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path: root/drivers/tty/serial/kgdb_nmi.c
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Diffstat (limited to 'drivers/tty/serial/kgdb_nmi.c')
-rw-r--r--drivers/tty/serial/kgdb_nmi.c402
1 files changed, 402 insertions, 0 deletions
diff --git a/drivers/tty/serial/kgdb_nmi.c b/drivers/tty/serial/kgdb_nmi.c
new file mode 100644
index 000000000000..d185247ba1aa
--- /dev/null
+++ b/drivers/tty/serial/kgdb_nmi.c
@@ -0,0 +1,402 @@
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
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
45static bool kgdb_nmi_tty_enabled;
46
47static 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
58static struct tty_driver *kgdb_nmi_tty_driver;
59
60static 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
66static 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
81struct 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
87static 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
98static void kgdb_tty_poke(void)
99{
100 tick_program_event(ktime_get(), 0);
101}
102#else
103static inline void kgdb_tty_poke(void) {}
104#endif
105
106static struct tty_port *kgdb_nmi_port;
107
108static 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
126static 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 */
181bool 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 */
202static 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
225static 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
234static 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
242static const struct tty_port_operations kgdb_nmi_tty_port_ops = {
243 .activate = kgdb_nmi_tty_activate,
244 .shutdown = kgdb_nmi_tty_shutdown,
245};
246
247static 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;
268err:
269 kfree(priv);
270 return ret;
271}
272
273static 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
281static 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
288static 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
295static 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
302static 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
308static 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
317static 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
327static 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
333int 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;
373err_kdb_reg:
374 tty_unregister_driver(kgdb_nmi_tty_driver);
375err_drv_reg:
376 put_tty_driver(kgdb_nmi_tty_driver);
377 return ret;
378}
379EXPORT_SYMBOL_GPL(kgdb_register_nmi_console);
380
381int 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}
402EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console);