maps-fault.c

   1 #include <stdlib.h>
   2 #include <string.h>
   3 #include <sys/mman.h>
   4 #include <sys/types.h>
   5 #include <sys/stat.h>
   6 #include "arch.h"
   7 #include "maps.h"
   8 #include "random.h"
   9
  10 /*
  11  * Routine to perform various kinds of write operations to a mapping
  12  * that we created.
  13  */
  14 void dirty_mapping(struct map *map)
  15 {
  16         char *p = map->ptr;
  17         unsigned int i;
  18         unsigned int num_pages = map->size / page_size;
  19
  20         /* Check mapping is writable, or we'll segv.
  21          * TODO: Perhaps we should do that, and trap it, mark it writable,
  22          * then reprotect after we dirtied it ? */
  23         if (!(map->prot & PROT_WRITE))
  24                 return;
  25
  26         switch (rand() % 6) {
  27         case 0:
  28                 /* Just fault in one page. */
  29                 p[rand() % map->size] = rand();
  30                 break;
  31
  32         case 1:
  33                 /* fault in the whole mapping. */
  34                 for (i = 0; i < map->size; i += page_size)
  35                         p[i] = rand();
  36                 break;
  37
  38         case 2:
  39                 /* every other page. */
  40                 for (i = 0; i < map->size; i += (page_size * 2))
  41                         p[i] = rand();
  42                 break;
  43
  44         case 3:
  45                 /* whole mapping in reverse */
  46                 for (i = (map->size - page_size); i > 0; i -= page_size)
  47                         p[i] = rand();
  48                 break;
  49
  50         case 4:
  51                 /* fault in a random set of map->size pages. (some may be faulted >once) */
  52                 for (i = 0; i < num_pages; i++)
  53                         p[(rand() % (num_pages + 1)) * page_size] = rand();
  54                 break;
  55
  56         case 5:
  57                 /* fault in the last page in a mapping
  58                  * Fill it with ascii, in the hope we do something like
  59                  * a strlen and go off the end. */
  60                 memset((void *) p + (map->size - page_size), 'A', page_size);
  61                 break;
  62         }
  63 }