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a6377d90 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
24b4b67d SP |
2 | /* |
3 | * linux/drivers/char/ttyprintk.c | |
4 | * | |
5 | * Copyright (C) 2010 Samo Pogacnik | |
24b4b67d SP |
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> | |
b24313a8 | 17 | #include <linux/module.h> |
24b4b67d SP |
18 | |
19 | struct ttyprintk_port { | |
20 | struct tty_port port; | |
21 | struct mutex port_write_mutex; | |
22 | }; | |
23 | ||
24 | static struct ttyprintk_port tpk_port; | |
25 | ||
26 | /* | |
27 | * Our simple preformatting supports transparent output of (time-stamped) | |
28 | * printk messages (also suitable for logging service): | |
29 | * - any cr is replaced by nl | |
30 | * - adds a ttyprintk source tag in front of each line | |
0b3191d4 JP |
31 | * - too long message is fragmented, with '\'nl between fragments |
32 | * - TPK_STR_SIZE isn't really the write_room limiting factor, because | |
24b4b67d SP |
33 | * it is emptied on the fly during preformatting. |
34 | */ | |
35 | #define TPK_STR_SIZE 508 /* should be bigger then max expected line length */ | |
36 | #define TPK_MAX_ROOM 4096 /* we could assume 4K for instance */ | |
acef6660 PK |
37 | #define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL) |
38 | ||
24b4b67d SP |
39 | static int tpk_curr; |
40 | ||
0b3191d4 JP |
41 | static char tpk_buffer[TPK_STR_SIZE + 4]; |
42 | ||
43 | static void tpk_flush(void) | |
44 | { | |
45 | if (tpk_curr > 0) { | |
46 | tpk_buffer[tpk_curr] = '\0'; | |
acef6660 | 47 | printk(TPK_PREFIX "[U] %s\n", tpk_buffer); |
0b3191d4 JP |
48 | tpk_curr = 0; |
49 | } | |
50 | } | |
51 | ||
24b4b67d SP |
52 | static int tpk_printk(const unsigned char *buf, int count) |
53 | { | |
24b4b67d SP |
54 | int i = tpk_curr; |
55 | ||
56 | if (buf == NULL) { | |
0b3191d4 | 57 | tpk_flush(); |
24b4b67d SP |
58 | return i; |
59 | } | |
60 | ||
61 | for (i = 0; i < count; i++) { | |
0b3191d4 | 62 | if (tpk_curr >= TPK_STR_SIZE) { |
24b4b67d | 63 | /* end of tmp buffer reached: cut the message in two */ |
0b3191d4 JP |
64 | tpk_buffer[tpk_curr++] = '\\'; |
65 | tpk_flush(); | |
66 | } | |
67 | ||
68 | switch (buf[i]) { | |
69 | case '\r': | |
70 | tpk_flush(); | |
71 | if ((i + 1) < count && buf[i + 1] == '\n') | |
72 | i++; | |
73 | break; | |
74 | case '\n': | |
75 | tpk_flush(); | |
76 | break; | |
77 | default: | |
78 | tpk_buffer[tpk_curr++] = buf[i]; | |
79 | break; | |
24b4b67d SP |
80 | } |
81 | } | |
82 | ||
83 | return count; | |
84 | } | |
85 | ||
86 | /* | |
87 | * TTY operations open function. | |
88 | */ | |
89 | static int tpk_open(struct tty_struct *tty, struct file *filp) | |
90 | { | |
91 | tty->driver_data = &tpk_port; | |
92 | ||
93 | return tty_port_open(&tpk_port.port, tty, filp); | |
94 | } | |
95 | ||
96 | /* | |
97 | * TTY operations close function. | |
98 | */ | |
99 | static void tpk_close(struct tty_struct *tty, struct file *filp) | |
100 | { | |
101 | struct ttyprintk_port *tpkp = tty->driver_data; | |
102 | ||
103 | mutex_lock(&tpkp->port_write_mutex); | |
104 | /* flush tpk_printk buffer */ | |
105 | tpk_printk(NULL, 0); | |
106 | mutex_unlock(&tpkp->port_write_mutex); | |
107 | ||
108 | tty_port_close(&tpkp->port, tty, filp); | |
109 | } | |
110 | ||
111 | /* | |
112 | * TTY operations write function. | |
113 | */ | |
114 | static int tpk_write(struct tty_struct *tty, | |
115 | const unsigned char *buf, int count) | |
116 | { | |
117 | struct ttyprintk_port *tpkp = tty->driver_data; | |
118 | int ret; | |
119 | ||
120 | ||
121 | /* exclusive use of tpk_printk within this tty */ | |
122 | mutex_lock(&tpkp->port_write_mutex); | |
123 | ret = tpk_printk(buf, count); | |
124 | mutex_unlock(&tpkp->port_write_mutex); | |
125 | ||
126 | return ret; | |
127 | } | |
128 | ||
129 | /* | |
130 | * TTY operations write_room function. | |
131 | */ | |
132 | static int tpk_write_room(struct tty_struct *tty) | |
133 | { | |
134 | return TPK_MAX_ROOM; | |
135 | } | |
136 | ||
137 | /* | |
138 | * TTY operations ioctl function. | |
139 | */ | |
6caa76b7 | 140 | static int tpk_ioctl(struct tty_struct *tty, |
24b4b67d SP |
141 | unsigned int cmd, unsigned long arg) |
142 | { | |
143 | struct ttyprintk_port *tpkp = tty->driver_data; | |
144 | ||
145 | if (!tpkp) | |
146 | return -EINVAL; | |
147 | ||
148 | switch (cmd) { | |
149 | /* Stop TIOCCONS */ | |
150 | case TIOCCONS: | |
151 | return -EOPNOTSUPP; | |
152 | default: | |
153 | return -ENOIOCTLCMD; | |
154 | } | |
155 | return 0; | |
156 | } | |
157 | ||
158 | static const struct tty_operations ttyprintk_ops = { | |
159 | .open = tpk_open, | |
160 | .close = tpk_close, | |
161 | .write = tpk_write, | |
162 | .write_room = tpk_write_room, | |
163 | .ioctl = tpk_ioctl, | |
164 | }; | |
165 | ||
9b95d95d | 166 | static const struct tty_port_operations null_ops = { }; |
24b4b67d SP |
167 | |
168 | static struct tty_driver *ttyprintk_driver; | |
169 | ||
170 | static int __init ttyprintk_init(void) | |
171 | { | |
172 | int ret = -ENOMEM; | |
24b4b67d | 173 | |
536a3440 JS |
174 | mutex_init(&tpk_port.port_write_mutex); |
175 | ||
0019b408 JS |
176 | ttyprintk_driver = tty_alloc_driver(1, |
177 | TTY_DRIVER_RESET_TERMIOS | | |
178 | TTY_DRIVER_REAL_RAW | | |
179 | TTY_DRIVER_UNNUMBERED_NODE); | |
c3a6344a DC |
180 | if (IS_ERR(ttyprintk_driver)) |
181 | return PTR_ERR(ttyprintk_driver); | |
24b4b67d | 182 | |
191c5f10 | 183 | tty_port_init(&tpk_port.port); |
b5325a02 | 184 | tpk_port.port.ops = &null_ops; |
191c5f10 | 185 | |
24b4b67d SP |
186 | ttyprintk_driver->driver_name = "ttyprintk"; |
187 | ttyprintk_driver->name = "ttyprintk"; | |
188 | ttyprintk_driver->major = TTYAUX_MAJOR; | |
189 | ttyprintk_driver->minor_start = 3; | |
24b4b67d SP |
190 | ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE; |
191 | ttyprintk_driver->init_termios = tty_std_termios; | |
192 | ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET; | |
24b4b67d | 193 | tty_set_operations(ttyprintk_driver, &ttyprintk_ops); |
b19e2ca7 | 194 | tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0); |
24b4b67d SP |
195 | |
196 | ret = tty_register_driver(ttyprintk_driver); | |
197 | if (ret < 0) { | |
198 | printk(KERN_ERR "Couldn't register ttyprintk driver\n"); | |
199 | goto error; | |
200 | } | |
201 | ||
24b4b67d SP |
202 | return 0; |
203 | ||
204 | error: | |
205 | put_tty_driver(ttyprintk_driver); | |
191c5f10 | 206 | tty_port_destroy(&tpk_port.port); |
24b4b67d SP |
207 | return ret; |
208 | } | |
b24313a8 TI |
209 | |
210 | static void __exit ttyprintk_exit(void) | |
211 | { | |
212 | tty_unregister_driver(ttyprintk_driver); | |
213 | put_tty_driver(ttyprintk_driver); | |
214 | tty_port_destroy(&tpk_port.port); | |
215 | } | |
216 | ||
db50d2f6 | 217 | device_initcall(ttyprintk_init); |
b24313a8 TI |
218 | module_exit(ttyprintk_exit); |
219 | ||
220 | MODULE_LICENSE("GPL"); |