selftests/bpf: Add test to access u32 ptr argument in tracing program

Adding verifier test for accessing u32 pointer argument in
tracing programs.

The test program loads 1nd argument of bpf_fentry_test9 function
which is u32 pointer and checks that verifier allows that.
Co-developed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20230410085908.98493-3-zhoufeng.zf@bytedance.com

net/bpf/test_run.c

@@ -541,6 +541,11 @@ int noinline bpf_fentry_test8(struct bpf_fentry_test_t *arg)
 	return (long)arg->a;
 }
 
+__bpf_kfunc u32 bpf_fentry_test9(u32 *a)
+{
+	return *a;
+}
+
 __bpf_kfunc int bpf_modify_return_test(int a, int *b)
 {
 	*b += 1;
@@ -855,7 +860,8 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog,
 		    bpf_fentry_test5(11, (void *)12, 13, 14, 15) != 65 ||
 		    bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111 ||
 		    bpf_fentry_test7((struct bpf_fentry_test_t *)0) != 0 ||
-		    bpf_fentry_test8(&arg) != 0)
+		    bpf_fentry_test8(&arg) != 0 ||
+		    bpf_fentry_test9(&retval) != 0)
 			goto out;
 		break;
 	case BPF_MODIFY_RETURN:

tools/testing/selftests/bpf/verifier/btf_ctx_access.c

@@ -10,3 +10,16 @@
 	.expected_attach_type = BPF_TRACE_FENTRY,
 	.kfunc = "bpf_modify_return_test",
 },
+
+{
+	"btf_ctx_access u32 pointer accept",
+	.insns = {
+	BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0),	/* load 1nd argument value (u32 pointer) */
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_EXIT_INSN(),
+	},
+	.result = ACCEPT,
+	.prog_type = BPF_PROG_TYPE_TRACING,
+	.expected_attach_type = BPF_TRACE_FENTRY,
+	.kfunc = "bpf_fentry_test9",
+},