209 lines
7.5 KiB
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209 lines
7.5 KiB
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<title>munmap</title>
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<basefont size="3"> <a name="munmap"></a> <a name="tag_03_400"></a><!-- munmap -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_400_01"></a>NAME</h4>
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<blockquote>munmap - unmap pages of memory</blockquote>
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<h4><a name="tag_03_400_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('MF')">MF|SHM</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/sys/mman.h.html">sys/mman.h</a>><br>
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<br>
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int munmap(void *</tt><i>addr</i><tt>, size_t</tt> <i>len</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border=
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"0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_400_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>munmap</i>() function shall remove any mappings for those entire pages containing any part of the address space of the
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process starting at <i>addr</i> and continuing for <i>len</i> bytes. Further references to these pages shall result in the
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generation of a SIGSEGV signal to the process. If there are no mappings in the specified address range, then <i>munmap</i>() has no
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effect.</p>
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<p>The implementation shall require that <i>addr</i> be a multiple of the page size {PAGESIZE}.</p>
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<p>If a mapping to be removed was private, any modifications made in this address range shall be discarded.</p>
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<p><sup>[<a href="javascript:open_code('ML')">ML|MLR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Any memory locks (see <a href="mlock.html"><i>mlock</i>()</a> and <a href="mlockall.html"><i>mlockall</i>()</a> ) associated with
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this address range shall be removed, as if by an appropriate call to <a href="../functions/munlock.html"><i>munlock</i>()</a>. <img
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src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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<p><sup>[<a href="javascript:open_code('TYM')">TYM</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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If a mapping removed from a typed memory object causes the corresponding address range of the memory pool to be inaccessible by any
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process in the system except through allocatable mappings (that is, mappings of typed memory objects opened with the
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POSIX_TYPED_MEM_MAP_ALLOCATABLE flag), then that range of the memory pool shall become deallocated and may become available to
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satisfy future typed memory allocation requests.</p>
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<p>A mapping removed from a typed memory object opened with the POSIX_TYPED_MEM_MAP_ALLOCATABLE flag shall not affect in any way
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the availability of that typed memory for allocation. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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<p>The behavior of this function is unspecified if the mapping was not established by a call to <a href=
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"../functions/mmap.html"><i>mmap</i>()</a>.</p>
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</blockquote>
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<h4><a name="tag_03_400_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, <i>munmap</i>() shall return 0; otherwise, it shall return -1 and set <i>errno</i> to indicate the
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error.</p>
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</blockquote>
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<h4><a name="tag_03_400_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>munmap</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd>Addresses in the range [<i>addr</i>,<i>addr</i>+<i>len</i>) are outside the valid range for the address space of a
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process.</dd>
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<dt>[EINVAL]</dt>
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<dd>The <i>len</i> argument is 0.</dd>
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<dt>[EINVAL]</dt>
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<dd>The <i>addr</i> argument is not a multiple of the page size as returned by <a href=
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"../functions/sysconf.html"><i>sysconf</i>()</a>.</dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_400_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_400_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>The <i>munmap</i>() function is only supported if the Memory Mapped Files option or the Shared Memory Objects option is
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supported.</p>
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</blockquote>
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<h4><a name="tag_03_400_08"></a>RATIONALE</h4>
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<blockquote>
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<p>The <i>munmap</i>() function corresponds to SVR4, just as the <a href="../functions/mmap.html"><i>mmap</i>()</a> function
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does.</p>
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<p>It is possible that an application has applied process memory locking to a region that contains shared memory. If this has
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occurred, the <i>munmap</i>() call ignores those locks and, if necessary, causes those locks to be removed.</p>
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</blockquote>
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<h4><a name="tag_03_400_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_400_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="mlock.html"><i>mlock</i>()</a> , <a href="mlockall.html"><i>mlockall</i>()</a> , <a href="mmap.html"><i>mmap</i>()</a>
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, <a href="posix_typed_mem_open.html"><i>posix_typed_mem_open</i>()</a> , <a href="sysconf.html"><i>sysconf</i>()</a> , the Base
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Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/signal.h.html"><i><signal.h></i></a>, <a href=
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"../basedefs/sys/mman.h.html"><i><sys/mman.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_400_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 4, Version 2.</p>
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</blockquote>
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<h4><a name="tag_03_400_12"></a>Issue 5</h4>
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<blockquote>
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<p>Moved from X/OPEN UNIX extension to BASE.</p>
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<p>Aligned with <i>munmap</i>() in the POSIX Realtime Extension as follows:</p>
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<ul>
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<li>
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<p>The DESCRIPTION is extensively reworded.</p>
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</li>
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<li>
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<p>The SIGBUS error is no longer permitted to be generated.</p>
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</li>
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</ul>
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</blockquote>
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<h4><a name="tag_03_400_13"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>munmap</i>() function is marked as part of the Memory Mapped Files and Shared Memory Objects option.</p>
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<p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p>
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<ul>
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<li>
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<p>The DESCRIPTION is updated to state that implementations require <i>addr</i> to be a multiple of the page size.</p>
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</li>
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<li>
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<p>The [EINVAL] error conditions are added.</p>
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</li>
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</ul>
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<p>The following changes are made for alignment with IEEE Std 1003.1j-2000:</p>
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<ul>
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<li>
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<p>Semantics for typed memory objects are added to the DESCRIPTION.</p>
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</li>
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<li>
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<p>The <a href="../functions/posix_typed_mem_open.html"><i>posix_typed_mem_open</i>()</a> function is added to the SEE ALSO
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section.</p>
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</li>
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</ul>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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UNIX ® is a registered Trademark of The Open Group.<br>
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POSIX ® is a registered Trademark of The IEEE.<br>
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