maps.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 "list.h"
   8 #include "child.h"
   9 #include "maps.h"
  10 #include "random.h"
  11 #include "shm.h"
  12 #include "trinity.h"    // page_size
  13
  14 /* Walk a list, get a random element */
  15 static struct map * __get_map(struct list_head *head, unsigned int max)
  16 {
  17         struct list_head *node;
  18
  19         unsigned int i, j = 0;
  20
  21         i = rand() % max;
  22
  23         list_for_each(node, head) {
  24                 struct map *m;
  25
  26                 m = (struct map *) node;
  27
  28                 if (i == j)
  29                         return m;
  30                 j++;
  31         }
  32         return NULL;
  33 }
  34
  35 /* Return a pointer a previous mmap() that we did, either during startup,
  36  * or from a fuzz result. */
  37 struct map * get_map(void)
  38 {
  39         struct map *map;
  40         bool local = FALSE;
  41
  42         /* We can get called by child processes, and also during startup by
  43          * the main process when it constructs page_rand etc.
  44          * If we're not running in child context, just do shared mappings.
  45          * because main doesn't have any 'local' mappings.
  46          */
  47         if (this_child != 0) {
  48                 if (shm->num_mappings[this_child] > 0)
  49                         local = rand_bool();
  50         }
  51
  52         if (local == TRUE)
  53                 map = __get_map(&shm->mappings[this_child]->list, shm->num_mappings[this_child]);
  54         else
  55                 map = __get_map(&shared_mappings->list, num_shared_mappings);
  56
  57         return map;
  58 }
  59
  60 static void delete_local_mapping(int childno, struct map *map)
  61 {
  62         list_del(&map->list);
  63         shm->num_mappings[childno]--;
  64 }
  65
  66 /* Called from munmap()'s ->post routine. */
  67 void delete_mapping(int childno, struct map *map)
  68 {
  69         if (map->type == MAP_LOCAL)
  70                 delete_local_mapping(childno, map);
  71
  72         /* Right now, we don't want to delete MAP_GLOBAL mappings */
  73 }
  74
  75 /* used in several sanitise_* functions. */
  76 struct map * common_set_mmap_ptr_len(int childno)
  77 {
  78         struct map *map;
  79
  80         map = (struct map *) shm->a1[childno];
  81         shm->scratch[childno] = (unsigned long) map;    /* Save this for ->post */
  82         if (map == NULL) {
  83                 shm->a1[childno] = 0;
  84                 shm->a2[childno] = 0;
  85                 return NULL;
  86         }
  87
  88         shm->a1[childno] = (unsigned long) map->ptr;
  89         shm->a2[childno] = map->size;           //TODO: Munge this.
  90
  91         return map;
  92 }
  93
  94 /*
  95  * Routine to perform various kinds of write operations to a mapping
  96  * that we created.
  97  */
  98 void dirty_mapping(struct map *map)
  99 {
 100         char *p = map->ptr;
 101         unsigned int i;
 102         unsigned int num_pages = map->size / page_size;
 103
 104         /* Check mapping is writable, or we'll segv.
 105          * TODO: Perhaps we should do that, and trap it, mark it writable,
 106          * then reprotect after we dirtied it ? */
 107         if (!(map->prot & PROT_WRITE))
 108                 return;
 109
 110         switch (rand() % 6) {
 111         case 0:
 112                 /* Just fault in one page. */
 113                 p[rand() % map->size] = rand();
 114                 break;
 115
 116         case 1:
 117                 /* fault in the whole mapping. */
 118                 for (i = 0; i < map->size; i += page_size)
 119                         p[i] = rand();
 120                 break;
 121
 122         case 2:
 123                 /* every other page. */
 124                 for (i = 0; i < map->size; i += (page_size * 2))
 125                         p[i] = rand();
 126                 break;
 127
 128         case 3:
 129                 /* whole mapping in reverse */
 130                 for (i = (map->size - page_size); i > 0; i -= page_size)
 131                         p[i] = rand();
 132                 break;
 133
 134         case 4:
 135                 /* fault in a random set of map->size pages. (some may be faulted >once) */
 136                 for (i = 0; i < num_pages; i++)
 137                         p[(rand() % (num_pages + 1)) * page_size] = rand();
 138                 break;
 139
 140         case 5:
 141                 /* fault in the last page in a mapping
 142                  * Fill it with ascii, in the hope we do something like
 143                  * a strlen and go off the end. */
 144                 memset((void *) p + (map->size - page_size), 'A', page_size);
 145                 break;
 146         }
 147 }