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

<h2>memory_object_data_request</h2>\r<hr>\r<p>\r<strong>Server Interface</strong> - Request that memory manager page-in specified data.\r<h3>SYNOPSIS</h3>\r<pre>\r<strong>kern_return_t   memory_object_data_request</strong>\r                <strong>(memory_object_t</strong>                  <var>memory_object</var>,\r                 <strong>memory_object_control_t</strong>         <var>memory_control</var>,\r                 <strong>vm_offset_t</strong>                             <var>offset</var>,\r                 <strong>vm_size_t</strong>                               <var>length</var>,\r                 <strong>vm_prot_t</strong>                       <var>desired_access</var><strong>);</strong>\r\r\r<strong>kern_return_t   seqnos_memory_object_data_request</strong>\r                <strong>(memory_object_t</strong>                  <var>memory_object</var>,\r                 <strong>mach_port_seqno_t</strong>                        <var>seqno</var>,\r                 <strong>memory_object_control_t</strong>         <var>memory_control</var>,\r                 <strong>vm_offset_t</strong>                             <var>offset</var>,\r                 <strong>vm_size_t</strong>                               <var>length</var>,\r                 <strong>vm_prot_t</strong>                       <var>desired_access</var><strong>);</strong>\r</pre>\r<h3>PARAMETERS</h3>\r<dl>\r<p>\r<dt> <var>memory_object</var> \r<dd>\r[in abstract-memory-object (receive) right]\rThe abstract memory\robject port that represents the memory object data.\r<p>\r<dt> <var>seqno</var> \r<dd>\r[in scalar]\rThe sequence number of this message relative to the abstract \rmemory object port.\r<p>\r<dt> <var>memory_control</var> \r<dd>\r[in memory-cache-control send right]\rThe memory cache control port \rto be used for a response by the memory manager.  If the memory\robject has been supplied to more than one kernel, this parameter\ridentifies the kernel that is making the call.\r<p>\r<dt> <var>offset</var> \r<dd>\r[in scalar]\rThe offset within the memory object.\r<p>\r<dt> <var>length</var> \r<dd>\r[in scalar]\rThe number of bytes requested, starting at <var>offset</var>.  The\rnumber converts to an integral number of virtual pages.\r<p>\r<dt> <var>desired_access</var> \r<dd>\r[in scalar]\rThe memory access modes to be allowed for the cached \rdata.  Possible values are obtained by or'ing together the following\rvalues:\r<dl>\r<p>\r<dt> <strong>VM_PROT_READ</strong>\r<dd>\rAllows read access.\r<p>\r<dt> <strong>VM_PROT_WRITE</strong>\r<dd>\rAllows write access.\r<p>\r<dt> <strong>VM_PROT_EXECUTE</strong>\r<dd>\rAllows execute access.\r</dl>\r</dl>\r<h3>DESCRIPTION</h3>\r<p>\rA <strong>memory_object_data_request</strong> function is called as\rthe result of a kernel \rmessage requesting data from the specified memory object, for at least the\raccess specified.\r<p>\rThe kernel issues this call after a cache miss (that is, a page\rfault for which the \rkernel does not have the data).  The kernel requests only amounts\rof data that are \rmultiples of the page size included in the\r<strong>memory_object_init</strong> or <strong>memory_object_create</strong> call.\r<p>\rThe memory manager is expected to use <strong>memory_object_data_supply</strong> to\rreturn at least the specified data, with as much access as it\rcan allow.  If the\rmemory manager cannot provide the data (for example, because\rof a hardware error), \rit can use the <strong>memory_object_data_error</strong> call.  The\rmemory manager can also \ruse <strong>memory_object_data_unavailable</strong> to tell the kernel\rto supply zero-filled \rmemory for the region.\r<h3>RETURN VALUES</h3>\r<p>\rOnly generic errors apply.\r<h3>RELATED INFORMATION</h3>\r<p>\rFunctions:\r<a href="memory_object_data_error.html"><strong>memory_object_data_error</strong></a>,\r<a href="memory_object_data_supply.html"><strong>memory_object_data_supply</strong></a>,\r<a href="MO_data_unavailable.html"><strong>memory_object_data_unavailable</strong></a>,\r<a href="memory_object_server.html"><strong>memory_object_server</strong></a>,\r<a href="SMO_server.html"><strong>seqnos_memory_object_server</strong></a>.\r\r