freebsd man page for pmap_extract_and_hold

PMAP_EXTRACT(9) 					   BSD Kernel Developer's Manual					   PMAP_EXTRACT(9)

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.

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>.

BSD
								   July 21, 2003							       BSD