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 fragmeted, with '\'nl between fragments 35 * - TPK_STR_SIZE isn't really the write_room limiting factor, bcause 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 const char *tpk_tag = "[U] "; /* U for User */ 41 static int tpk_curr; 42 43 static int tpk_printk(const unsigned char *buf, int count) 44 { 45 static char tmp[TPK_STR_SIZE + 4]; 46 int i = tpk_curr; 47 48 if (buf == NULL) { 49 /* flush tmp[] */ 50 if (tpk_curr > 0) { 51 /* non nl or cr terminated message - add nl */ 52 tmp[tpk_curr + 0] = '\n'; 53 tmp[tpk_curr + 1] = '\0'; 54 printk(KERN_INFO "%s%s", tpk_tag, tmp); 55 tpk_curr = 0; 56 } 57 return i; 58 } 59 60 for (i = 0; i < count; i++) { 61 tmp[tpk_curr] = buf[i]; 62 if (tpk_curr < TPK_STR_SIZE) { 63 switch (buf[i]) { 64 case '\r': 65 /* replace cr with nl */ 66 tmp[tpk_curr + 0] = '\n'; 67 tmp[tpk_curr + 1] = '\0'; 68 printk(KERN_INFO "%s%s", tpk_tag, tmp); 69 tpk_curr = 0; 70 if ((i + 1) < count && buf[i + 1] == '\n') 71 i++; 72 break; 73 case '\n': 74 tmp[tpk_curr + 1] = '\0'; 75 printk(KERN_INFO "%s%s", tpk_tag, tmp); 76 tpk_curr = 0; 77 break; 78 default: 79 tpk_curr++; 80 } 81 } else { 82 /* end of tmp buffer reached: cut the message in two */ 83 tmp[tpk_curr + 1] = '\\'; 84 tmp[tpk_curr + 2] = '\n'; 85 tmp[tpk_curr + 3] = '\0'; 86 printk(KERN_INFO "%s%s", tpk_tag, tmp); 87 tpk_curr = 0; 88 } 89 } 90 91 return count; 92 } 93 94 /* 95 * TTY operations open function. 96 */ 97 static int tpk_open(struct tty_struct *tty, struct file *filp) 98 { 99 tty->driver_data = &tpk_port; 100 101 return tty_port_open(&tpk_port.port, tty, filp); 102 } 103 104 /* 105 * TTY operations close function. 106 */ 107 static void tpk_close(struct tty_struct *tty, struct file *filp) 108 { 109 struct ttyprintk_port *tpkp = tty->driver_data; 110 111 mutex_lock(&tpkp->port_write_mutex); 112 /* flush tpk_printk buffer */ 113 tpk_printk(NULL, 0); 114 mutex_unlock(&tpkp->port_write_mutex); 115 116 tty_port_close(&tpkp->port, tty, filp); 117 } 118 119 /* 120 * TTY operations write function. 121 */ 122 static int tpk_write(struct tty_struct *tty, 123 const unsigned char *buf, int count) 124 { 125 struct ttyprintk_port *tpkp = tty->driver_data; 126 int ret; 127 128 129 /* exclusive use of tpk_printk within this tty */ 130 mutex_lock(&tpkp->port_write_mutex); 131 ret = tpk_printk(buf, count); 132 mutex_unlock(&tpkp->port_write_mutex); 133 134 return ret; 135 } 136 137 /* 138 * TTY operations write_room function. 139 */ 140 static int tpk_write_room(struct tty_struct *tty) 141 { 142 return TPK_MAX_ROOM; 143 } 144 145 /* 146 * TTY operations ioctl function. 147 */ 148 static int tpk_ioctl(struct tty_struct *tty, 149 unsigned int cmd, unsigned long arg) 150 { 151 struct ttyprintk_port *tpkp = tty->driver_data; 152 153 if (!tpkp) 154 return -EINVAL; 155 156 switch (cmd) { 157 /* Stop TIOCCONS */ 158 case TIOCCONS: 159 return -EOPNOTSUPP; 160 default: 161 return -ENOIOCTLCMD; 162 } 163 return 0; 164 } 165 166 static const struct tty_operations ttyprintk_ops = { 167 .open = tpk_open, 168 .close = tpk_close, 169 .write = tpk_write, 170 .write_room = tpk_write_room, 171 .ioctl = tpk_ioctl, 172 }; 173 174 static struct tty_port_operations null_ops = { }; 175 176 static struct tty_driver *ttyprintk_driver; 177 178 static int __init ttyprintk_init(void) 179 { 180 int ret = -ENOMEM; 181 182 mutex_init(&tpk_port.port_write_mutex); 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 = &null_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 return 0; 211 212 error: 213 put_tty_driver(ttyprintk_driver); 214 tty_port_destroy(&tpk_port.port); 215 return ret; 216 } 217 218 static void __exit ttyprintk_exit(void) 219 { 220 tty_unregister_driver(ttyprintk_driver); 221 put_tty_driver(ttyprintk_driver); 222 tty_port_destroy(&tpk_port.port); 223 } 224 225 device_initcall(ttyprintk_init); 226 module_exit(ttyprintk_exit); 227 228 MODULE_LICENSE("GPL"); 229