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(lock: &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(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(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(local_kgdb_io_ops: &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(local_kgdb_io_ops: &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: &cptr))
191 goto do_register;
192
193 p = tty_find_polling_driver(name: cptr, line: &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(local_kgdb_io_ops: &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(local_kgdb_io_ops: &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(lock: &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(name: "kgdboc", PLATFORM_DEVID_NONE);
286 if (!kgdboc_pdev) {
287 ret = -ENOMEM;
288 goto err_did_register;
289 }
290
291 ret = platform_device_add(pdev: kgdboc_pdev);
292 if (!ret)
293 return 0;
294
295 platform_device_put(pdev: 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(lock: &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(p: config, q: 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(lock: &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: 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(p: config, q: 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(level: 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(p: kgdboc_earlycon_param, q: opt,
579 size: 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(local_kgdb_io_ops: &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(opt: 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

source code of linux/drivers/tty/serial/kgdboc.c