blob: 129dc5be6028178344ba81f8225a8322e7c57d1a [file] [log] [blame]
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -07001/*
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>
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -070018#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>
Greg Kroah-Hartman16559ae2013-02-04 15:35:26 -080025#include <linux/serial_core.h>
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -070026#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
33static int kgdb_nmi_knock = 1;
34module_param_named(knock, kgdb_nmi_knock, int, 0600);
35MODULE_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
41static char *kgdb_nmi_magic = "$3#33";
42module_param_named(magic, kgdb_nmi_magic, charp, 0600);
43MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)");
44
Daniel Thompsonc8b29f02014-07-16 14:30:13 +010045static atomic_t kgdb_nmi_num_readers = ATOMIC_INIT(0);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -070046
Daniel Thompsonbd71a1c2014-05-29 09:48:46 +010047static int kgdb_nmi_console_setup(struct console *co, char *options)
48{
Daniel Thompson287f03c2014-09-03 12:57:52 +010049 arch_kgdb_ops.enable_nmi(1);
50
Daniel Thompsonbd71a1c2014-05-29 09:48:46 +010051 /* The NMI console uses the dbg_io_ops to issue console messages. To
52 * avoid duplicate messages during kdb sessions we must inform kdb's
53 * I/O utilities that messages sent to the console will automatically
54 * be displayed on the dbg_io.
55 */
56 dbg_io_ops->is_console = true;
57
58 return 0;
59}
60
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -070061static void kgdb_nmi_console_write(struct console *co, const char *s, uint c)
62{
63 int i;
64
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -070065 for (i = 0; i < c; i++)
66 dbg_io_ops->write_char(s[i]);
67}
68
69static struct tty_driver *kgdb_nmi_tty_driver;
70
71static struct tty_driver *kgdb_nmi_console_device(struct console *co, int *idx)
72{
73 *idx = co->index;
74 return kgdb_nmi_tty_driver;
75}
76
77static struct console kgdb_nmi_console = {
78 .name = "ttyNMI",
Daniel Thompsonbd71a1c2014-05-29 09:48:46 +010079 .setup = kgdb_nmi_console_setup,
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -070080 .write = kgdb_nmi_console_write,
81 .device = kgdb_nmi_console_device,
Daniel Thompson287f03c2014-09-03 12:57:52 +010082 .flags = CON_PRINTBUFFER | CON_ANYTIME,
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -070083 .index = -1,
84};
85
86/*
87 * This is usually the maximum rate on debug ports. We make fifo large enough
88 * to make copy-pasting to the terminal usable.
89 */
90#define KGDB_NMI_BAUD 115200
91#define KGDB_NMI_FIFO_SIZE roundup_pow_of_two(KGDB_NMI_BAUD / 8 / HZ)
92
93struct kgdb_nmi_tty_priv {
94 struct tty_port port;
Daniel Thompson8a0ff602014-05-29 09:48:45 +010095 struct timer_list timer;
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -070096 STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo;
97};
98
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -070099static struct tty_port *kgdb_nmi_port;
100
101static void kgdb_tty_recv(int ch)
102{
103 struct kgdb_nmi_tty_priv *priv;
104 char c = ch;
105
106 if (!kgdb_nmi_port || ch < 0)
107 return;
108 /*
Daniel Thompson8a0ff602014-05-29 09:48:45 +0100109 * Can't use port->tty->driver_data as tty might be not there. Timer
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700110 * will check for tty and will get the ref, but here we don't have to
111 * do that, and actually, we can't: we're in NMI context, no locks are
112 * possible.
113 */
Daniel Thompson06d18282014-05-29 09:48:44 +0100114 priv = container_of(kgdb_nmi_port, struct kgdb_nmi_tty_priv, port);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700115 kfifo_in(&priv->fifo, &c, 1);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700116}
117
118static int kgdb_nmi_poll_one_knock(void)
119{
120 static int n;
121 int c = -1;
122 const char *magic = kgdb_nmi_magic;
123 size_t m = strlen(magic);
124 bool printch = 0;
125
126 c = dbg_io_ops->read_char();
127 if (c == NO_POLL_CHAR)
128 return c;
129
130 if (!kgdb_nmi_knock && (c == '\r' || c == '\n')) {
131 return 1;
132 } else if (c == magic[n]) {
133 n = (n + 1) % m;
134 if (!n)
135 return 1;
136 printch = 1;
137 } else {
138 n = 0;
139 }
140
Daniel Thompsonc8b29f02014-07-16 14:30:13 +0100141 if (atomic_read(&kgdb_nmi_num_readers)) {
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700142 kgdb_tty_recv(c);
143 return 0;
144 }
145
146 if (printch) {
147 kdb_printf("%c", c);
148 return 0;
149 }
150
151 kdb_printf("\r%s %s to enter the debugger> %*s",
152 kgdb_nmi_knock ? "Type" : "Hit",
153 kgdb_nmi_knock ? magic : "<return>", (int)m, "");
154 while (m--)
155 kdb_printf("\b");
156 return 0;
157}
158
159/**
160 * kgdb_nmi_poll_knock - Check if it is time to enter the debugger
161 *
162 * "Serial ports are often noisy, especially when muxed over another port (we
163 * often use serial over the headset connector). Noise on the async command
164 * line just causes characters that are ignored, on a command line that blocked
165 * execution noise would be catastrophic." -- Colin Cross
166 *
167 * So, this function implements KGDB/KDB knocking on the serial line: we won't
168 * enter the debugger until we receive a known magic phrase (which is actually
169 * "$3#33", known as "escape to KDB" command. There is also a relaxed variant
170 * of knocking, i.e. just pressing the return key is enough to enter the
171 * debugger. And if knocking is disabled, the function always returns 1.
172 */
173bool kgdb_nmi_poll_knock(void)
174{
175 if (kgdb_nmi_knock < 0)
176 return 1;
177
178 while (1) {
179 int ret;
180
181 ret = kgdb_nmi_poll_one_knock();
182 if (ret == NO_POLL_CHAR)
183 return 0;
184 else if (ret == 1)
185 break;
186 }
187 return 1;
188}
189
190/*
191 * The tasklet is cheap, it does not cause wakeups when reschedules itself,
192 * instead it waits for the next tick.
193 */
194static void kgdb_nmi_tty_receiver(unsigned long data)
195{
196 struct kgdb_nmi_tty_priv *priv = (void *)data;
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700197 char ch;
198
Daniel Thompson8a0ff602014-05-29 09:48:45 +0100199 priv->timer.expires = jiffies + (HZ/100);
200 add_timer(&priv->timer);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700201
Daniel Thompsonc8b29f02014-07-16 14:30:13 +0100202 if (likely(!atomic_read(&kgdb_nmi_num_readers) ||
203 !kfifo_len(&priv->fifo)))
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700204 return;
205
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700206 while (kfifo_out(&priv->fifo, &ch, 1))
Jiri Slaby92a19f92013-01-03 15:53:03 +0100207 tty_insert_flip_char(&priv->port, ch, TTY_NORMAL);
Jiri Slaby2e124b42013-01-03 15:53:06 +0100208 tty_flip_buffer_push(&priv->port);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700209}
210
211static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty)
212{
Daniel Thompson06d18282014-05-29 09:48:44 +0100213 struct kgdb_nmi_tty_priv *priv =
214 container_of(port, struct kgdb_nmi_tty_priv, port);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700215
216 kgdb_nmi_port = port;
Daniel Thompson8a0ff602014-05-29 09:48:45 +0100217 priv->timer.expires = jiffies + (HZ/100);
218 add_timer(&priv->timer);
219
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700220 return 0;
221}
222
223static void kgdb_nmi_tty_shutdown(struct tty_port *port)
224{
Daniel Thompson06d18282014-05-29 09:48:44 +0100225 struct kgdb_nmi_tty_priv *priv =
226 container_of(port, struct kgdb_nmi_tty_priv, port);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700227
Daniel Thompson8a0ff602014-05-29 09:48:45 +0100228 del_timer(&priv->timer);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700229 kgdb_nmi_port = NULL;
230}
231
232static const struct tty_port_operations kgdb_nmi_tty_port_ops = {
233 .activate = kgdb_nmi_tty_activate,
234 .shutdown = kgdb_nmi_tty_shutdown,
235};
236
237static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty)
238{
239 struct kgdb_nmi_tty_priv *priv;
240 int ret;
241
242 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
243 if (!priv)
244 return -ENOMEM;
245
246 INIT_KFIFO(priv->fifo);
Daniel Thompson8a0ff602014-05-29 09:48:45 +0100247 setup_timer(&priv->timer, kgdb_nmi_tty_receiver, (unsigned long)priv);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700248 tty_port_init(&priv->port);
249 priv->port.ops = &kgdb_nmi_tty_port_ops;
250 tty->driver_data = priv;
251
252 ret = tty_port_install(&priv->port, drv, tty);
253 if (ret) {
254 pr_err("%s: can't install tty port: %d\n", __func__, ret);
255 goto err;
256 }
257 return 0;
258err:
Jiri Slaby191c5f12012-11-15 09:49:56 +0100259 tty_port_destroy(&priv->port);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700260 kfree(priv);
261 return ret;
262}
263
264static void kgdb_nmi_tty_cleanup(struct tty_struct *tty)
265{
266 struct kgdb_nmi_tty_priv *priv = tty->driver_data;
267
268 tty->driver_data = NULL;
Jiri Slaby191c5f12012-11-15 09:49:56 +0100269 tty_port_destroy(&priv->port);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700270 kfree(priv);
271}
272
273static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file)
274{
275 struct kgdb_nmi_tty_priv *priv = tty->driver_data;
Daniel Thompsonc8b29f02014-07-16 14:30:13 +0100276 unsigned int mode = file->f_flags & O_ACCMODE;
277 int ret;
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700278
Daniel Thompsonc8b29f02014-07-16 14:30:13 +0100279 ret = tty_port_open(&priv->port, tty, file);
280 if (!ret && (mode == O_RDONLY || mode == O_RDWR))
281 atomic_inc(&kgdb_nmi_num_readers);
282
283 return ret;
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700284}
285
286static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file)
287{
288 struct kgdb_nmi_tty_priv *priv = tty->driver_data;
Daniel Thompsonc8b29f02014-07-16 14:30:13 +0100289 unsigned int mode = file->f_flags & O_ACCMODE;
290
291 if (mode == O_RDONLY || mode == O_RDWR)
292 atomic_dec(&kgdb_nmi_num_readers);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700293
294 tty_port_close(&priv->port, tty, file);
295}
296
297static void kgdb_nmi_tty_hangup(struct tty_struct *tty)
298{
299 struct kgdb_nmi_tty_priv *priv = tty->driver_data;
300
301 tty_port_hangup(&priv->port);
302}
303
304static int kgdb_nmi_tty_write_room(struct tty_struct *tty)
305{
306 /* Actually, we can handle any amount as we use polled writes. */
307 return 2048;
308}
309
310static int kgdb_nmi_tty_write(struct tty_struct *tty, const unchar *buf, int c)
311{
312 int i;
313
314 for (i = 0; i < c; i++)
315 dbg_io_ops->write_char(buf[i]);
316 return c;
317}
318
319static const struct tty_operations kgdb_nmi_tty_ops = {
320 .open = kgdb_nmi_tty_open,
321 .close = kgdb_nmi_tty_close,
322 .install = kgdb_nmi_tty_install,
323 .cleanup = kgdb_nmi_tty_cleanup,
324 .hangup = kgdb_nmi_tty_hangup,
325 .write_room = kgdb_nmi_tty_write_room,
326 .write = kgdb_nmi_tty_write,
327};
328
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700329int kgdb_register_nmi_console(void)
330{
331 int ret;
332
333 if (!arch_kgdb_ops.enable_nmi)
334 return 0;
335
336 kgdb_nmi_tty_driver = alloc_tty_driver(1);
337 if (!kgdb_nmi_tty_driver) {
338 pr_err("%s: cannot allocate tty\n", __func__);
339 return -ENOMEM;
340 }
341 kgdb_nmi_tty_driver->driver_name = "ttyNMI";
342 kgdb_nmi_tty_driver->name = "ttyNMI";
343 kgdb_nmi_tty_driver->num = 1;
344 kgdb_nmi_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
345 kgdb_nmi_tty_driver->subtype = SERIAL_TYPE_NORMAL;
346 kgdb_nmi_tty_driver->flags = TTY_DRIVER_REAL_RAW;
347 kgdb_nmi_tty_driver->init_termios = tty_std_termios;
348 tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios,
349 KGDB_NMI_BAUD, KGDB_NMI_BAUD);
350 tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops);
351
352 ret = tty_register_driver(kgdb_nmi_tty_driver);
353 if (ret) {
354 pr_err("%s: can't register tty driver: %d\n", __func__, ret);
355 goto err_drv_reg;
356 }
357
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700358 register_console(&kgdb_nmi_console);
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700359
360 return 0;
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700361err_drv_reg:
362 put_tty_driver(kgdb_nmi_tty_driver);
363 return ret;
364}
365EXPORT_SYMBOL_GPL(kgdb_register_nmi_console);
366
367int kgdb_unregister_nmi_console(void)
368{
369 int ret;
370
371 if (!arch_kgdb_ops.enable_nmi)
372 return 0;
373 arch_kgdb_ops.enable_nmi(0);
374
Anton Vorontsov0c57dfc2012-09-24 14:27:56 -0700375 ret = unregister_console(&kgdb_nmi_console);
376 if (ret)
377 return ret;
378
379 ret = tty_unregister_driver(kgdb_nmi_tty_driver);
380 if (ret)
381 return ret;
382 put_tty_driver(kgdb_nmi_tty_driver);
383
384 return 0;
385}
386EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console);