selftests/bpf: Add tests for raw_tp NULL args

Add tests to ensure that arguments are correctly marked based on their
specified positions, and whether they get marked correctly as maybe
null. For modules, all tracepoint parameters should be marked
PTR_MAYBE_NULL by default.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241213221929.3495062-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/prog_tests/raw_tp_null.c

@@ -3,11 +3,14 @@
 
 #include <test_progs.h>
 #include "raw_tp_null.skel.h"
+#include "raw_tp_null_fail.skel.h"
 
 void test_raw_tp_null(void)
 {
 	struct raw_tp_null *skel;
 
+	RUN_TESTS(raw_tp_null_fail);
+
 	skel = raw_tp_null__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "raw_tp_null__open_and_load"))
 		return;

tools/testing/selftests/bpf/progs/raw_tp_null_fail.c

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+/* Ensure module parameter has PTR_MAYBE_NULL */
+SEC("tp_btf/bpf_testmod_test_raw_tp_null")
+__failure __msg("R1 invalid mem access 'trusted_ptr_or_null_'")
+int test_raw_tp_null_bpf_testmod_test_raw_tp_null_arg_1(void *ctx) {
+    asm volatile("r1 = *(u64 *)(r1 +0); r1 = *(u64 *)(r1 +0);" ::: __clobber_all);
+    return 0;
+}
+
+/* Check NULL marking */
+SEC("tp_btf/sched_pi_setprio")
+__failure __msg("R1 invalid mem access 'trusted_ptr_or_null_'")
+int test_raw_tp_null_sched_pi_setprio_arg_2(void *ctx) {
+    asm volatile("r1 = *(u64 *)(r1 +8); r1 = *(u64 *)(r1 +0);" ::: __clobber_all);
+    return 0;
+}