Merge tag 'linux-watchdog-5.9-rc1' of git://www.linux-watchdog.org/linux-watchdog
[linux-2.6-microblaze.git] / drivers / char / ttyprintk.c
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
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
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  */
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  */
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  */
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  */
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  */
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 static const struct tty_operations ttyprintk_ops = {
162         .open = tpk_open,
163         .close = tpk_close,
164         .write = tpk_write,
165         .write_room = tpk_write_room,
166         .ioctl = tpk_ioctl,
167 };
168
169 static const struct tty_port_operations null_ops = { };
170
171 static struct tty_driver *ttyprintk_driver;
172
173 static int __init ttyprintk_init(void)
174 {
175         int ret;
176
177         spin_lock_init(&tpk_port.spinlock);
178
179         ttyprintk_driver = tty_alloc_driver(1,
180                         TTY_DRIVER_RESET_TERMIOS |
181                         TTY_DRIVER_REAL_RAW |
182                         TTY_DRIVER_UNNUMBERED_NODE);
183         if (IS_ERR(ttyprintk_driver))
184                 return PTR_ERR(ttyprintk_driver);
185
186         tty_port_init(&tpk_port.port);
187         tpk_port.port.ops = &null_ops;
188
189         ttyprintk_driver->driver_name = "ttyprintk";
190         ttyprintk_driver->name = "ttyprintk";
191         ttyprintk_driver->major = TTYAUX_MAJOR;
192         ttyprintk_driver->minor_start = 3;
193         ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
194         ttyprintk_driver->init_termios = tty_std_termios;
195         ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
196         tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
197         tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
198
199         ret = tty_register_driver(ttyprintk_driver);
200         if (ret < 0) {
201                 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
202                 goto error;
203         }
204
205         return 0;
206
207 error:
208         put_tty_driver(ttyprintk_driver);
209         tty_port_destroy(&tpk_port.port);
210         return ret;
211 }
212
213 static void __exit ttyprintk_exit(void)
214 {
215         tty_unregister_driver(ttyprintk_driver);
216         put_tty_driver(ttyprintk_driver);
217         tty_port_destroy(&tpk_port.port);
218 }
219
220 device_initcall(ttyprintk_init);
221 module_exit(ttyprintk_exit);
222
223 MODULE_LICENSE("GPL");