VM_MMAP_GUARD_SIZE
len = VM_MMAP_GUARD_SIZE + totalsize + VM_MMAP_GUARD_SIZE;
baseaddr = ptr + VM_MMAP_GUARD_SIZE;
len2 = VM_MMAP_GUARD_SIZE + len + VM_MMAP_GUARD_SIZE;
ptr = mmap(base + VM_MMAP_GUARD_SIZE, len, PROT_RW, flags, fd, 0);