2 * Fast486 386/486 CPU Emulation Library
5 * Copyright (C) 2013 Aleksandar Andrejevic <theflash AT sdf DOT lonestar DOT org>
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.
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.
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.
22 /* INCLUDES *******************************************************************/
32 /* PUBLIC FUNCTIONS ***********************************************************/
35 Fast486ReadMemory(PFAST486_STATE State
,
36 FAST486_SEG_REGS SegmentReg
,
43 PFAST486_SEG_REG CachedDescriptor
;
45 ASSERT(SegmentReg
< FAST486_NUM_SEG_REGS
);
47 /* Get the cached descriptor */
48 CachedDescriptor
= &State
->SegmentRegs
[SegmentReg
];
50 if ((Offset
+ Size
- 1) > CachedDescriptor
->Limit
)
52 /* Read beyond limit */
53 Fast486Exception(State
, FAST486_EXCEPTION_GP
);
57 /* Check for protected mode */
58 if (State
->ControlRegisters
[0] & FAST486_CR0_PE
)
60 /* Privilege checks */
62 if (!CachedDescriptor
->Present
)
64 Fast486Exception(State
, FAST486_EXCEPTION_NP
);
68 if ((!InstFetch
&& (GET_SEGMENT_RPL(CachedDescriptor
->Selector
) > CachedDescriptor
->Dpl
))
69 || (Fast486GetCurrentPrivLevel(State
) > CachedDescriptor
->Dpl
))
71 Fast486Exception(State
, FAST486_EXCEPTION_GP
);
77 if (!CachedDescriptor
->Executable
)
79 /* Data segment not executable */
80 Fast486Exception(State
, FAST486_EXCEPTION_GP
);
86 if (CachedDescriptor
->Executable
&& (!CachedDescriptor
->ReadWrite
))
88 /* Code segment not readable */
89 Fast486Exception(State
, FAST486_EXCEPTION_GP
);
95 /* Find the linear address */
96 LinearAddress
= CachedDescriptor
->Base
+ Offset
;
98 /* Read from the linear address */
99 return Fast486ReadLinearMemory(State
, LinearAddress
, Buffer
, Size
);
103 Fast486WriteMemory(PFAST486_STATE State
,
104 FAST486_SEG_REGS SegmentReg
,
110 PFAST486_SEG_REG CachedDescriptor
;
112 ASSERT(SegmentReg
< FAST486_NUM_SEG_REGS
);
114 /* Get the cached descriptor */
115 CachedDescriptor
= &State
->SegmentRegs
[SegmentReg
];
117 if ((Offset
+ Size
- 1) > CachedDescriptor
->Limit
)
119 /* Write beyond limit */
120 Fast486Exception(State
, FAST486_EXCEPTION_GP
);
124 /* Check for protected mode */
125 if (State
->ControlRegisters
[0] & FAST486_CR0_PE
)
127 /* Privilege checks */
129 if (!CachedDescriptor
->Present
)
131 Fast486Exception(State
, FAST486_EXCEPTION_NP
);
135 if ((GET_SEGMENT_RPL(CachedDescriptor
->Selector
) > CachedDescriptor
->Dpl
)
136 || (Fast486GetCurrentPrivLevel(State
) > CachedDescriptor
->Dpl
))
138 Fast486Exception(State
, FAST486_EXCEPTION_GP
);
142 if (CachedDescriptor
->Executable
)
144 /* Code segment not writable */
145 Fast486Exception(State
, FAST486_EXCEPTION_GP
);
148 else if (!CachedDescriptor
->ReadWrite
)
150 /* Data segment not writeable */
151 Fast486Exception(State
, FAST486_EXCEPTION_GP
);
156 /* Find the linear address */
157 LinearAddress
= CachedDescriptor
->Base
+ Offset
;
159 /* Write to the linear address */
160 return Fast486WriteLinearMemory(State
, LinearAddress
, Buffer
, Size
);
164 Fast486InterruptInternal(PFAST486_STATE State
,
165 USHORT SegmentSelector
,
167 BOOLEAN InterruptGate
)
169 /* Check for protected mode */
170 if (State
->ControlRegisters
[FAST486_REG_CR0
] & FAST486_CR0_PE
)
173 USHORT OldSs
= State
->SegmentRegs
[FAST486_REG_SS
].Selector
;
174 ULONG OldEsp
= State
->GeneralRegs
[FAST486_REG_ESP
].Long
;
176 /* Check if the interrupt handler is more privileged */
177 if (Fast486GetCurrentPrivLevel(State
) > GET_SEGMENT_RPL(SegmentSelector
))
180 if (!Fast486ReadLinearMemory(State
,
185 /* Exception occurred */
189 /* Check the new (higher) privilege level */
190 switch (GET_SEGMENT_RPL(SegmentSelector
))
194 if (!Fast486LoadSegment(State
, FAST486_REG_SS
, Tss
.Ss0
))
196 /* Exception occurred */
199 State
->GeneralRegs
[FAST486_REG_ESP
].Long
= Tss
.Esp0
;
206 if (!Fast486LoadSegment(State
, FAST486_REG_SS
, Tss
.Ss1
))
208 /* Exception occurred */
211 State
->GeneralRegs
[FAST486_REG_ESP
].Long
= Tss
.Esp1
;
218 if (!Fast486LoadSegment(State
, FAST486_REG_SS
, Tss
.Ss2
))
220 /* Exception occurred */
223 State
->GeneralRegs
[FAST486_REG_ESP
].Long
= Tss
.Esp2
;
230 /* Should never reach here! */
235 /* Push SS selector */
236 if (!Fast486StackPush(State
, OldSs
)) return FALSE
;
238 /* Push stack pointer */
239 if (!Fast486StackPush(State
, OldEsp
)) return FALSE
;
244 if (State
->SegmentRegs
[FAST486_REG_CS
].Size
)
246 /* Set OPSIZE, because INT always pushes 16-bit values in real mode */
247 State
->PrefixFlags
|= FAST486_PREFIX_OPSIZE
;
252 if (!Fast486StackPush(State
, State
->Flags
.Long
)) return FALSE
;
254 /* Push CS selector */
255 if (!Fast486StackPush(State
, State
->SegmentRegs
[FAST486_REG_CS
].Selector
)) return FALSE
;
257 /* Push the instruction pointer */
258 if (!Fast486StackPush(State
, State
->InstPtr
.Long
)) return FALSE
;
262 /* Disable interrupts after a jump to an interrupt gate handler */
263 State
->Flags
.If
= FALSE
;
267 if (!Fast486LoadSegment(State
, FAST486_REG_CS
, SegmentSelector
))
269 /* An exception occurred during the jump */
273 if (State
->SegmentRegs
[FAST486_REG_CS
].Size
)
275 /* 32-bit code segment, use EIP */
276 State
->InstPtr
.Long
= Offset
;
280 /* 16-bit code segment, use IP */
281 State
->InstPtr
.LowWord
= LOWORD(Offset
);
289 Fast486ExceptionWithErrorCode(PFAST486_STATE State
,
290 FAST486_EXCEPTIONS ExceptionCode
,
293 FAST486_IDT_ENTRY IdtEntry
;
295 /* Increment the exception count */
296 State
->ExceptionCount
++;
298 /* Check if the exception occurred more than once */
299 if (State
->ExceptionCount
> 1)
301 /* Then this is a double fault */
302 ExceptionCode
= FAST486_EXCEPTION_DF
;
305 /* Check if this is a triple fault */
306 if (State
->ExceptionCount
== 3)
313 /* Restore the IP to the saved IP */
314 State
->InstPtr
= State
->SavedInstPtr
;
316 if (!Fast486GetIntVector(State
, ExceptionCode
, &IdtEntry
))
319 * If this function failed, that means Fast486Exception
320 * was called again, so just return in this case.
325 /* Perform the interrupt */
326 if (!Fast486InterruptInternal(State
,
328 MAKELONG(IdtEntry
.Offset
, IdtEntry
.OffsetHigh
),
332 * If this function failed, that means Fast486Exception
333 * was called again, so just return in this case.
338 if (EXCEPTION_HAS_ERROR_CODE(ExceptionCode
)
339 && (State
->ControlRegisters
[FAST486_REG_CR0
] & FAST486_CR0_PE
))
341 /* Push the error code */
342 if (!Fast486StackPush(State
, ErrorCode
))
345 * If this function failed, that means Fast486Exception
346 * was called again, so just return in this case.
352 /* Reset the exception count */
353 State
->ExceptionCount
= 0;