cvs commit: src/sys/amd64/amd64 pmap.c

[Alan Cox]

alc         2008-06-01 07:37:18 UTC

  FreeBSD src repository

  Modified files:
    sys/amd64/amd64      pmap.c 
  Log:
  SVN rev 179471 on 2008-06-01 07:36:59Z by alc
  
  Correct an error in pmap_promote_pde() that may result in an errant
  promotion within the kernel's address space.  Specifically,
  pmap_promote_pde() is only called when the page table page (PTP) that
  is referenced by the given PDE has a full "use count", i.e., its
  wire_count is 512.  Although this guarantees for a user address space
  that all 512 PTEs in the PTP hold valid mappings, the same is not true
  of the kernel's address space.  A kernel PTP always has a use count of
  512 regardless of the state of the PTEs.  Therefore,
  pmap_promote_pde() should not assume (or assert) that the first PTE in
  the PTP is valid.
  
  Revision  Changes    Path
  1.619     +3 -5      src/sys/amd64/amd64/pmap.c