[PATCH v4 bpf-next 4/6] selftests/bpf: Add a test case for kptr_rcu.

[Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>]

From: Alexei Starovoitov <ast@xxxxxxxxxx>

Tweak existing map_kptr test to check kptr_rcu.

Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Acked-by: David Vernet <void@xxxxxxxxxxxxx>
---
 tools/testing/selftests/bpf/progs/map_kptr.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/map_kptr.c b/tools/testing/selftests/bpf/progs/map_kptr.c
index 3fe7cde4cbfd..3903d30217b8 100644
--- a/tools/testing/selftests/bpf/progs/map_kptr.c
+++ b/tools/testing/selftests/bpf/progs/map_kptr.c
@@ -118,6 +118,7 @@ extern struct prog_test_ref_kfunc *bpf_kfunc_call_test_acquire(unsigned long *sp
 extern struct prog_test_ref_kfunc *
 bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int b) __ksym;
 extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
+void bpf_kfunc_call_test_ref(struct prog_test_ref_kfunc *p) __ksym;
 
 #define WRITE_ONCE(x, val) ((*(volatile typeof(x) *) &(x)) = (val))
 
@@ -147,12 +148,23 @@ static void test_kptr_ref(struct map_value *v)
 	WRITE_ONCE(v->unref_ptr, p);
 	if (!p)
 		return;
+	/*
+	 * p is rcu_ptr_prog_test_ref_kfunc,
+	 * because bpf prog is non-sleepable and runs in RCU CS.
+	 * p can be passed to kfunc that requires KF_RCU.
+	 */
+	bpf_kfunc_call_test_ref(p);
 	if (p->a + p->b > 100)
 		return;
 	/* store NULL */
 	p = bpf_kptr_xchg(&v->ref_ptr, NULL);
 	if (!p)
 		return;
+	/*
+	 * p is trusted_ptr_prog_test_ref_kfunc.
+	 * p can be passed to kfunc that requires KF_RCU.
+	 */
+	bpf_kfunc_call_test_ref(p);
 	if (p->a + p->b > 100) {
 		bpf_kfunc_call_test_release(p);
 		return;
-- 
2.39.2