add directory study

study/sabre/os/files/ProtectedMode/DPMI1.0Spec/descriptor-rules.html

@@ -0,0 +1,79 @@
+
+
+The following table shows the DPMI client's restrictions on usage of
+previously allocated descriptors as input parameters to DPMI
+functions.  The columns represent the ways the DPMI host allocates
+descriptors for its clients.  (The first two columns represent LDT
+descriptor management functions which allocate descriptors, the third
+column represents DOS memory functions, and the last column represents
+"other" descriptors, i.e., unallocated descriptors or descriptors used
+by the DPMI host for internal purposes.)  Each row represents a set of
+functions where a client passes those previously allocated
+descriptor(s) to the host as input parameters.  A `N' indicates that
+an "Invalid Selector" error will be generated if the given descriptor
+is used in the specified function.<p>
+
+Note that a `Y' for a given entry does not indicate that the function
+will succeed, only that it will not generate an "Invalid Selector"
+error.  Similarly, an `N' does not necessarily indicate a descriptor
+is invalid for referencing memory, only that it cannot be used with
+that particular function.  This chart does not address the usage of
+descriptors in pointers. <p>
+
+For example, descriptors allocated by the Allocate LDT Descriptor function
+may be used in any of the interrogation and modification functions of
+LDT Descriptor Management, as well as the functions which set
+exception handlers and interrupt vectors.  They may not be passed to
+Allocate Specific LDT Descriptor or the DOS Memory Block Functions.<p>
+
+<table border=1 cellspacing=0 cellpadding=4>
+
+<tr> <td>&nbsp;</td> <th colspan=4>Descriptor Allocators</th></tr>
+
+<tr> <th>Functions referring to allocated descriptors</th>
+
+<td>Allocate LDT Descriptor, Allocate Specfic LDT Descriptor, Create Alias descriptr, Initial CS, DS, SS</td>
+
+<td>Segment to Descriptor, PSP, Environment Pointer, Callback DS, Locked Stack SS</td>
+
+<td>Allocate/Resize DOS Memory Block</td>
+
+<td> GDT-based Descriptor, System Descriptor, Unallocated Descriptor</td></tr>
+
+<tr><td>Interrogation Functions: Get Segment Base Address, Get Descriptor, Get Multiple Descriptor, Create Segment Alias</td>
+
+<td align=center>Y</td> <td align=center>Y</td> <td align=center>Y</td> <td align=center>N</td></tr>
+
+<tr><td> Modification Functions: Set Segment Base Address, Set Segment Limit, Set Descriptor Access Rights, Set Descriptor, Set Multiple Descriptors, Free LDT Descriptor</td>
+
+<td align=center>Y</td> <td align=center>N</td> <td align=center>N</td> <td align=center>N</td></tr>
+
+<tr><td> Allocate Specific LDT Descriptor</td>
+
+<td align=center>N</td> <td align=center>N</td> <td align=center>N</td> <td align=center>Y(1)</td></tr>
+
+<tr><td>Free/Resize DOS Memory Block</td>
+
+<td align=center>N</td> <td align=center>N</td> <td align=center>Y</td> <td align=center>N</td></tr>
+
+<tr><td>Set Exception Handler/Interrupt Vector</td>
+
+<td align=center>Y</td> <td align=center>Y(3)</td> <td align=center>Y</td> <td align=center>Y(2)</td></tr>
+
+</table><p>
+
+Notes:
+
+<ol>
+
+<li> Unallocated descriptors within the range of the LDT only.
+
+<li> GDT-Based segment descriptors only.
+
+<li> Although this call will succeed, a fault will result if the
+exception or interrupt occurs, since the segment can never be made
+executable.
+
+</ul>
+
+