- for (size = 0x40000000; size > 0; size = ((size >> 3) * 7) & ~0xFFF) {
- minefield_region = VirtualAlloc(NULL, size,
- MEM_RESERVE, PAGE_NOACCESS);
- if (minefield_region)
- break;
- }
- minefield_size = size;
-
- /*
- * Firstly, allocate a section of that to be the admin block.
- * We'll need a two-byte field for each page.
- */
- minefield_admin = minefield_region;
- minefield_npages = minefield_size / PAGESIZE;
- admin_size = (minefield_npages * 2 + PAGESIZE - 1) & ~(PAGESIZE - 1);
- minefield_npages = (minefield_size - admin_size) / PAGESIZE;
- minefield_pages = (char *) minefield_region + admin_size;
-
- /*
- * Commit the admin region.
- */
- VirtualAlloc(minefield_admin, minefield_npages * 2,
- MEM_COMMIT, PAGE_READWRITE);
-
- /*
- * Mark all pages as unused (0xFFFF).
- */
- for (i = 0; i < minefield_npages; i++)
- minefield_admin[i] = 0xFFFF;
-
- /*
- * Hide the admin region.
- */
- minefield_admin_hide(1);
-
- minefield_initialised = 1;
-}
-
-static void minefield_bomb(void)
-{
- div(1, *(int *) minefield_pages);
-}
-
-static void *minefield_alloc(int size)
-{
- int npages;
- int pos, lim, region_end, region_start;
- int start;
- int i;
-
- npages = (size + PAGESIZE - 1) / PAGESIZE;
-
- minefield_admin_hide(0);
-
- /*
- * Search from current position until we find a contiguous
- * bunch of npages+2 unused pages.
- */
- pos = minefield_curpos;
- lim = minefield_npages;
- while (1) {
- /* Skip over used pages. */
- while (pos < lim && minefield_admin[pos] != 0xFFFF)
- pos++;
- /* Count unused pages. */
- start = pos;
- while (pos < lim && pos - start < npages + 2 &&
- minefield_admin[pos] == 0xFFFF)
- pos++;
- if (pos - start == npages + 2)
- break;
- /* If we've reached the limit, reset the limit or stop. */
- if (pos >= lim) {
- if (lim == minefield_npages) {
- /* go round and start again at zero */
- lim = minefield_curpos;
- pos = 0;
- } else {
- minefield_admin_hide(1);
- return NULL;
- }
- }
- }
-
- minefield_curpos = pos - 1;
-
- /*
- * We have npages+2 unused pages starting at start. We leave
- * the first and last of these alone and use the rest.
- */
- region_end = (start + npages + 1) * PAGESIZE;
- region_start = region_end - size;
- /* FIXME: could align here if we wanted */
-
- /*
- * Update the admin region.
- */
- for (i = start + 2; i < start + npages - 1; i++)
- minefield_admin[i] = 0xFFFE; /* used but no region starts here */
- minefield_admin[start + 1] = region_start % PAGESIZE;
-
- minefield_admin_hide(1);
-
- VirtualAlloc((char *) minefield_pages + region_start, size,
- MEM_COMMIT, PAGE_READWRITE);
- return (char *) minefield_pages + region_start;
-}
-
-static void minefield_free(void *ptr)
-{
- int region_start, i, j;