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

<h2>vm_inherit</h2>\r<hr>\r<p>\r<strong>Function</strong> - Set a VM region's inheritance attribute.\r<p>\r<h3>SYNOPSIS</h3>\r<pre>\r<strong>kern_return_t   vm_inherit</strong>\r                 <strong>(vm_task_t</strong>                   <var>target_task</var>,\r                  <strong>vm_address_t</strong>                    <var>address</var>,\r                  <strong>vm_size_t</strong>                          <var>size</var>,\r                  <strong>vm_inherit_t</strong>            <var>new_inheritance</var><strong>);</strong>\r</pre>\r<h3>PARAMETERS</h3>\r<dl>\r<p>\r<dt> <var>target_task</var> \r<dd>\r[in task send right]\rThe port for the task whose address space contains \rthe region.\r<p>\r<dt> <var>address</var> \r<dd>\r[in scalar]\rThe starting address for the region.\r<p>\r<dt> <var>size</var> \r<dd>\r[in scalar]\rThe number of bytes in the region.\r<p>\r<dt> <var>new_inheritance</var> \r<dd>\r[in scalar]\rThe new inheritance attribute for the region.  Valid values are:\r<dl>\r<p>\r<dt> <strong>VM_INHERIT_SHARE</strong>\r<dd>\rAllows child tasks to share the region.\r<p>\r<dt> <strong>VM_INHERIT_COPY</strong>\r<dd>\rGives child tasks a copy of the region.\r<p>\r<dt> <strong>VM_INHERIT_NONE</strong>\r<dd>\rProvides no access to the region for child tasks.\r</dl>\r</dl>\r<h3>DESCRIPTION</h3>\r<p>\rThe <strong>vm_inherit</strong> function sets the inheritance attribute\rfor a region within the \rspecified task's address space.  The inheritance attribute determines\rthe type of \raccess established for child tasks at task creation.\r<p>\rBecause inheritance applies to virtual pages, the specified <var>address</var>\rand <var>size</var> are \rrounded to page boundaries, as follows: the region starts at\rthe beginning of the \rvirtual page containing <var>address</var>; it ends at the end of the virtual\rpage containing \r<var>address</var> + <var>size</var> - 1.  \rBecause of this rounding to virtual page boundaries, the \ramount of memory affected may be greater than <var>size</var>.  Use \r<strong>host_page_size</strong> to find the current virtual page size.\r<p>\rA parent and a child task can share the same physical memory only if the\rinheritance for the memory is set to <strong>VM_INHERIT_SHARE</strong> before\rthe child task is \rcreated.  Other than through the use of an external memory manager (see\r<strong>vm_map</strong>), this is the only way that two tasks can share memory.\r<p>\rNote that all the threads within a task share the task's memory.\r<h3>NOTES</h3>\r<p>\rThis interface is machine word length specific because of the virtual address\rparameter.\r<h3>RETURN VALUES</h3>\r<dl>\r<p>\r<dt> <strong>KERN_INVALID_ADDRESS</strong>\r<dd>\rThe address is illegal or specifies a non-allocated region.\r</dl>\r<h3>RELATED INFORMATION</h3>\r<p>\rFunctions:\r<a href="task_create.html"><strong>task_create</strong></a>,\r<a href="vm_map.html"><strong>vm_map</strong></a>,\r<a href="vm_region.html"><strong>vm_region</strong></a>,\r<a href="norma_task_clone.html"><strong>norma_task_create</strong></a>.\r