tracing/kprobe: Do not run kprobe boot tests if kprobe_event is on cmdline

When having kprobe trace event start up tests enabled and adding a
kprobe_event on the kernel command line, it produced the following:

 trace_kprobe: Testing kprobe tracing:
 WARNING: CPU: 5 PID: 1 at kernel/trace/trace_kprobe.c:1724 kprobe_trace_self_tests_init+0x32d/0x36b
 Modules linked in:
 CPU: 5 PID: 1 Comm: swapper/0 Not tainted 5.2.0-rc1-test+ #249
 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016
 RIP: 0010:kprobe_trace_self_tests_init+0x32d/0x36b
 Code: b7 e8 4f 8d a2 fe 85 c0 74 10 0f 0b 48 c7 c7 c8 1b 0d b7 ff c3 e8 19 af 99 fe 48 c7 c7 40 93 27 b7 e8 7f 1a a5 fe 85 c0 74 10 <0f> 0b 48 c7 c7 f8 1b 0d b7 ff c3 e8 f9 ae
9 a0 fe 85
 RSP: 0018:ffffb36e40653e08 EFLAGS: 00010286
 RAX: 00000000fffffff0 RBX: 0000000000000000 RCX: ffffb36e40653d5c
 RDX: 0000000000000000 RSI: ffffffffb72776e0 RDI: 0000000000000246
 RBP: ffff98414fe58ff8 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: ffff98415d8aa940 R12: 0000000000000000
 R13: ffffffffb737c1b0 R14: 0000000000000000 R15: 0000000000000000
 FS:  0000000000000000(0000) GS:ffff98415ea80000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007f959ce741b8 CR3: 000000011a210002 CR4: 00000000001606e0
 Call Trace:
  ? init_kprobe_trace+0x19e/0x19e
  ? do_early_param+0x8e/0x8e
  do_one_initcall+0x6f/0x2b4
  ? do_early_param+0x8e/0x8e
  kernel_init_freeable+0x21d/0x2c6
  ? rest_init+0x146/0x146
  kernel_init+0xa/0x10a
  ret_from_fork+0x3a/0x50
 ---[ end trace 488430c083a4c956 ]---

As with the trace events, if a trace event is set on the kernel command
line, the trace events start up tests are suspended. The kprobe start up
tests should do the same when a kprobe is enabled on the kernel command
line.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_kprobe.c

@@ -25,6 +25,7 @@
 
 /* Kprobe early definition from command line */
 static char kprobe_boot_events_buf[COMMAND_LINE_SIZE] __initdata;
+static bool kprobe_boot_events_enabled __initdata;
 
 static int __init set_kprobe_boot_events(char *str)
 {
@@ -1538,6 +1539,8 @@ static __init void setup_boot_kprobe_events(void)
 		ret = trace_run_command(cmd, create_or_delete_trace_kprobe);
 		if (ret)
 			pr_warn("Failed to add event(%d): %s\n", ret, cmd);
+		else
+			kprobe_boot_events_enabled = true;
 
 		cmd = p;
 	}
@@ -1611,6 +1614,11 @@ static __init int kprobe_trace_self_tests_init(void)
 	if (tracing_is_disabled())
 		return -ENODEV;
 
+	if (kprobe_boot_events_enabled) {
+		pr_info("Skipping kprobe tests due to kprobe_event on cmdline\n");
+		return 0;
+	}
+
 	target = kprobe_trace_selftest_target;
 
 	pr_info("Testing kprobe tracing: ");