both kprobe and fentry programs observe the hrtimer enqueue path. After the hrtimer_start_expires_user() conversion [1], nanosleep reaches hrtimer_start_range_ns_user() instead of hrtimer_start_range_ns(). Hard-coding either symbol makes the test fail either on bpf tree or on linux-next [2]. Update the test to resolve the target symbol at runtime via libbpf_find_vmlinux_btf_id(). This is a nice example of how to modify a BPF program to work on both older and newer kernel revision. [1] https://lore.kernel.org/all/20260408114952.062400833@kernel.org/ [2] https://github.com/kernel-patches/bpf/actions/runs/25485909958/job/74782902203 Signed-off-by: Ihor Solodrai Acked-by: Jiri Olsa Link: https://lore.kernel.org/r/20260509005730.250956-1-ihor.solodrai@linux.dev Signed-off-by: Alexei Starovoitov --- .../selftests/bpf/prog_tests/vmlinux.c | 45 ++++++++++++++++++- .../selftests/bpf/progs/test_vmlinux.c | 4 +- 2 files changed, 45 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/vmlinux.c b/tools/testing/selftests/bpf/prog_tests/vmlinux.c index 6fb2217d940b..b5fdd593910d 100644 --- a/tools/testing/selftests/bpf/prog_tests/vmlinux.c +++ b/tools/testing/selftests/bpf/prog_tests/vmlinux.c @@ -14,21 +14,61 @@ static void nsleep() (void)syscall(__NR_nanosleep, &ts, NULL); } +static const char *hrtimer_func = "hrtimer_start_range_ns"; + +static int setup_hrtimer_progs(struct test_vmlinux *skel) +{ + int err; + + if (libbpf_find_vmlinux_btf_id("hrtimer_start_range_ns_user", BPF_TRACE_FENTRY) > 0) + hrtimer_func = "hrtimer_start_range_ns_user"; + + err = bpf_program__set_attach_target(skel->progs.handle__fentry, 0, hrtimer_func); + if (err) + return err; + + /* + * Bare SEC("kprobe") has no target function, so attach it manually + * later after selecting the hrtimer function to probe. + */ + bpf_program__set_autoattach(skel->progs.handle__kprobe, false); + + return 0; +} + void test_vmlinux(void) { int err; struct test_vmlinux* skel; struct test_vmlinux__bss *bss; + struct bpf_link *kprobe_link = NULL; - skel = test_vmlinux__open_and_load(); - if (!ASSERT_OK_PTR(skel, "test_vmlinux__open_and_load")) + skel = test_vmlinux__open(); + if (!ASSERT_OK_PTR(skel, "test_vmlinux__open")) return; + + err = setup_hrtimer_progs(skel); + if (!ASSERT_OK(err, "setup_hrtimer_progs")) + goto cleanup; + + err = test_vmlinux__load(skel); + if (!ASSERT_OK(err, "test_vmlinux__load")) + goto cleanup; + bss = skel->bss; err = test_vmlinux__attach(skel); if (!ASSERT_OK(err, "test_vmlinux__attach")) goto cleanup; + /* manually attach kprobe with the selected function */ + if (hrtimer_func) { + kprobe_link = bpf_program__attach_kprobe(skel->progs.handle__kprobe, + false /* retprobe */, hrtimer_func); + if (!ASSERT_OK_PTR(kprobe_link, "bpf_program__attach_kprobe")) + goto cleanup; + } + /* trigger everything */ nsleep(); @@ -39,5 +79,6 @@ void test_vmlinux(void) ASSERT_TRUE(bss->fentry_called, "fentry"); cleanup: + bpf_link__destroy(kprobe_link); test_vmlinux__destroy(skel); } diff --git a/tools/testing/selftests/bpf/progs/test_vmlinux.c b/tools/testing/selftests/bpf/progs/test_vmlinux.c index 78b23934d9f8..eea556940df6 100644 --- a/tools/testing/selftests/bpf/progs/test_vmlinux.c +++ b/tools/testing/selftests/bpf/progs/test_vmlinux.c @@ -69,7 +69,7 @@ int BPF_PROG(handle__tp_btf, struct pt_regs *regs, long id) return 0; } -SEC("kprobe/hrtimer_start_range_ns") +SEC("kprobe") int BPF_KPROBE(handle__kprobe, struct hrtimer *timer, ktime_t tim, u64 delta_ns, const enum hrtimer_mode mode) { @@ -78,7 +78,7 @@ int BPF_KPROBE(handle__kprobe, struct hrtimer *timer, ktime_t tim, u64 delta_ns, return 0; } -SEC("fentry/hrtimer_start_range_ns") +SEC("fentry") int BPF_PROG(handle__fentry, struct hrtimer *timer, ktime_t tim, u64 delta_ns, const enum hrtimer_mode mode) {