VM._assert(isPageAligned(address) && isPageMultiple(size)); return VM_SysCall.sysMMapErrno(address,size,prot,flags,-1,0);
VM._assert(isPageAligned(address) && isPageMultiple(size) && isPageMultiple(offset)); return VM_SysCall.sysMMapErrno(address,Extent.fromIntSignExtend(size), prot, flags, fd, offset);
  public static Address mmap(Address address, Extent size, int prot, int flags) {    if (VM.VerifyAssertions)      VM._assert(isPageAligned(address) && isPageMultiple(size));    return VM_SysCall.sysMMapErrno(address,size,prot,flags,-1,0);  }