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