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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
24#define MAX_CONFIG_LEN 40
25
26static struct kgdb_io kgdboc_io_ops;
27
28/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
29static int configured = -1;
30
31static char config[MAX_CONFIG_LEN];
32static struct kparam_string kps = {
33 .string = config,
34 .maxlen = MAX_CONFIG_LEN,
35};
36
37static int kgdboc_use_kms; /* 1 if we use kernel mode switching */
38static struct tty_driver *kgdb_tty_driver;
39static int kgdb_tty_line;
40
41#ifdef CONFIG_KDB_KEYBOARD
42static int kgdboc_reset_connect(struct input_handler *handler,
43 struct input_dev *dev,
44 const struct input_device_id *id)
45{
46 input_reset_device(dev);
47
48 /* Return an error - we do not want to bind, just to reset */
49 return -ENODEV;
50}
51
52static void kgdboc_reset_disconnect(struct input_handle *handle)
53{
54 /* We do not expect anyone to actually bind to us */
55 BUG();
56}
57
58static const struct input_device_id kgdboc_reset_ids[] = {
59 {
60 .flags = INPUT_DEVICE_ID_MATCH_EVBIT,
61 .evbit = { BIT_MASK(EV_KEY) },
62 },
63 { }
64};
65
66static struct input_handler kgdboc_reset_handler = {
67 .connect = kgdboc_reset_connect,
68 .disconnect = kgdboc_reset_disconnect,
69 .name = "kgdboc_reset",
70 .id_table = kgdboc_reset_ids,
71};
72
73static DEFINE_MUTEX(kgdboc_reset_mutex);
74
75static void kgdboc_restore_input_helper(struct work_struct *dummy)
76{
77 /*
78 * We need to take a mutex to prevent several instances of
79 * this work running on different CPUs so they don't try
80 * to register again already registered handler.
81 */
82 mutex_lock(&kgdboc_reset_mutex);
83
84 if (input_register_handler(&kgdboc_reset_handler) == 0)
85 input_unregister_handler(&kgdboc_reset_handler);
86
87 mutex_unlock(&kgdboc_reset_mutex);
88}
89
90static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);
91
92static void kgdboc_restore_input(void)
93{
94 if (likely(system_state == SYSTEM_RUNNING))
95 schedule_work(&kgdboc_restore_input_work);
96}
97
98static int kgdboc_register_kbd(char **cptr)
99{
100 if (strncmp(*cptr, "kbd", 3) == 0 ||
101 strncmp(*cptr, "kdb", 3) == 0) {
102 if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
103 kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
104 kdb_poll_idx++;
105 if (cptr[0][3] == ',')
106 *cptr += 4;
107 else
108 return 1;
109 }
110 }
111 return 0;
112}
113
114static void kgdboc_unregister_kbd(void)
115{
116 int i;
117
118 for (i = 0; i < kdb_poll_idx; i++) {
119 if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
120 kdb_poll_idx--;
121 kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
122 kdb_poll_funcs[kdb_poll_idx] = NULL;
123 i--;
124 }
125 }
126 flush_work(&kgdboc_restore_input_work);
127}
128#else /* ! CONFIG_KDB_KEYBOARD */
129#define kgdboc_register_kbd(x) 0
130#define kgdboc_unregister_kbd()
131#define kgdboc_restore_input()
132#endif /* ! CONFIG_KDB_KEYBOARD */
133
134static void cleanup_kgdboc(void)
135{
136 if (kgdb_unregister_nmi_console())
137 return;
138 kgdboc_unregister_kbd();
139 if (configured == 1)
140 kgdb_unregister_io_module(&kgdboc_io_ops);
141}
142
143static int configure_kgdboc(void)
144{
145 struct tty_driver *p;
146 int tty_line = 0;
147 int err = -ENODEV;
148 char *cptr = config;
149 struct console *cons;
150
151 if (!strlen(config) || isspace(config[0])) {
152 err = 0;
153 goto noconfig;
154 }
155
156 kgdboc_io_ops.is_console = 0;
157 kgdb_tty_driver = NULL;
158
159 kgdboc_use_kms = 0;
160 if (strncmp(cptr, "kms,", 4) == 0) {
161 cptr += 4;
162 kgdboc_use_kms = 1;
163 }
164
165 if (kgdboc_register_kbd(&cptr))
166 goto do_register;
167
168 p = tty_find_polling_driver(cptr, &tty_line);
169 if (!p)
170 goto noconfig;
171
172 cons = console_drivers;
173 while (cons) {
174 int idx;
175 if (cons->device && cons->device(cons, &idx) == p &&
176 idx == tty_line) {
177 kgdboc_io_ops.is_console = 1;
178 break;
179 }
180 cons = cons->next;
181 }
182
183 kgdb_tty_driver = p;
184 kgdb_tty_line = tty_line;
185
186do_register:
187 err = kgdb_register_io_module(&kgdboc_io_ops);
188 if (err)
189 goto noconfig;
190
191 err = kgdb_register_nmi_console();
192 if (err)
193 goto nmi_con_failed;
194
195 configured = 1;
196
197 return 0;
198
199nmi_con_failed:
200 kgdb_unregister_io_module(&kgdboc_io_ops);
201noconfig:
202 kgdboc_unregister_kbd();
203 config[0] = 0;
204 configured = 0;
205 cleanup_kgdboc();
206
207 return err;
208}
209
210static int __init init_kgdboc(void)
211{
212 /* Already configured? */
213 if (configured == 1)
214 return 0;
215
216 return configure_kgdboc();
217}
218
219static int kgdboc_get_char(void)
220{
221 if (!kgdb_tty_driver)
222 return -1;
223 return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
224 kgdb_tty_line);
225}
226
227static void kgdboc_put_char(u8 chr)
228{
229 if (!kgdb_tty_driver)
230 return;
231 kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
232 kgdb_tty_line, chr);
233}
234
235static int param_set_kgdboc_var(const char *kmessage,
236 const struct kernel_param *kp)
237{
238 size_t len = strlen(kmessage);
239
240 if (len >= MAX_CONFIG_LEN) {
241 pr_err("config string too long\n");
242 return -ENOSPC;
243 }
244
245 /* Only copy in the string if the init function has not run yet */
246 if (configured < 0) {
247 strcpy(config, kmessage);
248 return 0;
249 }
250
251 if (kgdb_connected) {
252 pr_err("Cannot reconfigure while KGDB is connected.\n");
253
254 return -EBUSY;
255 }
256
257 strcpy(config, kmessage);
258 /* Chop out \n char as a result of echo */
259 if (len && config[len - 1] == '\n')
260 config[len - 1] = '\0';
261
262 if (configured == 1)
263 cleanup_kgdboc();
264
265 /* Go and configure with the new params. */
266 return configure_kgdboc();
267}
268
269static int dbg_restore_graphics;
270
271static void kgdboc_pre_exp_handler(void)
272{
273 if (!dbg_restore_graphics && kgdboc_use_kms) {
274 dbg_restore_graphics = 1;
275 con_debug_enter(vc_cons[fg_console].d);
276 }
277 /* Increment the module count when the debugger is active */
278 if (!kgdb_connected)
279 try_module_get(THIS_MODULE);
280
281 atomic_inc(&ignore_console_lock_warning);
282}
283
284static void kgdboc_post_exp_handler(void)
285{
286 atomic_dec(&ignore_console_lock_warning);
287
288 /* decrement the module count when the debugger detaches */
289 if (!kgdb_connected)
290 module_put(THIS_MODULE);
291 if (kgdboc_use_kms && dbg_restore_graphics) {
292 dbg_restore_graphics = 0;
293 con_debug_leave();
294 }
295 kgdboc_restore_input();
296}
297
298static struct kgdb_io kgdboc_io_ops = {
299 .name = "kgdboc",
300 .read_char = kgdboc_get_char,
301 .write_char = kgdboc_put_char,
302 .pre_exception = kgdboc_pre_exp_handler,
303 .post_exception = kgdboc_post_exp_handler,
304};
305
306#ifdef CONFIG_KGDB_SERIAL_CONSOLE
307static int kgdboc_option_setup(char *opt)
308{
309 if (!opt) {
310 pr_err("config string not provided\n");
311 return -EINVAL;
312 }
313
314 if (strlen(opt) >= MAX_CONFIG_LEN) {
315 pr_err("config string too long\n");
316 return -ENOSPC;
317 }
318 strcpy(config, opt);
319
320 return 0;
321}
322
323__setup("kgdboc=", kgdboc_option_setup);
324
325
326/* This is only available if kgdboc is a built in for early debugging */
327static int __init kgdboc_early_init(char *opt)
328{
329 /* save the first character of the config string because the
330 * init routine can destroy it.
331 */
332 char save_ch;
333
334 kgdboc_option_setup(opt);
335 save_ch = config[0];
336 init_kgdboc();
337 config[0] = save_ch;
338 return 0;
339}
340
341early_param("ekgdboc", kgdboc_early_init);
342#endif /* CONFIG_KGDB_SERIAL_CONSOLE */
343
344module_init(init_kgdboc);
345module_exit(cleanup_kgdboc);
346module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
347MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
348MODULE_DESCRIPTION("KGDB Console TTY Driver");
349MODULE_LICENSE("GPL");
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/irq_work.h>
23#include <linux/module.h>
24#include <linux/platform_device.h>
25#include <linux/serial_core.h>
26
27#define MAX_CONFIG_LEN 40
28
29static struct kgdb_io kgdboc_io_ops;
30
31/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
32static int configured = -1;
33static DEFINE_MUTEX(config_mutex);
34
35static char config[MAX_CONFIG_LEN];
36static struct kparam_string kps = {
37 .string = config,
38 .maxlen = MAX_CONFIG_LEN,
39};
40
41static int kgdboc_use_kms; /* 1 if we use kernel mode switching */
42static struct tty_driver *kgdb_tty_driver;
43static int kgdb_tty_line;
44
45static struct platform_device *kgdboc_pdev;
46
47#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
48static struct kgdb_io kgdboc_earlycon_io_ops;
49static int (*earlycon_orig_exit)(struct console *con);
50#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
51
52/*
53 * When we leave the debug trap handler we need to reset the keyboard status
54 * (since the original keyboard state gets partially clobbered by kdb use of
55 * the keyboard).
56 *
57 * The path to deliver the reset is somewhat circuitous.
58 *
59 * To deliver the reset we register an input handler, reset the keyboard and
60 * then deregister the input handler. However, to get this done right, we do
61 * have to carefully manage the calling context because we can only register
62 * input handlers from task context.
63 *
64 * In particular we need to trigger the action from the debug trap handler with
65 * all its NMI and/or NMI-like oddities. To solve this the kgdboc trap exit code
66 * (the "post_exception" callback) uses irq_work_queue(), which is NMI-safe, to
67 * schedule a callback from a hardirq context. From there we have to defer the
68 * work again, this time using schedule_work(), to get a callback using the
69 * system workqueue, which runs in task context.
70 */
71#ifdef CONFIG_KDB_KEYBOARD
72static int kgdboc_reset_connect(struct input_handler *handler,
73 struct input_dev *dev,
74 const struct input_device_id *id)
75{
76 input_reset_device(dev);
77
78 /* Return an error - we do not want to bind, just to reset */
79 return -ENODEV;
80}
81
82static void kgdboc_reset_disconnect(struct input_handle *handle)
83{
84 /* We do not expect anyone to actually bind to us */
85 BUG();
86}
87
88static const struct input_device_id kgdboc_reset_ids[] = {
89 {
90 .flags = INPUT_DEVICE_ID_MATCH_EVBIT,
91 .evbit = { BIT_MASK(EV_KEY) },
92 },
93 { }
94};
95
96static struct input_handler kgdboc_reset_handler = {
97 .connect = kgdboc_reset_connect,
98 .disconnect = kgdboc_reset_disconnect,
99 .name = "kgdboc_reset",
100 .id_table = kgdboc_reset_ids,
101};
102
103static DEFINE_MUTEX(kgdboc_reset_mutex);
104
105static void kgdboc_restore_input_helper(struct work_struct *dummy)
106{
107 /*
108 * We need to take a mutex to prevent several instances of
109 * this work running on different CPUs so they don't try
110 * to register again already registered handler.
111 */
112 mutex_lock(&kgdboc_reset_mutex);
113
114 if (input_register_handler(&kgdboc_reset_handler) == 0)
115 input_unregister_handler(&kgdboc_reset_handler);
116
117 mutex_unlock(&kgdboc_reset_mutex);
118}
119
120static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);
121
122static void kgdboc_queue_restore_input_helper(struct irq_work *unused)
123{
124 schedule_work(&kgdboc_restore_input_work);
125}
126
127static DEFINE_IRQ_WORK(kgdboc_restore_input_irq_work, kgdboc_queue_restore_input_helper);
128
129static void kgdboc_restore_input(void)
130{
131 if (likely(system_state == SYSTEM_RUNNING))
132 irq_work_queue(&kgdboc_restore_input_irq_work);
133}
134
135static int kgdboc_register_kbd(char **cptr)
136{
137 if (strncmp(*cptr, "kbd", 3) == 0 ||
138 strncmp(*cptr, "kdb", 3) == 0) {
139 if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
140 kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
141 kdb_poll_idx++;
142 if (cptr[0][3] == ',')
143 *cptr += 4;
144 else
145 return 1;
146 }
147 }
148 return 0;
149}
150
151static void kgdboc_unregister_kbd(void)
152{
153 int i;
154
155 for (i = 0; i < kdb_poll_idx; i++) {
156 if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
157 kdb_poll_idx--;
158 kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
159 kdb_poll_funcs[kdb_poll_idx] = NULL;
160 i--;
161 }
162 }
163 irq_work_sync(&kgdboc_restore_input_irq_work);
164 flush_work(&kgdboc_restore_input_work);
165}
166#else /* ! CONFIG_KDB_KEYBOARD */
167#define kgdboc_register_kbd(x) 0
168#define kgdboc_unregister_kbd()
169#define kgdboc_restore_input()
170#endif /* ! CONFIG_KDB_KEYBOARD */
171
172#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
173static void cleanup_earlycon(void)
174{
175 if (kgdboc_earlycon_io_ops.cons)
176 kgdb_unregister_io_module(&kgdboc_earlycon_io_ops);
177}
178#else /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
179static inline void cleanup_earlycon(void) { }
180#endif /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
181
182static void cleanup_kgdboc(void)
183{
184 cleanup_earlycon();
185
186 if (configured != 1)
187 return;
188
189 if (kgdb_unregister_nmi_console())
190 return;
191 kgdboc_unregister_kbd();
192 kgdb_unregister_io_module(&kgdboc_io_ops);
193}
194
195static int configure_kgdboc(void)
196{
197 struct tty_driver *p;
198 int tty_line = 0;
199 int err = -ENODEV;
200 char *cptr = config;
201 struct console *cons;
202 int cookie;
203
204 if (!strlen(config) || isspace(config[0])) {
205 err = 0;
206 goto noconfig;
207 }
208
209 kgdboc_io_ops.cons = NULL;
210 kgdb_tty_driver = NULL;
211
212 kgdboc_use_kms = 0;
213 if (strncmp(cptr, "kms,", 4) == 0) {
214 cptr += 4;
215 kgdboc_use_kms = 1;
216 }
217
218 if (kgdboc_register_kbd(&cptr))
219 goto do_register;
220
221 p = tty_find_polling_driver(cptr, &tty_line);
222 if (!p)
223 goto noconfig;
224
225 /*
226 * Take console_lock to serialize device() callback with
227 * other console operations. For example, fg_console is
228 * modified under console_lock when switching vt.
229 */
230 console_lock();
231
232 cookie = console_srcu_read_lock();
233 for_each_console_srcu(cons) {
234 int idx;
235 if (cons->device && cons->device(cons, &idx) == p &&
236 idx == tty_line) {
237 kgdboc_io_ops.cons = cons;
238 break;
239 }
240 }
241 console_srcu_read_unlock(cookie);
242
243 console_unlock();
244
245 kgdb_tty_driver = p;
246 kgdb_tty_line = tty_line;
247
248do_register:
249 err = kgdb_register_io_module(&kgdboc_io_ops);
250 if (err)
251 goto noconfig;
252
253 err = kgdb_register_nmi_console();
254 if (err)
255 goto nmi_con_failed;
256
257 configured = 1;
258
259 return 0;
260
261nmi_con_failed:
262 kgdb_unregister_io_module(&kgdboc_io_ops);
263noconfig:
264 kgdboc_unregister_kbd();
265 configured = 0;
266
267 return err;
268}
269
270static int kgdboc_probe(struct platform_device *pdev)
271{
272 int ret = 0;
273
274 mutex_lock(&config_mutex);
275 if (configured != 1) {
276 ret = configure_kgdboc();
277
278 /* Convert "no device" to "defer" so we'll keep trying */
279 if (ret == -ENODEV)
280 ret = -EPROBE_DEFER;
281 }
282 mutex_unlock(&config_mutex);
283
284 return ret;
285}
286
287static struct platform_driver kgdboc_platform_driver = {
288 .probe = kgdboc_probe,
289 .driver = {
290 .name = "kgdboc",
291 .suppress_bind_attrs = true,
292 },
293};
294
295static int __init init_kgdboc(void)
296{
297 int ret;
298
299 /*
300 * kgdboc is a little bit of an odd "platform_driver". It can be
301 * up and running long before the platform_driver object is
302 * created and thus doesn't actually store anything in it. There's
303 * only one instance of kgdb so anything is stored as global state.
304 * The platform_driver is only created so that we can leverage the
305 * kernel's mechanisms (like -EPROBE_DEFER) to call us when our
306 * underlying tty is ready. Here we init our platform driver and
307 * then create the single kgdboc instance.
308 */
309 ret = platform_driver_register(&kgdboc_platform_driver);
310 if (ret)
311 return ret;
312
313 kgdboc_pdev = platform_device_alloc("kgdboc", PLATFORM_DEVID_NONE);
314 if (!kgdboc_pdev) {
315 ret = -ENOMEM;
316 goto err_did_register;
317 }
318
319 ret = platform_device_add(kgdboc_pdev);
320 if (!ret)
321 return 0;
322
323 platform_device_put(kgdboc_pdev);
324
325err_did_register:
326 platform_driver_unregister(&kgdboc_platform_driver);
327 return ret;
328}
329
330static void exit_kgdboc(void)
331{
332 mutex_lock(&config_mutex);
333 cleanup_kgdboc();
334 mutex_unlock(&config_mutex);
335
336 platform_device_unregister(kgdboc_pdev);
337 platform_driver_unregister(&kgdboc_platform_driver);
338}
339
340static int kgdboc_get_char(void)
341{
342 if (!kgdb_tty_driver)
343 return -1;
344 return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
345 kgdb_tty_line);
346}
347
348static void kgdboc_put_char(u8 chr)
349{
350 if (!kgdb_tty_driver)
351 return;
352 kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
353 kgdb_tty_line, chr);
354}
355
356static int param_set_kgdboc_var(const char *kmessage,
357 const struct kernel_param *kp)
358{
359 size_t len = strlen(kmessage);
360 int ret = 0;
361
362 if (len >= MAX_CONFIG_LEN) {
363 pr_err("config string too long\n");
364 return -ENOSPC;
365 }
366
367 if (kgdb_connected) {
368 pr_err("Cannot reconfigure while KGDB is connected.\n");
369 return -EBUSY;
370 }
371
372 mutex_lock(&config_mutex);
373
374 strcpy(config, kmessage);
375 /* Chop out \n char as a result of echo */
376 if (len && config[len - 1] == '\n')
377 config[len - 1] = '\0';
378
379 if (configured == 1)
380 cleanup_kgdboc();
381
382 /*
383 * Configure with the new params as long as init already ran.
384 * Note that we can get called before init if someone loads us
385 * with "modprobe kgdboc kgdboc=..." or if they happen to use
386 * the odd syntax of "kgdboc.kgdboc=..." on the kernel command.
387 */
388 if (configured >= 0)
389 ret = configure_kgdboc();
390
391 /*
392 * If we couldn't configure then clear out the config. Note that
393 * specifying an invalid config on the kernel command line vs.
394 * through sysfs have slightly different behaviors. If we fail
395 * to configure what was specified on the kernel command line
396 * we'll leave it in the 'config' and return -EPROBE_DEFER from
397 * our probe. When specified through sysfs userspace is
398 * responsible for loading the tty driver before setting up.
399 */
400 if (ret)
401 config[0] = '\0';
402
403 mutex_unlock(&config_mutex);
404
405 return ret;
406}
407
408static int dbg_restore_graphics;
409
410static void kgdboc_pre_exp_handler(void)
411{
412 if (!dbg_restore_graphics && kgdboc_use_kms) {
413 dbg_restore_graphics = 1;
414 con_debug_enter(vc_cons[fg_console].d);
415 }
416 /* Increment the module count when the debugger is active */
417 if (!kgdb_connected)
418 try_module_get(THIS_MODULE);
419}
420
421static void kgdboc_post_exp_handler(void)
422{
423 /* decrement the module count when the debugger detaches */
424 if (!kgdb_connected)
425 module_put(THIS_MODULE);
426 if (kgdboc_use_kms && dbg_restore_graphics) {
427 dbg_restore_graphics = 0;
428 con_debug_leave();
429 }
430 kgdboc_restore_input();
431}
432
433static struct kgdb_io kgdboc_io_ops = {
434 .name = "kgdboc",
435 .read_char = kgdboc_get_char,
436 .write_char = kgdboc_put_char,
437 .pre_exception = kgdboc_pre_exp_handler,
438 .post_exception = kgdboc_post_exp_handler,
439};
440
441#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
442static int kgdboc_option_setup(char *opt)
443{
444 if (!opt) {
445 pr_err("config string not provided\n");
446 return 1;
447 }
448
449 if (strlen(opt) >= MAX_CONFIG_LEN) {
450 pr_err("config string too long\n");
451 return 1;
452 }
453 strcpy(config, opt);
454
455 return 1;
456}
457
458__setup("kgdboc=", kgdboc_option_setup);
459
460
461/* This is only available if kgdboc is a built in for early debugging */
462static int __init kgdboc_early_init(char *opt)
463{
464 kgdboc_option_setup(opt);
465 configure_kgdboc();
466 return 0;
467}
468
469early_param("ekgdboc", kgdboc_early_init);
470
471static int kgdboc_earlycon_get_char(void)
472{
473 char c;
474
475 if (!kgdboc_earlycon_io_ops.cons->read(kgdboc_earlycon_io_ops.cons,
476 &c, 1))
477 return NO_POLL_CHAR;
478
479 return c;
480}
481
482static void kgdboc_earlycon_put_char(u8 chr)
483{
484 kgdboc_earlycon_io_ops.cons->write(kgdboc_earlycon_io_ops.cons, &chr,
485 1);
486}
487
488static void kgdboc_earlycon_pre_exp_handler(void)
489{
490 struct console *con;
491 static bool already_warned;
492 int cookie;
493
494 if (already_warned)
495 return;
496
497 /*
498 * When the first normal console comes up the kernel will take all
499 * the boot consoles out of the list. Really, we should stop using
500 * the boot console when it does that but until a TTY is registered
501 * we have no other choice so we keep using it. Since not all
502 * serial drivers might be OK with this, print a warning once per
503 * boot if we detect this case.
504 */
505 cookie = console_srcu_read_lock();
506 for_each_console_srcu(con) {
507 if (con == kgdboc_earlycon_io_ops.cons)
508 break;
509 }
510 console_srcu_read_unlock(cookie);
511 if (con)
512 return;
513
514 already_warned = true;
515 pr_warn("kgdboc_earlycon is still using bootconsole\n");
516}
517
518static int kgdboc_earlycon_deferred_exit(struct console *con)
519{
520 /*
521 * If we get here it means the boot console is going away but we
522 * don't yet have a suitable replacement. Don't pass through to
523 * the original exit routine. We'll call it later in our deinit()
524 * function. For now, restore the original exit() function pointer
525 * as a sentinal that we've hit this point.
526 */
527 con->exit = earlycon_orig_exit;
528
529 return 0;
530}
531
532static void kgdboc_earlycon_deinit(void)
533{
534 if (!kgdboc_earlycon_io_ops.cons)
535 return;
536
537 if (kgdboc_earlycon_io_ops.cons->exit == kgdboc_earlycon_deferred_exit)
538 /*
539 * kgdboc_earlycon is exiting but original boot console exit
540 * was never called (AKA kgdboc_earlycon_deferred_exit()
541 * didn't ever run). Undo our trap.
542 */
543 kgdboc_earlycon_io_ops.cons->exit = earlycon_orig_exit;
544 else if (kgdboc_earlycon_io_ops.cons->exit)
545 /*
546 * We skipped calling the exit() routine so we could try to
547 * keep using the boot console even after it went away. We're
548 * finally done so call the function now.
549 */
550 kgdboc_earlycon_io_ops.cons->exit(kgdboc_earlycon_io_ops.cons);
551
552 kgdboc_earlycon_io_ops.cons = NULL;
553}
554
555static struct kgdb_io kgdboc_earlycon_io_ops = {
556 .name = "kgdboc_earlycon",
557 .read_char = kgdboc_earlycon_get_char,
558 .write_char = kgdboc_earlycon_put_char,
559 .pre_exception = kgdboc_earlycon_pre_exp_handler,
560 .deinit = kgdboc_earlycon_deinit,
561};
562
563#define MAX_CONSOLE_NAME_LEN (sizeof((struct console *) 0)->name)
564static char kgdboc_earlycon_param[MAX_CONSOLE_NAME_LEN] __initdata;
565static bool kgdboc_earlycon_late_enable __initdata;
566
567static int __init kgdboc_earlycon_init(char *opt)
568{
569 struct console *con;
570
571 kdb_init(KDB_INIT_EARLY);
572
573 /*
574 * Look for a matching console, or if the name was left blank just
575 * pick the first one we find.
576 */
577
578 /*
579 * Hold the console_list_lock to guarantee that no consoles are
580 * unregistered until the kgdboc_earlycon setup is complete.
581 * Trapping the exit() callback relies on exit() not being
582 * called until the trap is setup. This also allows safe
583 * traversal of the console list and race-free reading of @flags.
584 */
585 console_list_lock();
586 for_each_console(con) {
587 if (con->write && con->read &&
588 (con->flags & (CON_BOOT | CON_ENABLED)) &&
589 (!opt || !opt[0] || strcmp(con->name, opt) == 0))
590 break;
591 }
592
593 if (!con) {
594 /*
595 * Both earlycon and kgdboc_earlycon are initialized during
596 * early parameter parsing. We cannot guarantee earlycon gets
597 * in first and, in any case, on ACPI systems earlycon may
598 * defer its own initialization (usually to somewhere within
599 * setup_arch() ). To cope with either of these situations
600 * we can defer our own initialization to a little later in
601 * the boot.
602 */
603 if (!kgdboc_earlycon_late_enable) {
604 pr_info("No suitable earlycon yet, will try later\n");
605 if (opt)
606 strscpy(kgdboc_earlycon_param, opt,
607 sizeof(kgdboc_earlycon_param));
608 kgdboc_earlycon_late_enable = true;
609 } else {
610 pr_info("Couldn't find kgdb earlycon\n");
611 }
612 goto unlock;
613 }
614
615 kgdboc_earlycon_io_ops.cons = con;
616 pr_info("Going to register kgdb with earlycon '%s'\n", con->name);
617 if (kgdb_register_io_module(&kgdboc_earlycon_io_ops) != 0) {
618 kgdboc_earlycon_io_ops.cons = NULL;
619 pr_info("Failed to register kgdb with earlycon\n");
620 } else {
621 /* Trap exit so we can keep earlycon longer if needed. */
622 earlycon_orig_exit = con->exit;
623 con->exit = kgdboc_earlycon_deferred_exit;
624 }
625
626unlock:
627 console_list_unlock();
628
629 /* Non-zero means malformed option so we always return zero */
630 return 0;
631}
632
633early_param("kgdboc_earlycon", kgdboc_earlycon_init);
634
635/*
636 * This is only intended for the late adoption of an early console.
637 *
638 * It is not a reliable way to adopt regular consoles because we can not
639 * control what order console initcalls are made and, in any case, many
640 * regular consoles are registered much later in the boot process than
641 * the console initcalls!
642 */
643static int __init kgdboc_earlycon_late_init(void)
644{
645 if (kgdboc_earlycon_late_enable)
646 kgdboc_earlycon_init(kgdboc_earlycon_param);
647 return 0;
648}
649console_initcall(kgdboc_earlycon_late_init);
650
651#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
652
653module_init(init_kgdboc);
654module_exit(exit_kgdboc);
655module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
656MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
657MODULE_DESCRIPTION("KGDB Console TTY Driver");
658MODULE_LICENSE("GPL");