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 22 struct ttyprintk_port { 23 struct tty_port port; 24 struct mutex port_write_mutex; 25 }; 26 27 static 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 fragmented, with '\'nl between fragments 35 * - TPK_STR_SIZE isn't really the write_room limiting factor, because 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 */ 40 static int tpk_curr; 41 42 static char tpk_buffer[TPK_STR_SIZE + 4]; 43 44 static void tpk_flush(void) 45 { 46 if (tpk_curr > 0) { 47 tpk_buffer[tpk_curr] = '\0'; 48 pr_info("[U] %s\n", tpk_buffer); 49 tpk_curr = 0; 50 } 51 } 52 53 static 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 */ 90 static 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 */ 100 static void tpk_close(struct tty_struct *tty, struct file *filp) 101 { 102 struct ttyprintk_port *tpkp = tty->driver_data; 103 104 mutex_lock(&tpkp->port_write_mutex); 105 /* flush tpk_printk buffer */ 106 tpk_printk(NULL, 0); 107 mutex_unlock(&tpkp->port_write_mutex); 108 109 tty_port_close(&tpkp->port, tty, filp); 110 } 111 112 /* 113 * TTY operations write function. 114 */ 115 static int tpk_write(struct tty_struct *tty, 116 const unsigned char *buf, int count) 117 { 118 struct ttyprintk_port *tpkp = tty->driver_data; 119 int ret; 120 121 122 /* exclusive use of tpk_printk within this tty */ 123 mutex_lock(&tpkp->port_write_mutex); 124 ret = tpk_printk(buf, count); 125 mutex_unlock(&tpkp->port_write_mutex); 126 127 return ret; 128 } 129 130 /* 131 * TTY operations write_room function. 132 */ 133 static int tpk_write_room(struct tty_struct *tty) 134 { 135 return TPK_MAX_ROOM; 136 } 137 138 /* 139 * TTY operations ioctl function. 140 */ 141 static int tpk_ioctl(struct tty_struct *tty, 142 unsigned int cmd, unsigned long arg) 143 { 144 struct ttyprintk_port *tpkp = tty->driver_data; 145 146 if (!tpkp) 147 return -EINVAL; 148 149 switch (cmd) { 150 /* Stop TIOCCONS */ 151 case TIOCCONS: 152 return -EOPNOTSUPP; 153 default: 154 return -ENOIOCTLCMD; 155 } 156 return 0; 157 } 158 159 static const struct tty_operations ttyprintk_ops = { 160 .open = tpk_open, 161 .close = tpk_close, 162 .write = tpk_write, 163 .write_room = tpk_write_room, 164 .ioctl = tpk_ioctl, 165 }; 166 167 static const struct tty_port_operations null_ops = { }; 168 169 static struct tty_driver *ttyprintk_driver; 170 171 static int __init ttyprintk_init(void) 172 { 173 int ret = -ENOMEM; 174 175 mutex_init(&tpk_port.port_write_mutex); 176 177 ttyprintk_driver = tty_alloc_driver(1, 178 TTY_DRIVER_RESET_TERMIOS | 179 TTY_DRIVER_REAL_RAW | 180 TTY_DRIVER_UNNUMBERED_NODE); 181 if (IS_ERR(ttyprintk_driver)) 182 return PTR_ERR(ttyprintk_driver); 183 184 tty_port_init(&tpk_port.port); 185 tpk_port.port.ops = &null_ops; 186 187 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->type = TTY_DRIVER_TYPE_CONSOLE; 192 ttyprintk_driver->init_termios = tty_std_termios; 193 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET; 194 tty_set_operations(ttyprintk_driver, &ttyprintk_ops); 195 tty_port_link_device(&tpk_port.port, ttyprintk_driver, 0); 196 197 ret = tty_register_driver(ttyprintk_driver); 198 if (ret < 0) { 199 printk(KERN_ERR "Couldn't register ttyprintk driver\n"); 200 goto error; 201 } 202 203 return 0; 204 205 error: 206 put_tty_driver(ttyprintk_driver); 207 tty_port_destroy(&tpk_port.port); 208 return ret; 209 } 210 211 static void __exit ttyprintk_exit(void) 212 { 213 tty_unregister_driver(ttyprintk_driver); 214 put_tty_driver(ttyprintk_driver); 215 tty_port_destroy(&tpk_port.port); 216 } 217 218 device_initcall(ttyprintk_init); 219 module_exit(ttyprintk_exit); 220 221 MODULE_LICENSE("GPL"); 222