[PATCH v3 bpf-next 4/5] selftests/bpf: Add a test case for kptr_rcu.

Alexei Starovoitov
2023-02-28T04:02:34Z

From: Alexei Starovoitov <ast@kernel.org>

Tweak existing map_kptr test to check kptr_rcu.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
tools/testing/selftests/bpf/progs/map_kptr.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/map_kptr.c b/tools/testing/selftests/bpf/progs/map_kptr.c
index 4a7da6cb5800..b041234ec68d 100644
--- a/tools/testing/selftests/bpf/progs/map_kptr.c
+++ b/tools/testing/selftests/bpf/progs/map_kptr.c
@@ -61,6 +61,7 @@ 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))

@@ -90,12 +91,23 @@ 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;
@@ -288,6 +300,8 @@ int test_map_kptr_ref2(struct __sk_buff *ctx)
if (p_st->cnt.refs.counter != 2)
return 6;

+ /* p_st is MEM_RCU, because we're in RCU CS */
+ bpf_kfunc_call_test_ref(p_st);
return 0;
}

--
2.30.2