kbind implementation: amd64

• OpenBSD/amd64 has "direct pmap": direct map in VA always maps all PA

• Copy new data into buffer in kernel

• uvm_fault(map, baseva, VM_FAULT_WIRE, VM_PROT_NONE)

  • force copy-on-write resolution

  • force page to be physically in memory and unpageable

  • physical page has "maximal" permissions for mapping

• pmap_extract(map->pmap, baseva, &paddr)

  kva = PMAP_DIRECT_MAP(paddr)

  • get kernel's direct mapped address of the underlying physical page

• bcopy(buffer, kva + offset, len)

  • update the wired-in physical page

• uvm_fault_unwire(map, last_baseva, last_baseva + PAGE_SIZE)

  • permit page to be paged again