1// Replacement for sys/mman.h which factors out platform differences.
2
3#include <sys/mman.h>
4
5#if defined(VGO_darwin)
6#  define MAP_ANONYMOUS MAP_ANON
7#endif
8
9
10#include <assert.h>
11#include <unistd.h>
12
13// Map a page, then unmap it, then return that address.  That
14// guarantees to give an address which will fault when accessed,
15// without making any assumptions about the layout of the address
16// space.
17
18__attribute__((unused))
19static void* get_unmapped_page(void)
20{
21   void* ptr;
22   int r;
23   long pagesz = sysconf(_SC_PAGE_SIZE);
24   assert(pagesz == 4096 || pagesz == 16384 || pagesz == 65536);
25   ptr = mmap(0, pagesz, PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
26   assert(ptr != (void*)-1);
27   r = munmap(ptr, pagesz);
28   assert(r == 0);
29   return ptr;
30}
31
32