drivers/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 extern struct minix_kerninfo *_minix_kerninfo;
  15
  16 /*==========================================================================*
  17  *                              do_new_kmess                                *
  18  *==========================================================================*/
  19 void do_new_kmess(void)
  20 {
  21 /* Notification for a new kernel message. */
  22   static struct kmessages *kmess;               /* entire kmess structure */
  23   static char print_buf[_KMESS_BUF_SIZE];       /* copy new message here */
  24   int i, r, next, bytes;
  25   static int prev_next = 0;
  26
  27   assert(_minix_kerninfo);
  28   kmess = _minix_kerninfo->kmessages;
  29
  30   /* Print only the new part. Determine how many new bytes there are with
  31    * help of the current and previous 'next' index. Note that the kernel
  32    * buffer is circular. This works fine if less than KMESS_BUF_SIZE bytes
  33    * are new data; else we miss % KMESS_BUF_SIZE here. Obtain 'next' only
  34    * once, since we are operating on shared memory here.
  35    * Check for size being positive, the buffer might as well be emptied!
  36    */
  37   next = kmess->km_next;
  38   bytes = ((next + _KMESS_BUF_SIZE) - prev_next) % _KMESS_BUF_SIZE;
  39   if (bytes > 0) {
  40       r= prev_next;                             /* start at previous old */
  41       i=0;
  42       while (bytes > 0) {
  43           print_buf[i] = kmess->km_buf[(r%_KMESS_BUF_SIZE)];
  44           bytes --;
  45           r ++;
  46           i ++;
  47       }
  48       /* Now terminate the new message and save it in the log. */
  49       print_buf[i] = 0;
  50       log_append(print_buf, i);
  51   }
  52
  53   /* Almost done, store 'next' so that we can determine what part of the
  54    * kernel messages buffer to print next time a notification arrives.
  55    */
  56   prev_next = next;
  57 }