Commit | Line | Data |
---|---|---|
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 | ||
c8b29f04 | 45 | static atomic_t kgdb_nmi_num_readers = ATOMIC_INIT(0); |
0c57dfcc | 46 | |
bd71a1c0 DT |
47 | static int kgdb_nmi_console_setup(struct console *co, char *options) |
48 | { | |
287f03c0 DT |
49 | arch_kgdb_ops.enable_nmi(1); |
50 | ||
bd71a1c0 DT |
51 | /* 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 | ||
0c57dfcc AV |
61 | static void kgdb_nmi_console_write(struct console *co, const char *s, uint c) |
62 | { | |
63 | int i; | |
64 | ||
0c57dfcc AV |
65 | for (i = 0; i < c; i++) |
66 | dbg_io_ops->write_char(s[i]); | |
67 | } | |
68 | ||
69 | static struct tty_driver *kgdb_nmi_tty_driver; | |
70 | ||
71 | static 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 | ||
77 | static struct console kgdb_nmi_console = { | |
78 | .name = "ttyNMI", | |
bd71a1c0 | 79 | .setup = kgdb_nmi_console_setup, |
0c57dfcc AV |
80 | .write = kgdb_nmi_console_write, |
81 | .device = kgdb_nmi_console_device, | |
287f03c0 | 82 | .flags = CON_PRINTBUFFER | CON_ANYTIME, |
0c57dfcc AV |
83 | .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 | ||
93 | struct kgdb_nmi_tty_priv { | |
94 | struct tty_port port; | |
8a0ff60f | 95 | struct timer_list timer; |
0c57dfcc AV |
96 | STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo; |
97 | }; | |
98 | ||
0c57dfcc AV |
99 | static struct tty_port *kgdb_nmi_port; |
100 | ||
101 | static 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 | /* | |
8a0ff60f | 109 | * Can't use port->tty->driver_data as tty might be not there. Timer |
0c57dfcc AV |
110 | * 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 | */ | |
06d18289 | 114 | priv = container_of(kgdb_nmi_port, struct kgdb_nmi_tty_priv, port); |
0c57dfcc | 115 | kfifo_in(&priv->fifo, &c, 1); |
0c57dfcc AV |
116 | } |
117 | ||
118 | static 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 | ||
c8b29f04 | 141 | if (atomic_read(&kgdb_nmi_num_readers)) { |
0c57dfcc AV |
142 | 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 | */ | |
173 | bool kgdb_nmi_poll_knock(void) | |
174 | { | |
175 | if (kgdb_nmi_knock < 0) | |
cbc7f6bd | 176 | return true; |
0c57dfcc AV |
177 | |
178 | while (1) { | |
179 | int ret; | |
180 | ||
181 | ret = kgdb_nmi_poll_one_knock(); | |
182 | if (ret == NO_POLL_CHAR) | |
cbc7f6bd | 183 | return false; |
0c57dfcc AV |
184 | else if (ret == 1) |
185 | break; | |
186 | } | |
cbc7f6bd | 187 | return true; |
0c57dfcc AV |
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 | */ | |
194 | static void kgdb_nmi_tty_receiver(unsigned long data) | |
195 | { | |
196 | struct kgdb_nmi_tty_priv *priv = (void *)data; | |
0c57dfcc AV |
197 | char ch; |
198 | ||
8a0ff60f DT |
199 | priv->timer.expires = jiffies + (HZ/100); |
200 | add_timer(&priv->timer); | |
0c57dfcc | 201 | |
c8b29f04 DT |
202 | if (likely(!atomic_read(&kgdb_nmi_num_readers) || |
203 | !kfifo_len(&priv->fifo))) | |
0c57dfcc AV |
204 | return; |
205 | ||
0c57dfcc | 206 | while (kfifo_out(&priv->fifo, &ch, 1)) |
92a19f9c | 207 | tty_insert_flip_char(&priv->port, ch, TTY_NORMAL); |
2e124b4a | 208 | tty_flip_buffer_push(&priv->port); |
0c57dfcc AV |
209 | } |
210 | ||
211 | static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty) | |
212 | { | |
06d18289 DT |
213 | struct kgdb_nmi_tty_priv *priv = |
214 | container_of(port, struct kgdb_nmi_tty_priv, port); | |
0c57dfcc AV |
215 | |
216 | kgdb_nmi_port = port; | |
8a0ff60f DT |
217 | priv->timer.expires = jiffies + (HZ/100); |
218 | add_timer(&priv->timer); | |
219 | ||
0c57dfcc AV |
220 | return 0; |
221 | } | |
222 | ||
223 | static void kgdb_nmi_tty_shutdown(struct tty_port *port) | |
224 | { | |
06d18289 DT |
225 | struct kgdb_nmi_tty_priv *priv = |
226 | container_of(port, struct kgdb_nmi_tty_priv, port); | |
0c57dfcc | 227 | |
8a0ff60f | 228 | del_timer(&priv->timer); |
0c57dfcc AV |
229 | kgdb_nmi_port = NULL; |
230 | } | |
231 | ||
232 | static const struct tty_port_operations kgdb_nmi_tty_port_ops = { | |
233 | .activate = kgdb_nmi_tty_activate, | |
234 | .shutdown = kgdb_nmi_tty_shutdown, | |
235 | }; | |
236 | ||
237 | static 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); | |
8a0ff60f | 247 | setup_timer(&priv->timer, kgdb_nmi_tty_receiver, (unsigned long)priv); |
0c57dfcc AV |
248 | 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; | |
258 | err: | |
191c5f10 | 259 | tty_port_destroy(&priv->port); |
0c57dfcc AV |
260 | kfree(priv); |
261 | return ret; | |
262 | } | |
263 | ||
264 | static 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; | |
191c5f10 | 269 | tty_port_destroy(&priv->port); |
0c57dfcc AV |
270 | kfree(priv); |
271 | } | |
272 | ||
273 | static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file) | |
274 | { | |
275 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
c8b29f04 DT |
276 | unsigned int mode = file->f_flags & O_ACCMODE; |
277 | int ret; | |
278 | ||
279 | ret = tty_port_open(&priv->port, tty, file); | |
280 | if (!ret && (mode == O_RDONLY || mode == O_RDWR)) | |
281 | atomic_inc(&kgdb_nmi_num_readers); | |
0c57dfcc | 282 | |
c8b29f04 | 283 | return ret; |
0c57dfcc AV |
284 | } |
285 | ||
286 | static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file) | |
287 | { | |
288 | struct kgdb_nmi_tty_priv *priv = tty->driver_data; | |
c8b29f04 DT |
289 | unsigned int mode = file->f_flags & O_ACCMODE; |
290 | ||
291 | if (mode == O_RDONLY || mode == O_RDWR) | |
292 | atomic_dec(&kgdb_nmi_num_readers); | |
0c57dfcc AV |
293 | |
294 | tty_port_close(&priv->port, tty, file); | |
295 | } | |
296 | ||
297 | static 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 | ||
304 | static 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 | ||
310 | static 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 | ||
319 | static 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 | ||
0c57dfcc AV |
329 | int 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 | ||
0c57dfcc | 358 | register_console(&kgdb_nmi_console); |
0c57dfcc AV |
359 | |
360 | return 0; | |
0c57dfcc AV |
361 | err_drv_reg: |
362 | put_tty_driver(kgdb_nmi_tty_driver); | |
363 | return ret; | |
364 | } | |
365 | EXPORT_SYMBOL_GPL(kgdb_register_nmi_console); | |
366 | ||
367 | int 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 | ||
0c57dfcc AV |
375 | 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 | } | |
386 | EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console); |