Commit | Line | Data |
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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> | |
0c57dfcc AV |
18 | #include <linux/slab.h> |
19 | #include <linux/errno.h> | |
20 | #include <linux/atomic.h> | |
21 | #include <linux/console.h> | |
22 | #include <linux/tty.h> | |
23 | #include <linux/tty_driver.h> | |
24 | #include <linux/tty_flip.h> | |
16559ae4 | 25 | #include <linux/serial_core.h> |
0c57dfcc AV |
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; | |
0c57dfcc AV |
205 | char ch; |
206 | ||
207 | tasklet_schedule(&priv->tlet); | |
208 | ||
209 | if (likely(!kgdb_nmi_tty_enabled || !kfifo_len(&priv->fifo))) | |
210 | return; | |
211 | ||
0c57dfcc | 212 | while (kfifo_out(&priv->fifo, &ch, 1)) |
92a19f9c | 213 | tty_insert_flip_char(&priv->port, ch, TTY_NORMAL); |
2e124b4a | 214 | tty_flip_buffer_push(&priv->port); |
0c57dfcc AV |
215 | } |
216 | ||
217 | static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty) | |
218 | { | |
219 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
220 | ||
221 | kgdb_nmi_port = port; | |
222 | tasklet_schedule(&priv->tlet); | |
223 | return 0; | |
224 | } | |
225 | ||
226 | static void kgdb_nmi_tty_shutdown(struct tty_port *port) | |
227 | { | |
228 | struct kgdb_nmi_tty_priv *priv = port->tty->driver_data; | |
229 | ||
230 | tasklet_kill(&priv->tlet); | |
231 | kgdb_nmi_port = NULL; | |
232 | } | |
233 | ||
234 | static const struct tty_port_operations kgdb_nmi_tty_port_ops = { | |
235 | .activate = kgdb_nmi_tty_activate, | |
236 | .shutdown = kgdb_nmi_tty_shutdown, | |
237 | }; | |
238 | ||
239 | static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty) | |
240 | { | |
241 | struct kgdb_nmi_tty_priv *priv; | |
242 | int ret; | |
243 | ||
244 | priv = kzalloc(sizeof(*priv), GFP_KERNEL); | |
245 | if (!priv) | |
246 | return -ENOMEM; | |
247 | ||
248 | INIT_KFIFO(priv->fifo); | |
249 | tasklet_init(&priv->tlet, kgdb_nmi_tty_receiver, (unsigned long)priv); | |
250 | tty_port_init(&priv->port); | |
251 | priv->port.ops = &kgdb_nmi_tty_port_ops; | |
252 | tty->driver_data = priv; | |
253 | ||
254 | ret = tty_port_install(&priv->port, drv, tty); | |
255 | if (ret) { | |
256 | pr_err("%s: can't install tty port: %d\n", __func__, ret); | |
257 | goto err; | |
258 | } | |
259 | return 0; | |
260 | err: | |
191c5f10 | 261 | tty_port_destroy(&priv->port); |
0c57dfcc AV |
262 | kfree(priv); |
263 | return ret; | |
264 | } | |
265 | ||
266 | static void kgdb_nmi_tty_cleanup(struct tty_struct *tty) | |
267 | { | |
268 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
269 | ||
270 | tty->driver_data = NULL; | |
191c5f10 | 271 | tty_port_destroy(&priv->port); |
0c57dfcc AV |
272 | kfree(priv); |
273 | } | |
274 | ||
275 | static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file) | |
276 | { | |
277 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
278 | ||
279 | return tty_port_open(&priv->port, tty, file); | |
280 | } | |
281 | ||
282 | static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file) | |
283 | { | |
284 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
285 | ||
286 | tty_port_close(&priv->port, tty, file); | |
287 | } | |
288 | ||
289 | static void kgdb_nmi_tty_hangup(struct tty_struct *tty) | |
290 | { | |
291 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
292 | ||
293 | tty_port_hangup(&priv->port); | |
294 | } | |
295 | ||
296 | static int kgdb_nmi_tty_write_room(struct tty_struct *tty) | |
297 | { | |
298 | /* Actually, we can handle any amount as we use polled writes. */ | |
299 | return 2048; | |
300 | } | |
301 | ||
302 | static int kgdb_nmi_tty_write(struct tty_struct *tty, const unchar *buf, int c) | |
303 | { | |
304 | int i; | |
305 | ||
306 | for (i = 0; i < c; i++) | |
307 | dbg_io_ops->write_char(buf[i]); | |
308 | return c; | |
309 | } | |
310 | ||
311 | static const struct tty_operations kgdb_nmi_tty_ops = { | |
312 | .open = kgdb_nmi_tty_open, | |
313 | .close = kgdb_nmi_tty_close, | |
314 | .install = kgdb_nmi_tty_install, | |
315 | .cleanup = kgdb_nmi_tty_cleanup, | |
316 | .hangup = kgdb_nmi_tty_hangup, | |
317 | .write_room = kgdb_nmi_tty_write_room, | |
318 | .write = kgdb_nmi_tty_write, | |
319 | }; | |
320 | ||
321 | static int kgdb_nmi_enable_console(int argc, const char *argv[]) | |
322 | { | |
323 | kgdb_nmi_tty_enabled = !(argc == 1 && !strcmp(argv[1], "off")); | |
324 | return 0; | |
325 | } | |
326 | ||
327 | int kgdb_register_nmi_console(void) | |
328 | { | |
329 | int ret; | |
330 | ||
331 | if (!arch_kgdb_ops.enable_nmi) | |
332 | return 0; | |
333 | ||
334 | kgdb_nmi_tty_driver = alloc_tty_driver(1); | |
335 | if (!kgdb_nmi_tty_driver) { | |
336 | pr_err("%s: cannot allocate tty\n", __func__); | |
337 | return -ENOMEM; | |
338 | } | |
339 | kgdb_nmi_tty_driver->driver_name = "ttyNMI"; | |
340 | kgdb_nmi_tty_driver->name = "ttyNMI"; | |
341 | kgdb_nmi_tty_driver->num = 1; | |
342 | kgdb_nmi_tty_driver->type = TTY_DRIVER_TYPE_SERIAL; | |
343 | kgdb_nmi_tty_driver->subtype = SERIAL_TYPE_NORMAL; | |
344 | kgdb_nmi_tty_driver->flags = TTY_DRIVER_REAL_RAW; | |
345 | kgdb_nmi_tty_driver->init_termios = tty_std_termios; | |
346 | tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios, | |
347 | KGDB_NMI_BAUD, KGDB_NMI_BAUD); | |
348 | tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops); | |
349 | ||
350 | ret = tty_register_driver(kgdb_nmi_tty_driver); | |
351 | if (ret) { | |
352 | pr_err("%s: can't register tty driver: %d\n", __func__, ret); | |
353 | goto err_drv_reg; | |
354 | } | |
355 | ||
356 | ret = kdb_register("nmi_console", kgdb_nmi_enable_console, "[off]", | |
357 | "switch to Linux NMI console", 0); | |
358 | if (ret) { | |
359 | pr_err("%s: can't register kdb command: %d\n", __func__, ret); | |
360 | goto err_kdb_reg; | |
361 | } | |
362 | ||
363 | register_console(&kgdb_nmi_console); | |
364 | arch_kgdb_ops.enable_nmi(1); | |
365 | ||
366 | return 0; | |
367 | err_kdb_reg: | |
368 | tty_unregister_driver(kgdb_nmi_tty_driver); | |
369 | err_drv_reg: | |
370 | put_tty_driver(kgdb_nmi_tty_driver); | |
371 | return ret; | |
372 | } | |
373 | EXPORT_SYMBOL_GPL(kgdb_register_nmi_console); | |
374 | ||
375 | int kgdb_unregister_nmi_console(void) | |
376 | { | |
377 | int ret; | |
378 | ||
379 | if (!arch_kgdb_ops.enable_nmi) | |
380 | return 0; | |
381 | arch_kgdb_ops.enable_nmi(0); | |
382 | ||
383 | kdb_unregister("nmi_console"); | |
384 | ||
385 | ret = unregister_console(&kgdb_nmi_console); | |
386 | if (ret) | |
387 | return ret; | |
388 | ||
389 | ret = tty_unregister_driver(kgdb_nmi_tty_driver); | |
390 | if (ret) | |
391 | return ret; | |
392 | put_tty_driver(kgdb_nmi_tty_driver); | |
393 | ||
394 | return 0; | |
395 | } | |
396 | EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console); |