summaryrefslogtreecommitdiff
path: root/drivers/tty/serial/kgdboc.c
blob: a3ed9b34e2abb557374f91c64e23a1bad4cb16b2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
// SPDX-License-Identifier: GPL-2.0
/*
 * Based on the same principle as kgdboe using the NETPOLL api, this
 * driver uses a console polling api to implement a gdb serial inteface
 * which is multiplexed on a console port.
 *
 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
 *
 * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/ctype.h>
#include <linux/kgdb.h>
#include <linux/kdb.h>
#include <linux/tty.h>
#include <linux/console.h>
#include <linux/vt_kern.h>
#include <linux/input.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/serial_core.h>

#define MAX_CONFIG_LEN		40

static struct kgdb_io		kgdboc_io_ops;

/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
static int configured		= -1;
static DEFINE_MUTEX(config_mutex);

static char config[MAX_CONFIG_LEN];
static struct kparam_string kps = {
	.string			= config,
	.maxlen			= MAX_CONFIG_LEN,
};

static int kgdboc_use_kms;  /* 1 if we use kernel mode switching */
static struct tty_driver	*kgdb_tty_driver;
static int			kgdb_tty_line;

static struct platform_device *kgdboc_pdev;

#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static struct kgdb_io		kgdboc_earlycon_io_ops;
static int                      (*earlycon_orig_exit)(struct console *con);
#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */

#ifdef CONFIG_KDB_KEYBOARD
static int kgdboc_reset_connect(struct input_handler *handler,
				struct input_dev *dev,
				const struct input_device_id *id)
{
	input_reset_device(dev);

	/* Return an error - we do not want to bind, just to reset */
	return -ENODEV;
}

static void kgdboc_reset_disconnect(struct input_handle *handle)
{
	/* We do not expect anyone to actually bind to us */
	BUG();
}

static const struct input_device_id kgdboc_reset_ids[] = {
	{
		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
		.evbit = { BIT_MASK(EV_KEY) },
	},
	{ }
};

static struct input_handler kgdboc_reset_handler = {
	.connect	= kgdboc_reset_connect,
	.disconnect	= kgdboc_reset_disconnect,
	.name		= "kgdboc_reset",
	.id_table	= kgdboc_reset_ids,
};

static DEFINE_MUTEX(kgdboc_reset_mutex);

static void kgdboc_restore_input_helper(struct work_struct *dummy)
{
	/*
	 * We need to take a mutex to prevent several instances of
	 * this work running on different CPUs so they don't try
	 * to register again already registered handler.
	 */
	mutex_lock(&kgdboc_reset_mutex);

	if (input_register_handler(&kgdboc_reset_handler) == 0)
		input_unregister_handler(&kgdboc_reset_handler);

	mutex_unlock(&kgdboc_reset_mutex);
}

static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);

static void kgdboc_restore_input(void)
{
	if (likely(system_state == SYSTEM_RUNNING))
		schedule_work(&kgdboc_restore_input_work);
}

static int kgdboc_register_kbd(char **cptr)
{
	if (strncmp(*cptr, "kbd", 3) == 0 ||
		strncmp(*cptr, "kdb", 3) == 0) {
		if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
			kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
			kdb_poll_idx++;
			if (cptr[0][3] == ',')
				*cptr += 4;
			else
				return 1;
		}
	}
	return 0;
}

static void kgdboc_unregister_kbd(void)
{
	int i;

	for (i = 0; i < kdb_poll_idx; i++) {
		if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
			kdb_poll_idx--;
			kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
			kdb_poll_funcs[kdb_poll_idx] = NULL;
			i--;
		}
	}
	flush_work(&kgdboc_restore_input_work);
}
#else /* ! CONFIG_KDB_KEYBOARD */
#define kgdboc_register_kbd(x) 0
#define kgdboc_unregister_kbd()
#define kgdboc_restore_input()
#endif /* ! CONFIG_KDB_KEYBOARD */

#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static void cleanup_earlycon(void)
{
	if (kgdboc_earlycon_io_ops.cons)
		kgdb_unregister_io_module(&kgdboc_earlycon_io_ops);
}
#else /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
static inline void cleanup_earlycon(void) { }
#endif /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */

static void cleanup_kgdboc(void)
{
	cleanup_earlycon();

	if (configured != 1)
		return;

	if (kgdb_unregister_nmi_console())
		return;
	kgdboc_unregister_kbd();
	kgdb_unregister_io_module(&kgdboc_io_ops);
}

static int configure_kgdboc(void)
{
	struct tty_driver *p;
	int tty_line = 0;
	int err = -ENODEV;
	char *cptr = config;
	struct console *cons;

	if (!strlen(config) || isspace(config[0])) {
		err = 0;
		goto noconfig;
	}

	kgdboc_io_ops.cons = NULL;
	kgdb_tty_driver = NULL;

	kgdboc_use_kms = 0;
	if (strncmp(cptr, "kms,", 4) == 0) {
		cptr += 4;
		kgdboc_use_kms = 1;
	}

	if (kgdboc_register_kbd(&cptr))
		goto do_register;

	/*
	 * tty_find_polling_driver() can call uart_set_options()
	 * (via poll_init) to configure the uart. Take the console_list_lock
	 * in order to synchronize against register_console(), which can also
	 * configure the uart via uart_set_options(). This also allows safe
	 * traversal of the console list.
	 */
	console_list_lock();

	p = tty_find_polling_driver(cptr, &tty_line);
	if (!p) {
		console_list_unlock();
		goto noconfig;
	}

	/*
	 * Take console_lock to serialize device() callback with
	 * other console operations. For example, fg_console is
	 * modified under console_lock when switching vt.
	 */
	console_lock();

	for_each_console(cons) {
		int idx;
		if (cons->device && cons->device(cons, &idx) == p &&
		    idx == tty_line) {
			kgdboc_io_ops.cons = cons;
			break;
		}
	}

	console_unlock();

	console_list_unlock();

	kgdb_tty_driver = p;
	kgdb_tty_line = tty_line;

do_register:
	err = kgdb_register_io_module(&kgdboc_io_ops);
	if (err)
		goto noconfig;

	err = kgdb_register_nmi_console();
	if (err)
		goto nmi_con_failed;

	configured = 1;

	return 0;

nmi_con_failed:
	kgdb_unregister_io_module(&kgdboc_io_ops);
noconfig:
	kgdboc_unregister_kbd();
	configured = 0;

	return err;
}

static int kgdboc_probe(struct platform_device *pdev)
{
	int ret = 0;

	mutex_lock(&config_mutex);
	if (configured != 1) {
		ret = configure_kgdboc();

		/* Convert "no device" to "defer" so we'll keep trying */
		if (ret == -ENODEV)
			ret = -EPROBE_DEFER;
	}
	mutex_unlock(&config_mutex);

	return ret;
}

static struct platform_driver kgdboc_platform_driver = {
	.probe = kgdboc_probe,
	.driver = {
		.name = "kgdboc",
		.suppress_bind_attrs = true,
	},
};

static int __init init_kgdboc(void)
{
	int ret;

	/*
	 * kgdboc is a little bit of an odd "platform_driver".  It can be
	 * up and running long before the platform_driver object is
	 * created and thus doesn't actually store anything in it.  There's
	 * only one instance of kgdb so anything is stored as global state.
	 * The platform_driver is only created so that we can leverage the
	 * kernel's mechanisms (like -EPROBE_DEFER) to call us when our
	 * underlying tty is ready.  Here we init our platform driver and
	 * then create the single kgdboc instance.
	 */
	ret = platform_driver_register(&kgdboc_platform_driver);
	if (ret)
		return ret;

	kgdboc_pdev = platform_device_alloc("kgdboc", PLATFORM_DEVID_NONE);
	if (!kgdboc_pdev) {
		ret = -ENOMEM;
		goto err_did_register;
	}

	ret = platform_device_add(kgdboc_pdev);
	if (!ret)
		return 0;

	platform_device_put(kgdboc_pdev);

err_did_register:
	platform_driver_unregister(&kgdboc_platform_driver);
	return ret;
}

static void exit_kgdboc(void)
{
	mutex_lock(&config_mutex);
	cleanup_kgdboc();
	mutex_unlock(&config_mutex);

	platform_device_unregister(kgdboc_pdev);
	platform_driver_unregister(&kgdboc_platform_driver);
}

static int kgdboc_get_char(void)
{
	if (!kgdb_tty_driver)
		return -1;
	return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
						kgdb_tty_line);
}

static void kgdboc_put_char(u8 chr)
{
	if (!kgdb_tty_driver)
		return;
	kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
					kgdb_tty_line, chr);
}

static int param_set_kgdboc_var(const char *kmessage,
				const struct kernel_param *kp)
{
	size_t len = strlen(kmessage);
	int ret = 0;

	if (len >= MAX_CONFIG_LEN) {
		pr_err("config string too long\n");
		return -ENOSPC;
	}

	if (kgdb_connected) {
		pr_err("Cannot reconfigure while KGDB is connected.\n");
		return -EBUSY;
	}

	mutex_lock(&config_mutex);

	strcpy(config, kmessage);
	/* Chop out \n char as a result of echo */
	if (len && config[len - 1] == '\n')
		config[len - 1] = '\0';

	if (configured == 1)
		cleanup_kgdboc();

	/*
	 * Configure with the new params as long as init already ran.
	 * Note that we can get called before init if someone loads us
	 * with "modprobe kgdboc kgdboc=..." or if they happen to use
	 * the odd syntax of "kgdboc.kgdboc=..." on the kernel command.
	 */
	if (configured >= 0)
		ret = configure_kgdboc();

	/*
	 * If we couldn't configure then clear out the config.  Note that
	 * specifying an invalid config on the kernel command line vs.
	 * through sysfs have slightly different behaviors.  If we fail
	 * to configure what was specified on the kernel command line
	 * we'll leave it in the 'config' and return -EPROBE_DEFER from
	 * our probe.  When specified through sysfs userspace is
	 * responsible for loading the tty driver before setting up.
	 */
	if (ret)
		config[0] = '\0';

	mutex_unlock(&config_mutex);

	return ret;
}

static int dbg_restore_graphics;

static void kgdboc_pre_exp_handler(void)
{
	if (!dbg_restore_graphics && kgdboc_use_kms) {
		dbg_restore_graphics = 1;
		con_debug_enter(vc_cons[fg_console].d);
	}
	/* Increment the module count when the debugger is active */
	if (!kgdb_connected)
		try_module_get(THIS_MODULE);
}

static void kgdboc_post_exp_handler(void)
{
	/* decrement the module count when the debugger detaches */
	if (!kgdb_connected)
		module_put(THIS_MODULE);
	if (kgdboc_use_kms && dbg_restore_graphics) {
		dbg_restore_graphics = 0;
		con_debug_leave();
	}
	kgdboc_restore_input();
}

static struct kgdb_io kgdboc_io_ops = {
	.name			= "kgdboc",
	.read_char		= kgdboc_get_char,
	.write_char		= kgdboc_put_char,
	.pre_exception		= kgdboc_pre_exp_handler,
	.post_exception		= kgdboc_post_exp_handler,
};

#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static int kgdboc_option_setup(char *opt)
{
	if (!opt) {
		pr_err("config string not provided\n");
		return 1;
	}

	if (strlen(opt) >= MAX_CONFIG_LEN) {
		pr_err("config string too long\n");
		return 1;
	}
	strcpy(config, opt);

	return 1;
}

__setup("kgdboc=", kgdboc_option_setup);


/* This is only available if kgdboc is a built in for early debugging */
static int __init kgdboc_early_init(char *opt)
{
	kgdboc_option_setup(opt);
	configure_kgdboc();
	return 0;
}

early_param("ekgdboc", kgdboc_early_init);

static int kgdboc_earlycon_get_char(void)
{
	char c;

	if (!kgdboc_earlycon_io_ops.cons->read(kgdboc_earlycon_io_ops.cons,
					       &c, 1))
		return NO_POLL_CHAR;

	return c;
}

static void kgdboc_earlycon_put_char(u8 chr)
{
	kgdboc_earlycon_io_ops.cons->write(kgdboc_earlycon_io_ops.cons, &chr,
					   1);
}

static void kgdboc_earlycon_pre_exp_handler(void)
{
	struct console *con;
	static bool already_warned;
	int cookie;

	if (already_warned)
		return;

	/*
	 * When the first normal console comes up the kernel will take all
	 * the boot consoles out of the list.  Really, we should stop using
	 * the boot console when it does that but until a TTY is registered
	 * we have no other choice so we keep using it.  Since not all
	 * serial drivers might be OK with this, print a warning once per
	 * boot if we detect this case.
	 */
	cookie = console_srcu_read_lock();
	for_each_console_srcu(con) {
		if (con == kgdboc_earlycon_io_ops.cons)
			break;
	}
	console_srcu_read_unlock(cookie);
	if (con)
		return;

	already_warned = true;
	pr_warn("kgdboc_earlycon is still using bootconsole\n");
}

static int kgdboc_earlycon_deferred_exit(struct console *con)
{
	/*
	 * If we get here it means the boot console is going away but we
	 * don't yet have a suitable replacement.  Don't pass through to
	 * the original exit routine.  We'll call it later in our deinit()
	 * function.  For now, restore the original exit() function pointer
	 * as a sentinal that we've hit this point.
	 */
	con->exit = earlycon_orig_exit;

	return 0;
}

static void kgdboc_earlycon_deinit(void)
{
	if (!kgdboc_earlycon_io_ops.cons)
		return;

	if (kgdboc_earlycon_io_ops.cons->exit == kgdboc_earlycon_deferred_exit)
		/*
		 * kgdboc_earlycon is exiting but original boot console exit
		 * was never called (AKA kgdboc_earlycon_deferred_exit()
		 * didn't ever run).  Undo our trap.
		 */
		kgdboc_earlycon_io_ops.cons->exit = earlycon_orig_exit;
	else if (kgdboc_earlycon_io_ops.cons->exit)
		/*
		 * We skipped calling the exit() routine so we could try to
		 * keep using the boot console even after it went away.  We're
		 * finally done so call the function now.
		 */
		kgdboc_earlycon_io_ops.cons->exit(kgdboc_earlycon_io_ops.cons);

	kgdboc_earlycon_io_ops.cons = NULL;
}

static struct kgdb_io kgdboc_earlycon_io_ops = {
	.name			= "kgdboc_earlycon",
	.read_char		= kgdboc_earlycon_get_char,
	.write_char		= kgdboc_earlycon_put_char,
	.pre_exception		= kgdboc_earlycon_pre_exp_handler,
	.deinit			= kgdboc_earlycon_deinit,
};

#define MAX_CONSOLE_NAME_LEN (sizeof((struct console *) 0)->name)
static char kgdboc_earlycon_param[MAX_CONSOLE_NAME_LEN] __initdata;
static bool kgdboc_earlycon_late_enable __initdata;

static int __init kgdboc_earlycon_init(char *opt)
{
	struct console *con;

	kdb_init(KDB_INIT_EARLY);

	/*
	 * Look for a matching console, or if the name was left blank just
	 * pick the first one we find.
	 */

	/*
	 * Hold the console_list_lock to guarantee that no consoles are
	 * unregistered until the kgdboc_earlycon setup is complete.
	 * Trapping the exit() callback relies on exit() not being
	 * called until the trap is setup. This also allows safe
	 * traversal of the console list and race-free reading of @flags.
	 */
	console_list_lock();
	for_each_console(con) {
		if (con->write && con->read &&
		    (con->flags & (CON_BOOT | CON_ENABLED)) &&
		    (!opt || !opt[0] || strcmp(con->name, opt) == 0))
			break;
	}

	if (!con) {
		/*
		 * Both earlycon and kgdboc_earlycon are initialized during
		 * early parameter parsing. We cannot guarantee earlycon gets
		 * in first and, in any case, on ACPI systems earlycon may
		 * defer its own initialization (usually to somewhere within
		 * setup_arch() ). To cope with either of these situations
		 * we can defer our own initialization to a little later in
		 * the boot.
		 */
		if (!kgdboc_earlycon_late_enable) {
			pr_info("No suitable earlycon yet, will try later\n");
			if (opt)
				strscpy(kgdboc_earlycon_param, opt,
					sizeof(kgdboc_earlycon_param));
			kgdboc_earlycon_late_enable = true;
		} else {
			pr_info("Couldn't find kgdb earlycon\n");
		}
		goto unlock;
	}

	kgdboc_earlycon_io_ops.cons = con;
	pr_info("Going to register kgdb with earlycon '%s'\n", con->name);
	if (kgdb_register_io_module(&kgdboc_earlycon_io_ops) != 0) {
		kgdboc_earlycon_io_ops.cons = NULL;
		pr_info("Failed to register kgdb with earlycon\n");
	} else {
		/* Trap exit so we can keep earlycon longer if needed. */
		earlycon_orig_exit = con->exit;
		con->exit = kgdboc_earlycon_deferred_exit;
	}

unlock:
	console_list_unlock();

	/* Non-zero means malformed option so we always return zero */
	return 0;
}

early_param("kgdboc_earlycon", kgdboc_earlycon_init);

/*
 * This is only intended for the late adoption of an early console.
 *
 * It is not a reliable way to adopt regular consoles because we can not
 * control what order console initcalls are made and, in any case, many
 * regular consoles are registered much later in the boot process than
 * the console initcalls!
 */
static int __init kgdboc_earlycon_late_init(void)
{
	if (kgdboc_earlycon_late_enable)
		kgdboc_earlycon_init(kgdboc_earlycon_param);
	return 0;
}
console_initcall(kgdboc_earlycon_late_init);

#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */

module_init(init_kgdboc);
module_exit(exit_kgdboc);
module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
MODULE_DESCRIPTION("KGDB Console TTY Driver");
MODULE_LICENSE("GPL");