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 #include <linux/kernel.h>
12 #include <linux/ctype.h>
13 #include <linux/kgdb.h>
14 #include <linux/kdb.h>
15 #include <linux/tty.h>
16 #include <linux/console.h>
17 #include <linux/vt_kern.h>
18 #include <linux/input.h>
19 #include <linux/module.h>
20
21 #define MAX_CONFIG_LEN 40
22
23 static struct kgdb_io kgdboc_io_ops;
24
25 /* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
26 static int configured = -1;
27
28 static char config[MAX_CONFIG_LEN];
29 static struct kparam_string kps = {
30 .string = config,
31 .maxlen = MAX_CONFIG_LEN,
32 };
33
34 static int kgdboc_use_kms; /* 1 if we use kernel mode switching */
35 static struct tty_driver *kgdb_tty_driver;
36 static int kgdb_tty_line;
37
38 #ifdef CONFIG_KDB_KEYBOARD
kgdboc_reset_connect(struct input_handler * handler,struct input_dev * dev,const struct input_device_id * id)39 static int kgdboc_reset_connect(struct input_handler *handler,
40 struct input_dev *dev,
41 const struct input_device_id *id)
42 {
43 input_reset_device(dev);
44
45 /* Return an error - we do not want to bind, just to reset */
46 return -ENODEV;
47 }
48
kgdboc_reset_disconnect(struct input_handle * handle)49 static void kgdboc_reset_disconnect(struct input_handle *handle)
50 {
51 /* We do not expect anyone to actually bind to us */
52 BUG();
53 }
54
55 static const struct input_device_id kgdboc_reset_ids[] = {
56 {
57 .flags = INPUT_DEVICE_ID_MATCH_EVBIT,
58 .evbit = { BIT_MASK(EV_KEY) },
59 },
60 { }
61 };
62
63 static struct input_handler kgdboc_reset_handler = {
64 .connect = kgdboc_reset_connect,
65 .disconnect = kgdboc_reset_disconnect,
66 .name = "kgdboc_reset",
67 .id_table = kgdboc_reset_ids,
68 };
69
70 static DEFINE_MUTEX(kgdboc_reset_mutex);
71
kgdboc_restore_input_helper(struct work_struct * dummy)72 static void kgdboc_restore_input_helper(struct work_struct *dummy)
73 {
74 /*
75 * We need to take a mutex to prevent several instances of
76 * this work running on different CPUs so they don't try
77 * to register again already registered handler.
78 */
79 mutex_lock(&kgdboc_reset_mutex);
80
81 if (input_register_handler(&kgdboc_reset_handler) == 0)
82 input_unregister_handler(&kgdboc_reset_handler);
83
84 mutex_unlock(&kgdboc_reset_mutex);
85 }
86
87 static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);
88
kgdboc_restore_input(void)89 static void kgdboc_restore_input(void)
90 {
91 if (likely(system_state == SYSTEM_RUNNING))
92 schedule_work(&kgdboc_restore_input_work);
93 }
94
kgdboc_register_kbd(char ** cptr)95 static int kgdboc_register_kbd(char **cptr)
96 {
97 if (strncmp(*cptr, "kbd", 3) == 0 ||
98 strncmp(*cptr, "kdb", 3) == 0) {
99 if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
100 kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
101 kdb_poll_idx++;
102 if (cptr[0][3] == ',')
103 *cptr += 4;
104 else
105 return 1;
106 }
107 }
108 return 0;
109 }
110
kgdboc_unregister_kbd(void)111 static void kgdboc_unregister_kbd(void)
112 {
113 int i;
114
115 for (i = 0; i < kdb_poll_idx; i++) {
116 if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
117 kdb_poll_idx--;
118 kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
119 kdb_poll_funcs[kdb_poll_idx] = NULL;
120 i--;
121 }
122 }
123 flush_work(&kgdboc_restore_input_work);
124 }
125 #else /* ! CONFIG_KDB_KEYBOARD */
126 #define kgdboc_register_kbd(x) 0
127 #define kgdboc_unregister_kbd()
128 #define kgdboc_restore_input()
129 #endif /* ! CONFIG_KDB_KEYBOARD */
130
kgdboc_option_setup(char * opt)131 static int kgdboc_option_setup(char *opt)
132 {
133 if (strlen(opt) >= MAX_CONFIG_LEN) {
134 printk(KERN_ERR "kgdboc: config string too long\n");
135 return -ENOSPC;
136 }
137 strcpy(config, opt);
138
139 return 0;
140 }
141
142 __setup("kgdboc=", kgdboc_option_setup);
143
cleanup_kgdboc(void)144 static void cleanup_kgdboc(void)
145 {
146 if (kgdb_unregister_nmi_console())
147 return;
148 kgdboc_unregister_kbd();
149 if (configured == 1)
150 kgdb_unregister_io_module(&kgdboc_io_ops);
151 }
152
configure_kgdboc(void)153 static int configure_kgdboc(void)
154 {
155 struct tty_driver *p;
156 int tty_line = 0;
157 int err;
158 char *cptr = config;
159 struct console *cons;
160
161 err = kgdboc_option_setup(config);
162 if (err || !strlen(config) || isspace(config[0]))
163 goto noconfig;
164
165 err = -ENODEV;
166 kgdboc_io_ops.is_console = 0;
167 kgdb_tty_driver = NULL;
168
169 kgdboc_use_kms = 0;
170 if (strncmp(cptr, "kms,", 4) == 0) {
171 cptr += 4;
172 kgdboc_use_kms = 1;
173 }
174
175 if (kgdboc_register_kbd(&cptr))
176 goto do_register;
177
178 p = tty_find_polling_driver(cptr, &tty_line);
179 if (!p)
180 goto noconfig;
181
182 cons = console_drivers;
183 while (cons) {
184 int idx;
185 if (cons->device && cons->device(cons, &idx) == p &&
186 idx == tty_line) {
187 kgdboc_io_ops.is_console = 1;
188 break;
189 }
190 cons = cons->next;
191 }
192
193 kgdb_tty_driver = p;
194 kgdb_tty_line = tty_line;
195
196 do_register:
197 err = kgdb_register_io_module(&kgdboc_io_ops);
198 if (err)
199 goto noconfig;
200
201 err = kgdb_register_nmi_console();
202 if (err)
203 goto nmi_con_failed;
204
205 configured = 1;
206
207 return 0;
208
209 nmi_con_failed:
210 kgdb_unregister_io_module(&kgdboc_io_ops);
211 noconfig:
212 kgdboc_unregister_kbd();
213 config[0] = 0;
214 configured = 0;
215 cleanup_kgdboc();
216
217 return err;
218 }
219
init_kgdboc(void)220 static int __init init_kgdboc(void)
221 {
222 /* Already configured? */
223 if (configured == 1)
224 return 0;
225
226 return configure_kgdboc();
227 }
228
kgdboc_get_char(void)229 static int kgdboc_get_char(void)
230 {
231 if (!kgdb_tty_driver)
232 return -1;
233 return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
234 kgdb_tty_line);
235 }
236
kgdboc_put_char(u8 chr)237 static void kgdboc_put_char(u8 chr)
238 {
239 if (!kgdb_tty_driver)
240 return;
241 kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
242 kgdb_tty_line, chr);
243 }
244
param_set_kgdboc_var(const char * kmessage,const struct kernel_param * kp)245 static int param_set_kgdboc_var(const char *kmessage,
246 const struct kernel_param *kp)
247 {
248 int len = strlen(kmessage);
249
250 if (len >= MAX_CONFIG_LEN) {
251 printk(KERN_ERR "kgdboc: config string too long\n");
252 return -ENOSPC;
253 }
254
255 /* Only copy in the string if the init function has not run yet */
256 if (configured < 0) {
257 strcpy(config, kmessage);
258 return 0;
259 }
260
261 if (kgdb_connected) {
262 printk(KERN_ERR
263 "kgdboc: Cannot reconfigure while KGDB is connected.\n");
264
265 return -EBUSY;
266 }
267
268 strcpy(config, kmessage);
269 /* Chop out \n char as a result of echo */
270 if (config[len - 1] == '\n')
271 config[len - 1] = '\0';
272
273 if (configured == 1)
274 cleanup_kgdboc();
275
276 /* Go and configure with the new params. */
277 return configure_kgdboc();
278 }
279
280 static int dbg_restore_graphics;
281
kgdboc_pre_exp_handler(void)282 static void kgdboc_pre_exp_handler(void)
283 {
284 if (!dbg_restore_graphics && kgdboc_use_kms) {
285 dbg_restore_graphics = 1;
286 con_debug_enter(vc_cons[fg_console].d);
287 }
288 /* Increment the module count when the debugger is active */
289 if (!kgdb_connected)
290 try_module_get(THIS_MODULE);
291 }
292
kgdboc_post_exp_handler(void)293 static void kgdboc_post_exp_handler(void)
294 {
295 /* decrement the module count when the debugger detaches */
296 if (!kgdb_connected)
297 module_put(THIS_MODULE);
298 if (kgdboc_use_kms && dbg_restore_graphics) {
299 dbg_restore_graphics = 0;
300 con_debug_leave();
301 }
302 kgdboc_restore_input();
303 }
304
305 static struct kgdb_io kgdboc_io_ops = {
306 .name = "kgdboc",
307 .read_char = kgdboc_get_char,
308 .write_char = kgdboc_put_char,
309 .pre_exception = kgdboc_pre_exp_handler,
310 .post_exception = kgdboc_post_exp_handler,
311 };
312
313 #ifdef CONFIG_KGDB_SERIAL_CONSOLE
314 /* This is only available if kgdboc is a built in for early debugging */
kgdboc_early_init(char * opt)315 static int __init kgdboc_early_init(char *opt)
316 {
317 /* save the first character of the config string because the
318 * init routine can destroy it.
319 */
320 char save_ch;
321
322 kgdboc_option_setup(opt);
323 save_ch = config[0];
324 init_kgdboc();
325 config[0] = save_ch;
326 return 0;
327 }
328
329 early_param("ekgdboc", kgdboc_early_init);
330 #endif /* CONFIG_KGDB_SERIAL_CONSOLE */
331
332 module_init(init_kgdboc);
333 module_exit(cleanup_kgdboc);
334 module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
335 MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
336 MODULE_DESCRIPTION("KGDB Console TTY Driver");
337 MODULE_LICENSE("GPL");
338
