| Message ID | 20200701175315.1161242-1-haoluo@google.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf-next,v2] selftests/bpf: Switch test_vmlinux to use hrtimer_range_start_ns. | expand |
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 <haoluo@google.com> > Acked-by: Andrii Nakryiko <andriin@fb.com> Thanks! Acked-by: Yonghong Song <yhs@fb.com>
On Wed, Jul 1, 2020 at 11:04 AM Yonghong Song <yhs@fb.com> 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 <haoluo@google.com> > > Acked-by: Andrii Nakryiko <andriin@fb.com> > > Thanks! > Acked-by: Yonghong Song <yhs@fb.com> Applied. Thanks
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; }