[PATCH bpf v2] selftests/bpf: Use both hrtimer enqueue helpers in vmlinux test

[PATCH bpf v2] selftests/bpf: Use both hrtimer enqueue helpers in vmlinux test

[Ihor Solodrai]

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>

---

v1->v2:
  * Use bpf_program__set_attach_target() and bpf_program__attach_kprobe()
    to avoid duplicating BPF programs (Amery)
v1: https://lore.kernel.org/all/20260507113915.24988-1-ihor.solodrai@linux.dev/

---
 .../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)
 {
-- 
2.54.0

Re: [PATCH bpf v2] selftests/bpf: Use both hrtimer enqueue helpers in vmlinux test

[Jiri Olsa]

On Fri, May 08, 2026 at 05:57:30PM -0700, Ihor Solodrai wrote:
> 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.

iiuc this will help before the [1] fully propagates everywhere,
also good as an example

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> 
> [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>
> 
> ---
> 
> v1->v2:
>   * Use bpf_program__set_attach_target() and bpf_program__attach_kprobe()
>     to avoid duplicating BPF programs (Amery)
> v1: https://lore.kernel.org/all/20260507113915.24988-1-ihor.solodrai@linux.dev/
> 
> ---
>  .../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)
>  {
> -- 
> 2.54.0
> 
> 

Re: [PATCH bpf v2] selftests/bpf: Use both hrtimer enqueue helpers in vmlinux test

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Fri,  8 May 2026 17:57:30 -0700 you wrote:
> 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].
> 
> [...]

Here is the summary with links:
  - [bpf,v2] selftests/bpf: Use both hrtimer enqueue helpers in vmlinux test
    https://git.kernel.org/bpf/bpf-next/c/25bb05dd06cc

You are awesome, thank you!
-- 
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