1 /*
2 * linux/drivers/char/ttyprintk.c
3 *
4 * Copyright (C) 2010 Samo Pogacnik
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the smems of the GNU General Public License as published by
8 * the Free Software Foundation; version 2 of the License.
9 */
10
11 /*
12 * This pseudo device allows user to make printk messages. It is possible
13 * to store "console" messages inline with kernel messages for better analyses
14 * of the boot process, for example.
15 */
16
17 #include <linux/device.h>
18 #include <linux/serial.h>
19 #include <linux/tty.h>
20 #include <linux/module.h>
21 #include <linux/spinlock.h>
22
23 struct ttyprintk_port {
24 struct tty_port port;
25 spinlock_t spinlock;
26 };
27
28 static struct ttyprintk_port tpk_port;
29
30 /*
31 * Our simple preformatting supports transparent output of (time-stamped)
32 * printk messages (also suitable for logging service):
33 * - any cr is replaced by nl
34 * - adds a ttyprintk source tag in front of each line
35 * - too long message is fragmented, with '\'nl between fragments
36 * - TPK_STR_SIZE isn't really the write_room limiting factor, because
37 * it is emptied on the fly during preformatting.
38 */
39 #define TPK_STR_SIZE 508 /* should be bigger then max expected line length */
40 #define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */
41 static int tpk_curr;
42
43 static char tpk_buffer[TPK_STR_SIZE + 4];
44
tpk_flush(void)45 static void tpk_flush(void)
46 {
47 if (tpk_curr > 0) {
48 tpk_buffer[tpk_curr] = '\0';
49 pr_info("[U] %s\n", tpk_buffer);
50 tpk_curr = 0;
51 }
52 }
53
tpk_printk(const unsigned char * buf,int count)54 static int tpk_printk(const unsigned char *buf, int count)
55 {
56 int i = tpk_curr;
57
58 if (buf == NULL) {
59 tpk_flush();
60 return i;
61 }
62
63 for (i = 0; i < count; i++) {
64 if (tpk_curr >= TPK_STR_SIZE) {
65 /* end of tmp buffer reached: cut the message in two */
66 tpk_buffer[tpk_curr++] = '\\';
67 tpk_flush();
68 }
69
70 switch (buf[i]) {
71 case '\r':
72 tpk_flush();
73 if ((i + 1) < count && buf[i + 1] == '\n')
74 i++;
75 break;
76 case '\n':
77 tpk_flush();
78 break;
79 default:
80 tpk_buffer[tpk_curr++] = buf[i];
81 break;
82 }
83 }
84
85 return count;
86 }
87
88 /*
89 * TTY operations open function.
90 */
tpk_open(struct tty_struct * tty,struct file * filp)91 static int tpk_open(struct tty_struct *tty, struct file *filp)
92 {
93 tty->driver_data = &tpk_port;
94
95 return tty_port_open(&tpk_port.port, tty, filp);
96 }
97
98 /*
99 * TTY operations close function.
100 */
tpk_close(struct tty_struct * tty,struct file * filp)101 static void tpk_close(struct tty_struct *tty, struct file *filp)
102 {
103 struct ttyprintk_port *tpkp = tty->driver_data;
104 unsigned long flags;
105
106 spin_lock_irqsave(&tpkp->spinlock, flags);
107 /* flush tpk_printk buffer */
108 tpk_printk(NULL, 0);
109 spin_unlock_irqrestore(&tpkp->spinlock, flags);
110
111 tty_port_close(&tpkp->port, tty, filp);
112 }
113
114 /*
115 * TTY operations write function.
116 */
tpk_write(struct tty_struct * tty,const unsigned char * buf,int count)117 static int tpk_write(struct tty_struct *tty,
118 const unsigned char *buf, int count)
119 {
120 struct ttyprintk_port *tpkp = tty->driver_data;
121 unsigned long flags;
122 int ret;
123
124
125 /* exclusive use of tpk_printk within this tty */
126 spin_lock_irqsave(&tpkp->spinlock, flags);
127 ret = tpk_printk(buf, count);
128 spin_unlock_irqrestore(&tpkp->spinlock, flags);
129
130 return ret;
131 }
132
133 /*
134 * TTY operations write_room function.
135 */
tpk_write_room(struct tty_struct * tty)136 static int tpk_write_room(struct tty_struct *tty)
137 {
138 return TPK_MAX_ROOM;
139 }
140
141 /*
142 * TTY operations ioctl function.
143 */
tpk_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)144 static int tpk_ioctl(struct tty_struct *tty,
145 unsigned int cmd, unsigned long arg)
146 {
147 struct ttyprintk_port *tpkp = tty->driver_data;
148
149 if (!tpkp)
150 return -EINVAL;
151
152 switch (cmd) {
153 /* Stop TIOCCONS */
154 case TIOCCONS:
155 return -EOPNOTSUPP;
156 default:
157 return -ENOIOCTLCMD;
158 }
159 return 0;
160 }
161
162 /*
163 * TTY operations hangup function.
164 */
tpk_hangup(struct tty_struct * tty)165 static void tpk_hangup(struct tty_struct *tty)
166 {
167 struct ttyprintk_port *tpkp = tty->driver_data;
168
169 tty_port_hangup(&tpkp->port);
170 }
171
172 static const struct tty_operations ttyprintk_ops = {
173 .open = tpk_open,
174 .close = tpk_close,
175 .write = tpk_write,
176 .write_room = tpk_write_room,
177 .ioctl = tpk_ioctl,
178 .hangup = tpk_hangup,
179 };
180
181 static const struct tty_port_operations null_ops = { };
182
183 static struct tty_driver *ttyprintk_driver;
184
ttyprintk_init(void)185 static int __init ttyprintk_init(void)
186 {
187 int ret = -ENOMEM;
188
189 spin_lock_init(&tpk_port.spinlock);
190
191 ttyprintk_driver = tty_alloc_driver(1,
192 TTY_DRIVER_RESET_TERMIOS |
193 TTY_DRIVER_REAL_RAW |
194 TTY_DRIVER_UNNUMBERED_NODE);
195 if (IS_ERR(ttyprintk_driver))
196 return PTR_ERR(ttyprintk_driver);
197
198 tty_port_init(&tpk_port.port);
199 tpk_port.port.ops = &null_ops;
200
201 ttyprintk_driver->driver_name = "ttyprintk";
202 ttyprintk_driver->name = "ttyprintk";
203 ttyprintk_driver->major = TTYAUX_MAJOR;
204 ttyprintk_driver->minor_start = 3;
205 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
206 ttyprintk_driver->init_termios = tty_std_termios;
207 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
208 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
209 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
210
211 ret = tty_register_driver(ttyprintk_driver);
212 if (ret < 0) {
213 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
214 goto error;
215 }
216
217 return 0;
218
219 error:
220 put_tty_driver(ttyprintk_driver);
221 tty_port_destroy(&tpk_port.port);
222 return ret;
223 }
224
ttyprintk_exit(void)225 static void __exit ttyprintk_exit(void)
226 {
227 tty_unregister_driver(ttyprintk_driver);
228 put_tty_driver(ttyprintk_driver);
229 tty_port_destroy(&tpk_port.port);
230 }
231
232 device_initcall(ttyprintk_init);
233 module_exit(ttyprintk_exit);
234
235 MODULE_LICENSE("GPL");
236