Descriptors Window Menu

The Descriptor Table menu, a context menu accessed by right-clicking on a table entry, features an easy way to segue into either a Code window or Memory window based on the highlighted descriptor.

Descriptors menu

View as Code menu item. This selection opens a Code window at the address of the selected descriptor table entry. Code can then be viewed and breakpoints can be set through the open Code window.

View as Memory menu item. A Memory window opens at the selected descriptor table entry. Memory can then be examined or changed.

Properties menu item. Clicking on the Properties menu item causes a Descriptors  dialog box to display. The information in each dialog box varies, depending on the type of descriptor, but there are three sections in each: Descriptor type, Attributes, and Values. They are described in more detail below.

Note: The information in these columns can be edited to modify existing descriptors or to add new descriptors.

Sample Properties dialog box

• Descriptor Type Section. The Descriptor Type section displays the descriptor type selected from the Descriptor Type drop down list box. The displayed descriptor type is one of several included in a drop down list. For application descriptor types (i.e., Code and Data descriptors), this dialog box includes check boxes whose default states define the descriptor status. With exception of the TSS Busy bit, no status is defined for system descriptor types (i.e., the LDT, TSS, and gate-type descriptors).

Note: Enabling or disabling these options changes the values displayed for Bytes 7-4 in the Values section of dialog box.

• Attributes Section. The Attributes section contains check boxes where default enabled/disabled states define the attributes of each descriptor. This area also contains a text box that displays the default Descriptor Privilege Level and, for call-gate descriptors, a second text box that displays the default Dword count.

Note: Enabling or disabling the attributes in the Attributes section of the dialog box changes the values displayed for Bytes 7-4 in the Values section.

• Values Section. The Values section contains text boxes that are labeled Base and Limit or Selector and Offset. These text boxes display the base address and limit values for code, data, TSS, and LDT descriptors and the selector and offset values for call, interrupt, and trap-gate descriptors. Only the selector is displayed for task-gate descriptors.

The Values section also contains text boxes labeled Bytes 7-4 and Bytes 3-0. These text boxes display the values defined for each field in a descriptor's 8-byte data structure. These fields, in addition to defining a descriptor's base address and limit or selector and offset, define its type, status, and attributes.