minix/drivers/system/log/diag.c

   1 /* This file handle diagnostic output that is sent to the LOG driver. Output
   2  * can be either from the kernel, or from other system processes. Output from
   3  * system processes is also routed through the kernel. The kernel notifies
   4  * this driver with a SIGKMESS signal if any messages are available.
   5  *
   6  * Changes:
   7  *      21 July 2005:   Created  (Jorrit N. Herder)
   8  */
   9
  10 #include "log.h"
  11
  12 #include <assert.h>
  13
  14 /*==========================================================================*
  15  *                              do_new_kmess                                *
  16  *==========================================================================*/
  17 void do_new_kmess(void)
  18 {
  19 /* Notification for a new kernel message. */
  20   static struct kmessages *kmess;               /* entire kmess structure */
  21   static char print_buf[_KMESS_BUF_SIZE];       /* copy new message here */
  22   int i, r, next, bytes;
  23   static int prev_next = 0;
  24
  25   kmess = get_minix_kerninfo()->kmessages;
  26
  27   /* Print only the new part. Determine how many new bytes there are with
  28    * help of the current and previous 'next' index. Note that the kernel
  29    * buffer is circular. This works fine if less than KMESS_BUF_SIZE bytes
  30    * are new data; else we miss % KMESS_BUF_SIZE here. Obtain 'next' only
  31    * once, since we are operating on shared memory here.
  32    * Check for size being positive, the buffer might as well be emptied!
  33    */
  34   next = kmess->km_next;
  35   bytes = ((next + _KMESS_BUF_SIZE) - prev_next) % _KMESS_BUF_SIZE;
  36   if (bytes > 0) {
  37       r= prev_next;                             /* start at previous old */
  38       i=0;
  39       while (bytes > 0) {
  40           print_buf[i] = kmess->km_buf[(r%_KMESS_BUF_SIZE)];
  41           bytes --;
  42           r ++;
  43           i ++;
  44       }
  45       /* Now terminate the new message and save it in the log. */
  46       print_buf[i] = 0;
  47       log_append(print_buf, i);
  48   }
  49
  50   /* Almost done, store 'next' so that we can determine what part of the
  51    * kernel messages buffer to print next time a notification arrives.
  52    */
  53   prev_next = next;
  54 }