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selftests/bpf: Switch test_vmlinux to use hrtimer_range_start_ns. 

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] af3b56289b 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>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200701175315.1161242-1-haoluo@google.com
This commit is contained in:
Hao Luo 2020-07-01 10:53:15 -07:00 committed by Alexei Starovoitov
parent 6b207d66aa
commit 8d821b5db7
1 changed files with 8 additions and 8 deletions
tools/testing/selftests/bpf/progs
test_vmlinux.c

16
tools/testing/selftests/bpf/progs/test_vmlinux.c
View File

@ -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;
}