[PATCH bpf v1 08/10] selftests/bpf: Test sched_process_wait nullable argument

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

Add a load-time verifier test that dereferences argument 0 of the
sched_process_wait tp_btf program without checking it. The test expects the
nullable-pointer diagnostic, so it is accepted unexpectedly before the fix
and rejected as expected after it.

Add a successful control that checks the argument for NULL before the
dereference. This ensures the nullable marking preserves legitimate access
to the pid when the tracepoint supplies one.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 .../selftests/bpf/progs/raw_tp_null_fail.c      | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/raw_tp_null_fail.c b/tools/testing/selftests/bpf/progs/raw_tp_null_fail.c
index 7e8842bf9000..725d73c9ffe1 100644
--- a/tools/testing/selftests/bpf/progs/raw_tp_null_fail.c
+++ b/tools/testing/selftests/bpf/progs/raw_tp_null_fail.c
@@ -58,3 +58,20 @@ int test_tp_btf_signal_deliver_info_no_deref(void *ctx)
 	asm volatile("r1 = *(u64 *)(r1 +8); r1 = *(u32 *)(r1 +0);" ::: __clobber_all);
 	return 0;
 }
+
+SEC("tp_btf/sched_process_wait")
+__failure __msg("R1 invalid mem access 'trusted_ptr_or_null_'")
+int test_raw_tp_null_sched_process_wait_arg_1(void *ctx)
+{
+	asm volatile("r1 = *(u64 *)(r1 +0); r1 = *(u32 *)(r1 +0);" ::: __clobber_all);
+	return 0;
+}
+
+SEC("tp_btf/sched_process_wait")
+__success
+int test_raw_tp_null_sched_process_wait_arg_1_checked(void *ctx)
+{
+	asm volatile("r1 = *(u64 *)(r1 +0); if r1 == 0 goto +1; "
+		     "r1 = *(u32 *)(r1 +0);" ::: __clobber_all);
+	return 0;
+}
-- 
2.53.0