iAPX 286 Operating System Writers Guide 1983

Table of ContentsCHAPTER 1PageINTRODUCTION TO PROTECTED MULTITASKING ON THE iAPX 286Tasks ........................:................................................................................... 1-1Structure of a Program .............................................................................. 1-1Segmented Memory .................................................................................. 1-1Multitasking .... ... ................................................................... ..................... 1-1Privilege Levels ............................................................................................. 1-3Levels of Segments ................................................................. 0.................. 1-4Rules of Privilege ....................................................... 0................................ 1-4Software System Structure ........................................................................... 1-4Role of the Operating System ...................................................................... 1-6Common O.S. Functions ........................................................................... 1-7O.S. Functions in a Dynamic Environment ................................................. 1-8Constructing the Initial Run-Time Environment ............................................. 1-8Building a Static System ............................................................................ 1-9Building a Dynamic System ....................................................................... 1-9CHAPTER 2USING HARDWARE PROTECTION FEATURESAddressing Mechanism ................................................................................ .Descriptors ................................................................................................... .Descriptor Format ..................................................................................... .Control Flow Transfer .................................................................................. .Gate Descriptors ...................................................................................... .Control Transfer Mechanisms .................. : ................................................ .Privilege Rules for Gated Intersegment Transfers ................................... ..Descriptor Tables ......................................................................................... .Local Descriptor Table .............................................................................. .Global Descriptor Table ............................................................................ .Interrupt Descriptor Table ......................................................................... .Selectors ...................................................................................................... .Format of Selector .................................................................................... .Null Selector ............................................................................................. .Alias Descriptors .............................................................................. ; ........... .Explicit Variation of Type .......................................................................... .Variation of Length ................................................................................... .Sharing Segments among Tasks ............................................................. ..Protection and Integrity with Aliasing ........................................................ .Example of Descriptor Manipulation ............................................................. .Slot Management ......................................................................................... .2-12-22-22-72-82-92-112-122-142-142-152-152-152-172-172-182-182-192-192-202-22VI121960-001