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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> |
9a655c77 | 18 | #include <linux/spinlock.h> |
24b4b67d SP |
19 | |
20 | struct ttyprintk_port { | |
21 | struct tty_port port; | |
9a655c77 | 22 | spinlock_t spinlock; |
24b4b67d SP |
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 | |
0b3191d4 JP |
32 | * - too long message is fragmented, with '\'nl between fragments |
33 | * - TPK_STR_SIZE isn't really the write_room limiting factor, because | |
24b4b67d SP |
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 */ | |
acef6660 PK |
38 | #define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL) |
39 | ||
24b4b67d SP |
40 | static int tpk_curr; |
41 | ||
0b3191d4 JP |
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'; | |
acef6660 | 48 | printk(TPK_PREFIX "[U] %s\n", tpk_buffer); |
0b3191d4 JP |
49 | tpk_curr = 0; |
50 | } | |
51 | } | |
52 | ||
24b4b67d SP |
53 | static int tpk_printk(const unsigned char *buf, int count) |
54 | { | |
24b4b67d SP |
55 | int i = tpk_curr; |
56 | ||
57 | if (buf == NULL) { | |
0b3191d4 | 58 | tpk_flush(); |
24b4b67d SP |
59 | return i; |
60 | } | |
61 | ||
62 | for (i = 0; i < count; i++) { | |
0b3191d4 | 63 | if (tpk_curr >= TPK_STR_SIZE) { |
24b4b67d | 64 | /* end of tmp buffer reached: cut the message in two */ |
0b3191d4 JP |
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; | |
24b4b67d SP |
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; | |
9a655c77 | 103 | unsigned long flags; |
24b4b67d | 104 | |
9a655c77 | 105 | spin_lock_irqsave(&tpkp->spinlock, flags); |
24b4b67d SP |
106 | /* flush tpk_printk buffer */ |
107 | tpk_printk(NULL, 0); | |
9a655c77 | 108 | spin_unlock_irqrestore(&tpkp->spinlock, flags); |
24b4b67d SP |
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; | |
9a655c77 | 120 | unsigned long flags; |
24b4b67d SP |
121 | int ret; |
122 | ||
123 | ||
124 | /* exclusive use of tpk_printk within this tty */ | |
9a655c77 | 125 | spin_lock_irqsave(&tpkp->spinlock, flags); |
24b4b67d | 126 | ret = tpk_printk(buf, count); |
9a655c77 | 127 | spin_unlock_irqrestore(&tpkp->spinlock, flags); |
24b4b67d SP |
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 | */ | |
6caa76b7 | 143 | static int tpk_ioctl(struct tty_struct *tty, |
24b4b67d SP |
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 | ||
9b95d95d | 169 | static const struct tty_port_operations null_ops = { }; |
24b4b67d SP |
170 | |
171 | static struct tty_driver *ttyprintk_driver; | |
172 | ||
173 | static int __init ttyprintk_init(void) | |
174 | { | |
87758935 | 175 | int ret; |
24b4b67d | 176 | |
9a655c77 | 177 | spin_lock_init(&tpk_port.spinlock); |
536a3440 | 178 | |
0019b408 JS |
179 | ttyprintk_driver = tty_alloc_driver(1, |
180 | TTY_DRIVER_RESET_TERMIOS | | |
181 | TTY_DRIVER_REAL_RAW | | |
182 | TTY_DRIVER_UNNUMBERED_NODE); | |
c3a6344a DC |
183 | if (IS_ERR(ttyprintk_driver)) |
184 | return PTR_ERR(ttyprintk_driver); | |
24b4b67d | 185 | |
191c5f10 | 186 | tty_port_init(&tpk_port.port); |
b5325a02 | 187 | tpk_port.port.ops = &null_ops; |
191c5f10 | 188 | |
24b4b67d SP |
189 | ttyprintk_driver->driver_name = "ttyprintk"; |
190 | ttyprintk_driver->name = "ttyprintk"; | |
191 | ttyprintk_driver->major = TTYAUX_MAJOR; | |
192 | ttyprintk_driver->minor_start = 3; | |
24b4b67d SP |
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; | |
24b4b67d | 196 | tty_set_operations(ttyprintk_driver, &ttyprintk_ops); |
b19e2ca7 | 197 | tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0); |
24b4b67d SP |
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 | ||
24b4b67d SP |
205 | return 0; |
206 | ||
207 | error: | |
208 | put_tty_driver(ttyprintk_driver); | |
191c5f10 | 209 | tty_port_destroy(&tpk_port.port); |
24b4b67d SP |
210 | return ret; |
211 | } | |
b24313a8 TI |
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 | ||
db50d2f6 | 220 | device_initcall(ttyprintk_init); |
b24313a8 TI |
221 | module_exit(ttyprintk_exit); |
222 | ||
223 | MODULE_LICENSE("GPL"); |