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 haoluo@google.com Acked-by: Andrii Nakryiko andriin@fb.com --- 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; }