drivers/char/ttyprintk.c

   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,
 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);