kernel/printk.c

/* */
This source file includes following definitions.
sys_syslog
printk
register_console
   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  */
  13 
  14 #include <stdarg.h>
  15 
  16 #include <asm/segment.h>
  17 #include <asm/system.h>
  18 
  19 #include <linux/errno.h>
  20 #include <linux/sched.h>
  21 #include <linux/kernel.h>
  22 #include <linux/mm.h>
  23 
  24 #define LOG_BUF_LEN     4096
  25 
  26 static char buf[1024];
  27 
  28 extern void console_print(const char *);
  29 
  30 #define DEFAULT_MESSAGE_LOGLEVEL 7 /* KERN_DEBUG */
  31 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything more serious than KERN_DEBUG */
  32 
  33 unsigned long log_size = 0;
  34 struct wait_queue * log_wait = NULL;
  35 int console_loglevel = DEFAULT_CONSOLE_LOGLEVEL;
  36 
  37 static void (*console_print_proc)(const char *) = 0;
  38 static char log_buf[LOG_BUF_LEN];
  39 static unsigned long log_start = 0;
  40 static unsigned long logged_chars = 0;
  41 
  42 /*
  43  * Commands to sys_syslog:
  44  *
  45  *      0 -- Close the log.  Currently a NOP.
  46  *      1 -- Open the log. Currently a NOP.
  47  *      2 -- Read from the log.
  48  *      3 -- Read up to the last 4k of messages in the ring buffer.
  49  *      4 -- Read and clear last 4k of messages in the ring buffer
  50  *      5 -- Clear ring buffer.
  51  *      6 -- Disable printk's to console
  52  *      7 -- Enable printk's to console
  53  *      8 -- Set level of messages printed to console
  54  */
  55 asmlinkage int sys_syslog(int type, char * buf, int len)
     /*  */
  56 {
  57         unsigned long i, j, count;
  58         int do_clear = 0;
  59         char c;
  60         int error;
  61 
  62         if ((type != 3) && !suser())
  63                 return -EPERM;
  64         switch (type) {
  65                 case 0:         /* Close log */
  66                         return 0;
  67                 case 1:         /* Open log */
  68                         return 0;
  69                 case 2:         /* Read from log */
  70                         if (!buf || len < 0)
  71                                 return -EINVAL;
  72                         if (!len)
  73                                 return 0;
  74                         error = verify_area(VERIFY_WRITE,buf,len);
  75                         if (error)
  76                                 return error;
  77                         cli();
  78                         while (!log_size) {
  79                                 if (current->signal & ~current->blocked) {
  80                                         sti();
  81                                         return -ERESTARTSYS;
  82                                 }
  83                                 interruptible_sleep_on(&log_wait);
  84                         }
  85                         i = 0;
  86                         while (log_size && i < len) {
  87                                 c = *((char *) log_buf+log_start);
  88                                 log_start++;
  89                                 log_size--;
  90                                 log_start &= LOG_BUF_LEN-1;
  91                                 sti();
  92                                 put_fs_byte(c,buf);
  93                                 buf++;
  94                                 i++;
  95                                 cli();
  96                         }
  97                         sti();
  98                         return i;
  99                 case 4:         /* Read/clear last kernel messages */
 100                         do_clear = 1; 
 101                         /* FALL THRU */
 102                 case 3:         /* Read last kernel messages */
 103                         if (!buf || len < 0)
 104                                 return -EINVAL;
 105                         if (!len)
 106                                 return 0;
 107                         error = verify_area(VERIFY_WRITE,buf,len);
 108                         if (error)
 109                                 return error;
 110                         count = len;
 111                         if (count > LOG_BUF_LEN)
 112                                 count = LOG_BUF_LEN;
 113                         if (count > logged_chars)
 114                                 count = logged_chars;
 115                         j = log_start + log_size - count;
 116                         for (i = 0; i < count; i++) {
 117                                 c = *((char *) log_buf+(j++ & (LOG_BUF_LEN-1)));
 118                                 put_fs_byte(c, buf++);
 119                         }
 120                         if (do_clear)
 121                                 logged_chars = 0;
 122                         return i;
 123                 case 5:         /* Clear ring buffer */
 124                         logged_chars = 0;
 125                         return 0;
 126                 case 6:         /* Disable logging to console */
 127                         console_loglevel = 1; /* only panic messages shown */
 128                         return 0;
 129                 case 7:         /* Enable logging to console */
 130                         console_loglevel = DEFAULT_CONSOLE_LOGLEVEL;
 131                         return 0;
 132                 case 8:
 133                         if (len < 1 || len > 8)
 134                                 return -EINVAL;
 135                         console_loglevel = len;
 136                         return 0;
 137         }
 138         return -EINVAL;
 139 }
 140 
 141 
 142 asmlinkage int printk(const char *fmt, ...)
     /*  */
 143 {
 144         va_list args;
 145         int i;
 146         char *msg, *p, *buf_end;
 147         static char msg_level = -1;
 148         long flags;
 149 
 150         save_flags(flags);
 151         cli();
 152         va_start(args, fmt);
 153         i = vsprintf(buf + 3, fmt, args); /* hopefully i < sizeof(buf)-4 */
 154         buf_end = buf + 3 + i;
 155         va_end(args);
 156         for (p = buf + 3; p < buf_end; p++) {
 157                 msg = p;
 158                 if (msg_level < 0) {
 159                         if (
 160                                 p[0] != '<' ||
 161                                 p[1] < '0' || 
 162                                 p[1] > '7' ||
 163                                 p[2] != '>'
 164                         ) {
 165                                 p -= 3;
 166                                 p[0] = '<';
 167                                 p[1] = DEFAULT_MESSAGE_LOGLEVEL - 1 + '0';
 168                                 p[2] = '>';
 169                         } else
 170                                 msg += 3;
 171                         msg_level = p[1] - '0';
 172                 }
 173                 for (; p < buf_end; p++) {
 174                         log_buf[(log_start+log_size) & (LOG_BUF_LEN-1)] = *p;
 175                         if (log_size < LOG_BUF_LEN)
 176                                 log_size++;
 177                         else {
 178                                 log_start++;
 179                                 log_start &= LOG_BUF_LEN-1;
 180                         }
 181                         logged_chars++;
 182                         if (*p == '\n')
 183                                 break;
 184                 }
 185                 if (msg_level < console_loglevel && console_print_proc) {
 186                         char tmp = p[1];
 187                         p[1] = '\0';
 188                         (*console_print_proc)(msg);
 189                         p[1] = tmp;
 190                 }
 191                 if (*p == '\n')
 192                         msg_level = -1;
 193         }
 194         restore_flags(flags);
 195         wake_up_interruptible(&log_wait);
 196         return i;
 197 }
 198 
 199 /*
 200  * The console driver calls this routine during kernel initialization
 201  * to register the console printing procedure with printk() and to
 202  * print any messages that were printed by the kernel before the
 203  * console driver was initialized.
 204  */
 205 void register_console(void (*proc)(const char *))
     /*  */
 206 {
 207         int     i,j;
 208         int     p = log_start;
 209         char    buf[16];
 210         char    msg_level = -1;
 211         char    *q;
 212 
 213         console_print_proc = proc;
 214 
 215         for (i=0,j=0; i < log_size; i++) {
 216                 buf[j++] = log_buf[p];
 217                 p++; p &= LOG_BUF_LEN-1;
 218                 if (buf[j-1] != '\n' && i < log_size - 1 && j < sizeof(buf)-1)
 219                         continue;
 220                 buf[j] = 0;
 221                 q = buf;
 222                 if (msg_level < 0) {
 223                         msg_level = buf[1] - '0';
 224                         q = buf + 3;
 225                 }
 226                 if (msg_level < console_loglevel)
 227                         (*proc)(q);
 228                 if (buf[j-1] == '\n')
 229                         msg_level = -1;
 230                 j = 0;
 231         }
 232 }
/* */
root/kernel/printk.c

DEFINITIONS
