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 21 struct ttyprintk_port { 22 struct tty_port port; 23 struct mutex port_write_mutex; 24 }; 25 26 static 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 fragmeted, with '\'nl between fragments 34 * - TPK_STR_SIZE isn't really the write_room limiting factor, bcause 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 static const char *tpk_tag = "[U] "; /* U for User */ 40 static int tpk_curr; 41 42 static int tpk_printk(const unsigned char *buf, int count) 43 { 44 static char tmp[TPK_STR_SIZE + 4]; 45 int i = tpk_curr; 46 47 if (buf == NULL) { 48 /* flush tmp[] */ 49 if (tpk_curr > 0) { 50 /* non nl or cr terminated message - add nl */ 51 tmp[tpk_curr + 0] = '\n'; 52 tmp[tpk_curr + 1] = '\0'; 53 printk(KERN_INFO "%s%s", tpk_tag, tmp); 54 tpk_curr = 0; 55 } 56 return i; 57 } 58 59 for (i = 0; i < count; i++) { 60 tmp[tpk_curr] = buf[i]; 61 if (tpk_curr < TPK_STR_SIZE) { 62 switch (buf[i]) { 63 case '\r': 64 /* replace cr with nl */ 65 tmp[tpk_curr + 0] = '\n'; 66 tmp[tpk_curr + 1] = '\0'; 67 printk(KERN_INFO "%s%s", tpk_tag, tmp); 68 tpk_curr = 0; 69 if (buf[i + 1] == '\n') 70 i++; 71 break; 72 case '\n': 73 tmp[tpk_curr + 1] = '\0'; 74 printk(KERN_INFO "%s%s", tpk_tag, tmp); 75 tpk_curr = 0; 76 break; 77 default: 78 tpk_curr++; 79 } 80 } else { 81 /* end of tmp buffer reached: cut the message in two */ 82 tmp[tpk_curr + 1] = '\\'; 83 tmp[tpk_curr + 2] = '\n'; 84 tmp[tpk_curr + 3] = '\0'; 85 printk(KERN_INFO "%s%s", tpk_tag, tmp); 86 tpk_curr = 0; 87 } 88 } 89 90 return count; 91 } 92 93 /* 94 * TTY operations open function. 95 */ 96 static int tpk_open(struct tty_struct *tty, struct file *filp) 97 { 98 tty->driver_data = &tpk_port; 99 100 return tty_port_open(&tpk_port.port, tty, filp); 101 } 102 103 /* 104 * TTY operations close function. 105 */ 106 static void tpk_close(struct tty_struct *tty, struct file *filp) 107 { 108 struct ttyprintk_port *tpkp = tty->driver_data; 109 110 mutex_lock(&tpkp->port_write_mutex); 111 /* flush tpk_printk buffer */ 112 tpk_printk(NULL, 0); 113 mutex_unlock(&tpkp->port_write_mutex); 114 115 tty_port_close(&tpkp->port, tty, filp); 116 } 117 118 /* 119 * TTY operations write function. 120 */ 121 static int tpk_write(struct tty_struct *tty, 122 const unsigned char *buf, int count) 123 { 124 struct ttyprintk_port *tpkp = tty->driver_data; 125 int ret; 126 127 128 /* exclusive use of tpk_printk within this tty */ 129 mutex_lock(&tpkp->port_write_mutex); 130 ret = tpk_printk(buf, count); 131 mutex_unlock(&tpkp->port_write_mutex); 132 133 return ret; 134 } 135 136 /* 137 * TTY operations write_room function. 138 */ 139 static int tpk_write_room(struct tty_struct *tty) 140 { 141 return TPK_MAX_ROOM; 142 } 143 144 /* 145 * TTY operations ioctl function. 146 */ 147 static int tpk_ioctl(struct tty_struct *tty, struct file *file, 148 unsigned int cmd, unsigned long arg) 149 { 150 struct ttyprintk_port *tpkp = tty->driver_data; 151 152 if (!tpkp) 153 return -EINVAL; 154 155 switch (cmd) { 156 /* Stop TIOCCONS */ 157 case TIOCCONS: 158 return -EOPNOTSUPP; 159 default: 160 return -ENOIOCTLCMD; 161 } 162 return 0; 163 } 164 165 static const struct tty_operations ttyprintk_ops = { 166 .open = tpk_open, 167 .close = tpk_close, 168 .write = tpk_write, 169 .write_room = tpk_write_room, 170 .ioctl = tpk_ioctl, 171 }; 172 173 struct tty_port_operations null_ops = { }; 174 175 static struct tty_driver *ttyprintk_driver; 176 177 static int __init ttyprintk_init(void) 178 { 179 int ret = -ENOMEM; 180 void *rp; 181 182 ttyprintk_driver = alloc_tty_driver(1); 183 if (!ttyprintk_driver) 184 return ret; 185 186 ttyprintk_driver->owner = THIS_MODULE; 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->num = 1; 192 ttyprintk_driver->type = TTY_DRIVER_TYPE_CONSOLE; 193 ttyprintk_driver->init_termios = tty_std_termios; 194 ttyprintk_driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET; 195 ttyprintk_driver->flags = TTY_DRIVER_RESET_TERMIOS | 196 TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV; 197 tty_set_operations(ttyprintk_driver, &ttyprintk_ops); 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 /* create our unnumbered device */ 206 rp = device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 3), NULL, 207 ttyprintk_driver->name); 208 if (IS_ERR(rp)) { 209 printk(KERN_ERR "Couldn't create ttyprintk device\n"); 210 ret = PTR_ERR(rp); 211 goto error; 212 } 213 214 tty_port_init(&tpk_port.port); 215 tpk_port.port.ops = &null_ops; 216 mutex_init(&tpk_port.port_write_mutex); 217 218 return 0; 219 220 error: 221 put_tty_driver(ttyprintk_driver); 222 ttyprintk_driver = NULL; 223 return ret; 224 } 225 module_init(ttyprintk_init); 226