1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Based on the same principle as kgdboe using the NETPOLL api, this
4 * driver uses a console polling api to implement a gdb serial inteface
5 * which is multiplexed on a console port.
6 *
7 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
8 *
9 * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
10 */
11
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
14#include <linux/kernel.h>
15#include <linux/ctype.h>
16#include <linux/kgdb.h>
17#include <linux/kdb.h>
18#include <linux/tty.h>
19#include <linux/console.h>
20#include <linux/vt_kern.h>
21#include <linux/input.h>
22#include <linux/module.h>
23#include <linux/platform_device.h>
24#include <linux/serial_core.h>
25
26#define MAX_CONFIG_LEN		40
27
28static struct kgdb_io		kgdboc_io_ops;
29
30/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
31static int configured		= -1;
32static DEFINE_MUTEX(config_mutex);
33
34static char config[MAX_CONFIG_LEN];
35static struct kparam_string kps = {
36	.string			= config,
37	.maxlen			= MAX_CONFIG_LEN,
38};
39
40static int kgdboc_use_kms;  /* 1 if we use kernel mode switching */
41static struct tty_driver	*kgdb_tty_driver;
42static int			kgdb_tty_line;
43
44static struct platform_device *kgdboc_pdev;
45
46#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
47static struct kgdb_io		kgdboc_earlycon_io_ops;
48static int                      (*earlycon_orig_exit)(struct console *con);
49#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
50
51#ifdef CONFIG_KDB_KEYBOARD
52static int kgdboc_reset_connect(struct input_handler *handler,
53				struct input_dev *dev,
54				const struct input_device_id *id)
55{
56	input_reset_device(dev);
57
58	/* Return an error - we do not want to bind, just to reset */
59	return -ENODEV;
60}
61
62static void kgdboc_reset_disconnect(struct input_handle *handle)
63{
64	/* We do not expect anyone to actually bind to us */
65	BUG();
66}
67
68static const struct input_device_id kgdboc_reset_ids[] = {
69	{
70		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
71		.evbit = { BIT_MASK(EV_KEY) },
72	},
73	{ }
74};
75
76static struct input_handler kgdboc_reset_handler = {
77	.connect	= kgdboc_reset_connect,
78	.disconnect	= kgdboc_reset_disconnect,
79	.name		= "kgdboc_reset",
80	.id_table	= kgdboc_reset_ids,
81};
82
83static DEFINE_MUTEX(kgdboc_reset_mutex);
84
85static void kgdboc_restore_input_helper(struct work_struct *dummy)
86{
87	/*
88	 * We need to take a mutex to prevent several instances of
89	 * this work running on different CPUs so they don't try
90	 * to register again already registered handler.
91	 */
92	mutex_lock(&kgdboc_reset_mutex);
93
94	if (input_register_handler(&kgdboc_reset_handler) == 0)
95		input_unregister_handler(&kgdboc_reset_handler);
96
97	mutex_unlock(&kgdboc_reset_mutex);
98}
99
100static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);
101
102static void kgdboc_restore_input(void)
103{
104	if (likely(system_state == SYSTEM_RUNNING))
105		schedule_work(&kgdboc_restore_input_work);
106}
107
108static int kgdboc_register_kbd(char **cptr)
109{
110	if (strncmp(*cptr, "kbd", 3) == 0 ||
111		strncmp(*cptr, "kdb", 3) == 0) {
112		if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
113			kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
114			kdb_poll_idx++;
115			if (cptr[0][3] == ',')
116				*cptr += 4;
117			else
118				return 1;
119		}
120	}
121	return 0;
122}
123
124static void kgdboc_unregister_kbd(void)
125{
126	int i;
127
128	for (i = 0; i < kdb_poll_idx; i++) {
129		if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
130			kdb_poll_idx--;
131			kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
132			kdb_poll_funcs[kdb_poll_idx] = NULL;
133			i--;
134		}
135	}
136	flush_work(&kgdboc_restore_input_work);
137}
138#else /* ! CONFIG_KDB_KEYBOARD */
139#define kgdboc_register_kbd(x) 0
140#define kgdboc_unregister_kbd()
141#define kgdboc_restore_input()
142#endif /* ! CONFIG_KDB_KEYBOARD */
143
144#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
145static void cleanup_earlycon(void)
146{
147	if (kgdboc_earlycon_io_ops.cons)
148		kgdb_unregister_io_module(&kgdboc_earlycon_io_ops);
149}
150#else /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
151static inline void cleanup_earlycon(void) { }
152#endif /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
153
154static void cleanup_kgdboc(void)
155{
156	cleanup_earlycon();
157
158	if (configured != 1)
159		return;
160
161	if (kgdb_unregister_nmi_console())
162		return;
163	kgdboc_unregister_kbd();
164	kgdb_unregister_io_module(&kgdboc_io_ops);
165}
166
167static int configure_kgdboc(void)
168{
169	struct tty_driver *p;
170	int tty_line = 0;
171	int err = -ENODEV;
172	char *cptr = config;
173	struct console *cons;
174	int cookie;
175
176	if (!strlen(config) || isspace(config[0])) {
177		err = 0;
178		goto noconfig;
179	}
180
181	kgdboc_io_ops.cons = NULL;
182	kgdb_tty_driver = NULL;
183
184	kgdboc_use_kms = 0;
185	if (strncmp(cptr, "kms,", 4) == 0) {
186		cptr += 4;
187		kgdboc_use_kms = 1;
188	}
189
190	if (kgdboc_register_kbd(&cptr))
191		goto do_register;
192
193	p = tty_find_polling_driver(cptr, &tty_line);
194	if (!p)
195		goto noconfig;
196
197	/*
198	 * Take console_lock to serialize device() callback with
199	 * other console operations. For example, fg_console is
200	 * modified under console_lock when switching vt.
201	 */
202	console_lock();
203
204	cookie = console_srcu_read_lock();
205	for_each_console_srcu(cons) {
206		int idx;
207		if (cons->device && cons->device(cons, &idx) == p &&
208		    idx == tty_line) {
209			kgdboc_io_ops.cons = cons;
210			break;
211		}
212	}
213	console_srcu_read_unlock(cookie);
214
215	console_unlock();
216
217	kgdb_tty_driver = p;
218	kgdb_tty_line = tty_line;
219
220do_register:
221	err = kgdb_register_io_module(&kgdboc_io_ops);
222	if (err)
223		goto noconfig;
224
225	err = kgdb_register_nmi_console();
226	if (err)
227		goto nmi_con_failed;
228
229	configured = 1;
230
231	return 0;
232
233nmi_con_failed:
234	kgdb_unregister_io_module(&kgdboc_io_ops);
235noconfig:
236	kgdboc_unregister_kbd();
237	configured = 0;
238
239	return err;
240}
241
242static int kgdboc_probe(struct platform_device *pdev)
243{
244	int ret = 0;
245
246	mutex_lock(&config_mutex);
247	if (configured != 1) {
248		ret = configure_kgdboc();
249
250		/* Convert "no device" to "defer" so we'll keep trying */
251		if (ret == -ENODEV)
252			ret = -EPROBE_DEFER;
253	}
254	mutex_unlock(&config_mutex);
255
256	return ret;
257}
258
259static struct platform_driver kgdboc_platform_driver = {
260	.probe = kgdboc_probe,
261	.driver = {
262		.name = "kgdboc",
263		.suppress_bind_attrs = true,
264	},
265};
266
267static int __init init_kgdboc(void)
268{
269	int ret;
270
271	/*
272	 * kgdboc is a little bit of an odd "platform_driver".  It can be
273	 * up and running long before the platform_driver object is
274	 * created and thus doesn't actually store anything in it.  There's
275	 * only one instance of kgdb so anything is stored as global state.
276	 * The platform_driver is only created so that we can leverage the
277	 * kernel's mechanisms (like -EPROBE_DEFER) to call us when our
278	 * underlying tty is ready.  Here we init our platform driver and
279	 * then create the single kgdboc instance.
280	 */
281	ret = platform_driver_register(&kgdboc_platform_driver);
282	if (ret)
283		return ret;
284
285	kgdboc_pdev = platform_device_alloc("kgdboc", PLATFORM_DEVID_NONE);
286	if (!kgdboc_pdev) {
287		ret = -ENOMEM;
288		goto err_did_register;
289	}
290
291	ret = platform_device_add(kgdboc_pdev);
292	if (!ret)
293		return 0;
294
295	platform_device_put(kgdboc_pdev);
296
297err_did_register:
298	platform_driver_unregister(&kgdboc_platform_driver);
299	return ret;
300}
301
302static void exit_kgdboc(void)
303{
304	mutex_lock(&config_mutex);
305	cleanup_kgdboc();
306	mutex_unlock(&config_mutex);
307
308	platform_device_unregister(kgdboc_pdev);
309	platform_driver_unregister(&kgdboc_platform_driver);
310}
311
312static int kgdboc_get_char(void)
313{
314	if (!kgdb_tty_driver)
315		return -1;
316	return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
317						kgdb_tty_line);
318}
319
320static void kgdboc_put_char(u8 chr)
321{
322	if (!kgdb_tty_driver)
323		return;
324	kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
325					kgdb_tty_line, chr);
326}
327
328static int param_set_kgdboc_var(const char *kmessage,
329				const struct kernel_param *kp)
330{
331	size_t len = strlen(kmessage);
332	int ret = 0;
333
334	if (len >= MAX_CONFIG_LEN) {
335		pr_err("config string too long\n");
336		return -ENOSPC;
337	}
338
339	if (kgdb_connected) {
340		pr_err("Cannot reconfigure while KGDB is connected.\n");
341		return -EBUSY;
342	}
343
344	mutex_lock(&config_mutex);
345
346	strcpy(config, kmessage);
347	/* Chop out \n char as a result of echo */
348	if (len && config[len - 1] == '\n')
349		config[len - 1] = '\0';
350
351	if (configured == 1)
352		cleanup_kgdboc();
353
354	/*
355	 * Configure with the new params as long as init already ran.
356	 * Note that we can get called before init if someone loads us
357	 * with "modprobe kgdboc kgdboc=..." or if they happen to use
358	 * the odd syntax of "kgdboc.kgdboc=..." on the kernel command.
359	 */
360	if (configured >= 0)
361		ret = configure_kgdboc();
362
363	/*
364	 * If we couldn't configure then clear out the config.  Note that
365	 * specifying an invalid config on the kernel command line vs.
366	 * through sysfs have slightly different behaviors.  If we fail
367	 * to configure what was specified on the kernel command line
368	 * we'll leave it in the 'config' and return -EPROBE_DEFER from
369	 * our probe.  When specified through sysfs userspace is
370	 * responsible for loading the tty driver before setting up.
371	 */
372	if (ret)
373		config[0] = '\0';
374
375	mutex_unlock(&config_mutex);
376
377	return ret;
378}
379
380static int dbg_restore_graphics;
381
382static void kgdboc_pre_exp_handler(void)
383{
384	if (!dbg_restore_graphics && kgdboc_use_kms) {
385		dbg_restore_graphics = 1;
386		con_debug_enter(vc_cons[fg_console].d);
387	}
388	/* Increment the module count when the debugger is active */
389	if (!kgdb_connected)
390		try_module_get(THIS_MODULE);
391}
392
393static void kgdboc_post_exp_handler(void)
394{
395	/* decrement the module count when the debugger detaches */
396	if (!kgdb_connected)
397		module_put(THIS_MODULE);
398	if (kgdboc_use_kms && dbg_restore_graphics) {
399		dbg_restore_graphics = 0;
400		con_debug_leave();
401	}
402	kgdboc_restore_input();
403}
404
405static struct kgdb_io kgdboc_io_ops = {
406	.name			= "kgdboc",
407	.read_char		= kgdboc_get_char,
408	.write_char		= kgdboc_put_char,
409	.pre_exception		= kgdboc_pre_exp_handler,
410	.post_exception		= kgdboc_post_exp_handler,
411};
412
413#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
414static int kgdboc_option_setup(char *opt)
415{
416	if (!opt) {
417		pr_err("config string not provided\n");
418		return 1;
419	}
420
421	if (strlen(opt) >= MAX_CONFIG_LEN) {
422		pr_err("config string too long\n");
423		return 1;
424	}
425	strcpy(config, opt);
426
427	return 1;
428}
429
430__setup("kgdboc=", kgdboc_option_setup);
431
432
433/* This is only available if kgdboc is a built in for early debugging */
434static int __init kgdboc_early_init(char *opt)
435{
436	kgdboc_option_setup(opt);
437	configure_kgdboc();
438	return 0;
439}
440
441early_param("ekgdboc", kgdboc_early_init);
442
443static int kgdboc_earlycon_get_char(void)
444{
445	char c;
446
447	if (!kgdboc_earlycon_io_ops.cons->read(kgdboc_earlycon_io_ops.cons,
448					       &c, 1))
449		return NO_POLL_CHAR;
450
451	return c;
452}
453
454static void kgdboc_earlycon_put_char(u8 chr)
455{
456	kgdboc_earlycon_io_ops.cons->write(kgdboc_earlycon_io_ops.cons, &chr,
457					   1);
458}
459
460static void kgdboc_earlycon_pre_exp_handler(void)
461{
462	struct console *con;
463	static bool already_warned;
464	int cookie;
465
466	if (already_warned)
467		return;
468
469	/*
470	 * When the first normal console comes up the kernel will take all
471	 * the boot consoles out of the list.  Really, we should stop using
472	 * the boot console when it does that but until a TTY is registered
473	 * we have no other choice so we keep using it.  Since not all
474	 * serial drivers might be OK with this, print a warning once per
475	 * boot if we detect this case.
476	 */
477	cookie = console_srcu_read_lock();
478	for_each_console_srcu(con) {
479		if (con == kgdboc_earlycon_io_ops.cons)
480			break;
481	}
482	console_srcu_read_unlock(cookie);
483	if (con)
484		return;
485
486	already_warned = true;
487	pr_warn("kgdboc_earlycon is still using bootconsole\n");
488}
489
490static int kgdboc_earlycon_deferred_exit(struct console *con)
491{
492	/*
493	 * If we get here it means the boot console is going away but we
494	 * don't yet have a suitable replacement.  Don't pass through to
495	 * the original exit routine.  We'll call it later in our deinit()
496	 * function.  For now, restore the original exit() function pointer
497	 * as a sentinal that we've hit this point.
498	 */
499	con->exit = earlycon_orig_exit;
500
501	return 0;
502}
503
504static void kgdboc_earlycon_deinit(void)
505{
506	if (!kgdboc_earlycon_io_ops.cons)
507		return;
508
509	if (kgdboc_earlycon_io_ops.cons->exit == kgdboc_earlycon_deferred_exit)
510		/*
511		 * kgdboc_earlycon is exiting but original boot console exit
512		 * was never called (AKA kgdboc_earlycon_deferred_exit()
513		 * didn't ever run).  Undo our trap.
514		 */
515		kgdboc_earlycon_io_ops.cons->exit = earlycon_orig_exit;
516	else if (kgdboc_earlycon_io_ops.cons->exit)
517		/*
518		 * We skipped calling the exit() routine so we could try to
519		 * keep using the boot console even after it went away.  We're
520		 * finally done so call the function now.
521		 */
522		kgdboc_earlycon_io_ops.cons->exit(kgdboc_earlycon_io_ops.cons);
523
524	kgdboc_earlycon_io_ops.cons = NULL;
525}
526
527static struct kgdb_io kgdboc_earlycon_io_ops = {
528	.name			= "kgdboc_earlycon",
529	.read_char		= kgdboc_earlycon_get_char,
530	.write_char		= kgdboc_earlycon_put_char,
531	.pre_exception		= kgdboc_earlycon_pre_exp_handler,
532	.deinit			= kgdboc_earlycon_deinit,
533};
534
535#define MAX_CONSOLE_NAME_LEN (sizeof((struct console *) 0)->name)
536static char kgdboc_earlycon_param[MAX_CONSOLE_NAME_LEN] __initdata;
537static bool kgdboc_earlycon_late_enable __initdata;
538
539static int __init kgdboc_earlycon_init(char *opt)
540{
541	struct console *con;
542
543	kdb_init(KDB_INIT_EARLY);
544
545	/*
546	 * Look for a matching console, or if the name was left blank just
547	 * pick the first one we find.
548	 */
549
550	/*
551	 * Hold the console_list_lock to guarantee that no consoles are
552	 * unregistered until the kgdboc_earlycon setup is complete.
553	 * Trapping the exit() callback relies on exit() not being
554	 * called until the trap is setup. This also allows safe
555	 * traversal of the console list and race-free reading of @flags.
556	 */
557	console_list_lock();
558	for_each_console(con) {
559		if (con->write && con->read &&
560		    (con->flags & (CON_BOOT | CON_ENABLED)) &&
561		    (!opt || !opt[0] || strcmp(con->name, opt) == 0))
562			break;
563	}
564
565	if (!con) {
566		/*
567		 * Both earlycon and kgdboc_earlycon are initialized during
568		 * early parameter parsing. We cannot guarantee earlycon gets
569		 * in first and, in any case, on ACPI systems earlycon may
570		 * defer its own initialization (usually to somewhere within
571		 * setup_arch() ). To cope with either of these situations
572		 * we can defer our own initialization to a little later in
573		 * the boot.
574		 */
575		if (!kgdboc_earlycon_late_enable) {
576			pr_info("No suitable earlycon yet, will try later\n");
577			if (opt)
578				strscpy(kgdboc_earlycon_param, opt,
579					sizeof(kgdboc_earlycon_param));
580			kgdboc_earlycon_late_enable = true;
581		} else {
582			pr_info("Couldn't find kgdb earlycon\n");
583		}
584		goto unlock;
585	}
586
587	kgdboc_earlycon_io_ops.cons = con;
588	pr_info("Going to register kgdb with earlycon '%s'\n", con->name);
589	if (kgdb_register_io_module(&kgdboc_earlycon_io_ops) != 0) {
590		kgdboc_earlycon_io_ops.cons = NULL;
591		pr_info("Failed to register kgdb with earlycon\n");
592	} else {
593		/* Trap exit so we can keep earlycon longer if needed. */
594		earlycon_orig_exit = con->exit;
595		con->exit = kgdboc_earlycon_deferred_exit;
596	}
597
598unlock:
599	console_list_unlock();
600
601	/* Non-zero means malformed option so we always return zero */
602	return 0;
603}
604
605early_param("kgdboc_earlycon", kgdboc_earlycon_init);
606
607/*
608 * This is only intended for the late adoption of an early console.
609 *
610 * It is not a reliable way to adopt regular consoles because we can not
611 * control what order console initcalls are made and, in any case, many
612 * regular consoles are registered much later in the boot process than
613 * the console initcalls!
614 */
615static int __init kgdboc_earlycon_late_init(void)
616{
617	if (kgdboc_earlycon_late_enable)
618		kgdboc_earlycon_init(kgdboc_earlycon_param);
619	return 0;
620}
621console_initcall(kgdboc_earlycon_late_init);
622
623#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
624
625module_init(init_kgdboc);
626module_exit(exit_kgdboc);
627module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
628MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
629MODULE_DESCRIPTION("KGDB Console TTY Driver");
630MODULE_LICENSE("GPL");
631