netdev - [PATCH bpf-next] selftests/bpf: guarantee that useep() calls nanosleep() syscall

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Date:   Wed, 11 Mar 2020 11:53:45 -0700
From:   Andrii Nakryiko <andriin@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>
CC:     <andrii.nakryiko@...il.com>, <kernel-team@...com>,
        Andrii Nakryiko <andriin@...com>, Julia Kartseva <hex@...com>
Subject: [PATCH bpf-next] selftests/bpf: guarantee that useep() calls nanosleep() syscall

Some implementations of C runtime library won't call nanosleep() syscall from
usleep(). But a bunch of kprobe/tracepoint selftests rely on nanosleep being
called to trigger them. To make this more reliable, "override" usleep
implementation and call nanosleep explicitly.

Cc: Julia Kartseva <hex@...com>
Signed-off-by: Andrii Nakryiko <andriin@...com>
---
 tools/testing/selftests/bpf/test_progs.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index a969c77e9456..2b0bc1171c9c 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -29,6 +29,15 @@ struct prog_test_def {
 	int old_error_cnt;
 };
 
+/* Override C runtime library's usleep() implementation to ensure nanosleep()
+ * is always called. Usleep is frequently used in selftests as a way to
+ * trigger kprobe and tracepoints.
+ */
+int usleep(useconds_t usec)
+{
+	return syscall(__NR_nanosleep, usec * 1000UL);
+}
+
 static bool should_run(struct test_selector *sel, int num, const char *name)
 {
 	int i;
-- 
2.17.1