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 | ||
bd71a1c0 DT |
47 | static int kgdb_nmi_console_setup(struct console *co, char *options) |
48 | { | |
49 | /* The NMI console uses the dbg_io_ops to issue console messages. To | |
50 | * avoid duplicate messages during kdb sessions we must inform kdb's | |
51 | * I/O utilities that messages sent to the console will automatically | |
52 | * be displayed on the dbg_io. | |
53 | */ | |
54 | dbg_io_ops->is_console = true; | |
55 | ||
56 | return 0; | |
57 | } | |
58 | ||
0c57dfcc AV |
59 | static void kgdb_nmi_console_write(struct console *co, const char *s, uint c) |
60 | { | |
61 | int i; | |
62 | ||
0c57dfcc AV |
63 | for (i = 0; i < c; i++) |
64 | dbg_io_ops->write_char(s[i]); | |
65 | } | |
66 | ||
67 | static struct tty_driver *kgdb_nmi_tty_driver; | |
68 | ||
69 | static struct tty_driver *kgdb_nmi_console_device(struct console *co, int *idx) | |
70 | { | |
71 | *idx = co->index; | |
72 | return kgdb_nmi_tty_driver; | |
73 | } | |
74 | ||
75 | static struct console kgdb_nmi_console = { | |
76 | .name = "ttyNMI", | |
bd71a1c0 | 77 | .setup = kgdb_nmi_console_setup, |
0c57dfcc AV |
78 | .write = kgdb_nmi_console_write, |
79 | .device = kgdb_nmi_console_device, | |
80 | .flags = CON_PRINTBUFFER | CON_ANYTIME | CON_ENABLED, | |
81 | .index = -1, | |
82 | }; | |
83 | ||
84 | /* | |
85 | * This is usually the maximum rate on debug ports. We make fifo large enough | |
86 | * to make copy-pasting to the terminal usable. | |
87 | */ | |
88 | #define KGDB_NMI_BAUD 115200 | |
89 | #define KGDB_NMI_FIFO_SIZE roundup_pow_of_two(KGDB_NMI_BAUD / 8 / HZ) | |
90 | ||
91 | struct kgdb_nmi_tty_priv { | |
92 | struct tty_port port; | |
8a0ff60f | 93 | struct timer_list timer; |
0c57dfcc AV |
94 | STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo; |
95 | }; | |
96 | ||
0c57dfcc AV |
97 | static struct tty_port *kgdb_nmi_port; |
98 | ||
99 | static void kgdb_tty_recv(int ch) | |
100 | { | |
101 | struct kgdb_nmi_tty_priv *priv; | |
102 | char c = ch; | |
103 | ||
104 | if (!kgdb_nmi_port || ch < 0) | |
105 | return; | |
106 | /* | |
8a0ff60f | 107 | * Can't use port->tty->driver_data as tty might be not there. Timer |
0c57dfcc AV |
108 | * will check for tty and will get the ref, but here we don't have to |
109 | * do that, and actually, we can't: we're in NMI context, no locks are | |
110 | * possible. | |
111 | */ | |
06d18289 | 112 | priv = container_of(kgdb_nmi_port, struct kgdb_nmi_tty_priv, port); |
0c57dfcc | 113 | kfifo_in(&priv->fifo, &c, 1); |
0c57dfcc AV |
114 | } |
115 | ||
116 | static int kgdb_nmi_poll_one_knock(void) | |
117 | { | |
118 | static int n; | |
119 | int c = -1; | |
120 | const char *magic = kgdb_nmi_magic; | |
121 | size_t m = strlen(magic); | |
122 | bool printch = 0; | |
123 | ||
124 | c = dbg_io_ops->read_char(); | |
125 | if (c == NO_POLL_CHAR) | |
126 | return c; | |
127 | ||
128 | if (!kgdb_nmi_knock && (c == '\r' || c == '\n')) { | |
129 | return 1; | |
130 | } else if (c == magic[n]) { | |
131 | n = (n + 1) % m; | |
132 | if (!n) | |
133 | return 1; | |
134 | printch = 1; | |
135 | } else { | |
136 | n = 0; | |
137 | } | |
138 | ||
139 | if (kgdb_nmi_tty_enabled) { | |
140 | kgdb_tty_recv(c); | |
141 | return 0; | |
142 | } | |
143 | ||
144 | if (printch) { | |
145 | kdb_printf("%c", c); | |
146 | return 0; | |
147 | } | |
148 | ||
149 | kdb_printf("\r%s %s to enter the debugger> %*s", | |
150 | kgdb_nmi_knock ? "Type" : "Hit", | |
151 | kgdb_nmi_knock ? magic : "<return>", (int)m, ""); | |
152 | while (m--) | |
153 | kdb_printf("\b"); | |
154 | return 0; | |
155 | } | |
156 | ||
157 | /** | |
158 | * kgdb_nmi_poll_knock - Check if it is time to enter the debugger | |
159 | * | |
160 | * "Serial ports are often noisy, especially when muxed over another port (we | |
161 | * often use serial over the headset connector). Noise on the async command | |
162 | * line just causes characters that are ignored, on a command line that blocked | |
163 | * execution noise would be catastrophic." -- Colin Cross | |
164 | * | |
165 | * So, this function implements KGDB/KDB knocking on the serial line: we won't | |
166 | * enter the debugger until we receive a known magic phrase (which is actually | |
167 | * "$3#33", known as "escape to KDB" command. There is also a relaxed variant | |
168 | * of knocking, i.e. just pressing the return key is enough to enter the | |
169 | * debugger. And if knocking is disabled, the function always returns 1. | |
170 | */ | |
171 | bool kgdb_nmi_poll_knock(void) | |
172 | { | |
173 | if (kgdb_nmi_knock < 0) | |
174 | return 1; | |
175 | ||
176 | while (1) { | |
177 | int ret; | |
178 | ||
179 | ret = kgdb_nmi_poll_one_knock(); | |
180 | if (ret == NO_POLL_CHAR) | |
181 | return 0; | |
182 | else if (ret == 1) | |
183 | break; | |
184 | } | |
185 | return 1; | |
186 | } | |
187 | ||
188 | /* | |
189 | * The tasklet is cheap, it does not cause wakeups when reschedules itself, | |
190 | * instead it waits for the next tick. | |
191 | */ | |
192 | static void kgdb_nmi_tty_receiver(unsigned long data) | |
193 | { | |
194 | struct kgdb_nmi_tty_priv *priv = (void *)data; | |
0c57dfcc AV |
195 | char ch; |
196 | ||
8a0ff60f DT |
197 | priv->timer.expires = jiffies + (HZ/100); |
198 | add_timer(&priv->timer); | |
0c57dfcc AV |
199 | |
200 | if (likely(!kgdb_nmi_tty_enabled || !kfifo_len(&priv->fifo))) | |
201 | return; | |
202 | ||
0c57dfcc | 203 | while (kfifo_out(&priv->fifo, &ch, 1)) |
92a19f9c | 204 | tty_insert_flip_char(&priv->port, ch, TTY_NORMAL); |
2e124b4a | 205 | tty_flip_buffer_push(&priv->port); |
0c57dfcc AV |
206 | } |
207 | ||
208 | static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty) | |
209 | { | |
06d18289 DT |
210 | struct kgdb_nmi_tty_priv *priv = |
211 | container_of(port, struct kgdb_nmi_tty_priv, port); | |
0c57dfcc AV |
212 | |
213 | kgdb_nmi_port = port; | |
8a0ff60f DT |
214 | priv->timer.expires = jiffies + (HZ/100); |
215 | add_timer(&priv->timer); | |
216 | ||
0c57dfcc AV |
217 | return 0; |
218 | } | |
219 | ||
220 | static void kgdb_nmi_tty_shutdown(struct tty_port *port) | |
221 | { | |
06d18289 DT |
222 | struct kgdb_nmi_tty_priv *priv = |
223 | container_of(port, struct kgdb_nmi_tty_priv, port); | |
0c57dfcc | 224 | |
8a0ff60f | 225 | del_timer(&priv->timer); |
0c57dfcc AV |
226 | kgdb_nmi_port = NULL; |
227 | } | |
228 | ||
229 | static const struct tty_port_operations kgdb_nmi_tty_port_ops = { | |
230 | .activate = kgdb_nmi_tty_activate, | |
231 | .shutdown = kgdb_nmi_tty_shutdown, | |
232 | }; | |
233 | ||
234 | static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty) | |
235 | { | |
236 | struct kgdb_nmi_tty_priv *priv; | |
237 | int ret; | |
238 | ||
239 | priv = kzalloc(sizeof(*priv), GFP_KERNEL); | |
240 | if (!priv) | |
241 | return -ENOMEM; | |
242 | ||
243 | INIT_KFIFO(priv->fifo); | |
8a0ff60f | 244 | setup_timer(&priv->timer, kgdb_nmi_tty_receiver, (unsigned long)priv); |
0c57dfcc AV |
245 | tty_port_init(&priv->port); |
246 | priv->port.ops = &kgdb_nmi_tty_port_ops; | |
247 | tty->driver_data = priv; | |
248 | ||
249 | ret = tty_port_install(&priv->port, drv, tty); | |
250 | if (ret) { | |
251 | pr_err("%s: can't install tty port: %d\n", __func__, ret); | |
252 | goto err; | |
253 | } | |
254 | return 0; | |
255 | err: | |
191c5f10 | 256 | tty_port_destroy(&priv->port); |
0c57dfcc AV |
257 | kfree(priv); |
258 | return ret; | |
259 | } | |
260 | ||
261 | static void kgdb_nmi_tty_cleanup(struct tty_struct *tty) | |
262 | { | |
263 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
264 | ||
265 | tty->driver_data = NULL; | |
191c5f10 | 266 | tty_port_destroy(&priv->port); |
0c57dfcc AV |
267 | kfree(priv); |
268 | } | |
269 | ||
270 | static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file) | |
271 | { | |
272 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
273 | ||
274 | return tty_port_open(&priv->port, tty, file); | |
275 | } | |
276 | ||
277 | static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file) | |
278 | { | |
279 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
280 | ||
281 | tty_port_close(&priv->port, tty, file); | |
282 | } | |
283 | ||
284 | static void kgdb_nmi_tty_hangup(struct tty_struct *tty) | |
285 | { | |
286 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
287 | ||
288 | tty_port_hangup(&priv->port); | |
289 | } | |
290 | ||
291 | static int kgdb_nmi_tty_write_room(struct tty_struct *tty) | |
292 | { | |
293 | /* Actually, we can handle any amount as we use polled writes. */ | |
294 | return 2048; | |
295 | } | |
296 | ||
297 | static int kgdb_nmi_tty_write(struct tty_struct *tty, const unchar *buf, int c) | |
298 | { | |
299 | int i; | |
300 | ||
301 | for (i = 0; i < c; i++) | |
302 | dbg_io_ops->write_char(buf[i]); | |
303 | return c; | |
304 | } | |
305 | ||
306 | static const struct tty_operations kgdb_nmi_tty_ops = { | |
307 | .open = kgdb_nmi_tty_open, | |
308 | .close = kgdb_nmi_tty_close, | |
309 | .install = kgdb_nmi_tty_install, | |
310 | .cleanup = kgdb_nmi_tty_cleanup, | |
311 | .hangup = kgdb_nmi_tty_hangup, | |
312 | .write_room = kgdb_nmi_tty_write_room, | |
313 | .write = kgdb_nmi_tty_write, | |
314 | }; | |
315 | ||
316 | static int kgdb_nmi_enable_console(int argc, const char *argv[]) | |
317 | { | |
318 | kgdb_nmi_tty_enabled = !(argc == 1 && !strcmp(argv[1], "off")); | |
319 | return 0; | |
320 | } | |
321 | ||
322 | int kgdb_register_nmi_console(void) | |
323 | { | |
324 | int ret; | |
325 | ||
326 | if (!arch_kgdb_ops.enable_nmi) | |
327 | return 0; | |
328 | ||
329 | kgdb_nmi_tty_driver = alloc_tty_driver(1); | |
330 | if (!kgdb_nmi_tty_driver) { | |
331 | pr_err("%s: cannot allocate tty\n", __func__); | |
332 | return -ENOMEM; | |
333 | } | |
334 | kgdb_nmi_tty_driver->driver_name = "ttyNMI"; | |
335 | kgdb_nmi_tty_driver->name = "ttyNMI"; | |
336 | kgdb_nmi_tty_driver->num = 1; | |
337 | kgdb_nmi_tty_driver->type = TTY_DRIVER_TYPE_SERIAL; | |
338 | kgdb_nmi_tty_driver->subtype = SERIAL_TYPE_NORMAL; | |
339 | kgdb_nmi_tty_driver->flags = TTY_DRIVER_REAL_RAW; | |
340 | kgdb_nmi_tty_driver->init_termios = tty_std_termios; | |
341 | tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios, | |
342 | KGDB_NMI_BAUD, KGDB_NMI_BAUD); | |
343 | tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops); | |
344 | ||
345 | ret = tty_register_driver(kgdb_nmi_tty_driver); | |
346 | if (ret) { | |
347 | pr_err("%s: can't register tty driver: %d\n", __func__, ret); | |
348 | goto err_drv_reg; | |
349 | } | |
350 | ||
351 | ret = kdb_register("nmi_console", kgdb_nmi_enable_console, "[off]", | |
352 | "switch to Linux NMI console", 0); | |
353 | if (ret) { | |
354 | pr_err("%s: can't register kdb command: %d\n", __func__, ret); | |
355 | goto err_kdb_reg; | |
356 | } | |
357 | ||
358 | register_console(&kgdb_nmi_console); | |
359 | arch_kgdb_ops.enable_nmi(1); | |
360 | ||
361 | return 0; | |
362 | err_kdb_reg: | |
363 | tty_unregister_driver(kgdb_nmi_tty_driver); | |
364 | err_drv_reg: | |
365 | put_tty_driver(kgdb_nmi_tty_driver); | |
366 | return ret; | |
367 | } | |
368 | EXPORT_SYMBOL_GPL(kgdb_register_nmi_console); | |
369 | ||
370 | int kgdb_unregister_nmi_console(void) | |
371 | { | |
372 | int ret; | |
373 | ||
374 | if (!arch_kgdb_ops.enable_nmi) | |
375 | return 0; | |
376 | arch_kgdb_ops.enable_nmi(0); | |
377 | ||
378 | kdb_unregister("nmi_console"); | |
379 | ||
380 | ret = unregister_console(&kgdb_nmi_console); | |
381 | if (ret) | |
382 | return ret; | |
383 | ||
384 | ret = tty_unregister_driver(kgdb_nmi_tty_driver); | |
385 | if (ret) | |
386 | return ret; | |
387 | put_tty_driver(kgdb_nmi_tty_driver); | |
388 | ||
389 | return 0; | |
390 | } | |
391 | EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console); |