source: branches/minix3-book/kernel/utility.c@ 9

/* This file contains a collection of miscellaneous procedures:
 *   panic:         abort MINIX due to a fatal error
 *   kprintf:       diagnostic output for the kernel 
 *
 * Changes:
 *   Dec 10, 2004   kernel printing to circular buffer  (Jorrit N. Herder)
 * 
 * This file contains the routines that take care of kernel messages, i.e.,
 * diagnostic output within the kernel. Kernel messages are not directly
 * displayed on the console, because this must be done by the output driver. 
 * Instead, the kernel accumulates characters in a buffer and notifies the
 * output driver when a new message is ready. 
 */

#include <minix/com.h>
#include "kernel.h"
#include <stdarg.h>
#include <unistd.h>
#include <stddef.h>
#include <stdlib.h>
#include <signal.h>
#include "proc.h"

#define END_OF_KMESS    -1
FORWARD _PROTOTYPE(void kputc, (int c));

/*===========================================================================*
 *                              panic                                        *
 *===========================================================================*/
PUBLIC void panic(mess,nr)
_CONST char *mess;
int nr;
{
/* The system has run aground of a fatal kernel error. Terminate execution. */
  static int panicking = 0;
  if (panicking ++) return;             /* prevent recursive panics */

  if (mess != NULL) {
        kprintf("\nKernel panic: %s", mess);
        if (nr != NO_NUM) kprintf(" %d", nr);
        kprintf("\n",NO_NUM);
  }

  /* Abort MINIX. */
  prepare_shutdown(RBT_PANIC);
}

/*===========================================================================*
 *                              kprintf                                      *
 *===========================================================================*/
PUBLIC void kprintf(const char *fmt, ...)       /* format to be printed */
{
  int c;                                        /* next character in fmt */
  int d;
  unsigned long u;                              /* hold number argument */
  int base;                                     /* base of number arg */
  int negative = 0;                             /* print minus sign */
  static char x2c[] = "0123456789ABCDEF";       /* nr conversion table */
  char ascii[8 * sizeof(long) / 3 + 2];         /* string for ascii number */
  char *s = NULL;                               /* string to be printed */
  va_list argp;                                 /* optional arguments */
  
  va_start(argp, fmt);                          /* init variable arguments */

  while((c=*fmt++) != 0) {

      if (c == '%') {                           /* expect format '%key' */
          switch(c = *fmt++) {                  /* determine what to do */

          /* Known keys are %d, %u, %x, %s, and %%. This is easily extended 
           * with number types like %b and %o by providing a different base.
           * Number type keys don't set a string to 's', but use the general
           * conversion after the switch statement.
           */ 
          case 'd':                             /* output decimal */
              d = va_arg(argp, signed int);
              if (d < 0) { negative = 1; u = -d; }  else { u = d; }
              base = 10;
              break;
          case 'u':                             /* output unsigned long */
              u = va_arg(argp, unsigned long);
              base = 10;
              break;
          case 'x':                             /* output hexadecimal */
              u = va_arg(argp, unsigned long);
              base = 0x10;
              break;
          case 's':                             /* output string */
              s = va_arg(argp, char *);
              if (s == NULL) s = "(null)";
              break;
          case '%':                             /* output percent */
              s = "%";                           
              break;                    

          /* Unrecognized key. */
          default:                              /* echo back %key */
              s = "%?";                         
              s[1] = c;                         /* set unknown key */
          }

          /* Assume a number if no string is set. Convert to ascii. */
          if (s == NULL) {
              s = ascii + sizeof(ascii)-1;
              *s = 0;                   
              do {  *--s = x2c[(u % base)]; }   /* work backwards */
              while ((u /= base) > 0); 
          }

          /* This is where the actual output for format "%key" is done. */
          if (negative) kputc('-');             /* print sign if negative */
          while(*s != 0) { kputc(*s++); }       /* print string/ number */
          s = NULL;                             /* reset for next round */
      }
      else {
          kputc(c);                             /* print and continue */
      }
  }
  kputc(END_OF_KMESS);                          /* terminate output */
  va_end(argp);                                 /* end variable arguments */
}

/*===========================================================================*
 *                              kputc                                        *
 *===========================================================================*/
PRIVATE void kputc(c)
int c;                                  /* character to append */
{
/* Accumulate a single character for a kernel message. Send a notification
 * to the output driver if an END_OF_KMESS is encountered. 
 */
  if (c != END_OF_KMESS) {
      kmess.km_buf[kmess.km_next] = c;  /* put normal char in buffer */
      if (kmess.km_size < KMESS_BUF_SIZE)
          kmess.km_size += 1;           
      kmess.km_next = (kmess.km_next + 1) % KMESS_BUF_SIZE;
  } else {
      send_sig(OUTPUT_PROC_NR, SIGKMESS);
  }
}