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1PAGE 60,132
2TITLE INDEGDT - 386 XMA Emulator - Build Global Descriptor Table
3
4COMMENT #
5* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
6* *
7* MODULE NAME : INDEGDT *
8* *
9* *
10* 5669-196 (C) COPYRIGHT 1988 Microsoft Corp. *
11* *
12* DESCRIPTIVE NAME: Build the Global Descriptor Table (GDT) *
13* *
14* STATUS (LEVEL) : Version (0) Level (1.0) *
15* *
16* FUNCTION : Build the Global Descriptor Table (GDT) for the 80386 *
17* XMA emulator *
18* *
19* MODULE TYPE : ASM *
20* *
21* REGISTER USAGE : 80386 Standard *
22* *
23* RESTRICTIONS : None *
24* *
25* DEPENDENCIES : None *
26* *
27* ENTRY POINT : GDT_BLD *
28* *
29* LINKAGE : Called NEAR from INDEINI *
30* *
31* INPUT PARMS : None *
32* *
33* RETURN PARMS : None *
34* *
35* OTHER EFFECTS : None *
36* *
37* EXIT NORMAL : Return to INDEINI *
38* *
39* EXIT ERROR : None *
40* *
41* EXTERNAL *
42* REFERENCES : None *
43* *
44* SUB-ROUTINES : SREG_2_24BITS - Convert the 16 bit value in AX to a 24 *
45* bit value in DH and AX. *
46* ADDOFF - Add the 16 bit offset in AX to the 24 bit value *
47* in DH and BX. *
48* *
49* MACROS : DESCR_DEF - Declare a descriptor entry *
50* DESCR_INIT - Initialize a descriptor *
51* *
52* CONTROL BLOCKS : INDEDAT - System data structures *
53* *
54* CHANGE ACTIVITY : *
55* *
56* $MOD(INDEGDT) COMP(LOAD) PROD(3270PC) : *
57* *
58* $D0=D0004700 410 870530 D : NEW FOR RELEASE 1.1 *
59* $P1=P0000293 410 870731 D : LIMIT LINES TO 80 CHARACTERS *
60* $P2=P0000312 410 870804 D : CHANGE COMPONENT FROM MISC TO LOAD *
61* $P3=P0000410 410 870918 D : RELOCATE DATA AREAS TO MAKE ROOM FOR BIT MAP *
62* *
63* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
64#
65
66 .286P ; Enable recognition of 286 privileged instructs.
67
68 .XLIST ; Turn off the listing
69 INCLUDE INDEDAT.INC ; Include system data structures
70 INCLUDE INDEACC.INC ; Include access byte definitions
71
72 IF1 ; Only include macros on the first pass
73 INCLUDE INDEDES.MAC ; Descriptor macros
74 ENDIF
75 .LIST ; Turn on the listing
76
77PROG SEGMENT PARA PUBLIC 'PROG'
78
79 ASSUME CS:PROG
80 ASSUME SS:NOTHING
81 ASSUME DS:PROG
82 ASSUME ES:NOTHING
83
84INDEGDT LABEL NEAR
85
86 PUBLIC INDEGDT
87 PUBLIC GDT_BLD
88 PUBLIC GDT_DATA_START
89 PUBLIC SREG_2_24BITS
90
91; The following data define a pre-initialized GDT. They represent
92; all structures which will exist when the emulator comes up.
93; THESE MUST BE INITIALIZED IN THE ORDER IN WHICH THEY APPEAR IN THE
94; GDT_DEF STRUCTURE DEFINITION AS IT APPEARS IN INDEDAT.INC. This data
95; area will be copied from the code segment to the final GDT resting
96; place during initialization.
97
98GDT_DATA_START LABEL WORD
99
100; First entry is unusable
101
102 DESCR_DEF SEG, 0, 0, 0, 0
103
104; The descriptor for GDT itself
105
106 DESCR_DEF SEG, GDT_LEN, GDT_LOC, 3, CPL0_DATA_ACCESS
107PAGE
108
109; The system IDT descriptor
110
111 DESCR_DEF SEG, SIDT_LEN, SIDT_LOC, 3, CPL0_DATA_ACCESS
112
113; The real system data area descriptor (XMA pages)
114
115 DESCR_DEF SEG, 0FFFFH, 0000H, 11H, CPL0_DATA_ACCESS
116
117; The virtual IDT descriptor (not needed so use for all memory)
118
119 DESCR_DEF SEG, MAX_SEG_LEN, NSEG@_LO, NSEG@_HI, CPL0_DATA_ACCESS
120
121; The LOADALL descriptor
122
123 DESCR_DEF SEG, 0, 0, 0, 0
124PAGE
125
126; Compatible monochrome display
127
128 DESCR_DEF SEG, MCRT_SIZE, MCRT@_LO, MCRT@_HI, CPL0_DATA_ACCESS
129
130; Compatible color display
131
132 DESCR_DEF SEG, CCRT_SIZE, CCRT@_LO, CCRT@_HI, CPL0_DATA_ACCESS
133
134; Enhanced color display - one entry for each 64K P1C
135
136 DESCR_DEF SEG, ECCRT_SIZE, ECCRT@_LO_LO, ECCRT@_LO_HI, CPL0_DATA_ACCESS
137
138; Second part of enhanced display P1C
139
140 DESCR_DEF SEG, ECCRT_SIZE, ECCRT@_HI_LO, ECCRT@_HI_HI, CPL0_DATA_ACCESS
141PAGE
142
143; Code segment for ROM code, system IDT
144
145 DESCR_DEF SEG, MAX_SEG_LEN, CSEG@_LO, CSEG@_HI, CPL0_CODE_ACCESS
146
147; Data segment for ROM code, system IDT
148
149 DESCR_DEF SEG, MAX_SEG_LEN, CSEG@_LO, CSEG@_HI, CPL0_CODE_ACCESS
150
151; Temporarily, the monitor is installed using the patch
152; segment descriptors in the GDT
153
154MSEG@_LO EQU 00000H
155MSEG@_HI EQU 008H
156
157
158; Code segment for patch code, system IDT
159
160 DESCR_DEF SEG, MAX_SEG_LEN, MSEG@_LO, MSEG@_HI, CPL0_CODE_ACCESS
161
162; Data segment for patch code, system IDT
163
164 DESCR_DEF SEG, MAX_SEG_LEN, MSEG@_LO, MSEG@_HI, CPL0_DATA_ACCESS
165PAGE
166
167; Code segment for ROM code, virtual IDT
168
169 DESCR_DEF SEG, MAX_SEG_LEN, CSEG@_LO, CSEG@_HI, CPL0_CODE_ACCESS
170
171; Data segment for ROM code, virtual IDT
172
173 DESCR_DEF SEG, MAX_SEG_LEN, CSEG@_LO, CSEG@_HI, CPL0_CODE_ACCESS
174
175; Code segment for patch code, virtual IDT
176
177 DESCR_DEF SEG, NULL_SEG_LEN, NSEG@_LO, NSEG@_HI, NULL_ACCESS
178
179; Data segment for patch code, virtual IDT
180
181 DESCR_DEF SEG, NULL_SEG_LEN, NSEG@_LO, NSEG@_HI, NULL_ACCESS
182PAGE
183
184; Temporary descriptors for ES, CS, SS, and DS
185
186 DESCR_DEF SEG, MAX_SEG_LEN, NSEG@_LO, NSEG@_HI, CPL0_DATA_ACCESS
187
188 DESCR_DEF SEG, MAX_SEG_LEN, NSEG@_LO, NSEG@_HI, CPL0_CODE_ACCESS
189
190 DESCR_DEF SEG, MAX_SEG_LEN, NSEG@_LO, NSEG@_HI, CPL0_DATA_ACCESS
191
192 DESCR_DEF SEG, MAX_SEG_LEN, NSEG@_LO, NSEG@_HI, CPL0_DATA_ACCESS
193PAGE
194
195; These DQ's pad out the space between the last MultiPC descriptor and the
196; PMVM descriptors. They don't need initialization.
197
198 DQ 9 DUP (0) ; These 9 are for the Monitor descriptors
199
200; This is for the keyboard owner (not used)
201
202 DQ 0
203
204; These 16 are for the virtual timer support
205
206 DQ 16 DUP (0)
207
208; The following 32 descriptors are for exception condition task gates.
209
210 REPT 32
211 DQ 0
212 ENDM
213
214; The following 16 pairs are for the hardware interrupt handling tasks.
215
216 REPT 16
217 DQ 0
218 DQ 0
219 ENDM
220
221; The following pair is for the DISPATCH task
222
223 DESCR_DEF SEG, TSS_LEN, DISPATCH_LOC, 3, <TSS_ACCESS OR FREE_TSS>
224 DESCR_DEF SEG, TSS_LEN, DISPATCH_LOC, 3, CPL0_DATA_ACCESS
225
226 DESCR_DEF SEG, 0, 0, 0,LDT_DESC
227
228; BASIC's segment
229
230 DESCR_DEF SEG, 07FFFH, 06000H, 0FH, CPL0_DATA_ACCESS
231
232; BIOS's segment
233
234 DESCR_DEF SEG, 01FFFH, 00000H, 0FH, CPL0_DATA_ACCESS
235
236 DQ 13 DUP (0) ; Reserved guys
237
238; The following guys are junk ! Used before the first TSS allocated. These
239; have to be in the PMVM location in the GDT.
240
241 DESCR_DEF SEG, TSS_LEN, 0C000H, 0, FREE_TSS ; For the TR
242
243 DESCR_DEF SEG, TSS_LEN, 0C000H, 0, CPL0_DATA_ACCESS ; TSS as data
244
245 DESCR_DEF SEG, GDT_LEN, 0D000H, 0, LDT_DESC ; For the LDTR
246
247 DESCR_DEF SEG, GDT_LEN, 0D000H, 0, CPL0_DATA_ACCESS ; LDT as data
248
249GDT_DATA_END LABEL WORD
250
251COPY_LEN EQU GDT_DATA_END-GDT_DATA_START
252
253;
254; End of pre-allocated GDT
255;
256
257PAGE
258
259GDT_BLD PROC NEAR
260
261; Copy the pre-initialized GDT into its proper location in memory
262
263 CLI ; All string operations go forward
264
265 MOV SI,OFFSET GDT_DATA_START ; DS:SI points to the pre-initialized
266 ; GDT above
267 MOV CX,COPY_LEN/2 ; CX = number of words to copy
268 MOV DI,GDT_LOC ; ES:DI points to the GDT location
269 REP MOVSW ; Copy GDT into its final resting place
270
271; Now let's initialize some of the GDT entries
272
273; Set up the descriptors for our code segment and data segment
274
275 MOV AX,CS ; Get our CS
276 CALL SREG_2_24BITS ; And convert it to a 24 bit offset
277 MOV BX,AX ; Get the monitor offset
278
279ALLSET:
280 DESCR_INIT SEG, SYS_PATCH_CS, 07FFFH, BX, DH, CPL0_CODE_ACCESS
281 DESCR_INIT SEG, SYS_PATCH_DS, 0FFFFH, BX, DH, CPL0_DATA_ACCESS
282
283; Initialize the descriptor for the GDT
284
285 MOV AX,ES ; Get the segment of the GDT
286 CALL SREG_2_24BITS ; Convert to a 24 bit offset
287 MOV DL,DH ; Save a copy of the hi byte
288 MOV BX,GDT_LOC ; Add on the offset of the GDT
289 CALL ADDOFF
290
291 DESCR_INIT SEG, GDT_PTR, GDT_LEN, BX, DH, CPL0_DATA_ACCESS
292
293; Initialize the descriptor for the IDT
294
295 MOV BX,SIDT_LOC ; DH,AX already contains the segment
296 ; converted to 24 bits so all we
297 CALL ADDOFF ; have to do is add on the offset
298
299 DESCR_INIT SEG, MON_IDT_PTR, SIDT_LEN, BX, DH, CPL0_DATA_ACCESS
300
301; Initialize the descriptor that accesses all of memory as data
302
303 DESCR_INIT BSEG, HUGE_PTR, 0FFFFH, 0, 0, CPL0_DATA_ACCESS
304
305; Initialize the descriptors for the V86 task's LDT
306
307 MOV BX,DISPATCH_LOC ; @P3C
308 CALL ADDOFF
309
310 DESCR_INIT SEG,SCRUBBER.VM_LDTR,00FFFH,BX,DH,LDT_DESC
311 DESCR_INIT SEG,SCRUBBER.LDT_PTR,00FFFH,BX,DH,CPL0_DATA_ACCESS
312
313; Initialize the descriptors for the V86 task's TR
314
315 MOV BX,DISPATCH_LOC ; @P3C
316 CALL ADDOFF
317
318 DESCR_INIT SEG,SCRUBBER.VM_TR,TSS_LEN,BX,DH,FREE_TSS_386 ; @P3C
319 DESCR_INIT SEG,SCRUBBER.TSS_PTR,TSS_LEN,BX,DH,CPL0_DATA_ACCESS; @P3C
320
321 RET
322
323GDT_BLD ENDP
324
325PAGE
326; SREG_2_24BITS converts the segment register 16 bit value in the AX register
327; into a 24 bit value in DH and AX
328;
329; Input : AX = segment register value
330;
331; Output: AX = 24 bit low word
332; DH = 24 bit high byte
333
334
335SREG_2_24BITS PROC NEAR
336
337; Put the high four bits of AH into the low four bits of DH
338
339 MOV DH,AH ; Get the high byte of the segment value
340 ; into DH
341 AND DH,0F0H ; Strip off the low nibble
342 SHR DH,4 ; Shift right four bits
343
344; Now shift AX left four bits
345
346 AND AH,00FH ; Strip high nibble from AH
347 ; This keeps the carry flag from being
348 ; set which could effect later ADDs.
349 SHL AX,4 ; Shift AX
350
351 RET
352
353SREG_2_24BITS ENDP
354
355PAGE
356; ADDOFF adds the 16 bit offset in BX to the 24 bit value in DL and AX. The
357; result is left in DH and BX.
358;
359; Input : DL = 24 bit high byte
360; AX = 24 bit low word
361; BX = offset to be added
362;
363; Output: DH = 24 bit high byte
364; BX = 24 bit low word
365
366ADDOFF PROC NEAR
367
368 MOV DH,DL ; Restore the high byte that was saved
369 ; in DL
370 ADD BX,AX ; Add on the offset
371 ADC DH,0 ; Add the carry, if any, to the high
372 ; byte
373 RET
374
375ADDOFF ENDP
376
377PROG ENDS
378
379 END
HIC SVNT DRACONES