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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");
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");