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