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