1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/drivers/char/ttyprintk.c
4 *
5 * Copyright (C) 2010 Samo Pogacnik
6 */
7
8 /*
9 * This pseudo device allows user to make printk messages. It is possible
10 * to store "console" messages inline with kernel messages for better analyses
11 * of the boot process, for example.
12 */
13
14 #include <linux/device.h>
15 #include <linux/serial.h>
16 #include <linux/tty.h>
17 #include <linux/module.h>
18 #include <linux/spinlock.h>
19
20 struct ttyprintk_port {
21 struct tty_port port;
22 spinlock_t spinlock;
23 };
24
25 static struct ttyprintk_port tpk_port;
26
27 /*
28 * Our simple preformatting supports transparent output of (time-stamped)
29 * printk messages (also suitable for logging service):
30 * - any cr is replaced by nl
31 * - adds a ttyprintk source tag in front of each line
32 * - too long message is fragmented, with '\'nl between fragments
33 * - TPK_STR_SIZE isn't really the write_room limiting factor, because
34 * it is emptied on the fly during preformatting.
35 */
36 #define TPK_STR_SIZE 508 /* should be bigger then max expected line length */
37 #define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */
38 #define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL)
39
40 static int tpk_curr;
41
42 static char tpk_buffer[TPK_STR_SIZE + 4];
43
tpk_flush(void)44 static void tpk_flush(void)
45 {
46 if (tpk_curr > 0) {
47 tpk_buffer[tpk_curr] = '\0';
48 printk(TPK_PREFIX "[U] %s\n", tpk_buffer);
49 tpk_curr = 0;
50 }
51 }
52
tpk_printk(const unsigned char * buf,int count)53 static int tpk_printk(const unsigned char *buf, int count)
54 {
55 int i = tpk_curr;
56
57 if (buf == NULL) {
58 tpk_flush();
59 return i;
60 }
61
62 for (i = 0; i < count; i++) {
63 if (tpk_curr >= TPK_STR_SIZE) {
64 /* end of tmp buffer reached: cut the message in two */
65 tpk_buffer[tpk_curr++] = '\\';
66 tpk_flush();
67 }
68
69 switch (buf[i]) {
70 case '\r':
71 tpk_flush();
72 if ((i + 1) < count && buf[i + 1] == '\n')
73 i++;
74 break;
75 case '\n':
76 tpk_flush();
77 break;
78 default:
79 tpk_buffer[tpk_curr++] = buf[i];
80 break;
81 }
82 }
83
84 return count;
85 }
86
87 /*
88 * TTY operations open function.
89 */
tpk_open(struct tty_struct * tty,struct file * filp)90 static int tpk_open(struct tty_struct *tty, struct file *filp)
91 {
92 tty->driver_data = &tpk_port;
93
94 return tty_port_open(&tpk_port.port, tty, filp);
95 }
96
97 /*
98 * TTY operations close function.
99 */
tpk_close(struct tty_struct * tty,struct file * filp)100 static void tpk_close(struct tty_struct *tty, struct file *filp)
101 {
102 struct ttyprintk_port *tpkp = tty->driver_data;
103 unsigned long flags;
104
105 spin_lock_irqsave(&tpkp->spinlock, flags);
106 /* flush tpk_printk buffer */
107 tpk_printk(NULL, 0);
108 spin_unlock_irqrestore(&tpkp->spinlock, flags);
109
110 tty_port_close(&tpkp->port, tty, filp);
111 }
112
113 /*
114 * TTY operations write function.
115 */
tpk_write(struct tty_struct * tty,const unsigned char * buf,int count)116 static int tpk_write(struct tty_struct *tty,
117 const unsigned char *buf, int count)
118 {
119 struct ttyprintk_port *tpkp = tty->driver_data;
120 unsigned long flags;
121 int ret;
122
123
124 /* exclusive use of tpk_printk within this tty */
125 spin_lock_irqsave(&tpkp->spinlock, flags);
126 ret = tpk_printk(buf, count);
127 spin_unlock_irqrestore(&tpkp->spinlock, flags);
128
129 return ret;
130 }
131
132 /*
133 * TTY operations write_room function.
134 */
tpk_write_room(struct tty_struct * tty)135 static int tpk_write_room(struct tty_struct *tty)
136 {
137 return TPK_MAX_ROOM;
138 }
139
140 /*
141 * TTY operations ioctl function.
142 */
tpk_ioctl(struct tty_struct * tty,unsigned int cmd,unsigned long arg)143 static int tpk_ioctl(struct tty_struct *tty,
144 unsigned int cmd, unsigned long arg)
145 {
146 struct ttyprintk_port *tpkp = tty->driver_data;
147
148 if (!tpkp)
149 return -EINVAL;
150
151 switch (cmd) {
152 /* Stop TIOCCONS */
153 case TIOCCONS:
154 return -EOPNOTSUPP;
155 default:
156 return -ENOIOCTLCMD;
157 }
158 return 0;
159 }
160
161 /*
162 * TTY operations hangup function.
163 */
tpk_hangup(struct tty_struct * tty)164 static void tpk_hangup(struct tty_struct *tty)
165 {
166 struct ttyprintk_port *tpkp = tty->driver_data;
167
168 tty_port_hangup(&tpkp->port);
169 }
170
171 static const struct tty_operations ttyprintk_ops = {
172 .open = tpk_open,
173 .close = tpk_close,
174 .write = tpk_write,
175 .write_room = tpk_write_room,
176 .ioctl = tpk_ioctl,
177 .hangup = tpk_hangup,
178 };
179
180 static const struct tty_port_operations null_ops = { };
181
182 static struct tty_driver *ttyprintk_driver;
183
ttyprintk_init(void)184 static int __init ttyprintk_init(void)
185 {
186 int ret;
187
188 spin_lock_init(&tpk_port.spinlock);
189
190 ttyprintk_driver = tty_alloc_driver(1,
191 TTY_DRIVER_RESET_TERMIOS |
192 TTY_DRIVER_REAL_RAW |
193 TTY_DRIVER_UNNUMBERED_NODE);
194 if (IS_ERR(ttyprintk_driver))
195 return PTR_ERR(ttyprintk_driver);
196
197 tty_port_init(&tpk_port.port);
198 tpk_port.port.ops = &null_ops;
199
200 ttyprintk_driver->driver_name = "ttyprintk";
201 ttyprintk_driver->name = "ttyprintk";
202 ttyprintk_driver->major = TTYAUX_MAJOR;
203 ttyprintk_driver->minor_start = 3;
204 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
205 ttyprintk_driver->init_termios = tty_std_termios;
206 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
207 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
208 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
209
210 ret = tty_register_driver(ttyprintk_driver);
211 if (ret < 0) {
212 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
213 goto error;
214 }
215
216 return 0;
217
218 error:
219 put_tty_driver(ttyprintk_driver);
220 tty_port_destroy(&tpk_port.port);
221 return ret;
222 }
223
ttyprintk_exit(void)224 static void __exit ttyprintk_exit(void)
225 {
226 tty_unregister_driver(ttyprintk_driver);
227 put_tty_driver(ttyprintk_driver);
228 tty_port_destroy(&tpk_port.port);
229 }
230
231 device_initcall(ttyprintk_init);
232 module_exit(ttyprintk_exit);
233
234 MODULE_LICENSE("GPL");
235