The test_vmlinux test uses hrtimer_nanosleep as hook to test tracing
programs. But in a kernel built by clang, which performs more aggresive
inlining, that function gets inlined into its caller SyS_nanosleep.
Therefore, even though fentry and kprobe do hook on the function,
they aren't triggered by the call to nanosleep in the test.
A possible fix is switching to use a function that is less likely to
be inlined, such as hrtimer_range_start_ns. The EXPORT_SYMBOL functions
shouldn't be inlined based on the description of [1], therefore safe
to use for this test. Also the arguments of this function include the
duration of sleep, therefore suitable for test verification.
[1] af3b56289be1 time: don't inline EXPORT_SYMBOL functions
Tested:
In a clang build kernel, before this change, the test fails:
test_vmlinux:PASS:skel_open 0 nsec
test_vmlinux:PASS:skel_attach 0 nsec
test_vmlinux:PASS:tp 0 nsec
test_vmlinux:PASS:raw_tp 0 nsec
test_vmlinux:PASS:tp_btf 0 nsec
test_vmlinux:FAIL:kprobe not called
test_vmlinux:FAIL:fentry not called
After switching to hrtimer_range_start_ns, the test passes:
test_vmlinux:PASS:skel_open 0 nsec
test_vmlinux:PASS:skel_attach 0 nsec
test_vmlinux:PASS:tp 0 nsec
test_vmlinux:PASS:raw_tp 0 nsec
test_vmlinux:PASS:tp_btf 0 nsec
test_vmlinux:PASS:kprobe 0 nsec
test_vmlinux:PASS:fentry 0 nsec
Signed-off-by: Hao Luo <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
---
Changelog since v1:
- More accurate commit messages
tools/testing/selftests/bpf/progs/test_vmlinux.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/test_vmlinux.c b/tools/testing/selftests/bpf/progs/test_vmlinux.c
index 5611b564d3b1..29fa09d6a6c6 100644
--- a/tools/testing/selftests/bpf/progs/test_vmlinux.c
+++ b/tools/testing/selftests/bpf/progs/test_vmlinux.c
@@ -63,20 +63,20 @@ int BPF_PROG(handle__tp_btf, struct pt_regs *regs, long id)
return 0;
}
-SEC("kprobe/hrtimer_nanosleep")
-int BPF_KPROBE(handle__kprobe,
- ktime_t rqtp, enum hrtimer_mode mode, clockid_t clockid)
+SEC("kprobe/hrtimer_start_range_ns")
+int BPF_KPROBE(handle__kprobe, struct hrtimer *timer, ktime_t tim, u64 delta_ns,
+ const enum hrtimer_mode mode)
{
- if (rqtp == MY_TV_NSEC)
+ if (tim == MY_TV_NSEC)
kprobe_called = true;
return 0;
}
-SEC("fentry/hrtimer_nanosleep")
-int BPF_PROG(handle__fentry,
- ktime_t rqtp, enum hrtimer_mode mode, clockid_t clockid)
+SEC("fentry/hrtimer_start_range_ns")
+int BPF_PROG(handle__fentry, struct hrtimer *timer, ktime_t tim, u64 delta_ns,
+ const enum hrtimer_mode mode)
{
- if (rqtp == MY_TV_NSEC)
+ if (tim == MY_TV_NSEC)
fentry_called = true;
return 0;
}
--
2.27.0.212.ge8ba1cc988-goog
On 7/1/20 10:53 AM, Hao Luo wrote:
> The test_vmlinux test uses hrtimer_nanosleep as hook to test tracing
> programs. But in a kernel built by clang, which performs more aggresive
> inlining, that function gets inlined into its caller SyS_nanosleep.
> Therefore, even though fentry and kprobe do hook on the function,
> they aren't triggered by the call to nanosleep in the test.
>
> A possible fix is switching to use a function that is less likely to
> be inlined, such as hrtimer_range_start_ns. The EXPORT_SYMBOL functions
> shouldn't be inlined based on the description of [1], therefore safe
> to use for this test. Also the arguments of this function include the
> duration of sleep, therefore suitable for test verification.
>
> [1] af3b56289be1 time: don't inline EXPORT_SYMBOL functions
>
> Tested:
> In a clang build kernel, before this change, the test fails:
>
> test_vmlinux:PASS:skel_open 0 nsec
> test_vmlinux:PASS:skel_attach 0 nsec
> test_vmlinux:PASS:tp 0 nsec
> test_vmlinux:PASS:raw_tp 0 nsec
> test_vmlinux:PASS:tp_btf 0 nsec
> test_vmlinux:FAIL:kprobe not called
> test_vmlinux:FAIL:fentry not called
>
> After switching to hrtimer_range_start_ns, the test passes:
>
> test_vmlinux:PASS:skel_open 0 nsec
> test_vmlinux:PASS:skel_attach 0 nsec
> test_vmlinux:PASS:tp 0 nsec
> test_vmlinux:PASS:raw_tp 0 nsec
> test_vmlinux:PASS:tp_btf 0 nsec
> test_vmlinux:PASS:kprobe 0 nsec
> test_vmlinux:PASS:fentry 0 nsec
>
> Signed-off-by: Hao Luo <[email protected]>
> Acked-by: Andrii Nakryiko <[email protected]>
Thanks!
Acked-by: Yonghong Song <[email protected]>
On Wed, Jul 1, 2020 at 11:04 AM Yonghong Song <[email protected]> wrote:
>
>
>
> On 7/1/20 10:53 AM, Hao Luo wrote:
> > The test_vmlinux test uses hrtimer_nanosleep as hook to test tracing
> > programs. But in a kernel built by clang, which performs more aggresive
> > inlining, that function gets inlined into its caller SyS_nanosleep.
> > Therefore, even though fentry and kprobe do hook on the function,
> > they aren't triggered by the call to nanosleep in the test.
> >
> > A possible fix is switching to use a function that is less likely to
> > be inlined, such as hrtimer_range_start_ns. The EXPORT_SYMBOL functions
> > shouldn't be inlined based on the description of [1], therefore safe
> > to use for this test. Also the arguments of this function include the
> > duration of sleep, therefore suitable for test verification.
> >
> > [1] af3b56289be1 time: don't inline EXPORT_SYMBOL functions
> >
> > Tested:
> > In a clang build kernel, before this change, the test fails:
> >
> > test_vmlinux:PASS:skel_open 0 nsec
> > test_vmlinux:PASS:skel_attach 0 nsec
> > test_vmlinux:PASS:tp 0 nsec
> > test_vmlinux:PASS:raw_tp 0 nsec
> > test_vmlinux:PASS:tp_btf 0 nsec
> > test_vmlinux:FAIL:kprobe not called
> > test_vmlinux:FAIL:fentry not called
> >
> > After switching to hrtimer_range_start_ns, the test passes:
> >
> > test_vmlinux:PASS:skel_open 0 nsec
> > test_vmlinux:PASS:skel_attach 0 nsec
> > test_vmlinux:PASS:tp 0 nsec
> > test_vmlinux:PASS:raw_tp 0 nsec
> > test_vmlinux:PASS:tp_btf 0 nsec
> > test_vmlinux:PASS:kprobe 0 nsec
> > test_vmlinux:PASS:fentry 0 nsec
> >
> > Signed-off-by: Hao Luo <[email protected]>
> > Acked-by: Andrii Nakryiko <[email protected]>
>
> Thanks!
> Acked-by: Yonghong Song <[email protected]>
Applied. Thanks