gistfile1.txt

[samuel@Dahlia:~/Projects/objection][master*]$ ./a.out 
page 0: 0x100021000
page 0: 0x100022000
^Z
[1]+  Stopped                 ./a.out
[samuel@Dahlia:~/Projects/objection][master*]$ vmmap a.out
Virtual Memory Map of process 31789 (a.out)
Output report format:  2.2  -- 64-bit process

==== Non-writable regions for process 31789
__TEXT                 0000000100000000-0000000100001000 [    4K] r-x/rwx SM=COW  /Users/samuel/Projects/objection/a.out
__LINKEDIT             0000000100002000-0000000100003000 [    4K] r--/rwx SM=COW  /Users/samuel/Projects/objection/a.out
STACK GUARD            0000000100003000-0000000100004000 [    4K] ---/rwx SM=NUL  
STACK GUARD            0000000100005000-0000000100007000 [    8K] ---/rwx SM=NUL  
STACK GUARD            0000000100012000-0000000100014000 [    8K] ---/rwx SM=NUL  
STACK GUARD            000000010001f000-0000000100020000 [    4K] ---/rwx SM=NUL  
MALLOC (admin)         0000000100020000-0000000100021000 [    4K] r--/rwx SM=PRV  
STACK GUARD            00007fff5bc00000-00007fff5f400000 [ 56.0M] ---/rwx SM=NUL  
__TEXT                 00007fff5fc00000-00007fff5fc3c000 [  240K] r-x/rwx SM=COW  /usr/lib/dyld
__LINKEDIT             00007fff5fc7b000-00007fff5fc8f000 [   80K] r--/rwx SM=COW  /usr/lib/dyld
__TEXT                 00007fff80642000-00007fff80647000 [   20K] r-x/r-x SM=COW  /usr/lib/system/libmathCommon.A.dylib
__TEXT                 00007fff8806c000-00007fff8822d000 [ 1796K] r-x/r-x SM=COW  /usr/lib/libSystem.B.dylib
__LINKEDIT             00007fff89297000-00007fff8b1dd000 [ 31.3M] r--/r-- SM=COW  /usr/lib/system/libmathCommon.A.dylib

==== Writable regions for process 31789
__DATA                 0000000100001000-0000000100002000 [    4K] rw-/rwx SM=PRV  /Users/samuel/Projects/objection/a.out
MALLOC (admin)         0000000100004000-0000000100005000 [    4K] rw-/rwx SM=PRV  
MALLOC (admin)         0000000100007000-0000000100012000 [   44K] rw-/rwx SM=PRV  
MALLOC (admin)         0000000100014000-000000010001f000 [   44K] rw-/rwx SM=PRV  
VM_ALLOCATE            0000000100021000-0000000100022000 [    4K] rw-/rwx SM=NUL  
Memory tag=240         0000000100022000-0000000100023000 [    4K] rw-/rwx SM=NUL  
MALLOC_TINY            0000000100100000-0000000100200000 [ 1024K] rw-/rwx SM=PRV  DefaultMallocZone_0x100004000
MALLOC_SMALL           0000000100800000-0000000101000000 [ 8192K] rw-/rwx SM=PRV  DefaultMallocZone_0x100004000
Stack                  00007fff5f400000-00007fff5fc00000 [ 8192K] rw-/rwx SM=PRV  thread 0
__DATA                 00007fff5fc3c000-00007fff5fc7b000 [  252K] rw-/rwx SM=COW  /usr/lib/dyld
__DATA                 00007fff710c3000-00007fff710e6000 [  140K] rw-/rwx SM=COW  /usr/lib/libSystem.B.dylib

==== Legend
SM=sharing mode:  
	COW=copy_on_write PRV=private NUL=empty ALI=aliased 
	SHM=shared ZER=zero_filled S/A=shared_alias

==== Summary for process 31789
ReadOnly portion of Libraries: Total=33.4M resident=6064K(18%) swapped_out_or_unallocated=27.4M(82%)
Writable regions: Total=17.1M written=64K(0%) resident=64K(0%) swapped_out=0K(0%) unallocated=17.0M(100%)

REGION TYPE             [ VIRTUAL]
===========             [ =======]
MALLOC                  [   9312K]
Memory tag=240          [      4K]
STACK GUARD             [   56.0M]
Stack                   [   8192K]
VM_ALLOCATE             [      4K]
__DATA                  [    396K]
__LINKEDIT              [   31.4M]
__TEXT                  [   2060K]

testmem.c

#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <mach/vm_statistics.h>

#define SIZE 4096

int main(int argc, char **argv, char **envp) {
  int i;
  void *page = NULL;

  /* Just pass -1 as the fd */
  page = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
  printf("page %i: %p\n", i, page);

  /* Use special Mach page tag */
  page = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, VM_MAKE_TAG(240), 0);
  printf("page %i: %p\n", i, page);

  for (;;) sleep(1);
}