[FAST486]
[reactos.git] / reactos / lib / fast486 / common.c
1 /*
2 * Fast486 386/486 CPU Emulation Library
3 * common.c
4 *
5 * Copyright (C) 2014 Aleksandar Andrejevic <theflash AT sdf DOT lonestar DOT org>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version 2
10 * of the License, or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20 */
21
22 /* INCLUDES *******************************************************************/
23
24 #include <windef.h>
25
26 // #define NDEBUG
27 #include <debug.h>
28
29 #include <fast486.h>
30 #include "common.h"
31
32 /* PUBLIC FUNCTIONS ***********************************************************/
33
34 BOOLEAN
35 Fast486ReadMemory(PFAST486_STATE State,
36 FAST486_SEG_REGS SegmentReg,
37 ULONG Offset,
38 BOOLEAN InstFetch,
39 PVOID Buffer,
40 ULONG Size)
41 {
42 ULONG LinearAddress;
43 PFAST486_SEG_REG CachedDescriptor;
44
45 ASSERT(SegmentReg < FAST486_NUM_SEG_REGS);
46
47 /* Get the cached descriptor */
48 CachedDescriptor = &State->SegmentRegs[SegmentReg];
49
50 if ((Offset + Size - 1) > CachedDescriptor->Limit)
51 {
52 /* Read beyond limit */
53 Fast486Exception(State, FAST486_EXCEPTION_GP);
54 return FALSE;
55 }
56
57 /* Check for protected mode */
58 if (State->ControlRegisters[0] & FAST486_CR0_PE)
59 {
60 /* Privilege checks */
61
62 if (!CachedDescriptor->Present)
63 {
64 Fast486Exception(State, FAST486_EXCEPTION_NP);
65 return FALSE;
66 }
67
68 if ((!InstFetch && (CachedDescriptor->Rpl > CachedDescriptor->Dpl))
69 || (Fast486GetCurrentPrivLevel(State) > CachedDescriptor->Dpl))
70 {
71 Fast486Exception(State, FAST486_EXCEPTION_GP);
72 return FALSE;
73 }
74
75 if (InstFetch)
76 {
77 if (!CachedDescriptor->Executable)
78 {
79 /* Data segment not executable */
80 Fast486Exception(State, FAST486_EXCEPTION_GP);
81 return FALSE;
82 }
83 }
84 else
85 {
86 if (CachedDescriptor->Executable && (!CachedDescriptor->ReadWrite))
87 {
88 /* Code segment not readable */
89 Fast486Exception(State, FAST486_EXCEPTION_GP);
90 return FALSE;
91 }
92 }
93 }
94
95 /* Find the linear address */
96 LinearAddress = CachedDescriptor->Base + Offset;
97
98 /* Read from the linear address */
99 return Fast486ReadLinearMemory(State, LinearAddress, Buffer, Size);
100 }
101
102 BOOLEAN
103 Fast486WriteMemory(PFAST486_STATE State,
104 FAST486_SEG_REGS SegmentReg,
105 ULONG Offset,
106 PVOID Buffer,
107 ULONG Size)
108 {
109 ULONG LinearAddress;
110 PFAST486_SEG_REG CachedDescriptor;
111
112 ASSERT(SegmentReg < FAST486_NUM_SEG_REGS);
113
114 /* Get the cached descriptor */
115 CachedDescriptor = &State->SegmentRegs[SegmentReg];
116
117 if ((Offset + Size - 1) > CachedDescriptor->Limit)
118 {
119 /* Write beyond limit */
120 Fast486Exception(State, FAST486_EXCEPTION_GP);
121 return FALSE;
122 }
123
124 /* Check for protected mode */
125 if (State->ControlRegisters[0] & FAST486_CR0_PE)
126 {
127 /* Privilege checks */
128
129 if (!CachedDescriptor->Present)
130 {
131 Fast486Exception(State, FAST486_EXCEPTION_NP);
132 return FALSE;
133 }
134
135 if ((CachedDescriptor->Rpl > CachedDescriptor->Dpl)
136 || (Fast486GetCurrentPrivLevel(State) > CachedDescriptor->Dpl))
137 {
138 Fast486Exception(State, FAST486_EXCEPTION_GP);
139 return FALSE;
140 }
141
142 if (CachedDescriptor->Executable)
143 {
144 /* Code segment not writable */
145 Fast486Exception(State, FAST486_EXCEPTION_GP);
146 return FALSE;
147 }
148 else if (!CachedDescriptor->ReadWrite)
149 {
150 /* Data segment not writeable */
151 Fast486Exception(State, FAST486_EXCEPTION_GP);
152 return FALSE;
153 }
154 }
155
156 /* Find the linear address */
157 LinearAddress = CachedDescriptor->Base + Offset;
158
159 /* Write to the linear address */
160 return Fast486WriteLinearMemory(State, LinearAddress, Buffer, Size);
161 }
162
163 BOOLEAN
164 Fast486InterruptInternal(PFAST486_STATE State,
165 USHORT SegmentSelector,
166 ULONG Offset,
167 ULONG GateType)
168 {
169 BOOLEAN GateSize = (GateType == FAST486_IDT_INT_GATE_32)
170 || (GateType == FAST486_IDT_TRAP_GATE_32);
171 BOOLEAN Success = FALSE;
172 ULONG OldPrefixFlags = State->PrefixFlags;
173
174 /* Check for protected mode */
175 if (State->ControlRegisters[FAST486_REG_CR0] & FAST486_CR0_PE)
176 {
177 FAST486_TSS Tss;
178 USHORT OldSs = State->SegmentRegs[FAST486_REG_SS].Selector;
179 ULONG OldEsp = State->GeneralRegs[FAST486_REG_ESP].Long;
180
181 if (GateSize != (State->SegmentRegs[FAST486_REG_CS].Size))
182 {
183 /*
184 * The gate size doesn't match the current operand size, so toggle
185 * the OPSIZE flag.
186 */
187 State->PrefixFlags ^= FAST486_PREFIX_OPSIZE;
188 }
189
190 /* Check if the interrupt handler is more privileged */
191 if (Fast486GetCurrentPrivLevel(State) > GET_SEGMENT_RPL(SegmentSelector))
192 {
193 /* Read the TSS */
194 if (!Fast486ReadLinearMemory(State,
195 State->TaskReg.Base,
196 &Tss,
197 sizeof(Tss)))
198 {
199 /* Exception occurred */
200 goto Cleanup;
201 }
202
203 /* Check the new (higher) privilege level */
204 switch (GET_SEGMENT_RPL(SegmentSelector))
205 {
206 case 0:
207 {
208 if (!Fast486LoadSegment(State, FAST486_REG_SS, Tss.Ss0))
209 {
210 /* Exception occurred */
211 goto Cleanup;
212 }
213 State->GeneralRegs[FAST486_REG_ESP].Long = Tss.Esp0;
214
215 break;
216 }
217
218 case 1:
219 {
220 if (!Fast486LoadSegment(State, FAST486_REG_SS, Tss.Ss1))
221 {
222 /* Exception occurred */
223 goto Cleanup;
224 }
225 State->GeneralRegs[FAST486_REG_ESP].Long = Tss.Esp1;
226
227 break;
228 }
229
230 case 2:
231 {
232 if (!Fast486LoadSegment(State, FAST486_REG_SS, Tss.Ss2))
233 {
234 /* Exception occurred */
235 goto Cleanup;
236 }
237 State->GeneralRegs[FAST486_REG_ESP].Long = Tss.Esp2;
238
239 break;
240 }
241
242 default:
243 {
244 /* Should never reach here! */
245 ASSERT(FALSE);
246 }
247 }
248
249 /* Push SS selector */
250 if (!Fast486StackPush(State, OldSs)) goto Cleanup;
251
252 /* Push stack pointer */
253 if (!Fast486StackPush(State, OldEsp)) goto Cleanup;
254 }
255 }
256 else
257 {
258 if (State->SegmentRegs[FAST486_REG_CS].Size)
259 {
260 /* Set OPSIZE, because INT always pushes 16-bit values in real mode */
261 State->PrefixFlags |= FAST486_PREFIX_OPSIZE;
262 }
263 }
264
265 /* Push EFLAGS */
266 if (!Fast486StackPush(State, State->Flags.Long)) goto Cleanup;
267
268 /* Push CS selector */
269 if (!Fast486StackPush(State, State->SegmentRegs[FAST486_REG_CS].Selector)) goto Cleanup;
270
271 /* Push the instruction pointer */
272 if (!Fast486StackPush(State, State->InstPtr.Long)) goto Cleanup;
273
274 if ((GateType == FAST486_IDT_INT_GATE) || (GateType == FAST486_IDT_INT_GATE_32))
275 {
276 /* Disable interrupts after a jump to an interrupt gate handler */
277 State->Flags.If = FALSE;
278 }
279
280 /* Load new CS */
281 if (!Fast486LoadSegment(State, FAST486_REG_CS, SegmentSelector))
282 {
283 /* An exception occurred during the jump */
284 goto Cleanup;
285 }
286
287 if (GateSize)
288 {
289 /* 32-bit code segment, use EIP */
290 State->InstPtr.Long = Offset;
291 }
292 else
293 {
294 /* 16-bit code segment, use IP */
295 State->InstPtr.LowWord = LOWORD(Offset);
296 }
297
298 Success = TRUE;
299
300 Cleanup:
301 /* Restore the prefix flags */
302 State->PrefixFlags = OldPrefixFlags;
303
304 return Success;
305 }
306
307 VOID
308 FASTCALL
309 Fast486ExceptionWithErrorCode(PFAST486_STATE State,
310 FAST486_EXCEPTIONS ExceptionCode,
311 ULONG ErrorCode)
312 {
313 FAST486_IDT_ENTRY IdtEntry;
314
315 /* Increment the exception count */
316 State->ExceptionCount++;
317
318 /* Check if the exception occurred more than once */
319 if (State->ExceptionCount > 1)
320 {
321 /* Then this is a double fault */
322 ExceptionCode = FAST486_EXCEPTION_DF;
323 }
324
325 /* Check if this is a triple fault */
326 if (State->ExceptionCount == 3)
327 {
328 DPRINT("Fast486ExceptionWithErrorCode(%04X:%08X) -- Triple fault\n",
329 State->SegmentRegs[FAST486_REG_CS].Selector,
330 State->InstPtr.Long);
331
332 /* Reset the CPU */
333 Fast486Reset(State);
334 return;
335 }
336
337 /* Restore the IP to the saved IP */
338 State->InstPtr = State->SavedInstPtr;
339
340 if (!Fast486GetIntVector(State, ExceptionCode, &IdtEntry))
341 {
342 /*
343 * If this function failed, that means Fast486Exception
344 * was called again, so just return in this case.
345 */
346 return;
347 }
348
349 /* Perform the interrupt */
350 if (!Fast486InterruptInternal(State,
351 IdtEntry.Selector,
352 MAKELONG(IdtEntry.Offset, IdtEntry.OffsetHigh),
353 IdtEntry.Type))
354 {
355 /*
356 * If this function failed, that means Fast486Exception
357 * was called again, so just return in this case.
358 */
359 return;
360 }
361
362 if (EXCEPTION_HAS_ERROR_CODE(ExceptionCode)
363 && (State->ControlRegisters[FAST486_REG_CR0] & FAST486_CR0_PE))
364 {
365 /* Push the error code */
366 if (!Fast486StackPush(State, ErrorCode))
367 {
368 /*
369 * If this function failed, that means Fast486Exception
370 * was called again, so just return in this case.
371 */
372 return;
373 }
374 }
375
376 /* Reset the exception count */
377 State->ExceptionCount = 0;
378 }
379
380 /* EOF */