From: Hao Luo <haoluo@google.com>
To: netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
linux-kselftest@vger.kernel.org
Cc: sdf@google.com, Shuah Khan <shuah@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andriin@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>, Hao Luo <haoluo@google.com>
Subject: [PATCH bpf-next] selftests/bpf: Switch test_vmlinux to use hrtimer_range_start_ns.
Date: Tue, 30 Jun 2020 11:49:22 -0700 [thread overview]
Message-ID: <20200630184922.455439-1-haoluo@google.com> (raw)
The test_vmlinux test uses hrtimer_nanosleep as hook to test tracing
programs. But it seems Clang may have done an aggressive optimization,
causing fentry and kprobe to not hook on this function properly on a
Clang build kernel.
A possible fix is switching to use a more reliable function, e.g. the
ones exported to kernel modules such as hrtimer_range_start_ns. After
we switch to using hrtimer_range_start_ns, the test passes again even
on a clang build kernel.
Tested:
In a clang build kernel, the test fail even when the flags
{fentry, kprobe}_called are set unconditionally in handle__kprobe()
and handle__fentry(), which implies the programs do not hook on
hrtimer_nanosleep() properly. This could be because clang's code
transformation is too aggressive.
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 we switch 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>
---
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
next reply other threads:[~2020-06-30 18:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-30 18:49 Hao Luo [this message]
2020-06-30 20:36 ` [PATCH bpf-next] selftests/bpf: Switch test_vmlinux to use hrtimer_range_start_ns Yonghong Song
2020-06-30 22:48 ` Hao Luo
2020-07-01 0:06 ` Bill Wendling
2020-07-01 0:10 ` Hao Luo
2020-07-01 2:26 ` Yonghong Song
2020-07-01 17:02 ` Hao Luo
2020-06-30 21:26 ` Andrii Nakryiko
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