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290 lines
4.6 KiB
290 lines
4.6 KiB
/*++
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Copyright (c) 1994 Microsoft Corporation
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Module Name:
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jmpops.c
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Abstract:
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This module implements the code to emulate jump opcodes.
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Author:
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David N. Cutler (davec) 13-Sep-1994
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Environment:
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Kernel mode only.
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Revision History:
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--*/
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#include "nthal.h"
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#include "emulate.h"
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VOID
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XmJcxzOp (
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IN PRXM_CONTEXT P
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)
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/*++
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Routine Description:
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This function emulates a jcxz instruction.
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Arguments:
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P - Supplies a pointer to the emulation context structure.
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Return Value:
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None.
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--*/
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{
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ULONG Condition;
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//
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// If eCX is zero, then set the new IP value.
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//
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if (P->OpsizePrefixActive != FALSE) {
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Condition = P->Gpr[ECX].Exx;
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} else {
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Condition = P->Gpr[CX].Xx;
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}
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if (Condition == 0) {
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P->Eip = P->DstValue.Word;
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XmTraceJumps(P);
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}
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return;
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}
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VOID
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XmJmpOp (
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IN PRXM_CONTEXT P
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)
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/*++
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Routine Description:
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This function emulates a jmp near relative instruction.
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Arguments:
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P - Supplies a pointer to the emulation context structure.
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Return Value:
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None.
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--*/
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{
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//
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// Set the destination segment, if required, and set the new IP.
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//
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P->Eip = P->DstValue.Long;
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if ((P->CurrentOpcode == 0xea) || (P->FunctionIndex != X86_JMP_OP)) {
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P->SegmentRegister[CS] = P->DstSegment;
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}
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XmTraceJumps(P);
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return;
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}
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VOID
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XmJxxOp (
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IN PRXM_CONTEXT P
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)
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/*++
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Routine Description:
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This function emulates conditional jump instructions.
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Arguments:
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P - Supplies a pointer to the emulation context structure.
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Return Value:
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None.
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--*/
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{
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ULONG Complement;
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ULONG Condition;
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//
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// Case on the jump control value.
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//
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Complement = P->SrcValue.Long & 1;
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switch (P->SrcValue.Long >> 1) {
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//
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// Jump if overflow/not overflow.
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//
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case 0:
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Condition = P->Eflags.EFLAG_OF;
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break;
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//
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// Jump if below/not below.
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//
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case 1:
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Condition = P->Eflags.EFLAG_CF;
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break;
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//
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// Jump if zero/not zero.
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//
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case 2:
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Condition = P->Eflags.EFLAG_ZF;
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break;
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//
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// Jump if below or equal/not below or equal.
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//
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case 3:
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Condition = P->Eflags.EFLAG_CF | P->Eflags.EFLAG_ZF;
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break;
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//
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// Jump if signed/not signed.
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//
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case 4:
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Condition = P->Eflags.EFLAG_SF;
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break;
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//
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// Jump if parity/not parity.
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//
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case 5:
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Condition = P->Eflags.EFLAG_PF;
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break;
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//
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// Jump if less/not less.
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//
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case 6:
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Condition = (P->Eflags.EFLAG_SF ^ P->Eflags.EFLAG_OF);
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break;
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//
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// Jump if less or equal/not less or equal.
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//
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case 7:
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Condition = (P->Eflags.EFLAG_SF ^ P->Eflags.EFLAG_OF) | P->Eflags.EFLAG_ZF;
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break;
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}
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//
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// If the specified condition is met, then set the new IP value.
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//
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if ((Condition ^ Complement) != 0) {
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P->Eip = P->DstValue.Word;
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XmTraceJumps(P);
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}
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return;
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}
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VOID
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XmLoopOp (
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IN PRXM_CONTEXT P
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)
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/*++
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Routine Description:
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This function emulates loop, loopz, or a loopnz instructions.
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Arguments:
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P - Supplies a pointer to the emulation context structure.
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Return Value:
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None.
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--*/
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{
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ULONG Condition;
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ULONG Result;
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ULONG Type;
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//
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// Set the address of the destination and compute the result value.
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//
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Result = P->Gpr[ECX].Exx - 1;
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P->DstLong = (UNALIGNED ULONG *)(&P->Gpr[ECX].Exx);
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if (P->OpaddrPrefixActive != FALSE) {
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P->DataType = LONG_DATA;
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} else {
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P->DataType = WORD_DATA;
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Result &= 0xffff;
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}
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XmStoreResult(P, Result);
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//
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// Isolate the loop type and test the appropriate condition.
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//
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// Type 0 - loopnz
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// 1 - loopz
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// 2 - loop
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//
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Type = P->CurrentOpcode & 3;
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if (Type == 0) {
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Condition = P->Eflags.EFLAG_ZF ^ 1;
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} else if (Type == 1) {
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Condition = P->Eflags.EFLAG_ZF;
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} else {
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Condition = TRUE;
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}
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//
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// If the loop condition is met, then set the new IP value.
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//
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if ((Condition != FALSE) && (Result != 0)) {
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P->Eip = P->DstValue.Word;
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XmTraceJumps(P);
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}
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return;
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}
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