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COMMENT #
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* *
* MODULE NAME : INDEACC *
* *
* *
* 5669-196 (C) COPYRIGHT 1988 Microsoft Corporation *
* *
* DESCRIPTIVE NAME: Access rights byte definitions for 80386 XMA emulator *
* *
* STATUS (LEVEL) : Version (0) Level (1.0) *
* *
* FUNCTION : This file defines the access rights bytes used in *
* descriptors that define the code and data segments. *
* *
* MODULE TYPE : INC *
* *
* REGISTER USAGE : 80386 Standard *
* *
* RESTRICTIONS : None *
* *
* DEPENDENCIES : None *
* *
* EXTERNAL *
* REFERENCES : None *
* *
* CHANGE ACTIVITY : *
* *
* $MAC(INDEACC) COMP(LOAD) PROD(3270PC) : *
* *
* $D0=D0004700 410 870530 D : NEW FOR WSP RELEASE 1.1 *
* $P1=P0000311 410 870804 D : RENAME MODULE'S LIBRARY FILE TYPE TO "INC" *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
#
PAGE
; RECORD DEFINITIONS FOR ACCESS RIGHTS BYTES
; ====== =========== === ====== ====== =====
;
; Data Segments - Interpretation of access rights for DS/ES/SS
; Define the bit fields for the access rights byte
DATA_ACC RECORD PRESENT:1,DPL:2,SEG_TYPE:1,XQTBLE:1,EXPDIR:1,WRTBLE:1,ACCESSED:1
; PRESENT (1 bit) 0 = segment not present in memory
; 1 = segment present in memory
;
; DPL (2 bits) Descriptor privilege level -- 0 to 3
;
; SEG_TYPE (1 bit) 0 = system segment
; 1 = application segment
;
; XQTBL (1 bit) 0 = segment is not executable (i.e., data)
; 1 = segment is executable (i.e., code)
;
; EXPDIR (1 bit) 0 = expand up, i.e., normal data segment
; 1 = expand down, i.e., stack segment
;
; WRTBLE (1 bit) 0 = data segment is read only
; 1 = data segment is read/write
;
; ACCESSED (1 bit) 0 = segment has not been accessed
; 1 = segment has been accessed
; Privilege level 3 read/write data segment access rights byte
CPL3_DATA_ACCESS EQU 11110011B ; Present
; DPL = 3
; Application segment
; Not executable (i.e. data)
; Expand up
; Readable/Writable
; Accessed
; Privilege level 0 read/write data segment access rights byte
CPL0_DATA_ACCESS EQU 10010011B ; Present
; DPL = 0
; Application segment
; Not executable (i.e. data)
; Expand up
; Readable/Writable
; Accessed
NULL_ACCESS EQU 00000000B ; Null (Not present)
; Descriptor privilege levels. These can be ANDed or ORed with the access
; rights byte to get the desired DPL for the descriptor.
DPL3 EQU 01100000B
DPL2 EQU 01000000B
DPL1 EQU 00100000B
DPL0 EQU 00000000B
PAGE
; Code Segments - Interpretation of access rights for CS.
; Identical to data segments except for two fields.
CODE_ACC RECORD DATA_HI:5,CONFORM:1,READABLE:1,DATA_LO:1
; DATA_HI (5 bits) Same five bits as described for data segments
; PPRESENT (1), DPL (2), SEG_TYPE (1) and
; XQTBL (1)
;
; CONFORM (1 bit) 0 = Non-conforming - cannot be called by
; someone with a different CPL
; 1 = Conforming - can be called by anyone
; regardless of CPL. CPL remains the same
;
; READABLE (1 bit) 0 = code segment is execute only
; 1 = data segment is executable and readable
;
; DATA_LO (1 bit) Same bit as described for data segments
; ACCESSED (1)
; Privilege level 3 conforming readable code segment access rights byte
; BUT...
; We switched the DPL to 0. Why? Because the DPL of the current code segment
; determines the current privilege level (CPL). Whatever is running at the
; time can only access data with a DPL >= CPL. So if the DPL for the code
; segment were 3 and we tried to access data with a DPL of 0 we would get a
; fault. By setting the DPL of the code segment to 0 we can access all data
; and will never be bothered by faults.
CPL3_CODE_ACCESS EQU 10011111B ; Present
; DPL = 0
; Application segment
; Executable (i.e. code)
; Conforming
; Readable
; Accessed
; Access rights to be able to read and write to a code segment. Code segments
; may not be written to. So this access byte will define the segment as a
; read/write data segment. It is the same as CPL3_DATA_ACCESS.
COMP_CODE_ACCESS EQU CPL3_DATA_ACCESS
; Privilege level 0 non-conforming readable code segment access rights byte
CPL0_CODE_ACCESS EQU 10011011B ; Present
; DPL = 0
; Application segment
; Executable (i.e. code)
; Non-conforming
; Readable
; Accessed
PAGE
; System Segments - Interpretation of access rights for TR/LDTR as well as
; the four gate types. The access rights byte for the
; GDTR and IDTR is undefined, meaning anyone can access
; the table (although not necessarily the segments
; defined in the table). The uppermost 4 bits are
; identical to those for data segments; the type field
; occupies the lowermost 4 bits.
SYSTEM_ACC RECORD DATA_H:4,DESC_TYPE:4
; DATA_H (4 bits) Same four bits as described for data segments
; PPRESENT (1), DPL (2) and SEG_TYPE (1)
;
; DESC_TYPE(4 bits) 0000 Intel Reserved
; 0001 Available 286 TSS
; 0010 LDT
; 0011 Busy 286 TSS
; 0100 Call Gate
; 0101 Task Gate
; 0110 286 Interrupt Gate
; 0111 286 Trap Gate
; 1000 Intel Reserved
; 1001 Available 386 TSS
; 1010 Intel Reserved
; 1011 Busy 386 TSS
; 1100 386 Call Gate
; 1101 Intel Reserved
; 1110 386 Interrupt Gate
; 1111 386 Trap Gate
;
; These equates cover the topmost 4 bits for system segment access
; rights bytes. They define the privilege level.
LDT_ACCESS EQU 11100000B ; Present, DPL = 3 for LDTs
TSS_ACCESS EQU 10000000B ; Present, DPL = 0 for TSSs
GATE_ACCESS EQU 10000000B ; Present, DPL = 0 for Gates
; These are for the type field. When "OR"ed with one of the above,
; you have a complete access rights byte.
LDT_DESC EQU 00000010B OR LDT_ACCESS
FREE_TSS EQU 00000001B OR TSS_ACCESS
FREE_TSS_386 EQU 00001001B OR TSS_ACCESS
BUSY_TSS EQU 00000011B OR TSS_ACCESS
CALL_GATE EQU 00000100B OR GATE_ACCESS
TASK_GATE EQU 00000101B OR GATE_ACCESS
INT_GATE EQU 00000110B OR GATE_ACCESS
TRAP_GATE EQU 00000111B OR GATE_ACCESS
|
