projects/linux·blob master · refs

232 lines · 5.2 KiB

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/console.h>
15#include <linux/device.h>
16#include <linux/serial.h>
17#include <linux/tty.h>
18#include <linux/module.h>
19#include <linux/spinlock.h>
20
21struct ttyprintk_port {
22 struct tty_port port;
23 spinlock_t spinlock;
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 fragmented, with '\'nl between fragments
34 * - TPK_STR_SIZE isn't really the write_room limiting factor, because
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 */
39#define TPK_PREFIX KERN_SOH __stringify(CONFIG_TTY_PRINTK_LEVEL)
40
41static int tpk_curr;
42
43static u8 tpk_buffer[TPK_STR_SIZE + 4];
44
45static void tpk_flush(void)
46{
47 if (tpk_curr > 0) {
48 tpk_buffer[tpk_curr] = '\0';
49 printk(TPK_PREFIX "[U] %s\n", tpk_buffer);
50 tpk_curr = 0;
51 }
52}
53
54static int tpk_printk(const u8 *buf, size_t count)
55{
56 size_t i;
57
58 for (i = 0; i < count; i++) {
59 if (tpk_curr >= TPK_STR_SIZE) {
60 /* end of tmp buffer reached: cut the message in two */
61 tpk_buffer[tpk_curr++] = '\\';
62 tpk_flush();
63 }
64
65 switch (buf[i]) {
66 case '\r':
67 tpk_flush();
68 if ((i + 1) < count && buf[i + 1] == '\n')
69 i++;
70 break;
71 case '\n':
72 tpk_flush();
73 break;
74 default:
75 tpk_buffer[tpk_curr++] = buf[i];
76 break;
77 }
78 }
79
80 return count;
81}
82
83/*
84 * TTY operations open function.
85 */
86static int tpk_open(struct tty_struct *tty, struct file *filp)
87{
88 tty->driver_data = &tpk_port;
89
90 return tty_port_open(&tpk_port.port, tty, filp);
91}
92
93/*
94 * TTY operations close function.
95 */
96static void tpk_close(struct tty_struct *tty, struct file *filp)
97{
98 struct ttyprintk_port *tpkp = tty->driver_data;
99
100 tty_port_close(&tpkp->port, tty, filp);
101}
102
103/*
104 * TTY operations write function.
105 */
106static ssize_t tpk_write(struct tty_struct *tty, const u8 *buf, size_t 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 struct tty_driver *ttyprintk_console_device(struct console *c,
167 int *index)
168{
169 *index = 0;
170 return ttyprintk_driver;
171}
172
173static struct console ttyprintk_console = {
174 .name = "ttyprintk",
175 .device = ttyprintk_console_device,
176};
177
178static int __init ttyprintk_init(void)
179{
180 int ret;
181
182 spin_lock_init(&tpk_port.spinlock);
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 = &tpk_port_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 register_console(&ttyprintk_console);
211
212 return 0;
213
214error:
215 tty_driver_kref_put(ttyprintk_driver);
216 tty_port_destroy(&tpk_port.port);
217 return ret;
218}
219
220static void __exit ttyprintk_exit(void)
221{
222 unregister_console(&ttyprintk_console);
223 tty_unregister_driver(ttyprintk_driver);
224 tty_driver_kref_put(ttyprintk_driver);
225 tty_port_destroy(&tpk_port.port);
226}
227
228device_initcall(ttyprintk_init);
229module_exit(ttyprintk_exit);
230
231MODULE_DESCRIPTION("TTY driver to output user messages via printk");
232MODULE_LICENSE("GPL");