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 <ihor.solodrai@linux.dev>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260509005730.250956-1-ihor.solodrai@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/vmlinux.c b/tools/testing/selftests/bpf/prog_tests/vmlinux.c
index 6fb2217d940b459beaeb8b52ad19efd04ab0ea87..b5fdd593910d8c583f3ac3f3f3be3feca18b1c26 100644 (file)
--- 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 78b23934d9f8fd34e7734487bfa3b5cc54741860..eea556940df6cfdda34fb281b22e4b666a0a6d8f 100644 (file)
--- 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)
 {