anchor.diff:                 (addr (+ +physical-map-base+ (ash frame 12))))
             (dotimes (i 512)
               (setf (sys.int::memref-unsigned-byte-64 addr i) 0))
  -          (setf (sys.int::memref-unsigned-byte-64 pdp pdpe) (logior (ash frame 12)
  -                                                                    +page-table-present+
  -                                                                    +page-table-write+))))
  -      (let ((pdir (+ +physical-map-base+ (logand (sys.int::memref-unsigned-byte-64 pdp pdpe) +page-table-address-mask+))))
  +          (setf (page-table-entry pdp pdpe) (logior (ash frame 12)
  +                                                    +page-table-present+
  +                                                    +page-table-write+))))
  +      (let ((pdir (+ +physical-map-base+ (logand (page-table-entry pdp pdpe) +page-table-address-mask+))))
           (when (not (page-present-p pdir pde))
             ;; No PT. Allocate one.
             (when (not allocate)
  
positive.code:                                     addr)
                 (or (disk-await-request *pager-disk-request*)
                     (panic "Unable to read page from disk"))))
          (setf (sys.int::memref-unsigned-byte-64 pte 0) (logior (ash frame 12)
                                                                 +page-table-present+
                                                                 (if (logtest sys.int::+block-map-writable+ block-info)
                                                                     +page-table-write+
                                                                     0)))
          #+(or)(debug-print-line "WFP " address " block " block-info " mapped to " (sys.int::memref-unsigned-byte-64 pte 0))
          ;; Perform stack aliasing at the PML4 level.
          (when (eql (ldb (byte sys.int::+address-tag-size+ sys.int::+address-tag-shift+) address)
                     sys.int::+address-tag-stack+)
  
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 pdir pde) (logior (ash frame 12)
                                                        +page-table-present+
                                                        +page-table-write+))))
          (let ((pt (+ +physical-map-base+ (logand (page-table-entry pdir pde) +page-table-address-mask+))))
            (+ pt (* pte 8)))))))
  
  (defun insert-into-block-cache (block-id addr)
  