anchor.diff:        ;; Examine the page table, if there's a present entry then the page
         ;; was mapped while acquiring the VM lock. Just return.
         (when (page-present-p pte 0)
  -        #+(or)(debug-print-line "WFP " address " block " block-info " already mapped " (sys.int::memref-unsigned-byte-64 pte 0))
  +        #+(or)(debug-print-line "WFP " address " block " block-info " already mapped " (page-table-entry pte 0))
           (return-from wait-for-page t))
         ;; Note that this test is done after the pte test. this is a hack to make
         ;; runtime-allocated stacks work before allocate-stack actually modifies the
  
positive.code:           (cond ((or (not (logtest sys.int::+block-map-present+ flags))
                       (logtest sys.int::+block-map-zero-fill+ flags))
                   ;; Page going away, but it's ok. It'll be back, zero-filled.
                   #+(or)(debug-print-line "  flush page " (+ base (* i #x1000)) "  " (sys.int::memref-unsigned-byte-64 pte 0))
                   (release-vm-page (ash (sys.int::memref-unsigned-byte-64 pte 0) -12))
                   (setf (sys.int::memref-unsigned-byte-64 pte 0) 0))
                  ((logtest sys.int::+block-map-writable+ flags)
                   ;; Mark writable.
                   (setf (sys.int::memref-unsigned-byte-64 pte 0) (logior (sys.int::memref-unsigned-byte-64 pte 0)
                                                                          +page-table-write+)))
                  (t
                   ;; Mark read-only.
                   (setf (sys.int::memref-unsigned-byte-64 pte 0) (logand (sys.int::memref-unsigned-byte-64 pte 0)
                                                                          (lognot +page-table-write+))))))))
      (flush-tlb)))
  
  (defun wait-for-page (address)
  
negative.code:              (addr (+ +physical-map-base+ (ash frame 12))))
          (dotimes (i 512)
            (setf (sys.int::memref-unsigned-byte-64 addr i) 0))
          (setf (page-table-entry cr3 pml4e) (logior (ash frame 12)
                                                     +page-table-present+
                                                     +page-table-write+))))
      (let ((pdp (+ +physical-map-base+ (logand (page-table-entry cr3 pml4e) +page-table-address-mask+))))
        (when (not (page-present-p pdp pdpe))
          ;; No PDir. Allocate one.
          (when (not allocate)
  