summaryrefslogtreecommitdiff
path: root/drivers/char/ttyprintk.c
blob: e93b0af9233906bf9ebb2ee99e8c8e4922c97895 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/drivers/char/ttyprintk.c
 *
 *  Copyright (C) 2010  Samo Pogacnik
 */

/*
 * This pseudo device allows user to make printk messages. It is possible
 * to store "console" messages inline with kernel messages for better analyses
 * of the boot process, for example.
 */

#include <linux/device.h>
#include <linux/serial.h>
#include <linux/tty.h>
#include <linux/module.h>
#include <linux/spinlock.h>

struct ttyprintk_port {
	struct tty_port port;
	spinlock_t spinlock;
};

static struct ttyprintk_port tpk_port;

/*
 * Our simple preformatting supports transparent output of (time-stamped)
 * printk messages (also suitable for logging service):
 * - any cr is replaced by nl
 * - adds a ttyprintk source tag in front of each line
 * - too long message is fragmented, with '\'nl between fragments
 * - TPK_STR_SIZE isn't really the write_room limiting factor, because
 *   it is emptied on the fly during preformatting.
 */
#define TPK_STR_SIZE 508 /* should be bigger then max expected line length */
#define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */
#define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL)

static int tpk_curr;

static char tpk_buffer[TPK_STR_SIZE + 4];

static void tpk_flush(void)
{
	if (tpk_curr > 0) {
		tpk_buffer[tpk_curr] = '\0';
		printk(TPK_PREFIX "[U] %s\n", tpk_buffer);
		tpk_curr = 0;
	}
}

static int tpk_printk(const unsigned char *buf, int count)
{
	int i = tpk_curr;

	if (buf == NULL) {
		tpk_flush();
		return i;
	}

	for (i = 0; i < count; i++) {
		if (tpk_curr >= TPK_STR_SIZE) {
			/* end of tmp buffer reached: cut the message in two */
			tpk_buffer[tpk_curr++] = '\\';
			tpk_flush();
		}

		switch (buf[i]) {
		case '\r':
			tpk_flush();
			if ((i + 1) < count && buf[i + 1] == '\n')
				i++;
			break;
		case '\n':
			tpk_flush();
			break;
		default:
			tpk_buffer[tpk_curr++] = buf[i];
			break;
		}
	}

	return count;
}

/*
 * TTY operations open function.
 */
static int tpk_open(struct tty_struct *tty, struct file *filp)
{
	tty->driver_data = &tpk_port;

	return tty_port_open(&tpk_port.port, tty, filp);
}

/*
 * TTY operations close function.
 */
static void tpk_close(struct tty_struct *tty, struct file *filp)
{
	struct ttyprintk_port *tpkp = tty->driver_data;
	unsigned long flags;

	spin_lock_irqsave(&tpkp->spinlock, flags);
	/* flush tpk_printk buffer */
	tpk_printk(NULL, 0);
	spin_unlock_irqrestore(&tpkp->spinlock, flags);

	tty_port_close(&tpkp->port, tty, filp);
}

/*
 * TTY operations write function.
 */
static int tpk_write(struct tty_struct *tty,
		const unsigned char *buf, int count)
{
	struct ttyprintk_port *tpkp = tty->driver_data;
	unsigned long flags;
	int ret;


	/* exclusive use of tpk_printk within this tty */
	spin_lock_irqsave(&tpkp->spinlock, flags);
	ret = tpk_printk(buf, count);
	spin_unlock_irqrestore(&tpkp->spinlock, flags);

	return ret;
}

/*
 * TTY operations write_room function.
 */
static unsigned int tpk_write_room(struct tty_struct *tty)
{
	return TPK_MAX_ROOM;
}

/*
 * TTY operations ioctl function.
 */
static int tpk_ioctl(struct tty_struct *tty,
			unsigned int cmd, unsigned long arg)
{
	struct ttyprintk_port *tpkp = tty->driver_data;

	if (!tpkp)
		return -EINVAL;

	switch (cmd) {
	/* Stop TIOCCONS */
	case TIOCCONS:
		return -EOPNOTSUPP;
	default:
		return -ENOIOCTLCMD;
	}
	return 0;
}

/*
 * TTY operations hangup function.
 */
static void tpk_hangup(struct tty_struct *tty)
{
	struct ttyprintk_port *tpkp = tty->driver_data;

	tty_port_hangup(&tpkp->port);
}

static const struct tty_operations ttyprintk_ops = {
	.open = tpk_open,
	.close = tpk_close,
	.write = tpk_write,
	.write_room = tpk_write_room,
	.ioctl = tpk_ioctl,
	.hangup = tpk_hangup,
};

static const struct tty_port_operations null_ops = { };

static struct tty_driver *ttyprintk_driver;

static int __init ttyprintk_init(void)
{
	int ret;

	spin_lock_init(&tpk_port.spinlock);

	ttyprintk_driver = tty_alloc_driver(1,
			TTY_DRIVER_RESET_TERMIOS |
			TTY_DRIVER_REAL_RAW |
			TTY_DRIVER_UNNUMBERED_NODE);
	if (IS_ERR(ttyprintk_driver))
		return PTR_ERR(ttyprintk_driver);

	tty_port_init(&tpk_port.port);
	tpk_port.port.ops = &null_ops;

	ttyprintk_driver->driver_name = "ttyprintk";
	ttyprintk_driver->name = "ttyprintk";
	ttyprintk_driver->major = TTYAUX_MAJOR;
	ttyprintk_driver->minor_start = 3;
	ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
	ttyprintk_driver->init_termios = tty_std_termios;
	ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
	tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
	tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);

	ret = tty_register_driver(ttyprintk_driver);
	if (ret < 0) {
		printk(KERN_ERR "Couldn't register ttyprintk driver\n");
		goto error;
	}

	return 0;

error:
	put_tty_driver(ttyprintk_driver);
	tty_port_destroy(&tpk_port.port);
	return ret;
}

static void __exit ttyprintk_exit(void)
{
	tty_unregister_driver(ttyprintk_driver);
	put_tty_driver(ttyprintk_driver);
	tty_port_destroy(&tpk_port.port);
}

device_initcall(ttyprintk_init);
module_exit(ttyprintk_exit);

MODULE_LICENSE("GPL");