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study/sabre/os/files/ProtectedMode/DPMI1.0Spec/api/310602.html

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+<h2>Mark Real Mode Region as Pageable
+<img src="../0.9.gif" alt="[0.9]" width=22 height=17></h2>
+
+Advises the DPMI host that the specified memory below the 1 MB
+boundary may be paged to disk.<p>
+
+<b>Call With</b><br>
+<img src="r/ax+bx+cx+si+di.gif" alt="" width=245 height=59><br>
+
+AX     = 0602H<br>
+BX:CX  = starting linear address of memory to mark as
+pageable<br>
+SI:DI  = size of region to be marked (bytes)<p>
+
+<b>Returns</b><br>
+<img src="r/ax+c.gif" alt="" width=245 height=59><br>
+
+<i>if function successful</i><br>
+Carry flag = clear<p>
+
+<i>if function unsuccessful</i><br>
+Carry flag = set<br>
+AX     = <a href="errors.html">error code</a>
+
+<table border=1 cellspacing=0 cellpadding=4>
+
+<tr><td>8002H</td><td>invalid state (region already marked as pageable)</td></tr>
+<tr><td>8025H</td><td>invalid linear address (region is above 1 MB boundary)</td></tr>
+</table>
+
+<h2>Notes</h2><ul>
+
+
+<li>If the function returns an error, none of the memory has been
+marked as pageable.<p>
+
+<li>If the specified region overlaps part of a page at the beginning
+or end of the region, the page(s) will not be marked as pageable.<p>
+
+<li>Pageability information for a real mode region is maintained as a
+binary state, not a count.  Therefore, multiple calls to this function
+for the same region have no effect.<p>
+
+<li>For compatibility with DPMI version 0.9 hosts, a client must call
+the Relock Real Mode Region function (<a href="310603.html">Int 31H
+Function 0603H</a>) to relock the memory region before terminating.
+Memory that remains unlocked after the client has terminated could
+result in fatal page faults when another program is executed in the
+same address space.  DPMI 1.0 hosts automatically relock real mode
+memory at client termination.<p>
+
+<li>Under some DPMI hosts, all conventional memory may be locked by
+default.  If a protected mode program is using memory in the first
+megabyte of address space, it is recommended that this function be
+used to turn off automatic page locking for regions of memory that
+will not be touched at interrupt time.<p>
+
+<li>The client must not mark memory as pageable in regions that it
+does not own; i.e. it may only mark as pageable memory that it has
+previously allocated with <a href="310100.html">Int 31H Function
+0100H</a> or by a direct call to DOS via the translation functions.
+For example, marking all free DOS memory as pageable under some DPMI
+hosts could cause a page fault to occur while inside of DOS, resulting
+in a crash.  Also, a client should not mark the DPMI host data area as
+pageable.<p>
+
+<li>Note that address space marked as pageable by this function can
+still be locked using the Lock Linear Region function (<a
+href="310600.html">Int 31H Function 0600H</a>).  This function is just
+an advisory service to allow memory that does not need to be locked to
+be paged out; it disables any automatic locking of real mode memory
+performed by the DPMI host.<p>
+
+<li>This function is ignored by DPMI implementations that do not
+support virtual memory; the function will return the Carry flag clear
+to indicate success, but has no other effect.  DPMI hosts which
+support virtual memory may also choose to ignore this function, but
+such hosts must be able to handle page faults transparently at
+arbitrary points during a client's execution, including within
+interrupt and exception handlers.<p>
+
+</ul>
+
+