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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
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");
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;
56
57 for (i = 0; i < count; i++) {
58 if (tpk_curr >= TPK_STR_SIZE) {
59 /* end of tmp buffer reached: cut the message in two */
60 tpk_buffer[tpk_curr++] = '\\';
61 tpk_flush();
62 }
63
64 switch (buf[i]) {
65 case '\r':
66 tpk_flush();
67 if ((i + 1) < count && buf[i + 1] == '\n')
68 i++;
69 break;
70 case '\n':
71 tpk_flush();
72 break;
73 default:
74 tpk_buffer[tpk_curr++] = buf[i];
75 break;
76 }
77 }
78
79 return count;
80}
81
82/*
83 * TTY operations open function.
84 */
85static int tpk_open(struct tty_struct *tty, struct file *filp)
86{
87 tty->driver_data = &tpk_port;
88
89 return tty_port_open(&tpk_port.port, tty, filp);
90}
91
92/*
93 * TTY operations close function.
94 */
95static void tpk_close(struct tty_struct *tty, struct file *filp)
96{
97 struct ttyprintk_port *tpkp = tty->driver_data;
98
99 tty_port_close(&tpkp->port, tty, filp);
100}
101
102/*
103 * TTY operations write function.
104 */
105static int tpk_write(struct tty_struct *tty,
106 const unsigned char *buf, int count)
107{
108 struct ttyprintk_port *tpkp = tty->driver_data;
109 unsigned long flags;
110 int ret;
111
112 /* exclusive use of tpk_printk within this tty */
113 spin_lock_irqsave(&tpkp->spinlock, flags);
114 ret = tpk_printk(buf, count);
115 spin_unlock_irqrestore(&tpkp->spinlock, flags);
116
117 return ret;
118}
119
120/*
121 * TTY operations write_room function.
122 */
123static unsigned int tpk_write_room(struct tty_struct *tty)
124{
125 return TPK_MAX_ROOM;
126}
127
128/*
129 * TTY operations hangup function.
130 */
131static void tpk_hangup(struct tty_struct *tty)
132{
133 struct ttyprintk_port *tpkp = tty->driver_data;
134
135 tty_port_hangup(&tpkp->port);
136}
137
138/*
139 * TTY port operations shutdown function.
140 */
141static void tpk_port_shutdown(struct tty_port *tport)
142{
143 struct ttyprintk_port *tpkp =
144 container_of(tport, struct ttyprintk_port, port);
145 unsigned long flags;
146
147 spin_lock_irqsave(&tpkp->spinlock, flags);
148 tpk_flush();
149 spin_unlock_irqrestore(&tpkp->spinlock, flags);
150}
151
152static const struct tty_operations ttyprintk_ops = {
153 .open = tpk_open,
154 .close = tpk_close,
155 .write = tpk_write,
156 .write_room = tpk_write_room,
157 .hangup = tpk_hangup,
158};
159
160static const struct tty_port_operations tpk_port_ops = {
161 .shutdown = tpk_port_shutdown,
162};
163
164static struct tty_driver *ttyprintk_driver;
165
166static int __init ttyprintk_init(void)
167{
168 int ret;
169
170 spin_lock_init(&tpk_port.spinlock);
171
172 ttyprintk_driver = tty_alloc_driver(1,
173 TTY_DRIVER_RESET_TERMIOS |
174 TTY_DRIVER_REAL_RAW |
175 TTY_DRIVER_UNNUMBERED_NODE);
176 if (IS_ERR(ttyprintk_driver))
177 return PTR_ERR(ttyprintk_driver);
178
179 tty_port_init(&tpk_port.port);
180 tpk_port.port.ops = &tpk_port_ops;
181
182 ttyprintk_driver->driver_name = "ttyprintk";
183 ttyprintk_driver->name = "ttyprintk";
184 ttyprintk_driver->major = TTYAUX_MAJOR;
185 ttyprintk_driver->minor_start = 3;
186 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE;
187 ttyprintk_driver->init_termios = tty_std_termios;
188 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET;
189 tty_set_operations(ttyprintk_driver, &ttyprintk_ops);
190 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0);
191
192 ret = tty_register_driver(ttyprintk_driver);
193 if (ret < 0) {
194 printk(KERN_ERR "Couldn't register ttyprintk driver\n");
195 goto error;
196 }
197
198 return 0;
199
200error:
201 put_tty_driver(ttyprintk_driver);
202 tty_port_destroy(&tpk_port.port);
203 return ret;
204}
205
206static void __exit ttyprintk_exit(void)
207{
208 tty_unregister_driver(ttyprintk_driver);
209 put_tty_driver(ttyprintk_driver);
210 tty_port_destroy(&tpk_port.port);
211}
212
213device_initcall(ttyprintk_init);
214module_exit(ttyprintk_exit);
215
216MODULE_LICENSE("GPL");