Selector Format

In protect mode, a Selector has 3 fields:

• Index, the left 13 bits, bits numbered 15-3

  This is an index into a descriptor table

  2.
  Table indicator, one bit, bit number 2

  • means GDT

  • means LDT
  3.
  RPL, the right 2 bits, numbered 1 & 0.

  Requested Privilege Level.

  perceived as a two bit value, range 0 to 3 00=most privileged, or ring 0; 11=least privileged, or ring 3.

  Note: The position of the bits makes a selector (with its 3 low order bits turned off) the offset into the table.

  +--------------------------------------+--+-----+|         I N D E X                     TI  RPL | fields
  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
   15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00  bit numbers
  

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