kernel/printk.c

   1 /*
   2  *  linux/kernel/printk.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  * Modified to make sys_syslog() more flexible: added commands to
   7  * return the last 4k of kernel messages, regardless of whether
   8  * they've been read or not.  Added option to suppress kernel printk's
   9  * to the console.  Added hook for sending the console messages
  10  * elsewhere, in preparation for a serial line console (someday).
  11  * Ted Ts'o, 2/11/93.
  12  * Modified for sysctl support, 1/8/97, Chris Horn.
  13  * Fixed SMP synchronization, 08/08/99, Manfred Spraul
  14  *     manfreds@colorfullife.com
  15  */
  16
  17 #include <linux/mm.h>
  18 #include <linux/tty_driver.h>
  19 #include <linux/smp_lock.h>
  20 #include <linux/console.h>
  21 #include <linux/init.h>
  22
  23 #include <asm/uaccess.h>
  24
  25 #define LOG_BUF_LEN     (16384)
  26 #define LOG_BUF_MASK    (LOG_BUF_LEN-1)
  27
  28 static char buf[1024];
  29
  30 /* printk's without a loglevel use this.. */
  31 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  32
  33 /* We show everything that is MORE important than this.. */
  34 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  35 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  36
  37 unsigned long log_size;
  38 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  39
  40 /* Keep together for sysctl support */
  41 int console_loglevel = DEFAULT_CONSOLE_LOGLEVEL;
  42 int default_message_loglevel = DEFAULT_MESSAGE_LOGLEVEL;
  43 int minimum_console_loglevel = MINIMUM_CONSOLE_LOGLEVEL;
  44 int default_console_loglevel = DEFAULT_CONSOLE_LOGLEVEL;
  45
  46 spinlock_t console_lock = SPIN_LOCK_UNLOCKED;
  47
  48 struct console *console_drivers;
  49 static char log_buf[LOG_BUF_LEN];
  50 static unsigned long log_start;
  51 static unsigned long logged_chars;
  52 struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
  53 static int preferred_console = -1;
  54
  55 /*
  56  *      Setup a list of consoles. Called from init/main.c
  57  */
  58 static int __init console_setup(char *str)
  59 {
  60         struct console_cmdline *c;
  61         char name[sizeof(c->name)];
  62         char *s, *options;
  63         int i, idx;
  64
  65         /*
  66          *      Decode str into name, index, options.
  67          */
  68         if (str[0] >= '0' && str[0] <= '9') {
  69                 strcpy(name, "ttyS");
  70                 strncpy(name + 4, str, sizeof(name) - 5);
  71         } else
  72                 strncpy(name, str, sizeof(name) - 1);
  73         name[sizeof(name) - 1] = 0;
  74         if ((options = strchr(str, ',')) != NULL)
  75                 *(options++) = 0;
  76 #ifdef __sparc__
  77         if (!strcmp(str, "ttya"))
  78                 strcpy(name, "ttyS0");
  79         if (!strcmp(str, "ttyb"))
  80                 strcpy(name, "ttyS1");
  81 #endif
  82         for(s = name; *s; s++)
  83                 if (*s >= '0' && *s <= '9')
  84                         break;
  85         idx = simple_strtoul(s, NULL, 10);
  86         *s = 0;
  87
  88         /*
  89          *      See if this tty is not yet registered, and
  90          *      if we have a slot free.
  91          */
  92         for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
  93                 if (strcmp(console_cmdline[i].name, name) == 0 &&
  94                           console_cmdline[i].index == idx) {
  95                                 preferred_console = i;
  96                                 return 1;
  97                 }
  98         if (i == MAX_CMDLINECONSOLES)
  99                 return 1;
 100         preferred_console = i;
 101         c = &console_cmdline[i];
 102         memcpy(c->name, name, sizeof(c->name));
 103         c->options = options;
 104         c->index = idx;
 105         return 1;
 106 }
 107
 108 __setup("console=", console_setup);
 109
 110 /*
 111  * Commands to do_syslog:
 112  *
 113  *      0 -- Close the log.  Currently a NOP.
 114  *      1 -- Open the log. Currently a NOP.
 115  *      2 -- Read from the log.
 116  *      3 -- Read all messages remaining in the ring buffer.
 117  *      4 -- Read and clear all messages remaining in the ring buffer
 118  *      5 -- Clear ring buffer.
 119  *      6 -- Disable printk's to console
 120  *      7 -- Enable printk's to console
 121  *      8 -- Set level of messages printed to console
 122  */
 123 int do_syslog(int type, char * buf, int len)
 124 {
 125         unsigned long i, j, limit, count;
 126         int do_clear = 0;
 127         char c;
 128         int error = -EPERM;
 129
 130         error = 0;
 131         switch (type) {
 132         case 0:         /* Close log */
 133                 break;
 134         case 1:         /* Open log */
 135                 break;
 136         case 2:         /* Read from log */
 137                 error = -EINVAL;
 138                 if (!buf || len < 0)
 139                         goto out;
 140                 error = 0;
 141                 if (!len)
 142                         goto out;
 143                 error = verify_area(VERIFY_WRITE,buf,len);
 144                 if (error)
 145                         goto out;
 146                 error = wait_event_interruptible(log_wait, log_size);
 147                 if (error)
 148                         goto out;
 149                 i = 0;
 150                 spin_lock_irq(&console_lock);
 151                 while (log_size && i < len) {
 152                         c = log_buf[log_start & LOG_BUF_MASK];
 153                         log_start++;
 154                         log_size--;
 155                         spin_unlock_irq(&console_lock);
 156                         __put_user(c,buf);
 157                         buf++;
 158                         i++;
 159                         spin_lock_irq(&console_lock);
 160                 }
 161                 spin_unlock_irq(&console_lock);
 162                 error = i;
 163                 break;
 164         case 4:         /* Read/clear last kernel messages */
 165                 do_clear = 1;
 166                 /* FALL THRU */
 167         case 3:         /* Read last kernel messages */
 168                 error = -EINVAL;
 169                 if (!buf || len < 0)
 170                         goto out;
 171                 error = 0;
 172                 if (!len)
 173                         goto out;
 174                 error = verify_area(VERIFY_WRITE,buf,len);
 175                 if (error)
 176                         goto out;
 177                 count = len;
 178                 if (count > LOG_BUF_LEN)
 179                         count = LOG_BUF_LEN;
 180                 spin_lock_irq(&console_lock);
 181                 if (count > logged_chars)
 182                         count = logged_chars;
 183                 if (do_clear)
 184                         logged_chars = 0;
 185                 limit = log_start + log_size;
 186                 /*
 187                  * __put_user() could sleep, and while we sleep
 188                  * printk() could overwrite the messages
 189                  * we try to copy to user space. Therefore
 190                  * the messages are copied in reverse. <manfreds>
 191                  */
 192                 for(i=0;i < count;i++) {
 193                         j = limit-1-i;
 194                         if (j+LOG_BUF_LEN < log_start+log_size)
 195                                 break;
 196                         c = log_buf[ j  & LOG_BUF_MASK ];
 197                         spin_unlock_irq(&console_lock);
 198                         __put_user(c,&buf[count-1-i]);
 199                         spin_lock_irq(&console_lock);
 200                 }
 201                 spin_unlock_irq(&console_lock);
 202                 error = i;
 203                 if(i != count) {
 204                         int offset = count-error;
 205                         /* buffer overflow during copy, correct user buffer. */
 206                         for(i=0;i<error;i++) {
 207                                 __get_user(c,&buf[i+offset]);
 208                                 __put_user(c,&buf[i]);
 209                         }
 210                 }
 211
 212                 break;
 213         case 5:         /* Clear ring buffer */
 214                 spin_lock_irq(&console_lock);
 215                 logged_chars = 0;
 216                 spin_unlock_irq(&console_lock);
 217                 break;
 218         case 6:         /* Disable logging to console */
 219                 spin_lock_irq(&console_lock);
 220                 console_loglevel = minimum_console_loglevel;
 221                 spin_unlock_irq(&console_lock);
 222                 break;
 223         case 7:         /* Enable logging to console */
 224                 spin_lock_irq(&console_lock);
 225                 console_loglevel = default_console_loglevel;
 226                 spin_unlock_irq(&console_lock);
 227                 break;
 228         case 8:
 229                 error = -EINVAL;
 230                 if (len < 1 || len > 8)
 231                         goto out;
 232                 if (len < minimum_console_loglevel)
 233                         len = minimum_console_loglevel;
 234                 spin_lock_irq(&console_lock);
 235                 console_loglevel = len;
 236                 spin_unlock_irq(&console_lock);
 237                 error = 0;
 238                 break;
 239         default:
 240                 error = -EINVAL;
 241                 break;
 242         }
 243 out:
 244         return error;
 245 }
 246
 247 asmlinkage long sys_syslog(int type, char * buf, int len)
 248 {
 249         if ((type != 3) && !capable(CAP_SYS_ADMIN))
 250                 return -EPERM;
 251         return do_syslog(type, buf, len);
 252 }
 253
 254 asmlinkage int printk(const char *fmt, ...)
 255 {
 256         va_list args;
 257         int i;
 258         char *msg, *p, *buf_end;
 259         int line_feed;
 260         static signed char msg_level = -1;
 261         long flags;
 262
 263         spin_lock_irqsave(&console_lock, flags);
 264         va_start(args, fmt);
 265         i = vsprintf(buf + 3, fmt, args); /* hopefully i < sizeof(buf)-4 */
 266         buf_end = buf + 3 + i;
 267         va_end(args);
 268         for (p = buf + 3; p < buf_end; p++) {
 269                 msg = p;
 270                 if (msg_level < 0) {
 271                         if (
 272                                 p[0] != '<' ||
 273                                 p[1] < '0' ||
 274                                 p[1] > '7' ||
 275                                 p[2] != '>'
 276                         ) {
 277                                 p -= 3;
 278                                 p[0] = '<';
 279                                 p[1] = default_message_loglevel + '0';
 280                                 p[2] = '>';
 281                         } else
 282                                 msg += 3;
 283                         msg_level = p[1] - '0';
 284                 }
 285                 line_feed = 0;
 286                 for (; p < buf_end; p++) {
 287                         log_buf[(log_start+log_size) & LOG_BUF_MASK] = *p;
 288                         if (log_size < LOG_BUF_LEN)
 289                                 log_size++;
 290                         else
 291                                 log_start++;
 292
 293                         logged_chars++;
 294                         if (*p == '\n') {
 295                                 line_feed = 1;
 296                                 break;
 297                         }
 298                 }
 299                 if (msg_level < console_loglevel && console_drivers) {
 300                         struct console *c = console_drivers;
 301                         while(c) {
 302                                 if ((c->flags & CON_ENABLED) && c->write)
 303                                         c->write(c, msg, p - msg + line_feed);
 304                                 c = c->next;
 305                         }
 306                 }
 307                 if (line_feed)
 308                         msg_level = -1;
 309         }
 310         spin_unlock_irqrestore(&console_lock, flags);
 311         wake_up_interruptible(&log_wait);
 312         return i;
 313 }
 314
 315 void console_print(const char *s)
 316 {
 317         struct console *c;
 318         unsigned long flags;
 319         int len = strlen(s);
 320
 321         spin_lock_irqsave(&console_lock, flags);
 322         c = console_drivers;
 323         while(c) {
 324                 if ((c->flags & CON_ENABLED) && c->write)
 325                         c->write(c, s, len);
 326                 c = c->next;
 327         }
 328         spin_unlock_irqrestore(&console_lock, flags);
 329 }
 330
 331 void unblank_console(void)
 332 {
 333         struct console *c;
 334         unsigned long flags;
 335
 336         spin_lock_irqsave(&console_lock, flags);
 337         c = console_drivers;
 338         while(c) {
 339                 if ((c->flags & CON_ENABLED) && c->unblank)
 340                         c->unblank();
 341                 c = c->next;
 342         }
 343         spin_unlock_irqrestore(&console_lock, flags);
 344 }
 345
 346 /*
 347  * The console driver calls this routine during kernel initialization
 348  * to register the console printing procedure with printk() and to
 349  * print any messages that were printed by the kernel before the
 350  * console driver was initialized.
 351  */
 352 void register_console(struct console * console)
 353 {
 354         int     i, j,len;
 355         int     p;
 356         char    buf[16];
 357         signed char msg_level = -1;
 358         char    *q;
 359         unsigned long flags;
 360
 361         /*
 362          *      See if we want to use this console driver. If we
 363          *      didn't select a console we take the first one
 364          *      that registers here.
 365          */
 366         if (preferred_console < 0) {
 367                 if (console->index < 0)
 368                         console->index = 0;
 369                 if (console->setup == NULL ||
 370                     console->setup(console, NULL) == 0) {
 371                         console->flags |= CON_ENABLED | CON_CONSDEV;
 372                         preferred_console = 0;
 373                 }
 374         }
 375
 376         /*
 377          *      See if this console matches one we selected on
 378          *      the command line.
 379          */
 380         for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) {
 381                 if (strcmp(console_cmdline[i].name, console->name) != 0)
 382                         continue;
 383                 if (console->index >= 0 &&
 384                     console->index != console_cmdline[i].index)
 385                         continue;
 386                 if (console->index < 0)
 387                         console->index = console_cmdline[i].index;
 388                 if (console->setup &&
 389                     console->setup(console, console_cmdline[i].options) != 0)
 390                         break;
 391                 console->flags |= CON_ENABLED;
 392                 console->index = console_cmdline[i].index;
 393                 if (i == preferred_console)
 394                         console->flags |= CON_CONSDEV;
 395                 break;
 396         }
 397
 398         if (!(console->flags & CON_ENABLED))
 399                 return;
 400
 401         /*
 402          *      Put this console in the list - keep the
 403          *      preferred driver at the head of the list.
 404          */
 405         spin_lock_irqsave(&console_lock, flags);
 406         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
 407                 console->next = console_drivers;
 408                 console_drivers = console;
 409         } else {
 410                 console->next = console_drivers->next;
 411                 console_drivers->next = console;
 412         }
 413         if ((console->flags & CON_PRINTBUFFER) == 0)
 414                 goto done;
 415         /*
 416          *      Print out buffered log messages.
 417          */
 418         p = log_start & LOG_BUF_MASK;
 419
 420         for (i=0,j=0; i < log_size; i++) {
 421                 buf[j++] = log_buf[p];
 422                 p = (p+1) & LOG_BUF_MASK;
 423                 if (buf[j-1] != '\n' && i < log_size - 1 && j < sizeof(buf)-1)
 424                         continue;
 425                 buf[j] = 0;
 426                 q = buf;
 427                 len = j;
 428                 if (msg_level < 0) {
 429                         if(buf[0] == '<' &&
 430                                 buf[1] >= '0' &&
 431                                 buf[1] <= '7' &&
 432                                 buf[2] == '>') {
 433                                 msg_level = buf[1] - '0';
 434                                 q = buf + 3;
 435                                 len -= 3;
 436                         } else
 437                         {
 438                                 msg_level = default_message_loglevel;
 439                         }
 440                 }
 441                 if (msg_level < console_loglevel)
 442                         console->write(console, q, len);
 443                 if (buf[j-1] == '\n')
 444                         msg_level = -1;
 445                 j = 0;
 446         }
 447 done:
 448         spin_unlock_irqrestore(&console_lock, flags);
 449 }
 450
 451
 452 int unregister_console(struct console * console)
 453 {
 454         struct console *a,*b;
 455         unsigned long flags;
 456         int res = 1;
 457
 458         spin_lock_irqsave(&console_lock, flags);
 459         if (console_drivers == console) {
 460                 console_drivers=console->next;
 461                 res = 0;
 462         } else
 463         {
 464                 for (a=console_drivers->next, b=console_drivers ;
 465                      a; b=a, a=b->next) {
 466                         if (a == console) {
 467                                 b->next = a->next;
 468                                 res = 0;
 469                                 break;
 470                         }
 471                 }
 472         }
 473
 474         /* If last console is removed, we re-enable picking the first
 475          * one that gets registered. Without that, pmac early boot console
 476          * would prevent fbcon from taking over.
 477          */
 478         if (console_drivers == NULL)
 479                 preferred_console = -1;
 480
 481
 482         spin_unlock_irqrestore(&console_lock, flags);
 483         return res;
 484 }
 485
 486 /*
 487  * Write a message to a certain tty, not just the console. This is used for
 488  * messages that need to be redirected to a specific tty.
 489  * We don't put it into the syslog queue right now maybe in the future if
 490  * really needed.
 491  */
 492 void tty_write_message(struct tty_struct *tty, char *msg)
 493 {
 494         if (tty && tty->driver.write)
 495                 tty->driver.write(tty, 0, msg, strlen(msg));
 496         return;
 497 }