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NAME

     pmap_extract, pmap_extract_and_hold - map a virtual address to a physical
     page

SYNOPSIS

     #include <sys/param.h>
     #include <vm/vm.h>
     #include <vm/pmap.h>

     vm_paddr_t
     pmap_extract(pmap_t pmap, vm_offset_t va);

     vm_paddr_t
     pmap_extract_and_hold(pmap_t pmap, vm_offset_t va, vm_prot_t prot);

DESCRIPTION

     The pmap_extract() function maps a virtual address to a physical page.
     In certain situations, callers may use pmap_extract_and_hold() instead,
     to ensure that the returned page is held.

     The pmap_extract_and_hold() function maps a virtual address to a physical
     page, and atomically holds the returned page for use by the caller, only
     if the mapping permits the given page protection.

IMPLEMENTATION NOTES

     Currently, the page protection requested by the caller is not verified.

     In the pmap_extract_and_hold() function, the Giant lock is held for the
     duration of the call to ensure that only a single caller is present.

RETURN VALUES

     The pmap_extract() function will return the physical page address
     associated with the virtual address va inside the physical map pmap.  If
     the mapping does not exist, or if the pmap parameter is NULL, then NULL
     will be returned.

     The pmap_extract_and_hold() function will return the physical page
     address associated with the virtual address va inside the physical map
     pmap.  If the mapping does not exist, the result is a no-op, and NULL
     will be returned.

SEE ALSO

     mutex(9), pmap(9)

AUTHORS

     The pmap_extract_and_hold() function was implemented by Alan L. Cox
     〈alc@imimic.com〉.  This manual page was written by Bruce M Simpson
     〈bms@spc.org〉.