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0c57dfcc AV |
1 | /* |
2 | * KGDB NMI serial console | |
3 | * | |
4 | * Copyright 2010 Google, Inc. | |
5 | * Arve Hjønnevåg <arve@android.com> | |
6 | * Colin Cross <ccross@android.com> | |
7 | * Copyright 2012 Linaro Ltd. | |
8 | * Anton Vorontsov <anton.vorontsov@linaro.org> | |
9 | * | |
10 | * This program is free software; you can redistribute it and/or modify it | |
11 | * under the terms of the GNU General Public License version 2 as published | |
12 | * by the Free Software Foundation. | |
13 | */ | |
14 | ||
15 | #include <linux/kernel.h> | |
16 | #include <linux/module.h> | |
17 | #include <linux/compiler.h> | |
18 | #include <linux/init.h> | |
19 | #include <linux/slab.h> | |
20 | #include <linux/errno.h> | |
21 | #include <linux/atomic.h> | |
22 | #include <linux/console.h> | |
23 | #include <linux/tty.h> | |
24 | #include <linux/tty_driver.h> | |
25 | #include <linux/tty_flip.h> | |
26 | #include <linux/interrupt.h> | |
27 | #include <linux/hrtimer.h> | |
28 | #include <linux/tick.h> | |
29 | #include <linux/kfifo.h> | |
30 | #include <linux/kgdb.h> | |
31 | #include <linux/kdb.h> | |
32 | ||
33 | static int kgdb_nmi_knock = 1; | |
34 | module_param_named(knock, kgdb_nmi_knock, int, 0600); | |
35 | MODULE_PARM_DESC(knock, "if set to 1 (default), the special '$3#33' command " \ | |
36 | "must be used to enter the debugger; when set to 0, " \ | |
37 | "hitting return key is enough to enter the debugger; " \ | |
38 | "when set to -1, the debugger is entered immediately " \ | |
39 | "upon NMI"); | |
40 | ||
41 | static char *kgdb_nmi_magic = "$3#33"; | |
42 | module_param_named(magic, kgdb_nmi_magic, charp, 0600); | |
43 | MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)"); | |
44 | ||
45 | static bool kgdb_nmi_tty_enabled; | |
46 | ||
47 | static void kgdb_nmi_console_write(struct console *co, const char *s, uint c) | |
48 | { | |
49 | int i; | |
50 | ||
51 | if (!kgdb_nmi_tty_enabled || atomic_read(&kgdb_active) >= 0) | |
52 | return; | |
53 | ||
54 | for (i = 0; i < c; i++) | |
55 | dbg_io_ops->write_char(s[i]); | |
56 | } | |
57 | ||
58 | static struct tty_driver *kgdb_nmi_tty_driver; | |
59 | ||
60 | static struct tty_driver *kgdb_nmi_console_device(struct console *co, int *idx) | |
61 | { | |
62 | *idx = co->index; | |
63 | return kgdb_nmi_tty_driver; | |
64 | } | |
65 | ||
66 | static struct console kgdb_nmi_console = { | |
67 | .name = "ttyNMI", | |
68 | .write = kgdb_nmi_console_write, | |
69 | .device = kgdb_nmi_console_device, | |
70 | .flags = CON_PRINTBUFFER | CON_ANYTIME | CON_ENABLED, | |
71 | .index = -1, | |
72 | }; | |
73 | ||
74 | /* | |
75 | * This is usually the maximum rate on debug ports. We make fifo large enough | |
76 | * to make copy-pasting to the terminal usable. | |
77 | */ | |
78 | #define KGDB_NMI_BAUD 115200 | |
79 | #define KGDB_NMI_FIFO_SIZE roundup_pow_of_two(KGDB_NMI_BAUD / 8 / HZ) | |
80 | ||
81 | struct kgdb_nmi_tty_priv { | |
82 | struct tty_port port; | |
83 | struct tasklet_struct tlet; | |
84 | STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo; | |
85 | }; | |
86 | ||
87 | static struct kgdb_nmi_tty_priv *kgdb_nmi_port_to_priv(struct tty_port *port) | |
88 | { | |
89 | return container_of(port, struct kgdb_nmi_tty_priv, port); | |
90 | } | |
91 | ||
92 | /* | |
93 | * Our debugging console is polled in a tasklet, so we'll check for input | |
94 | * every tick. In HZ-less mode, we should program the next tick. We have | |
95 | * to use the lowlevel stuff as no locks should be grabbed. | |
96 | */ | |
97 | #ifdef CONFIG_HIGH_RES_TIMERS | |
98 | static void kgdb_tty_poke(void) | |
99 | { | |
100 | tick_program_event(ktime_get(), 0); | |
101 | } | |
102 | #else | |
103 | static inline void kgdb_tty_poke(void) {} | |
104 | #endif | |
105 | ||
106 | static struct tty_port *kgdb_nmi_port; | |
107 | ||
108 | static void kgdb_tty_recv(int ch) | |
109 | { | |
110 | struct kgdb_nmi_tty_priv *priv; | |
111 | char c = ch; | |
112 | ||
113 | if (!kgdb_nmi_port || ch < 0) | |
114 | return; | |
115 | /* | |
116 | * Can't use port->tty->driver_data as tty might be not there. Tasklet | |
117 | * will check for tty and will get the ref, but here we don't have to | |
118 | * do that, and actually, we can't: we're in NMI context, no locks are | |
119 | * possible. | |
120 | */ | |
121 | priv = kgdb_nmi_port_to_priv(kgdb_nmi_port); | |
122 | kfifo_in(&priv->fifo, &c, 1); | |
123 | kgdb_tty_poke(); | |
124 | } | |
125 | ||
126 | static int kgdb_nmi_poll_one_knock(void) | |
127 | { | |
128 | static int n; | |
129 | int c = -1; | |
130 | const char *magic = kgdb_nmi_magic; | |
131 | size_t m = strlen(magic); | |
132 | bool printch = 0; | |
133 | ||
134 | c = dbg_io_ops->read_char(); | |
135 | if (c == NO_POLL_CHAR) | |
136 | return c; | |
137 | ||
138 | if (!kgdb_nmi_knock && (c == '\r' || c == '\n')) { | |
139 | return 1; | |
140 | } else if (c == magic[n]) { | |
141 | n = (n + 1) % m; | |
142 | if (!n) | |
143 | return 1; | |
144 | printch = 1; | |
145 | } else { | |
146 | n = 0; | |
147 | } | |
148 | ||
149 | if (kgdb_nmi_tty_enabled) { | |
150 | kgdb_tty_recv(c); | |
151 | return 0; | |
152 | } | |
153 | ||
154 | if (printch) { | |
155 | kdb_printf("%c", c); | |
156 | return 0; | |
157 | } | |
158 | ||
159 | kdb_printf("\r%s %s to enter the debugger> %*s", | |
160 | kgdb_nmi_knock ? "Type" : "Hit", | |
161 | kgdb_nmi_knock ? magic : "<return>", (int)m, ""); | |
162 | while (m--) | |
163 | kdb_printf("\b"); | |
164 | return 0; | |
165 | } | |
166 | ||
167 | /** | |
168 | * kgdb_nmi_poll_knock - Check if it is time to enter the debugger | |
169 | * | |
170 | * "Serial ports are often noisy, especially when muxed over another port (we | |
171 | * often use serial over the headset connector). Noise on the async command | |
172 | * line just causes characters that are ignored, on a command line that blocked | |
173 | * execution noise would be catastrophic." -- Colin Cross | |
174 | * | |
175 | * So, this function implements KGDB/KDB knocking on the serial line: we won't | |
176 | * enter the debugger until we receive a known magic phrase (which is actually | |
177 | * "$3#33", known as "escape to KDB" command. There is also a relaxed variant | |
178 | * of knocking, i.e. just pressing the return key is enough to enter the | |
179 | * debugger. And if knocking is disabled, the function always returns 1. | |
180 | */ | |
181 | bool kgdb_nmi_poll_knock(void) | |
182 | { | |
183 | if (kgdb_nmi_knock < 0) | |
184 | return 1; | |
185 | ||
186 | while (1) { | |
187 | int ret; | |
188 | ||
189 | ret = kgdb_nmi_poll_one_knock(); | |
190 | if (ret == NO_POLL_CHAR) | |
191 | return 0; | |
192 | else if (ret == 1) | |
193 | break; | |
194 | } | |
195 | return 1; | |
196 | } | |
197 | ||
198 | /* | |
199 | * The tasklet is cheap, it does not cause wakeups when reschedules itself, | |
200 | * instead it waits for the next tick. | |
201 | */ | |
202 | static void kgdb_nmi_tty_receiver(unsigned long data) | |
203 | { | |
204 | struct kgdb_nmi_tty_priv *priv = (void *)data; | |
205 | struct tty_struct *tty; | |
206 | char ch; | |
207 | ||
208 | tasklet_schedule(&priv->tlet); | |
209 | ||
210 | if (likely(!kgdb_nmi_tty_enabled || !kfifo_len(&priv->fifo))) | |
211 | return; | |
212 | ||
213 | /* Port is there, but tty might be hung up, check. */ | |
214 | tty = tty_port_tty_get(kgdb_nmi_port); | |
215 | if (!tty) | |
216 | return; | |
217 | ||
218 | while (kfifo_out(&priv->fifo, &ch, 1)) | |
219 | tty_insert_flip_char(priv->port.tty, ch, TTY_NORMAL); | |
220 | tty_flip_buffer_push(priv->port.tty); | |
221 | ||
222 | tty_kref_put(tty); | |
223 | } | |
224 | ||
225 | static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty) | |
226 | { | |
227 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
228 | ||
229 | kgdb_nmi_port = port; | |
230 | tasklet_schedule(&priv->tlet); | |
231 | return 0; | |
232 | } | |
233 | ||
234 | static void kgdb_nmi_tty_shutdown(struct tty_port *port) | |
235 | { | |
236 | struct kgdb_nmi_tty_priv *priv = port->tty->driver_data; | |
237 | ||
238 | tasklet_kill(&priv->tlet); | |
239 | kgdb_nmi_port = NULL; | |
240 | } | |
241 | ||
242 | static const struct tty_port_operations kgdb_nmi_tty_port_ops = { | |
243 | .activate = kgdb_nmi_tty_activate, | |
244 | .shutdown = kgdb_nmi_tty_shutdown, | |
245 | }; | |
246 | ||
247 | static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty) | |
248 | { | |
249 | struct kgdb_nmi_tty_priv *priv; | |
250 | int ret; | |
251 | ||
252 | priv = kzalloc(sizeof(*priv), GFP_KERNEL); | |
253 | if (!priv) | |
254 | return -ENOMEM; | |
255 | ||
256 | INIT_KFIFO(priv->fifo); | |
257 | tasklet_init(&priv->tlet, kgdb_nmi_tty_receiver, (unsigned long)priv); | |
258 | tty_port_init(&priv->port); | |
259 | priv->port.ops = &kgdb_nmi_tty_port_ops; | |
260 | tty->driver_data = priv; | |
261 | ||
262 | ret = tty_port_install(&priv->port, drv, tty); | |
263 | if (ret) { | |
264 | pr_err("%s: can't install tty port: %d\n", __func__, ret); | |
265 | goto err; | |
266 | } | |
267 | return 0; | |
268 | err: | |
269 | kfree(priv); | |
270 | return ret; | |
271 | } | |
272 | ||
273 | static void kgdb_nmi_tty_cleanup(struct tty_struct *tty) | |
274 | { | |
275 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
276 | ||
277 | tty->driver_data = NULL; | |
278 | kfree(priv); | |
279 | } | |
280 | ||
281 | static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file) | |
282 | { | |
283 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
284 | ||
285 | return tty_port_open(&priv->port, tty, file); | |
286 | } | |
287 | ||
288 | static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file) | |
289 | { | |
290 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
291 | ||
292 | tty_port_close(&priv->port, tty, file); | |
293 | } | |
294 | ||
295 | static void kgdb_nmi_tty_hangup(struct tty_struct *tty) | |
296 | { | |
297 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
298 | ||
299 | tty_port_hangup(&priv->port); | |
300 | } | |
301 | ||
302 | static int kgdb_nmi_tty_write_room(struct tty_struct *tty) | |
303 | { | |
304 | /* Actually, we can handle any amount as we use polled writes. */ | |
305 | return 2048; | |
306 | } | |
307 | ||
308 | static int kgdb_nmi_tty_write(struct tty_struct *tty, const unchar *buf, int c) | |
309 | { | |
310 | int i; | |
311 | ||
312 | for (i = 0; i < c; i++) | |
313 | dbg_io_ops->write_char(buf[i]); | |
314 | return c; | |
315 | } | |
316 | ||
317 | static const struct tty_operations kgdb_nmi_tty_ops = { | |
318 | .open = kgdb_nmi_tty_open, | |
319 | .close = kgdb_nmi_tty_close, | |
320 | .install = kgdb_nmi_tty_install, | |
321 | .cleanup = kgdb_nmi_tty_cleanup, | |
322 | .hangup = kgdb_nmi_tty_hangup, | |
323 | .write_room = kgdb_nmi_tty_write_room, | |
324 | .write = kgdb_nmi_tty_write, | |
325 | }; | |
326 | ||
327 | static int kgdb_nmi_enable_console(int argc, const char *argv[]) | |
328 | { | |
329 | kgdb_nmi_tty_enabled = !(argc == 1 && !strcmp(argv[1], "off")); | |
330 | return 0; | |
331 | } | |
332 | ||
333 | int kgdb_register_nmi_console(void) | |
334 | { | |
335 | int ret; | |
336 | ||
337 | if (!arch_kgdb_ops.enable_nmi) | |
338 | return 0; | |
339 | ||
340 | kgdb_nmi_tty_driver = alloc_tty_driver(1); | |
341 | if (!kgdb_nmi_tty_driver) { | |
342 | pr_err("%s: cannot allocate tty\n", __func__); | |
343 | return -ENOMEM; | |
344 | } | |
345 | kgdb_nmi_tty_driver->driver_name = "ttyNMI"; | |
346 | kgdb_nmi_tty_driver->name = "ttyNMI"; | |
347 | kgdb_nmi_tty_driver->num = 1; | |
348 | kgdb_nmi_tty_driver->type = TTY_DRIVER_TYPE_SERIAL; | |
349 | kgdb_nmi_tty_driver->subtype = SERIAL_TYPE_NORMAL; | |
350 | kgdb_nmi_tty_driver->flags = TTY_DRIVER_REAL_RAW; | |
351 | kgdb_nmi_tty_driver->init_termios = tty_std_termios; | |
352 | tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios, | |
353 | KGDB_NMI_BAUD, KGDB_NMI_BAUD); | |
354 | tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops); | |
355 | ||
356 | ret = tty_register_driver(kgdb_nmi_tty_driver); | |
357 | if (ret) { | |
358 | pr_err("%s: can't register tty driver: %d\n", __func__, ret); | |
359 | goto err_drv_reg; | |
360 | } | |
361 | ||
362 | ret = kdb_register("nmi_console", kgdb_nmi_enable_console, "[off]", | |
363 | "switch to Linux NMI console", 0); | |
364 | if (ret) { | |
365 | pr_err("%s: can't register kdb command: %d\n", __func__, ret); | |
366 | goto err_kdb_reg; | |
367 | } | |
368 | ||
369 | register_console(&kgdb_nmi_console); | |
370 | arch_kgdb_ops.enable_nmi(1); | |
371 | ||
372 | return 0; | |
373 | err_kdb_reg: | |
374 | tty_unregister_driver(kgdb_nmi_tty_driver); | |
375 | err_drv_reg: | |
376 | put_tty_driver(kgdb_nmi_tty_driver); | |
377 | return ret; | |
378 | } | |
379 | EXPORT_SYMBOL_GPL(kgdb_register_nmi_console); | |
380 | ||
381 | int kgdb_unregister_nmi_console(void) | |
382 | { | |
383 | int ret; | |
384 | ||
385 | if (!arch_kgdb_ops.enable_nmi) | |
386 | return 0; | |
387 | arch_kgdb_ops.enable_nmi(0); | |
388 | ||
389 | kdb_unregister("nmi_console"); | |
390 | ||
391 | ret = unregister_console(&kgdb_nmi_console); | |
392 | if (ret) | |
393 | return ret; | |
394 | ||
395 | ret = tty_unregister_driver(kgdb_nmi_tty_driver); | |
396 | if (ret) | |
397 | return ret; | |
398 | put_tty_driver(kgdb_nmi_tty_driver); | |
399 | ||
400 | return 0; | |
401 | } | |
402 | EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console); |