Intel IA-32 - Manual (Page 399)

Vol. 3A 9-25
PROCESSOR MANAGEMENT AND INITIALIZATION
79 LDT_reg DW ?
80 LDT_h DW ?
81 TRAP_reg DW ?
82 IO_map_base DW ?
83 TASK_STATE ENDS
84
85 ; basic structure of a descriptor
86 DESC STRUC
87 lim_0_15 DW ?
88 bas_0_15 DW ?
89 bas_16_23 DB ?
90 access DB ?
91 gran DB ?
92 bas_24_31 DB ?
93 DESC ENDS
94
95 ; structure for use with LGDT and LIDT instructions
96 TABLE_REG STRUC
97 table_lim DW ?
98 table_linear DD ?
99 TABLE_REG ENDS
100
101 ; offset of GDT and IDT descriptors in builder generated GDT
102 GDT_DESC_OFF EQU 1*SIZE(DESC)
103 IDT_DESC_OFF EQU 2*SIZE(DESC)
104
105 ; equates for building temporary GDT in RAM
106 LINEAR_SEL EQU 1*SIZE (DESC)
107 LINEAR_PROTO_LO EQU 00000FFFFH ; LINEAR_ALIAS
108 LINEAR_PROTO_HI EQU 000CF9200H
109
110 ; Protection Enable Bit in CR0
111 PE_BIT EQU 1B
112
113 ; ------------------------------------------------------------
114
115 ; ------------------------- DATA SEGMENT----------------------
116
117 ; Initially, this data segment starts at linear 0, according
118 ; to the processor’s power-up state.
119
120 STARTUP_DATA SEGMENT RW
121
122 free_mem_linear_base LABEL DWORD
123 TEMP_GDT LABEL BYTE ; must be first in segment
124 TEMP_GDT_NULL_DESC DESC <>
125 TEMP_GDT_LINEAR_DESC DESC <>