xnu-7195.60.75.tar.gz

[apple/xnu.git] / osfmk / man / vm_wire.html

<h2>vm_wire</h2>
<hr>
<p>
<strong>Function</strong> - Modify the target region's paging characteristics.
<h3>SYNOPSIS</h3>
<pre>
<strong>kern_return_t   vm_wire</strong>
                <strong>(host_priv_t</strong>                               <var>host</var>,
                 <strong>vm_task_t</strong>                          <var>target_task</var>,
                 <strong>vm_address_t</strong>                           <var>address</var>,
                 <strong>vm_size_t</strong>                                 <var>size</var>,
                 <strong>vm_prot_t</strong>                         <var>wired_access</var><strong>);</strong>
</pre>
<h3>PARAMETERS</h3>
<dl>
<p>
<dt> <var>host</var> 
<dd>
[in host-control send right]
The control port for the host for which
information is to be obtained.
<p>
<dt> <var>target_task</var> 
<dd>
[in task send right]
The port for the task whose address space contains 
the region.
<p>
<dt> <var>address</var> 
<dd>
[in scalar]
The starting address for the region.
<p>
<dt> <var>size</var> 
<dd>
[in scalar]
The number of bytes in the region.
<p>
<dt> <var>wired_access</var> 
<dd>
[in scalar]
The pageability of the region. The following values cause
the region to be wired and protected as specified
(values may be combined):
<dl>
<dt> <strong>VM_PROT_READ</strong>
<dt> <strong>VM_PROT_WRITE</strong>
<dt> <strong>VM_PROT_execute</strong>
</dl>
<p>
The following value causes the region to be unwired (made pageable):
<dl>
<dt> <strong>VM_PROT_NONE</strong>
</dl>
</dl>
<h3>DESCRIPTION</h3>
<p>
The <strong>vm_wire</strong> function sets the pageability privileges
for a region within the 
specified task's address space.  <var>wired_access</var> specifies the types
of accesses to 
the memory region which must not suffer from (internal) faults
of any kind after 
this call returns.  A non-null <var>wired_access</var> value indicates that
the page is to be 
"wired" into memory; a null value indicates "un-wiring".  The kernel maintains 
for the region a count of the number of times the region is wired.  A page is 
wired into physical memory if any task accessing it has a non-zero wired count 
for the page.
<p>
The region starts at the beginning of the virtual page containing
<var>address</var>; it ends at the end of the virtual page containing 
<var>address</var> + <var>size</var> - 1.  Because of this 
rounding to virtual page boundaries, the amount of memory affected may be 
greater than <var>size</var>.  Use <strong>host_page_size</strong> to find the current 
virtual page size.
<h3>NOTES</h3>
<p>
This interface is machine word length specific because of the virtual address
parameter.
<h3>RETURN VALUES</h3>
<dl>
<p>
<dt> <strong>KERN_INVALID_ADDRESS</strong>
<dd>
The address is illegal or specifies a non-allocated region.
</dl>
<h3>RELATED INFORMATION</h3>
<p>
Functions:
<a href="thread_wire.html"><strong>thread_wire</strong></a>.