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bddisasm/bdshemu/bdshemu_x86.c
Andrei Vlad LUTAS 54a2027333 Added 64-bit mul test case + made the code more readable.
2024-06-05 00:52:51 +03:00

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/*
* Copyright (c) 2020 Bitdefender
* SPDX-License-Identifier: Apache-2.0
*/
//
// bdshemu.c
//
#include "../inc/bdshemu.h"
#include "../bddisasm/include/bddisasm_crt.h"
#include "include/bdshemu_common.h"
#if defined(ND_ARCH_X64) || defined(ND_ARCH_X86)
#ifdef __clang__
#include <wmmintrin.h>
#else
#include <immintrin.h>
#endif // __clang__
#endif // defined(ND_ARCH_X64) || defined(ND_ARCH_X86)
//
// A generic emulator value.
//
typedef struct _SHEMU_VALUE
{
union
{
ND_UINT8 Bytes[ND_MAX_REGISTER_SIZE];
ND_UINT16 Words[ND_MAX_REGISTER_SIZE / sizeof(ND_UINT16)];
ND_UINT32 Dwords[ND_MAX_REGISTER_SIZE / sizeof(ND_UINT32)];
ND_UINT64 Qwords[ND_MAX_REGISTER_SIZE / sizeof(ND_UINT64)];
struct
{
ND_UINT16 FpuControlWord;
ND_UINT16 FpuStatusWord;
ND_UINT16 FpuTagWord;
ND_UINT16 Rsvd;
ND_UINT32 FpuDataPointer;
ND_UINT32 FpuInstructionPointer;
ND_UINT32 FpuLastInstructionOpcode;
} FpuEnvironment;
struct
{
ND_UINT16 FpuControlWord;
ND_UINT16 FpuStatuwsWord;
ND_UINT16 FpuTagWord;
ND_UINT16 FpuOpcode;
ND_UINT64 FpuRip;
ND_UINT64 FpuDataPointer;
ND_UINT32 Mxcsr;
ND_UINT32 MxcsrMask;
} XsaveArea;
struct
{
ND_UINT16 Limit;
ND_UINT64 Base;
} Descriptor;
} Value;
ND_OPERAND_SIZE Size;
} SHEMU_VALUE, *PSHEMU_VALUE;
enum
{
FM_LOGIC,
FM_SHL,
FM_SHR,
FM_SAR,
FM_SUB,
FM_ADD,
} FLAGS_MODE;
#define GET_OP(ctx, op, val) { \
shstatus = ShemuX86GetOperandValue(ctx, op, val); \
if (SHEMU_SUCCESS != shstatus) \
{ \
return shstatus; \
} \
}
#define SET_OP(ctx, op, val) { \
shstatus = ShemuX86SetOperandValue(ctx, op, val); \
if (SHEMU_SUCCESS != shstatus) \
{ \
return shstatus; \
} \
}
#define GET_FLAG(ctx, flg) (!!((ctx)->Arch.X86.Registers.RegFlags & (flg)))
#define SET_FLAG(ctx, flg, val) ShemuX86SetFlag(ctx, flg, val)
#define SET_FLAGS(ctx, dst, src1, src2, fm) ShemuX86SetFlags(ctx, dst.Value.Qwords[0], src1.Value.Qwords[0], \
src2.Value.Qwords[0], dst.Size, fm)
//
// ShemuX86SetFlag
//
static void
ShemuX86SetFlag(
SHEMU_CONTEXT *Context,
ND_UINT64 Flag,
ND_UINT64 Value
)
{
// {NF} present for instruction, no flags will be modified.
if (Context->Arch.X86.Instruction.HasNf)
{
return;
}
if (Value)
{
Context->Arch.X86.Registers.RegFlags |= Flag;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~Flag;
}
}
//
// ShemuX86SetFlags
//
static void
ShemuX86SetFlags(
SHEMU_CONTEXT *Context,
ND_UINT64 Dst,
ND_UINT64 Src1,
ND_UINT64 Src2,
ND_OPERAND_SIZE Size,
ND_UINT8 FlagsMode
)
{
ND_UINT8 pfArr[16] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
// {NF} present for instruction, no flags will be modified.
if (Context->Arch.X86.Instruction.HasNf)
{
return;
}
// Mask the operands with their respective size.
Dst = ND_TRIM(Size, Dst);
Src1 = ND_TRIM(Size, Src1);
Src2 = ND_TRIM(Size, Src2);
if (FlagsMode == FM_SHL || FlagsMode == FM_SHR || FlagsMode == FM_SAR)
{
// Shift with 0 count does not affect flags.
if (Src2 == 0)
{
return;
}
}
// PF set if the first bytes has an even number of 1 bits.
if ((pfArr[Dst & 0xF] + pfArr[(Dst >> 4) & 0xF]) % 2 == 0)
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_PF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_PF;
}
// ZF set if the result is zero.
if (Dst == 0)
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_ZF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_ZF;
}
// SF is set if the sign flag is set.
if (ND_GET_SIGN(Size, Dst) != 0)
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_SF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_SF;
}
// OF and CF are handled differently for some instructions.
if (FM_LOGIC == FlagsMode)
{
// OF and CF are cleared on logic instructions.
Context->Arch.X86.Registers.RegFlags &= ~(NDR_RFLAG_OF | NDR_RFLAG_CF);
}
else if (FM_SHL == FlagsMode)
{
// CF is the last bit shifted out of the destination.
if ((Src2 <= Size * 8ULL) && ND_GET_BIT((Size * 8ULL) - Src2, Src1))
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_CF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_CF;
}
if (Src2 == 1)
{
if (ND_GET_BIT(Size * 8ULL - 1, Src1) ^ ND_GET_BIT(Size * 8ULL - 2, Src1))
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_OF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_OF;
}
}
}
else if (FM_SHR == FlagsMode)
{
// CF is the last bit shifted out of the destination.
// Src2 - 1 is ok - this function does not get called if Src2 is 0.
if (ND_GET_BIT(Src2 - 1, Src1))
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_CF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_CF;
}
if (Src2 == 1)
{
if (ND_GET_BIT(Size * 8ULL - 1, Src1))
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_OF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_OF;
}
}
}
else if (FM_SAR == FlagsMode)
{
// CF is the last bit shifted out of the destination. In case of SAR, if the shift ammount exceeds the operand
// size, CF will be 1 if the result is -1, or 0 if the result is 0.
// Src2 - 1 is ok - this function does not get called if Src2 is 0.
if (ND_GET_BIT(Src2 - 1, Src1) || ((Src2 >= (ND_UINT64)Size * 8) && Dst != 0))
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_CF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_CF;
}
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_OF;
}
else
{
// Set CF.
if ((FM_SUB == FlagsMode) && ((Src1 < Src2) || (Src1 == Src2 && Dst != 0)))
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_CF;
}
else if ((FM_ADD == FlagsMode) && ((Dst < Src1) || (Dst == Src1 && Src2 != 0)))
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_CF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_CF;
}
// Set OF.
if (FM_SUB == FlagsMode)
{
if ((ND_GET_SIGN(Size, Src1) && !ND_GET_SIGN(Size, Src2) && !ND_GET_SIGN(Size, Dst)) ||
(!ND_GET_SIGN(Size, Src1) && ND_GET_SIGN(Size, Src2) && ND_GET_SIGN(Size, Dst)))
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_OF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_OF;
}
}
else if (FM_ADD == FlagsMode)
{
if (ND_GET_SIGN(Size, Src1) == ND_GET_SIGN(Size, Src2) &&
ND_GET_SIGN(Size, Src1) != ND_GET_SIGN(Size, Dst))
{
Context->Arch.X86.Registers.RegFlags |= NDR_RFLAG_OF;
}
else
{
Context->Arch.X86.Registers.RegFlags &= ~NDR_RFLAG_OF;
}
}
}
}
//
// ShemuX86EvalCondition
//
static ND_BOOL
ShemuX86EvalCondition(
SHEMU_CONTEXT *Context,
ND_UINT8 ConditionCode
)
{
switch (ConditionCode)
{
case ND_COND_OVERFLOW: // O
if (GET_FLAG(Context, NDR_RFLAG_OF) == 1)
{
return ND_TRUE;
}
break;
case ND_COND_NOT(ND_COND_OVERFLOW): // NO
if (GET_FLAG(Context, NDR_RFLAG_OF) == 0)
{
return ND_TRUE;
}
break;
case ND_COND_CARRY: // C/B/NAE
if (GET_FLAG(Context, NDR_RFLAG_CF) == 1)
{
return ND_TRUE;
}
break;
case ND_COND_NOT(ND_COND_CARRY): // NC/NB/AE
if (GET_FLAG(Context, NDR_RFLAG_CF) == 0)
{
return ND_TRUE;
}
break;
case ND_COND_ZERO: // E/Z
if (GET_FLAG(Context, NDR_RFLAG_ZF) == 1)
{
return ND_TRUE;
}
break;
case ND_COND_NOT(ND_COND_ZERO): // NE/NZ
if (GET_FLAG(Context, NDR_RFLAG_ZF) == 0)
{
return ND_TRUE;
}
break;
case ND_COND_BELOW_OR_EQUAL: // BE/NA
if ((GET_FLAG(Context, NDR_RFLAG_CF) | (GET_FLAG(Context, NDR_RFLAG_ZF))) == 1)
{
return ND_TRUE;
}
break;
case ND_COND_NOT(ND_COND_BELOW_OR_EQUAL): // A/NBE
if ((GET_FLAG(Context, NDR_RFLAG_CF) | (GET_FLAG(Context, NDR_RFLAG_ZF))) == 0)
{
return ND_TRUE;
}
break;
case ND_COND_SIGN: // S
if (GET_FLAG(Context, NDR_RFLAG_SF) == 1)
{
return ND_TRUE;
}
break;
case ND_COND_NOT(ND_COND_SIGN): // NS
if (GET_FLAG(Context, NDR_RFLAG_SF) == 0)
{
return ND_TRUE;
}
break;
case ND_COND_PARITY: // P
if (GET_FLAG(Context, NDR_RFLAG_PF) == 1)
{
return ND_TRUE;
}
break;
case ND_COND_NOT(ND_COND_PARITY): // NP
if (GET_FLAG(Context, NDR_RFLAG_PF) == 0)
{
return ND_TRUE;
}
break;
case ND_COND_LESS: // L/NGE
if ((GET_FLAG(Context, NDR_RFLAG_SF) ^ GET_FLAG(Context, NDR_RFLAG_OF)) == 1)
{
return ND_TRUE;
}
break;
case ND_COND_NOT(ND_COND_LESS): // NL/GE
if ((GET_FLAG(Context, NDR_RFLAG_SF) ^ GET_FLAG(Context, NDR_RFLAG_OF)) == 0)
{
return ND_TRUE;
}
break;
case ND_COND_LESS_OR_EQUAL: // LE/NG
if (((GET_FLAG(Context, NDR_RFLAG_SF) ^ GET_FLAG(Context, NDR_RFLAG_OF)) |
(GET_FLAG(Context, NDR_RFLAG_ZF))) == 1)
{
return ND_TRUE;
}
break;
case ND_COND_NOT(ND_COND_LESS_OR_EQUAL): // NLE/G
if (((GET_FLAG(Context, NDR_RFLAG_SF) ^ GET_FLAG(Context, NDR_RFLAG_OF)) |
(GET_FLAG(Context, NDR_RFLAG_ZF))) == 0)
{
return ND_TRUE;
}
break;
}
return ND_FALSE;
}
//
// ShemuX86GetGprValue
//
static ND_UINT64
ShemuX86GetGprValue(
SHEMU_CONTEXT *Context,
ND_UINT32 Reg,
ND_UINT32 Size,
ND_BOOL High8
)
{
if (High8 && Reg >= 4)
{
Reg = Reg - 4;
}
// Any read of the GPR, before being modified, counts as being "saved". The reason here is that we cannot
// easily track a proper save in memory, as the register may be copied in another register, and only then
// saved.
if (!(Context->Arch.X86.GprTracker[Reg] & GPR_TRACK_DIRTY))
{
Context->Arch.X86.GprTracker[Reg] |= GPR_TRACK_READ;
}
switch (Size)
{
case 1:
if (High8)
{
// AH, CH, DH or BH accessed.
return (*(&Context->Arch.X86.Registers.RegRax + Reg) >> 8) & 0xff;
}
else
{
return *(&Context->Arch.X86.Registers.RegRax + Reg) & 0xff;
}
case 2:
return *(&Context->Arch.X86.Registers.RegRax + Reg) & 0xffff;
case 4:
return *(&Context->Arch.X86.Registers.RegRax + Reg) & 0xffffffff;
default:
return *(&Context->Arch.X86.Registers.RegRax + Reg);
}
}
//
// ShemuX86GetGprValue
//
static void
ShemuX86SetGprValue(
SHEMU_CONTEXT *Context,
ND_UINT32 Reg,
ND_UINT32 Size,
ND_UINT64 Value,
ND_BOOL High8
)
{
if (High8 && Reg >= 4)
{
Reg = Reg - 4;
}
// If ZeroUpper semantic is enabled for APX instruction, make sure to zero out the destination.
// {ZU} can be either explicit (example: IMUL), or implicit (example: any {ND} instruction).
if (Context->Arch.X86.Instruction.HasZu || Context->Arch.X86.Instruction.HasNd)
{
*(&Context->Arch.X86.Registers.RegRax + Reg) = 0;
}
switch (Size)
{
case 1:
if (High8)
{
// AH, CH, DH or BH accessed.
*((ND_UINT8 *)(&Context->Arch.X86.Registers.RegRax + Reg) + 1) = Value & 0xFF;
}
else
{
*((ND_UINT8 *)(&Context->Arch.X86.Registers.RegRax + Reg)) = Value & 0xff;
}
break;
case 2:
*((ND_UINT16 *)(&Context->Arch.X86.Registers.RegRax + Reg)) = Value & 0xffff;
break;
case 4:
// Higher ND_UINT32 is always set to zero.
*(&Context->Arch.X86.Registers.RegRax + Reg) = Value & 0xffffffff;
break;
default:
*(&Context->Arch.X86.Registers.RegRax + Reg) = Value;
break;
}
// Mark the GPR as being dirty/written.
if (!(Context->Arch.X86.GprTracker[Reg] & GPR_TRACK_READ))
{
Context->Arch.X86.GprTracker[Reg] |= GPR_TRACK_DIRTY;
}
}
//
// ShemuX86GetSegValue
//
static ND_UINT64
ShemuX86GetSegValue(
SHEMU_CONTEXT *Context,
ND_UINT32 Reg
)
{
switch (Reg)
{
case NDR_ES:
return Context->Arch.X86.Segments.Es.Selector;
case NDR_CS:
return Context->Arch.X86.Segments.Cs.Selector;
case NDR_SS:
return Context->Arch.X86.Segments.Ss.Selector;
case NDR_DS:
return Context->Arch.X86.Segments.Ds.Selector;
case NDR_FS:
return Context->Arch.X86.Segments.Fs.Selector;
case NDR_GS:
return Context->Arch.X86.Segments.Gs.Selector;
}
return 0;
}
//
// ShemuX86SetSegValue
//
static void
ShemuX86SetSegValue(
SHEMU_CONTEXT *Context,
ND_UINT32 Reg,
ND_UINT16 Value
)
{
switch (Reg)
{
case NDR_ES:
Context->Arch.X86.Segments.Es.Selector = Value;
break;
case NDR_CS:
Context->Arch.X86.Segments.Cs.Selector = Value;
break;
case NDR_SS:
Context->Arch.X86.Segments.Ss.Selector = Value;
break;
case NDR_DS:
Context->Arch.X86.Segments.Ds.Selector = Value;
break;
case NDR_FS:
Context->Arch.X86.Segments.Fs.Selector = Value;
break;
case NDR_GS:
Context->Arch.X86.Segments.Gs.Selector = Value;
break;
}
}
//
// ShemuX86GetSegBase
//
static ND_UINT64
ShemuX86GetSegBase(
SHEMU_CONTEXT *Context,
ND_UINT32 Reg
)
{
switch (Reg)
{
case NDR_ES:
return Context->Arch.X86.Segments.Es.Base;
case NDR_CS:
return Context->Arch.X86.Segments.Cs.Base;
case NDR_SS:
return Context->Arch.X86.Segments.Ss.Base;
case NDR_DS:
return Context->Arch.X86.Segments.Ds.Base;
case NDR_FS:
return Context->Arch.X86.Segments.Fs.Base;
case NDR_GS:
return Context->Arch.X86.Segments.Gs.Base;
}
return 0;
}
//
// ShemuX86IsSelectorValid
//
static ND_BOOL
ShemuX86IsSelectorValid(
SHEMU_CONTEXT *Context,
ND_UINT32 Reg,
ND_UINT16 Value
)
{
// Allow NULL selectors in 64 bit mode inside ES, DS, FS, GS.
if ((Value == 0) && (Context->Arch.X86.Mode == ND_CODE_64) && (Reg != NDR_SS))
{
return ND_TRUE;
}
if ((Value & 0xFFF8) >= 0x80)
{
// Too large value.
return ND_FALSE;
}
if ((Value & 4) != 0)
{
// LDT selector.
return ND_FALSE;
}
if ((Context->Arch.X86.Ring == 0) && ((Value & 3) != 0))
{
// Ring 0 selector, with RPL != 0.
return ND_FALSE;
}
if ((Context->Arch.X86.Ring == 3) && ((Value & 3) != 3))
{
// Ring 3 selector, with RPL != 3.
return ND_FALSE;
}
return ND_TRUE;
}
//
// ShemuX86IsAddressAligned
//
static ND_BOOL
ShemuX86IsAddressAligned(
SHEMU_CONTEXT *Context,
ND_UINT64 Address
)
{
if (Context->Arch.X86.Mode == ND_CODE_64)
{
return Address % 8 == 0;
}
else
{
return Address % 4 == 0;
}
}
//
// ShemuX86TrackLoopStart
//
static void
ShemuX86TrackLoopStart(
SHEMU_CONTEXT *Context,
ND_UINT64 Rip,
ND_UINT64 Target
)
{
if (Context->LoopTrack.Active)
{
return;
}
Context->LoopTrack.Active = ND_TRUE;
Context->LoopTrack.Iteration = 1;
Context->LoopTrack.Address = Rip;
Context->LoopTrack.Target = Target;
if (!!(Context->Options & SHEMU_OPT_TRACE_LOOPS))
{
shemu_printf(Context, " Loop BEGIN from RIP 0x%016llx, TARGET 0x%016llx, ITER %llu\n",
Context->LoopTrack.Address, Context->LoopTrack.Target, Context->LoopTrack.Iteration);
}
}
//
// ShemuX86TrackLoopStop
//
static void
ShemuX86TrackLoopStop(
SHEMU_CONTEXT *Context
)
{
if (!Context->LoopTrack.Active)
{
return;
}
if (!!(Context->Options & SHEMU_OPT_TRACE_LOOPS))
{
shemu_printf(Context, " Loop BREAK from RIP 0x%016llx, TARGET 0x%016llx, ITER %llu\n",
Context->LoopTrack.Address, Context->LoopTrack.Target, Context->LoopTrack.Iteration);
}
Context->LoopTrack.Active = ND_FALSE;
Context->LoopTrack.Address = 0;
Context->LoopTrack.Target = 0;
Context->LoopTrack.Iteration = 0;
}
//
// ShemuX86TrackLoop
//
static ND_BOOL
ShemuX86TrackLoop(
SHEMU_CONTEXT *Context,
ND_BOOL Taken
)
{
ND_UINT64 rip, target;
// The address of the loop instruction itself, not the next instruction.
rip = Context->Arch.X86.Registers.RegRip - Context->Arch.X86.Instruction.Length;
// The branches we monitor always have a relative offset, which is the first operand.
target = Context->Arch.X86.Registers.RegRip + Context->Arch.X86.Instruction.Operands[0].Info.RelativeOffset.Rel;
if (target < rip)
{
// Case 1: Backward branch.
if (Taken)
{
// Taken backward branch instruction.
if (rip == Context->LoopTrack.Address)
{
// Current active loop, this is a new iteration. Example:
// label1: <--+
// ... |
// loop label1 ---+
// ...
// Update loop information.
Context->LoopTrack.Iteration++;
}
else
{
// New loop, or loop within our current loop. Always track the inner most loop. Example:
// label1: <--+
// ... |
// label2: <--+ |
// ... | |
// loop label2 ---+ |
// ... |
// loop label1 ---+
// ...
// Start tracking the (potentially new) loop.
ShemuX86TrackLoopStop(Context);
ShemuX86TrackLoopStart(Context, rip, target);
}
}
else
{
// Not taken backward branch instruction.
if (rip == Context->LoopTrack.Address)
{
// Current loop ends, the loop instruction is no longer taken. Example:
// label1:
// ...
// loop label1 ---+
// ... <--+
// Stop tracking.
ShemuX86TrackLoopStop(Context);
}
else
{
// Not taken backward branch, but not our current loop.
// Nothing to do.
}
}
}
else
{
// Case 2: Forward branch.
if (Taken)
{
// Taken forward branch instruction.
if (target < Context->LoopTrack.Target || target > Context->LoopTrack.Address)
{
// Break instruction. Example:
// label1:
// ...
// jnz label2 ---+
// ... |
// loop label1 |
// ... |
// label2: <--+
// ...
// Stop tracking.
ShemuX86TrackLoopStop(Context);
}
else
{
// If instruction. Example:
// label1:
// ...
// jnz label2 ---+
// ... |
// label2: <--+
// ...
// loop label1
// ...
// Nothing to do.
}
}
else
{
// Not taken forward branch instruction.
// Nothing to do.
}
}
// In theory, we can override whether the branch is taken or not, but for now, this is not used.
return Taken;
}
//
// ShemuX86ComputeLinearAddress
//
static ND_UINT64
ShemuX86ComputeLinearAddress(
SHEMU_CONTEXT *Context,
PND_OPERAND Operand
)
{
ND_UINT64 gla = 0;
if (Operand->Info.Memory.HasBase)
{
gla += ShemuX86GetGprValue(Context, Operand->Info.Memory.Base, Operand->Info.Memory.BaseSize, ND_FALSE);
}
if (Operand->Info.Memory.HasIndex)
{
gla += ShemuX86GetGprValue(Context, Operand->Info.Memory.Index, Operand->Info.Memory.IndexSize, ND_FALSE) *
Operand->Info.Memory.Scale;
}
// Note that this also handles the case where moffset (absolute addressing) is used, as HasDisp will be set when
// IsDirect is also set.
if (Operand->Info.Memory.HasDisp)
{
gla += Operand->Info.Memory.Disp;
}
if (Operand->Info.Memory.IsRipRel)
{
gla += Context->Arch.X86.Registers.RegRip;
}
// Special handling for BT, BTR, BTS, BTC instructions with bitbase addressing.
if (Operand->Info.Memory.IsBitbase)
{
ND_UINT64 bitbase, op1size, op2size, reg;
op1size = Context->Arch.X86.Instruction.Operands[0].Size;
op2size = Context->Arch.X86.Instruction.Operands[1].Size;
reg = ((ND_UINT64*)&Context->Arch.X86.Registers.RegRax)[Context->Arch.X86.Instruction.Operands[1].Info.Register.Reg];
// Note: only BT* with register source (NOT immediate) support bitbase addressing.
bitbase = ND_SIGN_EX(op2size, reg);
if (bitbase & (1ULL << 63))
{
gla -= ((~bitbase >> 3) & ~(op1size - 1)) + op1size;
}
else
{
gla += (bitbase >> 3) & ~(op1size - 1);
}
}
// Special handling for stack operations: if we have a PUSH, we have to subtract the accessed size, as, in fact,
// [RSP - size] is accessed, not [RSP].
if (Operand->Info.Memory.IsStack)
{
if (Operand->Access.Write || Operand->Access.CondWrite)
{
gla -= Operand->Size;
}
}
// Make sure we truncate the linear address to the address size.
switch (Context->Arch.X86.Instruction.AddrMode)
{
case ND_ADDR_32:
gla &= 0xFFFFFFFF;
break;
case ND_ADDR_16:
gla &= 0xFFFF;
default:
break;
}
// Memory operands usually have a segment. Note that we don't care about any segment checks, since we're most
// likely be provided with flat segments. If checks should be needed, dedicated callbacks should be added.
if (Operand->Info.Memory.HasSeg)
{
gla += ShemuX86GetSegBase(Context, Operand->Info.Memory.Seg);
if (Context->Arch.X86.Mode != ND_CODE_64)
{
// Truncate to 32 bit outside 64 bit.
gla &= 0xFFFFFFFF;
}
}
return gla;
}
//
// ShemuX86GetOperandValue
//
static SHEMU_STATUS
ShemuX86GetOperandValue(
SHEMU_CONTEXT *Context,
ND_UINT32 Operand,
SHEMU_VALUE *Value
)
{
SHEMU_STATUS status;
PND_OPERAND op = &Context->Arch.X86.Instruction.Operands[Operand];
Value->Size = op->Size;
if (Value->Size > sizeof(Value->Value))
{
return SHEMU_ABORT_OPERAND_NOT_SUPPORTED;
}
if (op->Type == ND_OP_REG)
{
switch (op->Info.Register.Type)
{
case ND_REG_GPR:
Value->Value.Qwords[0] = ShemuX86GetGprValue(Context, op->Info.Register.Reg, op->Size,
op->Info.Register.IsHigh8);
break;
case ND_REG_SEG:
Value->Value.Qwords[0] = ShemuX86GetSegValue(Context, op->Info.Register.Reg);
break;
case ND_REG_MMX:
Value->Value.Qwords[0] = Context->Arch.X86.MmxRegisters[op->Info.Register.Reg];
break;
case ND_REG_SSE:
shemu_memcpy(Value->Value.Bytes,
&Context->Arch.X86.SseRegisters[op->Info.Register.Reg],
op->Size);
break;
case ND_REG_RIP:
Value->Value.Qwords[0] = ND_TRIM(Value->Size, Context->Arch.X86.Registers.RegRip);
break;
case ND_REG_FLG:
Value->Value.Qwords[0] = Context->Arch.X86.Registers.RegFlags;
break;
case ND_REG_CR:
switch (op->Info.Register.Reg)
{
case NDR_CR0:
Value->Value.Qwords[0] = Context->Arch.X86.Registers.RegCr0;
break;
case NDR_CR2:
Value->Value.Qwords[0] = Context->Arch.X86.Registers.RegCr2;
break;
case NDR_CR3:
Value->Value.Qwords[0] = Context->Arch.X86.Registers.RegCr3;
break;
case NDR_CR4:
Value->Value.Qwords[0] = Context->Arch.X86.Registers.RegCr4;
break;
case NDR_CR8:
Value->Value.Qwords[0] = Context->Arch.X86.Registers.RegCr8;
break;
default:
return SHEMU_ABORT_REGISTER_NOT_SUPPORTED;
}
break;
default:
return SHEMU_ABORT_REGISTER_NOT_SUPPORTED;
}
}
else if (op->Type == ND_OP_MEM)
{
ND_UINT64 gla = ShemuX86ComputeLinearAddress(Context, op);
ND_UINT32 offsetPeb;
ND_UINT8 seg;
if (op->Info.Memory.IsAG)
{
// Address generation instruction, the result is the linear address itself.
Value->Value.Qwords[0] = gla;
goto done_gla;
}
if (Context->Arch.X86.Ring == 3)
{
// User-mode TIB offset that contains the PEB address.
offsetPeb = Context->Arch.X86.Mode == ND_CODE_32 ? 0x30 : 0x60;
seg = Context->Arch.X86.Mode == ND_CODE_32 ? ND_PREFIX_G2_SEG_FS : ND_PREFIX_G2_SEG_GS;
}
else
{
// Kernel-mode KPCR offset that contains the current KTHREAD address.
offsetPeb = Context->Arch.X86.Mode == ND_CODE_32 ? 0x124 : 0x188;
seg = Context->Arch.X86.Mode == ND_CODE_32 ? ND_PREFIX_G2_SEG_FS : ND_PREFIX_G2_SEG_GS;
}
// Check if this is a TIB/PCR access. Make sure the FS/GS register is used for the access, in order to avoid
// FALSE positives where legitimate code accesses a linear TIB directly.
// Note that this covers accesses to the PEB field inside the TIB.
if (Context->Arch.X86.Ring == 3)
{
if (Context->Arch.X86.Instruction.Seg == seg &&
gla == Context->TibBase + offsetPeb)
{
Context->Flags |= SHEMU_FLAG_TIB_ACCESS_PEB;
}
}
// Note that this covers accesses to the Wow32Reserved in Wow64 mode. That field can be used to issue
// syscalls.
if (gla == Context->TibBase + 0xC0 && Context->Arch.X86.Instruction.Seg == seg &&
Context->Arch.X86.Mode == ND_CODE_32)
{
Context->Flags |= SHEMU_FLAG_TIB_ACCESS_WOW32;
}
// Check for accesses inside the KUSER_SHARED_DATA (SharedUserData). This page contains some
// global system information, it may host shellcodes, and is hard-coded at this address. We
// only consider accesses to some SUD fields, in order to avoid false-positives.
if ((gla >= 0x7FFE02D4 && gla < 0x7FFE02D5) || // KdDebuggerEnabled
(gla >= 0x7FFE0308 && gla < 0x7FFE1310) || // SystemCall
(gla >= 0x7FFE0330 && gla < 0x7FFE1338)) // Cookie
{
Context->Flags |= SHEMU_FLAG_SUD_ACCESS;
}
// Check if we are reading a previously saved RIP. Ignore RET instructions, which naturally access the
// saved RIP.
if (Context->Arch.X86.Instruction.Category != ND_CAT_RET &&
ShemuIsStackPtr(Context, gla, op->Size) &&
ShemuStackBmpStateCheck(Context, gla - Context->StackBase, op->Size, STACK_BYTE_RIP))
{
PND_OPERAND dst = ND_NULL;
for (ND_UINT32 i = 0; i < Context->Arch.X86.Instruction.OperandsCount; i++)
{
// We fetch the first destination, if any. We ignore the current operand.
if ((i != Operand) && (Context->Arch.X86.Instruction.Operands[i].Access.Access & ND_ACCESS_ANY_WRITE))
{
dst = &Context->Arch.X86.Instruction.Operands[i];
break;
}
}
// We consider a LOAD_RIP detection only if the RIP value is loaded in:
// - Another memory location;
// - A register, which is not (excluding bank register access, such as PPOPA):
// - A segment register;
// - The RIP register;
// - The Flags register;
// Loads which are propagated to other operand types (RIP, segment register, etc.) or which are not
// propagated at all (RMW instructions) are not considered, since they don't store the RIP anywehere.
if ((dst != ND_NULL) &&
((dst->Type == ND_OP_BANK) ||
(dst->Type == ND_OP_MEM) ||
(dst->Type == ND_OP_REG &&
dst->Info.Register.Type != ND_REG_SEG &&
dst->Info.Register.Type != ND_REG_RIP &&
dst->Info.Register.Type != ND_REG_FLG)))
{
Context->Flags |= SHEMU_FLAG_LOAD_RIP;
}
}
// Get the memory value.
status = ShemuMemLoad(Context, gla, Value->Size, Value->Value.Bytes);
if (SHEMU_SUCCESS != status)
{
return status;
}
if (Context->Options & SHEMU_OPT_TRACE_MEMORY)
{
ShemuDisplayMemValue(Context, gla, Value->Size, Value->Value.Bytes, ND_TRUE);
}
// If this is a stack access, we need to update the stack pointer.
if (op->Info.Memory.IsStack)
{
ND_UINT64 regval = ShemuX86GetGprValue(Context, NDR_RSP, (2 << Context->Arch.X86.Instruction.DefStack), ND_FALSE);
regval += op->Size;
ShemuX86SetGprValue(Context, NDR_RSP, (2 << Context->Arch.X86.Instruction.DefStack), regval, ND_FALSE);
}
// If this is a string operation, make sure we update RSI/RDI.
if (op->Info.Memory.IsString)
{
ND_UINT64 regval = ShemuX86GetGprValue(Context, op->Info.Memory.Base, op->Info.Memory.BaseSize, ND_FALSE);
regval = GET_FLAG(Context, NDR_RFLAG_DF) ? regval - op->Size : regval + op->Size;
ShemuX86SetGprValue(Context, op->Info.Memory.Base, op->Info.Memory.BaseSize, regval, ND_FALSE);
}
done_gla:;
}
else if (op->Type == ND_OP_IMM)
{
Value->Value.Qwords[0] = op->Info.Immediate.Imm;
}
else if (op->Type == ND_OP_CONST)
{
Value->Value.Qwords[0] = op->Info.Constant.Const;
}
else if (op->Type == ND_OP_OFFS)
{
Value->Value.Qwords[0] = op->Info.RelativeOffset.Rel;
}
else
{
return SHEMU_ABORT_OPERAND_NOT_SUPPORTED;
}
return SHEMU_SUCCESS;
}
//
// ShemuX86SetOperandValue
//
static SHEMU_STATUS
ShemuX86SetOperandValue(
SHEMU_CONTEXT *Context,
ND_UINT32 Operand,
SHEMU_VALUE *Value
)
{
SHEMU_STATUS status;
PND_OPERAND op = &Context->Arch.X86.Instruction.Operands[Operand];
// If a stack address is being loaded, check if it points to a string built on the stack.
if (ShemuIsStackPtr(Context, Value->Value.Qwords[0], Context->StrThreshold))
{
ND_UINT64 sptr = Value->Value.Qwords[0];
ND_UINT32 i, stckstrlen = 0;
// Check if a string was saved on the stack. Typically used by shellcodes like this:
// PUSH str0
// PUSH str1
// ...
// PUSH strn
// Other variants may exist, but all we care about are stores on the stack, and all are checked.
for (i = 0; i < Context->StrThreshold; i++)
{
unsigned char c;
status = ShemuMemLoad(Context, sptr + i, 1, &c);
if (SHEMU_SUCCESS != status)
{
break;
}
if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') ||
c == '\\' || c == '/' || c == ':' || c == ' ')
{
stckstrlen++;
}
else
{
break;
}
}
if (stckstrlen >= Context->StrThreshold)
{
Context->Flags |= SHEMU_FLAG_STACK_STR;
}
}
if (op->Type == ND_OP_REG)
{
switch (op->Info.Register.Type)
{
case ND_REG_GPR:
if (Context->Arch.X86.Instruction.Instruction == ND_INS_XCHG &&
op->Info.Register.Reg == NDR_RSP &&
ShemuX86IsAddressAligned(Context, Value->Value.Qwords[0]))
{
// Conditions for a STACK_PIVOT detection:
// 1. The instruction is XCHG
// 2. The value loaded in the RSP register is naturally aligned
// 3. The value points either inside the shellcode or the stack area, and at least 64 bytes are valid
if (ShemuIsShellcodePtr(Context, Value->Value.Qwords[0], 64) ||
ShemuIsStackPtr(Context, Value->Value.Qwords[0], 64))
{
Context->Flags |= SHEMU_FLAG_STACK_PIVOT;
}
}
ShemuX86SetGprValue(Context, op->Info.Register.Reg, op->Size, Value->Value.Qwords[0],
op->Info.Register.IsHigh8);
break;
case ND_REG_SEG:
if (!ShemuX86IsSelectorValid(Context, op->Info.Register.Reg, Value->Value.Words[0]))
{
return SHEMU_ABORT_INVALID_SELECTOR;
}
ShemuX86SetSegValue(Context, op->Info.Register.Reg, Value->Value.Words[0]);
break;
case ND_REG_MMX:
Context->Arch.X86.MmxRegisters[op->Info.Register.Reg] = Value->Value.Qwords[0];
// Only log these when they're written.
if (Context->Options & SHEMU_OPT_TRACE_EMULATION)
{
shemu_printf(Context, " MM%d = 0x%016llx\n", op->Info.Register.Reg, Value->Value.Qwords[0]);
}
break;
case ND_REG_SSE:
if (Context->Arch.X86.Instruction.EncMode != ND_ENCM_LEGACY)
{
// Zero the entire register first, if we have a VEX/EVEX encoded instruction.
nd_memzero(&Context->Arch.X86.SseRegisters[op->Info.Register.Reg], ND_MAX_REGISTER_SIZE);
}
else
{
// Zero upper bits in the 128 bits register, if operand size is less than 16 bytes.
// Upper bits in the YMM/ZMM register are preserved.
nd_memzero(&Context->Arch.X86.SseRegisters[op->Info.Register.Reg], 16);
}
// Copy the value.
shemu_memcpy(&Context->Arch.X86.SseRegisters[op->Info.Register.Reg],
Value->Value.Bytes,
op->Size);
// Only log these when they're written.
if (Context->Options & SHEMU_OPT_TRACE_EMULATION)
{
shemu_printf(Context,
" %cMM%d (HI_32) = 0x%016llx%016llx%016llx%016llx\n",
op->Size == 16 ? 'X' : op->Size == 32 ? 'Y' : 'Z', op->Info.Register.Reg,
Value->Value.Qwords[7], Value->Value.Qwords[6],
Value->Value.Qwords[5], Value->Value.Qwords[4]);
shemu_printf(Context,
" %cMM%d (LO_32) = 0x%016llx%016llx%016llx%016llx\n",
op->Size == 16 ? 'X' : op->Size == 32 ? 'Y' : 'Z', op->Info.Register.Reg,
Value->Value.Qwords[3], Value->Value.Qwords[2],
Value->Value.Qwords[1], Value->Value.Qwords[0]);
}
break;
case ND_REG_RIP:
Context->Arch.X86.Registers.RegRip = ND_TRIM(Value->Size, Value->Value.Qwords[0]);
break;
case ND_REG_FLG:
if (op->Size == 2)
{
*((ND_UINT16*)&Context->Arch.X86.Registers.RegFlags) = Value->Value.Words[0];
}
else
{
Context->Arch.X86.Registers.RegFlags = Value->Value.Qwords[0];
}
// Handle reserved bits.
Context->Arch.X86.Registers.RegFlags |= (1ULL << 1);
Context->Arch.X86.Registers.RegFlags &= ~((1ULL << 3) | (1ULL << 5) | (1ULL << 15));
Context->Arch.X86.Registers.RegFlags &= 0x3FFFFF;
break;
case ND_REG_CR:
switch (op->Info.Register.Reg)
{
case NDR_CR0:
Context->Arch.X86.Registers.RegCr0 = Value->Value.Qwords[0];
break;
case NDR_CR2:
Context->Arch.X86.Registers.RegCr2 = Value->Value.Qwords[0];
break;
case NDR_CR3:
Context->Arch.X86.Registers.RegCr3 = Value->Value.Qwords[0];
break;
case NDR_CR4:
Context->Arch.X86.Registers.RegCr4 = Value->Value.Qwords[0];
break;
case NDR_CR8:
Context->Arch.X86.Registers.RegCr8 = Value->Value.Qwords[0];
break;
default:
return SHEMU_ABORT_REGISTER_NOT_SUPPORTED;
}
break;
default:
return SHEMU_ABORT_REGISTER_NOT_SUPPORTED;
}
}
else if (op->Type == ND_OP_MEM)
{
// Compute the GLA.
ND_UINT64 gla = ShemuX86ComputeLinearAddress(Context, op);
// Handle self-write. We store a 1 for each written byte inside the shellcode space. Once the modified bytes
// are executed, we can trigger the self-write detection.
if (ShemuIsShellcodePtr(Context, gla, op->Size))
{
ShemuShellBmpStateSet(Context, gla - Context->ShellcodeBase, op->Size, SHELL_BYTE_DIRTY);
}
// Handle RIP save on the stack.
if (ShemuIsStackPtr(Context, gla, MAX(op->Size, Context->Arch.X86.Instruction.WordLength)))
{
// Note: only Context->Arch.X86.Instruction.WordLength bits are flagged as RIP, as that is the RIP size.
if (Context->Arch.X86.Instruction.Instruction == ND_INS_CALLNR ||
Context->Arch.X86.Instruction.Instruction == ND_INS_CALLNI)
{
ShemuStackBmpStateSet(Context, gla - Context->StackBase,
Context->Arch.X86.Instruction.WordLength, STACK_BYTE_RIP);
}
else if (Context->Arch.X86.Instruction.Instruction == ND_INS_FNSTENV)
{
// OK: op->Size will be the FPU state size (28 bytes); we only emulate 32 & 64 bit forms, the RIP is
// always 4 bytes.
ShemuStackBmpStateSet(Context, (gla + 0xC) - Context->StackBase,
MIN(Context->Arch.X86.Instruction.WordLength, 4), STACK_BYTE_RIP);
}
else if (Context->Arch.X86.Instruction.Instruction == ND_INS_FXSAVE ||
Context->Arch.X86.Instruction.Instruction == ND_INS_FXSAVE64)
{
// OK: op->Size will be the FXSAVE size (512 bytes).
ShemuStackBmpStateSet(Context, (gla + 0x8) - Context->StackBase,
Context->Arch.X86.Instruction.WordLength, STACK_BYTE_RIP);
}
else
{
// Something is written on a previously saved RIP; reset it.
ShemuStackBmpStateClear(Context, gla - Context->StackBase, op->Size, STACK_BYTE_RIP);
}
}
// Set the value.
status = ShemuMemStore(Context, gla, MIN(op->Size, Value->Size), Value->Value.Bytes);
if (SHEMU_SUCCESS != status)
{
return status;
}
if (Context->Options & SHEMU_OPT_TRACE_MEMORY)
{
ShemuDisplayMemValue(Context, gla, Value->Size, Value->Value.Bytes, ND_FALSE);
}
// If this is a stack access, we need to update the stack pointer.
if (op->Info.Memory.IsStack)
{
ND_UINT64 regval = ShemuX86GetGprValue(Context, NDR_RSP, (2 << Context->Arch.X86.Instruction.DefStack), ND_FALSE);
regval -= op->Size;
ShemuX86SetGprValue(Context, NDR_RSP, (2 << Context->Arch.X86.Instruction.DefStack), regval, ND_FALSE);
}
// If this is a string operation, make sure we update RSI/RDI.
if (op->Info.Memory.IsString)
{
ND_UINT64 regval = ShemuX86GetGprValue(Context, op->Info.Memory.Base, op->Info.Memory.BaseSize, ND_FALSE);
regval = GET_FLAG(Context, NDR_RFLAG_DF) ? regval - op->Size : regval + op->Size;
ShemuX86SetGprValue(Context, op->Info.Memory.Base, op->Info.Memory.BaseSize, regval, ND_FALSE);
}
}
else
{
return SHEMU_ABORT_OPERAND_NOT_SUPPORTED;
}
return SHEMU_SUCCESS;
}
//
// ShemuX86Multiply64Unsigned
//
static void
ShemuX86Multiply64Unsigned(
SHEMU_VALUE *Operand1,
SHEMU_VALUE *Operand2,
SHEMU_VALUE *Result
)
{
ND_UINT64 p0, p1, p2, p3, p4;
// Multiply the 4 32-bit parts into 4 partial products.
p0 = (ND_UINT64)Operand1->Value.Dwords[0] * (ND_UINT64)Operand2->Value.Dwords[0];
p1 = (ND_UINT64)Operand1->Value.Dwords[0] * (ND_UINT64)Operand2->Value.Dwords[1];
p2 = (ND_UINT64)Operand1->Value.Dwords[1] * (ND_UINT64)Operand2->Value.Dwords[0];
p3 = (ND_UINT64)Operand1->Value.Dwords[1] * (ND_UINT64)Operand2->Value.Dwords[1];
p4 = (((p0 >> 32) + (p1 & 0xFFFFFFFF) + (p2 & 0xFFFFFFFF)) >> 32) & 0xFFFFFFFF;
// Fill in the final result (low & high 64-bit parts).
Result->Value.Qwords[0] = p0 + (p1 << 32) + (p2 << 32);
Result->Value.Qwords[1] = p3 + (p1 >> 32) + (p2 >> 32) + p4;
}
//
// ShemuX86Multiply64Signed
//
static void
ShemuX86Multiply64Signed(
SHEMU_VALUE *Operand1,
SHEMU_VALUE *Operand2,
SHEMU_VALUE *Result
)
{
ShemuX86Multiply64Unsigned(Operand1, Operand2, Result);
// Negate, if needed.
if (ND_GET_SIGN(8, Operand1->Value.Qwords[0]))
{
Result->Value.Qwords[1] -= Operand2->Value.Qwords[0];
}
// Negate, if needed.
if (ND_GET_SIGN(8, Operand2->Value.Qwords[0]))
{
Result->Value.Qwords[1] -= Operand1->Value.Qwords[0];
}
}
//
// ShemuX86CheckDiv
//
static ND_BOOL
ShemuX86CheckDiv(
ND_UINT64 Divident,
ND_UINT64 Divider,
ND_UINT8 Size // The size of the Source (Divider). The Divident is twice as large.
)
{
// Returns ND_TRUE if all checks are OK, and Divident / Divider will not cause #DE.
if (Divider == 0)
{
// Division by zero.
return ND_FALSE;
}
// If the result won't fit in the destination, a #DE would be generated.
switch (Size)
{
case 1:
if (((Divident >> 8) & 0xFF) >= Divider)
{
return ND_FALSE;
}
break;
case 2:
if (((Divident >> 16) & 0xFFFF) >= Divider)
{
return ND_FALSE;
}
break;
case 4:
if (((Divident >> 32) & 0xFFFFFFFF) >= Divider)
{
return ND_FALSE;
}
break;
default:
// 64 bit source division is not supported.
return ND_FALSE;
}
return ND_TRUE;
}
//
// ShemuX86CheckIdiv
//
static ND_BOOL
ShemuX86CheckIdiv(
ND_SINT64 Divident,
ND_SINT64 Divider,
ND_UINT8 Size // The size of the Source (Divider).
)
{
ND_BOOL neg1, neg2;
ND_UINT64 quotient, max;
neg1 = Divident < 0;
neg2 = Divider < 0;
if (neg1)
{
Divident = -Divident;
}
if (neg2)
{
Divider = -Divider;
}
// Do checks when dividing positive values.
if (!ShemuX86CheckDiv(Divident, Divider, Size))
{
return ND_FALSE;
}
// Get the positive quotient.
quotient = (ND_UINT64)Divident / (ND_UINT64)Divider;
max = (Size == 1) ? 0x80 : (Size == 2) ? 0x8000 : (Size == 4) ? 0x80000000 : 0x8000000000000000;
if (neg1 ^ neg2)
{
// The Divident and the Divider have different signs, the quotient must be negative. If it's positive => #DE.
if (ND_GET_SIGN(Size, quotient) && quotient != max)
{
return ND_FALSE;
}
}
else
{
// Both the Divident and the Divider are positive/negative, so a positive result must be produced. If it's
// negative => #DE.
if (ND_GET_SIGN(Size, quotient))
{
return ND_FALSE;
}
}
return ND_TRUE;
}
//
// ShemuX86CountZeroBits
//
static ND_UINT8
ShemuX86CountZeroBits(
ND_UINT64 Value,
ND_OPERAND_SIZE Size,
ND_BOOL Forward
)
{
ND_UINT8 cnt = 0;
if (Forward)
{
for (ND_UINT32 i = 0; i < Size * 8 && ND_GET_BIT(i, Value) == 0; i++, cnt++);
}
else
{
for (ND_SINT32 i = Size * 8 - 1; i >= 0 && ND_GET_BIT(i, Value) == 0; i--, cnt++);
}
return cnt;
}
//
// ShemuX86PrintContext
//
#ifndef BDDISASM_NO_FORMAT
static void
ShemuX86PrintContext(
SHEMU_CONTEXT *Context
)
{
char text[ND_MIN_BUF_SIZE] = { 0 };
char ibytes[ND_MAX_INSTRUCTION_LENGTH * 2 + 2] = { 0 };
NdToText(&Context->Arch.X86.Instruction, Context->Arch.X86.Registers.RegRip, ND_MIN_BUF_SIZE, text);
shemu_printf(Context, " RAX = 0x%016llx RCX = 0x%016llx RDX = 0x%016llx RBX = 0x%016llx\n",
Context->Arch.X86.Registers.RegRax, Context->Arch.X86.Registers.RegRcx,
Context->Arch.X86.Registers.RegRdx, Context->Arch.X86.Registers.RegRbx);
shemu_printf(Context, " RSP = 0x%016llx RBP = 0x%016llx RSI = 0x%016llx RDI = 0x%016llx\n",
Context->Arch.X86.Registers.RegRsp, Context->Arch.X86.Registers.RegRbp,
Context->Arch.X86.Registers.RegRsi, Context->Arch.X86.Registers.RegRdi);
shemu_printf(Context, " R8 = 0x%016llx R9 = 0x%016llx R10 = 0x%016llx R11 = 0x%016llx\n",
Context->Arch.X86.Registers.RegR8, Context->Arch.X86.Registers.RegR9,
Context->Arch.X86.Registers.RegR10, Context->Arch.X86.Registers.RegR11);
shemu_printf(Context, " R12 = 0x%016llx R13 = 0x%016llx R14 = 0x%016llx R15 = 0x%016llx\n",
Context->Arch.X86.Registers.RegR12, Context->Arch.X86.Registers.RegR13,
Context->Arch.X86.Registers.RegR14, Context->Arch.X86.Registers.RegR15);
if (Context->Options & SHEMU_OPT_SUPPORT_APX)
{
shemu_printf(Context, " R16 = 0x%016llx R17 = 0x%016llx R18 = 0x%016llx R19 = 0x%016llx\n",
Context->Arch.X86.Registers.RegR16, Context->Arch.X86.Registers.RegR17,
Context->Arch.X86.Registers.RegR18, Context->Arch.X86.Registers.RegR19);
shemu_printf(Context, " R20 = 0x%016llx R21 = 0x%016llx R22 = 0x%016llx R23 = 0x%016llx\n",
Context->Arch.X86.Registers.RegR20, Context->Arch.X86.Registers.RegR21,
Context->Arch.X86.Registers.RegR22, Context->Arch.X86.Registers.RegR23);
shemu_printf(Context, " R24 = 0x%016llx R25 = 0x%016llx R26 = 0x%016llx R27 = 0x%016llx\n",
Context->Arch.X86.Registers.RegR24, Context->Arch.X86.Registers.RegR25,
Context->Arch.X86.Registers.RegR26, Context->Arch.X86.Registers.RegR27);
shemu_printf(Context, " R28 = 0x%016llx R29 = 0x%016llx R30 = 0x%016llx R31 = 0x%016llx\n",
Context->Arch.X86.Registers.RegR28, Context->Arch.X86.Registers.RegR29,
Context->Arch.X86.Registers.RegR30, Context->Arch.X86.Registers.RegR31);
}
shemu_printf(Context, " RIP = 0x%016llx RFLAGS = 0x%016llx ",
Context->Arch.X86.Registers.RegRip, Context->Arch.X86.Registers.RegFlags);
shemu_printf(Context, " CF:%d PF:%d AF:%d ZF:%d SF:%d TF:%d IF:%d DF:%d OF:%d\n",
GET_FLAG(Context, NDR_RFLAG_CF),
GET_FLAG(Context, NDR_RFLAG_PF),
GET_FLAG(Context, NDR_RFLAG_AF),
GET_FLAG(Context, NDR_RFLAG_ZF),
GET_FLAG(Context, NDR_RFLAG_SF),
GET_FLAG(Context, NDR_RFLAG_TF),
GET_FLAG(Context, NDR_RFLAG_IF),
GET_FLAG(Context, NDR_RFLAG_DF),
GET_FLAG(Context, NDR_RFLAG_OF));
ShemuHexlify(Context->Arch.X86.Instruction.InstructionBytes, Context->Arch.X86.Instruction.Length,
ibytes, sizeof(ibytes));
shemu_printf(Context, "IP: 0x%016llx %-30s %s\n", Context->Arch.X86.Registers.RegRip, ibytes, text);
}
#else
#define ShemuX86PrintContext(Context)
#endif // !BDDISASM_NO_FORMAT
//
// ShemuX86Emulate
//
SHEMU_STATUS
ShemuX86Emulate(
SHEMU_CONTEXT *Context
)
{
ND_CONTEXT decodeCtx = { 0 };
SHEMU_VALUE res, dst, src;
ND_BOOL stop = ND_FALSE, cf, sled = ND_TRUE, taken = ND_FALSE;
ND_UINT16 cs = 0;
ND_UINT64 tsc = 0x1248fe7a5c30;
if (ND_NULL == Context)
{
return SHEMU_ABORT_INVALID_PARAMETER;
}
if (ND_NULL == Context->Shellcode)
{
return SHEMU_ABORT_INVALID_PARAMETER;
}
if (ND_NULL == Context->Stack)
{
return SHEMU_ABORT_INVALID_PARAMETER;
}
if (ND_NULL == Context->Intbuf)
{
return SHEMU_ABORT_INVALID_PARAMETER;
}
if (0 == (Context->Options & SHEMU_OPT_DIRECT_MAPPED_SHELL))
{
if (Context->StackSize + Context->ShellcodeSize > Context->IntbufSize)
{
return SHEMU_ABORT_INVALID_PARAMETER;
}
}
else
{
if (Context->StackSize > Context->IntbufSize)
{
return SHEMU_ABORT_INVALID_PARAMETER;
}
if (Context->AccessShellcode == ND_NULL)
{
// The AccessShellcode callback is mandatory when using the SHEMU_OPT_DIRECT_MAPPED_SHELL option.
return SHEMU_ABORT_INVALID_PARAMETER;
}
// It is unsafe to allow self-writes to proceed, so this options is forced when using
// SHEMU_OPT_DIRECT_MAPPED_SHELL emulation.
Context->Options |= SHEMU_OPT_BYPASS_SELF_WRITES;
}
if (Context->ArchType != SHEMU_ARCH_TYPE_X86)
{
return SHEMU_ABORT_INVALID_PARAMETER;
}
if (Context->NopThreshold == 0)
{
Context->NopThreshold = SHEMU_DEFAULT_NOP_THRESHOLD;
}
if (Context->StrThreshold == 0)
{
Context->StrThreshold = SHEMU_DEFAULT_STR_THRESHOLD;
}
decodeCtx.DefCode = Context->Arch.X86.Mode;
decodeCtx.DefData = Context->Arch.X86.Mode;
decodeCtx.DefStack = Context->Arch.X86.Mode;
decodeCtx.VendMode = ND_VEND_ANY;
decodeCtx.Options = 0;
decodeCtx.FeatMode = 0;
// Enable APX support.
if (Context->Options & SHEMU_OPT_SUPPORT_APX)
{
decodeCtx.FeatMode |= ND_FEAT_APX;
}
while (Context->InstructionsCount++ < Context->MaxInstructionsCount)
{
SHEMU_STATUS shstatus;
NDSTATUS ndstatus;
ND_UINT64 rip; // Offset, not actual linear address.
ND_UINT32 i, ilen;
ND_UINT8 ibytes[16];
ND_BOOL hasNd = ND_FALSE;
tsc++;
// Reset all the operands to 0.
nd_memzero(&res, sizeof(res));
nd_memzero(&dst, sizeof(dst));
nd_memzero(&src, sizeof(src));
// The stop flag has been set, this means we've reached a valid instruction, but that instruction cannot be
// emulated (for example, SYSCALL, INT, system instructions, etc).
if (stop)
{
return SHEMU_ABORT_CANT_EMULATE;
}
// If we already have a detection and we wish to stop on detections, do so now.
if ((0 != Context->Flags) && (0 != (Context->Options & SHEMU_OPT_STOP_ON_EXPLOIT)))
{
return SHEMU_ABORT_SHELLCODE_DETECTED;
}
// Make sure the RIP is pointing in the right area. We test only 1 byte - the decoder will make sure it can
// access as many bytes as needed and return error in case it can't.
if (!ShemuIsShellcodePtr(Context, Context->Arch.X86.Registers.RegRip, 1))
{
return SHEMU_ABORT_RIP_OUTSIDE;
}
// Get the offset inside the shellcode buffer.
rip = Context->Arch.X86.Registers.RegRip - Context->ShellcodeBase;
// Maximum number of bytes we can fetch. No more than 16 bytes.
ilen = (ND_UINT32)MIN(Context->ShellcodeSize - rip, sizeof(ibytes));
// Fetch instruction bytes.
shstatus = ShemuMemFetch(Context, Context->Arch.X86.Registers.RegRip, ilen, ibytes);
if (SHEMU_SUCCESS != shstatus)
{
return shstatus;
}
// Decode the next instruction.
ndstatus = NdDecodeWithContext(&Context->Arch.X86.Instruction, ibytes, ilen, &decodeCtx);
if (!ND_SUCCESS(ndstatus))
{
if (ND_STATUS_BUFFER_TOO_SMALL == ndstatus)
{
return SHEMU_ABORT_RIP_OUTSIDE;
}
else
{
return SHEMU_ABORT_DECODE_ERROR;
}
}
// Paranoid check...
if (!ShemuIsShellcodePtr(Context, Context->Arch.X86.Registers.RegRip, Context->Arch.X86.Instruction.Length))
{
return SHEMU_ABORT_RIP_OUTSIDE;
}
// Check if this is a new, unique, address being executed.
if (!ShemuShellBmpStateCheck(Context, rip, 1, SHELL_BYTE_FETCHED))
{
// If SHEMU_OPT_DIRECT_MAPPED_SHELL is not used, this will be incremented for each instruction.
Context->UniqueCount++;
// Note: The first instruction byte is marked using SHELL_BYTE_FETCHED, and subsequent bytes using
// SHELL_BYTE_IBYTES. For example, if we have the instruction "33C0 (XOR eax, eax)" at address 0x1000,
// the flags will be set as follows:
// Shellcode state for 0x1000: SHELL_BYTE_FETCHED (0x33, the opcode)
// Shellcode state for 0x1001: SHELL_BYTE_IBYTES (0xC0, subsequent bytes)
// Normally, these two flags should never be set together.
// Indicate that we've fetched an instruction from this address.
ShemuShellBmpStateSet(Context, rip, 1, SHELL_BYTE_FETCHED);
// Indicate that subsequent bytes are part of a fetched & emulated instruction.
ShemuShellBmpStateSet(Context, rip + 1, Context->Arch.X86.Instruction.Length - 1, SHELL_BYTE_IBYTES);
}
// Check if we just fetched an instruction from a previously written area, to raise self-write alert.
if (ShemuShellBmpStateCheck(Context, rip, Context->Arch.X86.Instruction.Length, SHELL_BYTE_DIRTY))
{
Context->Flags |= SHEMU_FLAG_WRITE_SELF;
}
// Dump the context.
if (Context->Options & SHEMU_OPT_TRACE_EMULATION)
{
ShemuX86PrintContext(Context);
}
// The RIP is incremented BEFORE actually emulating the instruction. This is what the CPU does as well.
Context->Arch.X86.Registers.RegRip += Context->Arch.X86.Instruction.Length;
// Bail out early if we encounter a privileged instruction.
if (Context->Arch.X86.Instruction.ValidModes.Ring3 == 0 && Context->Arch.X86.Ring == 3)
{
return SHEMU_ABORT_NO_PRIVILEGE;
}
// Some instruction types are unssuported.
if (Context->Arch.X86.Instruction.Category == ND_CAT_IO ||
Context->Arch.X86.Instruction.Category == ND_CAT_IOSTRINGOP)
{
return SHEMU_ABORT_INSTRUX_NOT_SUPPORTED;
}
// There are two important aspects of a NOP sled:
// 1. The NOPs must be at the beginning of the code;
// 2. The NOPs must be consecutive;
// We will only count consecutive NOPs if they're at the beginning of the code.
if (Context->Arch.X86.Instruction.Instruction != ND_INS_NOP)
{
sled = ND_FALSE;
}
// Count the total number of '00 00' (ADD [rax], al) instructions.
if (Context->Arch.X86.Instruction.InstructionBytes[0] == 0 &&
Context->Arch.X86.Instruction.InstructionBytes[1] == 0)
{
Context->NullCount++;
}
// FPU instructions are "pass-through", we just want to save the RIP, so we can emulate FNSTENV.
if ((Context->Arch.X86.Instruction.IsaSet == ND_SET_X87) &&
(Context->Arch.X86.Instruction.Instruction != ND_INS_FNSTENV))
{
PND_OPERAND pMemOp = ND_NULL;
Context->Arch.X86.Registers.FpuRip = Context->Arch.X86.Registers.RegRip - Context->Arch.X86.Instruction.Length;
// If the instruction uses a memory operand, validate it, and bail out if it points outside
// shellcode or stack memory.
if (Context->Arch.X86.Instruction.OperandsCount >= 1 &&
Context->Arch.X86.Instruction.Operands[0].Type == ND_OP_MEM)
{
pMemOp = &Context->Arch.X86.Instruction.Operands[0];
}
else if (Context->Arch.X86.Instruction.OperandsCount >= 2 &&
Context->Arch.X86.Instruction.Operands[1].Type == ND_OP_MEM)
{
pMemOp = &Context->Arch.X86.Instruction.Operands[1];
}
if (ND_NULL != pMemOp)
{
ND_UINT64 gla = ShemuX86ComputeLinearAddress(Context, pMemOp);
if (!ShemuIsShellcodePtr(Context, gla, pMemOp->Size) &&
!ShemuIsStackPtr(Context, gla, pMemOp->Size))
{
stop = ND_TRUE;
}
}
continue;
}
// This flag can only be set for APX instructions.
hasNd = !!Context->Arch.X86.Instruction.HasNd;
switch (Context->Arch.X86.Instruction.Instruction)
{
case ND_INS_FNSTENV:
if (Context->Arch.X86.Instruction.EfOpMode != ND_OPSZ_16)
{
src.Size = Context->Arch.X86.Instruction.Operands[0].Size;
src.Value.FpuEnvironment.FpuInstructionPointer = (ND_UINT32)Context->Arch.X86.Registers.FpuRip;
SET_OP(Context, 0, &src);
}
break;
case ND_INS_FXSAVE:
case ND_INS_FXSAVE64:
src.Size = MIN(Context->Arch.X86.Instruction.Operands[0].Size, sizeof(src.Value.XsaveArea));
src.Value.XsaveArea.FpuRip = Context->Arch.X86.Registers.FpuRip;
SET_OP(Context, 0, &src);
break;
case ND_INS_MOV_CR:
if (Context->Arch.X86.Ring != 0)
{
return SHEMU_ABORT_NO_PRIVILEGE;
}
// Fall through.
case ND_INS_MOV:
case ND_INS_MOVZX:
GET_OP(Context, 1, &src);
SET_OP(Context, 0, &src);
break;
case ND_INS_MOVSX:
case ND_INS_MOVSXD:
GET_OP(Context, 1, &src);
GET_OP(Context, 0, &dst);
dst.Value.Qwords[0] = ND_SIGN_EX(src.Size, src.Value.Qwords[0]);
SET_OP(Context, 0, &dst);
break;
case ND_INS_CMOVcc:
GET_OP(Context, 0, &dst);
GET_OP(Context, 1, &src);
if (ShemuX86EvalCondition(Context, Context->Arch.X86.Instruction.Condition))
{
SET_OP(Context, 0, &src);
}
else
{
// Write back the same value that was already present in destination. This has the side-effect of
// clearing the upper 32 bit in the 64 bit destination register while in long mode.
SET_OP(Context, 0, &dst);
}
break;
case ND_INS_SETcc:
if (ShemuX86EvalCondition(Context, Context->Arch.X86.Instruction.Condition))
{
src.Size = Context->Arch.X86.Instruction.Operands[0].Size;
src.Value.Qwords[0] = 1;
}
else
{
src.Size = Context->Arch.X86.Instruction.Operands[0].Size;
src.Value.Qwords[0] = 0;
}
SET_OP(Context, 0, &src);
break;
case ND_INS_XLATB:
GET_OP(Context, 1, &src);
SET_OP(Context, 0, &src);
break;
case ND_INS_XCHG:
GET_OP(Context, 1, &src);
GET_OP(Context, 0, &dst);
SET_OP(Context, 1, &dst);
SET_OP(Context, 0, &src);
break;
case ND_INS_XADD:
GET_OP(Context, 1, &src);
GET_OP(Context, 0, &dst);
res.Size = dst.Size;
res.Value.Qwords[0] = dst.Value.Qwords[0] + src.Value.Qwords[0];
SET_FLAGS(Context, res, dst, src, FM_ADD);
SET_OP(Context, 1, &dst);
SET_OP(Context, 0, &res);
break;
case ND_INS_CMPXCHG:
GET_OP(Context, 2, &src);
GET_OP(Context, 0, &dst);
res.Size = src.Size;
// Note: The accumulator is compared with the destination, not the other way around.
res.Value.Qwords[0] = src.Value.Qwords[0] - dst.Value.Qwords[0];
SET_FLAGS(Context, res, src, dst, FM_SUB);
if (src.Value.Qwords[0] == dst.Value.Qwords[0])
{
GET_OP(Context, 1, &src);
SET_OP(Context, 0, &src);
}
else
{
SET_OP(Context, 2, &dst);
}
break;
case ND_INS_ADD:
case ND_INS_ADC:
GET_OP(Context, hasNd ? 1 : 0, &dst);
GET_OP(Context, hasNd ? 2 : 1, &src);
res.Size = src.Size;
res.Value.Qwords[0] = dst.Value.Qwords[0] + src.Value.Qwords[0];
if (ND_INS_ADC == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Qwords[0] += GET_FLAG(Context, NDR_RFLAG_CF);
}
SET_FLAGS(Context, res, dst, src, FM_ADD);
SET_OP(Context, 0, &res);
break;
case ND_INS_SUB:
case ND_INS_SBB:
case ND_INS_CMP:
GET_OP(Context, hasNd ? 1 : 0, &dst);
GET_OP(Context, hasNd ? 2 : 1, &src);
res.Size = src.Size;
res.Value.Qwords[0] = dst.Value.Qwords[0] - src.Value.Qwords[0];
if (ND_INS_SBB == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Qwords[0] -= GET_FLAG(Context, NDR_RFLAG_CF);
}
SET_FLAGS(Context, res, dst, src, FM_SUB);
if (ND_INS_CMP != Context->Arch.X86.Instruction.Instruction)
{
SET_OP(Context, 0, &res);
}
break;
case ND_INS_INC:
GET_OP(Context, hasNd ? 1 : 0, &dst);
src.Size = dst.Size;
src.Value.Qwords[0] = 1;
res.Size = src.Size;
res.Value.Qwords[0] = dst.Value.Qwords[0] + src.Value.Qwords[0];
cf = GET_FLAG(Context, NDR_RFLAG_CF);
SET_FLAGS(Context, res, dst, src, FM_ADD);
SET_FLAG(Context, NDR_RFLAG_CF, cf);
SET_OP(Context, 0, &res);
break;
case ND_INS_DEC:
GET_OP(Context, hasNd ? 1 : 0, &dst);
src.Size = dst.Size;
src.Value.Qwords[0] = 1;
res.Size = src.Size;
res.Value.Qwords[0] = dst.Value.Qwords[0] - src.Value.Qwords[0];
cf = GET_FLAG(Context, NDR_RFLAG_CF);
SET_FLAGS(Context, res, dst, src, FM_SUB);
SET_FLAG(Context, NDR_RFLAG_CF, cf);
SET_OP(Context, 0, &res);
break;
case ND_INS_PUSH:
case ND_INS_PUSHP:
case ND_INS_PUSHF:
GET_OP(Context, 0, &src);
SET_OP(Context, 1, &src);
break;
case ND_INS_POP:
case ND_INS_POPP:
case ND_INS_POPF:
GET_OP(Context, 1, &src);
SET_OP(Context, 0, &src);
break;
case ND_INS_PUSH2:
case ND_INS_PUSH2P:
// APX extended EVEX can only be enabled in 64-bit mode, so it's safe to always assume 64-bit regs.
src.Size = 16;
src.Value.Qwords[0] = ShemuX86GetGprValue(Context, Context->Arch.X86.Instruction.Operands[1].Info.Register.Reg, 8, ND_FALSE);
src.Value.Qwords[1] = ShemuX86GetGprValue(Context, Context->Arch.X86.Instruction.Operands[0].Info.Register.Reg, 8, ND_FALSE);
SET_OP(Context, 2, &src);
break;
case ND_INS_POP2:
case ND_INS_POP2P:
// I know this looks weird, and you would expect a PUSH2 r1, r2 to have a complementary POP2 r1, r2, but
// according to the current APX specification, this is not the case. The right pair for PUSH2 r1, r2 is,
// in fact, POP2 r2, r1 (the order of the popped operands must be reversed to match the PUSH2).
GET_OP(Context, 2, &src);
ShemuX86SetGprValue(Context, Context->Arch.X86.Instruction.Operands[0].Info.Register.Reg, 8, src.Value.Qwords[0], ND_FALSE);
ShemuX86SetGprValue(Context, Context->Arch.X86.Instruction.Operands[1].Info.Register.Reg, 8, src.Value.Qwords[1], ND_FALSE);
break;
case ND_INS_PUSHA:
src.Size = 16;
src.Value.Words[7] = (ND_UINT16)ShemuX86GetGprValue(Context, NDR_AX, 2, ND_FALSE);
src.Value.Words[6] = (ND_UINT16)ShemuX86GetGprValue(Context, NDR_CX, 2, ND_FALSE);
src.Value.Words[5] = (ND_UINT16)ShemuX86GetGprValue(Context, NDR_DX, 2, ND_FALSE);
src.Value.Words[4] = (ND_UINT16)ShemuX86GetGprValue(Context, NDR_BX, 2, ND_FALSE);
src.Value.Words[3] = (ND_UINT16)ShemuX86GetGprValue(Context, NDR_SP, 2, ND_FALSE);
src.Value.Words[2] = (ND_UINT16)ShemuX86GetGprValue(Context, NDR_BP, 2, ND_FALSE);
src.Value.Words[1] = (ND_UINT16)ShemuX86GetGprValue(Context, NDR_SI, 2, ND_FALSE);
src.Value.Words[0] = (ND_UINT16)ShemuX86GetGprValue(Context, NDR_DI, 2, ND_FALSE);
SET_OP(Context, 1, &src); // Operand 1 is the stack (destination).
break;
case ND_INS_PUSHAD:
src.Size = 32;
src.Value.Dwords[7] = (ND_UINT32)ShemuX86GetGprValue(Context, NDR_EAX, 4, ND_FALSE);
src.Value.Dwords[6] = (ND_UINT32)ShemuX86GetGprValue(Context, NDR_ECX, 4, ND_FALSE);
src.Value.Dwords[5] = (ND_UINT32)ShemuX86GetGprValue(Context, NDR_EDX, 4, ND_FALSE);
src.Value.Dwords[4] = (ND_UINT32)ShemuX86GetGprValue(Context, NDR_EBX, 4, ND_FALSE);
src.Value.Dwords[3] = (ND_UINT32)ShemuX86GetGprValue(Context, NDR_ESP, 4, ND_FALSE);
src.Value.Dwords[2] = (ND_UINT32)ShemuX86GetGprValue(Context, NDR_EBP, 4, ND_FALSE);
src.Value.Dwords[1] = (ND_UINT32)ShemuX86GetGprValue(Context, NDR_ESI, 4, ND_FALSE);
src.Value.Dwords[0] = (ND_UINT32)ShemuX86GetGprValue(Context, NDR_EDI, 4, ND_FALSE);
SET_OP(Context, 1, &src); // Operand 1 is the stack (destination).
break;
case ND_INS_POPA:
GET_OP(Context, 1, &src); // Operand 1 is the stack (source).
ShemuX86SetGprValue(Context, NDR_AX, 2, src.Value.Words[7], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_CX, 2, src.Value.Words[6], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_DX, 2, src.Value.Words[5], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_BX, 2, src.Value.Words[4], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_BP, 2, src.Value.Words[2], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_SI, 2, src.Value.Words[1], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_DI, 2, src.Value.Words[0], ND_FALSE);
break;
case ND_INS_POPAD:
GET_OP(Context, 1, &src); // Operand 1 is the stack (source).
ShemuX86SetGprValue(Context, NDR_EAX, 4, src.Value.Dwords[7], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_ECX, 4, src.Value.Dwords[6], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_EDX, 4, src.Value.Dwords[5], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_EBX, 4, src.Value.Dwords[4], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_EBP, 4, src.Value.Dwords[2], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_ESI, 4, src.Value.Dwords[1], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_EDI, 4, src.Value.Dwords[0], ND_FALSE);
break;
case ND_INS_LEA:
GET_OP(Context, 1, &src);
SET_OP(Context, 0, &src);
break;
case ND_INS_SHL:
case ND_INS_SAL:
case ND_INS_SHR:
case ND_INS_SAR:
GET_OP(Context, hasNd ? 1 : 0, &dst);
GET_OP(Context, hasNd ? 2 : 1, &src);
if (dst.Size == 8)
{
src.Value.Qwords[0] &= 0x3f;
}
else
{
src.Value.Qwords[0] &= 0x1f;
}
res.Size = dst.Size;
if (ND_INS_SHL == Context->Arch.X86.Instruction.Instruction ||
ND_INS_SAL == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Qwords[0] = dst.Value.Qwords[0] << src.Value.Qwords[0];
}
else if (ND_INS_SHR == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Qwords[0] = dst.Value.Qwords[0] >> src.Value.Qwords[0];
}
else
{
ND_SINT64 val = ND_SIGN_EX(dst.Size, dst.Value.Qwords[0]);
val = val >> src.Value.Qwords[0];
res.Value.Qwords[0] = (ND_UINT64)val;
}
if (src.Value.Qwords[0] != 0)
{
// 0 bit shifts do not affect the flags.
if (ND_INS_SHL == Context->Arch.X86.Instruction.Instruction ||
ND_INS_SAL == Context->Arch.X86.Instruction.Instruction)
{
SET_FLAGS(Context, res, dst, src, FM_SHL);
}
else if (ND_INS_SHR == Context->Arch.X86.Instruction.Instruction)
{
SET_FLAGS(Context, res, dst, src, FM_SHR);
}
else
{
SET_FLAGS(Context, res, dst, src, FM_SAR);
}
}
SET_OP(Context, 0, &res);
break;
case ND_INS_RCL:
case ND_INS_RCR:
case ND_INS_ROL:
case ND_INS_ROR:
{
ND_UINT32 cnt, tempcnt, cntmask, bitwidth;
ND_UINT8 tempCF = 0;
GET_OP(Context, hasNd ? 1 : 0, &dst);
GET_OP(Context, hasNd ? 2 : 1, &src);
cnt = (ND_UINT32)src.Value.Qwords[0];
cntmask = ((dst.Size == 8) ? 0x3F : 0x1F);
tempcnt = (cnt & cntmask);
bitwidth = (ND_UINT32)dst.Size * 8;
if (ND_INS_RCL == Context->Arch.X86.Instruction.Instruction ||
ND_INS_RCR == Context->Arch.X86.Instruction.Instruction)
{
if (dst.Size == 1)
{
tempcnt %= 9;
}
else if (dst.Size == 2)
{
tempcnt %= 17;
}
}
else
{
tempcnt %= (dst.Size * 8);
}
if (ND_INS_RCL == Context->Arch.X86.Instruction.Instruction)
{
tempCF = GET_FLAG(Context, NDR_RFLAG_CF);
if (tempcnt != 0)
{
// tempcnt is in range [1, dst bit width].
ND_UINT64 left = (tempcnt == bitwidth) ? 0 : (dst.Value.Qwords[0] << tempcnt);
ND_UINT64 right = (tempcnt == 1) ? 0 : (dst.Value.Qwords[0] >> (bitwidth - tempcnt + 1));
SET_FLAG(Context, NDR_RFLAG_CF, ND_GET_BIT(bitwidth - tempcnt, dst.Value.Qwords[0]));
dst.Value.Qwords[0] = left | ((ND_UINT64)tempCF << (tempcnt - 1)) | right;
}
if ((cnt & cntmask) == 1)
{
SET_FLAG(Context, NDR_RFLAG_OF, ND_MSB(dst.Size, dst.Value.Qwords[0]) ^
GET_FLAG(Context, NDR_RFLAG_CF));
}
}
else if (ND_INS_RCR == Context->Arch.X86.Instruction.Instruction)
{
tempCF = GET_FLAG(Context, NDR_RFLAG_CF);
if ((cnt & cntmask) == 1)
{
SET_FLAG(Context, NDR_RFLAG_OF, ND_MSB(dst.Size, dst.Value.Qwords[0]) ^
GET_FLAG(Context, NDR_RFLAG_CF));
}
if (tempcnt != 0)
{
// tempcnt is in range [1, dst bit width].
ND_UINT64 left = (tempcnt == bitwidth) ? 0 : (dst.Value.Qwords[0] >> tempcnt);
ND_UINT64 right = (tempcnt == 1) ? 0 : (dst.Value.Qwords[0] << (bitwidth - tempcnt + 1));
SET_FLAG(Context, NDR_RFLAG_CF, ND_GET_BIT(tempcnt - 1, dst.Value.Qwords[0]));
dst.Value.Qwords[0] = left | ((ND_UINT64)tempCF << (bitwidth - tempcnt)) | right;
}
}
else if (ND_INS_ROL == Context->Arch.X86.Instruction.Instruction)
{
if (tempcnt != 0)
{
// tempcnt is in range [1, dst bit width - 1].
ND_UINT64 left = dst.Value.Qwords[0] << tempcnt;
ND_UINT64 right = dst.Value.Qwords[0] >> (bitwidth - tempcnt);
dst.Value.Qwords[0] = left | right;
}
if ((cnt & cntmask) != 0)
{
SET_FLAG(Context, NDR_RFLAG_CF, ND_LSB(dst.Size, dst.Value.Qwords[0]));
}
if ((cnt & cntmask) == 1)
{
SET_FLAG(Context, NDR_RFLAG_OF, ND_MSB(dst.Size, dst.Value.Qwords[0]) ^
GET_FLAG(Context, NDR_RFLAG_CF));
}
}
else // ND_INS_ROR
{
if (tempcnt != 0)
{
// tempcnt is in range [1, dst bit width - 1].
ND_UINT64 left = (dst.Value.Qwords[0] >> tempcnt);
ND_UINT64 right = (dst.Value.Qwords[0] << (bitwidth - tempcnt));
dst.Value.Qwords[0] = left | right;
}
if ((cnt & cntmask) != 0)
{
SET_FLAG(Context, NDR_RFLAG_CF, ND_MSB(dst.Size, dst.Value.Qwords[0]));
}
if ((cnt & cntmask) == 1)
{
SET_FLAG(Context, NDR_RFLAG_OF, ND_MSB(dst.Size, dst.Value.Qwords[0]) ^
ND_GET_BIT(dst.Size * 8ULL - 2, dst.Value.Qwords[0]));
}
}
SET_OP(Context, 0, &dst);
}
break;
case ND_INS_OR:
case ND_INS_XOR:
case ND_INS_AND:
case ND_INS_TEST:
GET_OP(Context, hasNd ? 1 : 0, &dst);
GET_OP(Context, hasNd ? 2 : 1, &src);
res.Size = dst.Size;
if (ND_INS_OR == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Qwords[0] = dst.Value.Qwords[0] | src.Value.Qwords[0];
}
else if (ND_INS_XOR == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Qwords[0] = dst.Value.Qwords[0] ^ src.Value.Qwords[0];
}
else
{
res.Value.Qwords[0] = dst.Value.Qwords[0] & src.Value.Qwords[0];
}
if (ND_INS_TEST != Context->Arch.X86.Instruction.Instruction)
{
SET_OP(Context, 0, &res);
}
SET_FLAGS(Context, res, dst, src, FM_LOGIC);
break;
case ND_INS_NOT:
GET_OP(Context, hasNd ? 1 : 0, &dst);
dst.Value.Qwords[0] = ~dst.Value.Qwords[0];
SET_OP(Context, 0, &dst);
break;
case ND_INS_NEG:
GET_OP(Context, hasNd ? 1 : 0, &src);
dst.Size = src.Size;
dst.Value.Qwords[0] = 0;
res.Size = src.Size;
res.Value.Qwords[0] = dst.Value.Qwords[0] - src.Value.Qwords[0];
SET_OP(Context, 0, &res);
SET_FLAGS(Context, res, dst, src, FM_SUB);
SET_FLAG(Context, NDR_RFLAG_CF, src.Value.Qwords[0] != 0);
break;
case ND_INS_BT:
case ND_INS_BTS:
case ND_INS_BTR:
case ND_INS_BTC:
GET_OP(Context, 0, &dst);
GET_OP(Context, 1, &src);
src.Value.Qwords[0] %= dst.Size * 8ULL;
// Store the bit inside CF.
SET_FLAG(Context, NDR_RFLAG_CF, (dst.Value.Qwords[0] >> src.Value.Qwords[0]) & 1);
if (ND_INS_BTS == Context->Arch.X86.Instruction.Instruction)
{
dst.Value.Qwords[0] |= (1ULL << src.Value.Qwords[0]);
}
else if (ND_INS_BTR == Context->Arch.X86.Instruction.Instruction)
{
dst.Value.Qwords[0] &= ~(1ULL << src.Value.Qwords[0]);
}
else if (ND_INS_BTC == Context->Arch.X86.Instruction.Instruction)
{
dst.Value.Qwords[0] ^= (1ULL << src.Value.Qwords[0]);
}
if (ND_INS_BT != Context->Arch.X86.Instruction.Instruction)
{
SET_OP(Context, 0, &dst);
}
break;
case ND_INS_Jcc:
// Initial condition evaluation.
taken = ShemuX86EvalCondition(Context, Context->Arch.X86.Instruction.Condition);
// Track the loop. This may override the taken/not taken state.
taken = ShemuX86TrackLoop(Context, taken);
if (taken)
{
// Modify the RIP if the branch is taken.
GET_OP(Context, 1, &res);
res.Value.Qwords[0] += Context->Arch.X86.Instruction.Operands[0].Info.RelativeOffset.Rel;
SET_OP(Context, 1, &res);
}
break;
case ND_INS_JrCXZ:
// Fetch the rCX value. It could be CX, ECX or RCX, depending on address size.
GET_OP(Context, 1, &dst);
// Initial condition evaluation.
taken = dst.Value.Qwords[0] == 0;
// Track the loop. This may override the taken/not taken state.
taken = ShemuX86TrackLoop(Context, taken);
if (taken)
{
// Modify the RIP if the branch is taken.
GET_OP(Context, 2, &res);
res.Value.Qwords[0] += Context->Arch.X86.Instruction.Operands[0].Info.RelativeOffset.Rel;
SET_OP(Context, 2, &res);
}
break;
case ND_INS_LOOP:
case ND_INS_LOOPNZ:
case ND_INS_LOOPZ:
// rCX is decremented first. Note that the size depends on address size.
GET_OP(Context, 1, &dst);
dst.Value.Qwords[0]--;
SET_OP(Context, 1, &dst);
// Initial condition evaluation.
taken = dst.Value.Qwords[0] > 0 &&
(((ND_INS_LOOPNZ == Context->Arch.X86.Instruction.Instruction) && (0 == GET_FLAG(Context, NDR_RFLAG_ZF))) ||
((ND_INS_LOOPZ == Context->Arch.X86.Instruction.Instruction) && (0 != GET_FLAG(Context, NDR_RFLAG_ZF))) ||
(ND_INS_LOOP == Context->Arch.X86.Instruction.Instruction));
// Track the loop. This may override the taken/not taken state.
taken = ShemuX86TrackLoop(Context, taken);
if (taken)
{
// Modify the RIP if the branch is taken.
GET_OP(Context, 2, &res);
res.Value.Qwords[0] += Context->Arch.X86.Instruction.Operands[0].Info.RelativeOffset.Rel;
SET_OP(Context, 2, &res);
}
break;
case ND_INS_JMPNR:
// Track loops.
ShemuX86TrackLoop(Context, ND_TRUE);
GET_OP(Context, 1, &res);
res.Value.Qwords[0] += Context->Arch.X86.Instruction.Operands[0].Info.RelativeOffset.Rel;
SET_OP(Context, 1, &res);
break;
case ND_INS_JMPNI:
GET_OP(Context, 0, &src);
SET_OP(Context, 1, &src); // Set the RIP to the new value.
break;
case ND_INS_CALLNR:
// Save the EIP on the stack.
GET_OP(Context, 1, &res);
SET_OP(Context, 2, &res);
res.Value.Qwords[0] += Context->Arch.X86.Instruction.Operands[0].Info.RelativeOffset.Rel;
SET_OP(Context, 1, &res);
break;
case ND_INS_CALLNI:
GET_OP(Context, 0, &src);
GET_OP(Context, 1, &dst); // The RIP
SET_OP(Context, 2, &dst); // Save the RIP on the stack.
SET_OP(Context, 1, &src); // Set the RIP to the new value.
break;
case ND_INS_RETN:
if (!Context->Arch.X86.Instruction.HasImm1)
{
// The simple RET form, 0xC3
GET_OP(Context, 1, &src);
SET_OP(Context, 0, &src);
}
else
{
// The RET Imm16 form, 0xC2
GET_OP(Context, 3, &src);
SET_OP(Context, 1, &src);
// Patch the RSP register.
GET_OP(Context, 2, &res);
res.Value.Qwords[0] += Context->Arch.X86.Instruction.Operands[0].Info.Immediate.Imm;
SET_OP(Context, 2, &res);
}
break;
case ND_INS_JMPFD:
case ND_INS_CALLFD:
cs = (ND_UINT16)Context->Arch.X86.Instruction.Operands[0].Info.Address.BaseSeg;
goto check_far_branch;
case ND_INS_JMPFI:
case ND_INS_CALLFI:
case ND_INS_IRET:
case ND_INS_RETF:
if (Context->Arch.X86.Instruction.Instruction == ND_INS_RETF)
{
if (Context->Arch.X86.Instruction.Operands[0].Type == ND_OP_IMM)
{
// RETF imm
GET_OP(Context, 3, &src);
}
else
{
// RETF
GET_OP(Context, 2, &src);
}
}
else if (Context->Arch.X86.Instruction.Instruction == ND_INS_IRET)
{
// IRET
GET_OP(Context, 2, &src);
}
else
{
// JMP/CALL far
GET_OP(Context, 0, &src);
}
// The destination code segment is the second WORD/DWORD/QWORD.
switch (Context->Arch.X86.Instruction.WordLength)
{
case 2:
cs = (ND_UINT16)src.Value.Words[1];
break;
case 4:
cs = (ND_UINT16)src.Value.Dwords[1];
break;
case 8:
cs = (ND_UINT16)src.Value.Qwords[1];
break;
default:
cs = 0;
break;
}
check_far_branch:
if (Context->Arch.X86.Mode == ND_CODE_32 && cs == 0x33)
{
Context->Flags |= SHEMU_FLAG_HEAVENS_GATE;
}
// We may, in the future, emulate far branches, but they imply some tricky context switches (including
// the default TEB), so it may not be as straight forward as it seems. For now, all we wish to achieve
// is detection of far branches in long-mode, from Wow 64.
stop = ND_TRUE;
break;
case ND_INS_LODS:
case ND_INS_STOS:
case ND_INS_MOVS:
// Fetch the rCX register, which is the third operand in case of repeated instructions.
while (Context->InstructionsCount < Context->MaxInstructionsCount)
{
// Get the RCX value.
GET_OP(Context, 2, &dst);
if (Context->Arch.X86.Instruction.IsRepeated && (dst.Value.Qwords[0] == 0))
{
break;
}
// Load the source into the destination.
GET_OP(Context, 1, &src);
SET_OP(Context, 0, &src);
if (Context->Arch.X86.Instruction.IsRepeated)
{
// Decrement RCX.
dst.Value.Qwords[0]--;
SET_OP(Context, 2, &dst);
}
else
{
break;
}
Context->InstructionsCount++;
}
break;
case ND_INS_SCAS:
case ND_INS_CMPS:
while (Context->InstructionsCount < Context->MaxInstructionsCount)
{
// Get the RCX value.
GET_OP(Context, 2, &dst);
if (Context->Arch.X86.Instruction.IsRepeated && (dst.Value.Qwords[0] == 0))
{
break;
}
// Move on with the source & destination.
nd_memzero(&dst, sizeof(dst));
GET_OP(Context, 0, &dst);
GET_OP(Context, 1, &src);
res.Size = dst.Size;
res.Value.Qwords[0] = dst.Value.Qwords[0] - src.Value.Qwords[0];
SET_FLAGS(Context, res, dst, src, FM_SUB);
if (Context->Arch.X86.Instruction.IsRepeated)
{
// Read RCX again & decrement it.
nd_memzero(&dst, sizeof(dst));
GET_OP(Context, 2, &dst);
dst.Value.Qwords[0]--;
SET_OP(Context, 2, &dst);
if (Context->Arch.X86.Instruction.HasRepRepzXrelease && !GET_FLAG(Context, NDR_RFLAG_ZF))
{
break;
}
if (Context->Arch.X86.Instruction.HasRepnzXacquireBnd && GET_FLAG(Context, NDR_RFLAG_ZF))
{
break;
}
}
else
{
break;
}
Context->InstructionsCount++;
}
break;
case ND_INS_MUL:
case ND_INS_IMUL:
if (Context->Arch.X86.Instruction.ExpOperandsCount == 1)
{
// MUL or IMUL with a single explicit operand.
GET_OP(Context, 0, &dst);
GET_OP(Context, 1, &src);
res.Size = dst.Size * 2;
}
else if (Context->Arch.X86.Instruction.ExpOperandsCount == 2)
{
// IMUL with 2 explicit operands.
GET_OP(Context, 0, &dst);
GET_OP(Context, 1, &src);
res.Size = dst.Size;
}
else
{
// IMUL with 3 operands. The first operand is the write-only destination.
// This also covers the {ND} form, which is equivalent to the 3 operand form.
GET_OP(Context, 1, &dst);
GET_OP(Context, 2, &src);
res.Size = dst.Size;
}
if (dst.Size == 1)
{
if (ND_INS_MUL == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Words[0] = dst.Value.Bytes[0] * src.Value.Bytes[0];
}
else
{
res.Value.Words[0] = (ND_SINT8)dst.Value.Bytes[0] * (ND_SINT8)src.Value.Bytes[0];
}
}
else if (dst.Size == 2)
{
if (ND_INS_MUL == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Dwords[0] = dst.Value.Words[0] * src.Value.Words[0];
}
else
{
res.Value.Dwords[0] = (ND_SINT16)dst.Value.Words[0] * (ND_SINT16)src.Value.Words[0];
}
}
else if (dst.Size == 4)
{
if (ND_INS_MUL == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Qwords[0] = dst.Value.Qwords[0] * src.Value.Qwords[0];
}
else
{
res.Value.Qwords[0] = (ND_SINT64)(ND_SINT32)dst.Value.Dwords[0] * (ND_SINT64)(ND_SINT32)src.Value.Dwords[0];
}
}
else
{
if (ND_INS_MUL == Context->Arch.X86.Instruction.Instruction)
{
ShemuX86Multiply64Unsigned(&dst, &src, &res);
}
else
{
ShemuX86Multiply64Signed(&dst, &src, &res);
}
}
if (Context->Arch.X86.Instruction.ExpOperandsCount == 1)
{
// The result is stored in AX, DX:AX, EDX:EAX or RDX:RAX for the single-operand form.
switch (dst.Size)
{
case 1:
ShemuX86SetGprValue(Context, NDR_AX, 2, res.Value.Words[0], ND_FALSE);
break;
case 2:
ShemuX86SetGprValue(Context, NDR_DX, 2, res.Value.Words[1], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_AX, 2, res.Value.Words[0], ND_FALSE);
break;
case 4:
ShemuX86SetGprValue(Context, NDR_EDX, 4, res.Value.Dwords[1], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_EAX, 4, res.Value.Dwords[0], ND_FALSE);
break;
case 8:
ShemuX86SetGprValue(Context, NDR_RDX, 8, res.Value.Qwords[1], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_RAX, 8, res.Value.Qwords[0], ND_FALSE);
break;
}
}
else
{
// The result is truncated and stored in the destination operand for the 2 & 3 operands forms.
SET_OP(Context, 0, &res);
}
// Set the flags.
if (ND_INS_MUL == Context->Arch.X86.Instruction.Instruction)
{
ND_UINT8 cfof = 0;
// CF and OF are set to 0 if the high part of the result is 0, otherwise they are set to 1.
switch (dst.Size)
{
case 1:
cfof = (0 == res.Value.Bytes[1]) ? 0 : 1;
break;
case 2:
cfof = (0 == res.Value.Words[1]) ? 0 : 1;
break;
case 4:
cfof = (0 == res.Value.Dwords[1]) ? 0 : 1;
break;
case 8:
cfof = (0 == res.Value.Qwords[1]) ? 0 : 1;
break;
}
SET_FLAG(Context, NDR_RFLAG_CF, cfof);
SET_FLAG(Context, NDR_RFLAG_OF, cfof);
}
else
{
// The CF and OF flags are set when the signed integer value of the intermediate product differs from
// the sign extended operand - size - truncated product, otherwise the CF and OF flags are cleared.
ND_UINT8 cfof = 0, sign = 0;
sign = ND_MSB(dst.Size, res.Value.Qwords[0]);
switch (dst.Size)
{
case 1:
cfof = (0 == res.Value.Bytes[1] && 0 == sign) ||
((ND_UINT8)-1 == res.Value.Bytes[1] && 1 == sign) ? 0 : 1;
break;
case 2:
cfof = (0 == res.Value.Words[1] && 0 == sign) ||
((ND_UINT16)-1 == res.Value.Words[1] && 1 == sign) ? 0 : 1;
break;
case 4:
cfof = (0 == res.Value.Dwords[1] && 0 == sign) ||
((ND_UINT32)-1 == res.Value.Dwords[1] && 1 == sign) ? 0 : 1;
break;
case 8:
cfof = (0 == res.Value.Qwords[1] && 0 == sign) ||
((ND_UINT64)-1 == res.Value.Qwords[1] && 1 == sign) ? 0 : 1;
break;
}
SET_FLAG(Context, NDR_RFLAG_CF, cfof);
SET_FLAG(Context, NDR_RFLAG_OF, cfof);
}
break;
case ND_INS_DIV:
case ND_INS_IDIV:
// DIV and IDIV only exist with a single explicit operand encoding. All flags are undefined.
// No {ND} form for DIV/IDIV.
GET_OP(Context, 0, &src);
if (src.Size == 1)
{
ND_UINT16 divident;
divident = (ND_UINT16)ShemuX86GetGprValue(Context, NDR_AX, 2, ND_FALSE);
if (ND_INS_DIV == Context->Arch.X86.Instruction.Instruction)
{
if (!ShemuX86CheckDiv(divident, src.Value.Bytes[0], 1))
{
stop = ND_TRUE;
break;
}
res.Value.Bytes[0] = (ND_UINT8)(divident / src.Value.Bytes[0]);
res.Value.Bytes[1] = (ND_UINT8)(divident % src.Value.Bytes[0]);
}
else
{
if (!ShemuX86CheckIdiv((ND_SINT64)(ND_SINT16)divident, (ND_SINT64)(ND_SINT8)src.Value.Bytes[0], 1))
{
stop = ND_TRUE;
break;
}
res.Value.Bytes[0] = (ND_SINT8)((ND_SINT16)divident / (ND_SINT8)src.Value.Bytes[0]);
res.Value.Bytes[1] = (ND_SINT8)((ND_SINT16)divident % (ND_SINT8)src.Value.Bytes[0]);
}
// Result in AX (AL - quotient, AH - reminder).
ShemuX86SetGprValue(Context, NDR_AX, 2, res.Value.Words[0], ND_FALSE);
}
else if (src.Size == 2)
{
ND_UINT32 divident;
divident = ((ND_UINT32)ShemuX86GetGprValue(Context, NDR_EDX, 2, ND_FALSE) << 16) |
(ND_UINT32)ShemuX86GetGprValue(Context, NDR_EAX, 2, ND_FALSE);
if (ND_INS_DIV == Context->Arch.X86.Instruction.Instruction)
{
if (!ShemuX86CheckDiv(divident, src.Value.Words[0], 2))
{
stop = ND_TRUE;
break;
}
res.Value.Words[0] = (ND_UINT16)(divident / src.Value.Words[0]);
res.Value.Words[1] = (ND_UINT16)(divident % src.Value.Words[0]);
}
else
{
if (!ShemuX86CheckIdiv((ND_SINT64)(ND_SINT32)divident, (ND_SINT64)(ND_SINT16)src.Value.Words[0], 2))
{
stop = ND_TRUE;
break;
}
res.Value.Words[0] = (ND_SINT16)((ND_SINT32)divident / (ND_SINT16)src.Value.Words[0]);
res.Value.Words[1] = (ND_SINT16)((ND_SINT32)divident % (ND_SINT16)src.Value.Words[0]);
}
ShemuX86SetGprValue(Context, NDR_DX, 2, res.Value.Words[1], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_AX, 2, res.Value.Words[0], ND_FALSE);
}
else if (src.Size == 4)
{
ND_UINT64 divident;
divident = ((ND_UINT64)ShemuX86GetGprValue(Context, NDR_EDX, 4, ND_FALSE) << 32) |
(ND_UINT64)ShemuX86GetGprValue(Context, NDR_EAX, 4, ND_FALSE);
if (ND_INS_DIV == Context->Arch.X86.Instruction.Instruction)
{
if (!ShemuX86CheckDiv(divident, src.Value.Dwords[0], 4))
{
stop = ND_TRUE;
break;
}
res.Value.Dwords[0] = (ND_UINT32)(divident / src.Value.Dwords[0]);
res.Value.Dwords[1] = (ND_UINT32)(divident % src.Value.Dwords[0]);
}
else
{
if (!ShemuX86CheckIdiv((ND_SINT64)divident, (ND_SINT64)(ND_SINT32)src.Value.Dwords[0], 4))
{
stop = ND_TRUE;
break;
}
res.Value.Dwords[0] = (ND_SINT32)((ND_SINT64)divident / (ND_SINT32)src.Value.Dwords[0]);
res.Value.Dwords[1] = (ND_SINT32)((ND_SINT64)divident % (ND_SINT32)src.Value.Dwords[0]);
}
ShemuX86SetGprValue(Context, NDR_EDX, 4, res.Value.Dwords[1], ND_FALSE);
ShemuX86SetGprValue(Context, NDR_EAX, 4, res.Value.Dwords[0], ND_FALSE);
}
else if (src.Size == 8)
{
/// Not implemented!
}
break;
case ND_INS_CLD:
SET_FLAG(Context, NDR_RFLAG_DF, 0);
break;
case ND_INS_STD:
SET_FLAG(Context, NDR_RFLAG_DF, 1);
break;
case ND_INS_CLC:
SET_FLAG(Context, NDR_RFLAG_CF, 0);
break;
case ND_INS_STC:
SET_FLAG(Context, NDR_RFLAG_CF, 1);
break;
case ND_INS_CMC:
Context->Arch.X86.Registers.RegFlags ^= NDR_RFLAG_CF;
break;
case ND_INS_STI:
if (Context->Arch.X86.Ring != 0)
{
return SHEMU_ABORT_NO_PRIVILEGE;
}
SET_FLAG(Context, NDR_RFLAG_IF, 1);
break;
case ND_INS_CLI:
if (Context->Arch.X86.Ring != 0)
{
return SHEMU_ABORT_NO_PRIVILEGE;
}
SET_FLAG(Context, NDR_RFLAG_IF, 0);
break;
case ND_INS_SAHF:
{
ND_UINT8 ah = (ND_UINT8)ShemuX86GetGprValue(Context, NDR_AH, 1, ND_TRUE);
// Handle reserved bits.
ah |= (1 << 1);
ah &= ~((1 << 3) | (1 << 5));
((ND_UINT8 *)&Context->Arch.X86.Registers.RegFlags)[0] = ah;
}
break;
case ND_INS_LAHF:
{
ND_UINT8 ah = ((ND_UINT8 *)&Context->Arch.X86.Registers.RegFlags)[0];
ShemuX86SetGprValue(Context, NDR_AH, 1, ah, ND_TRUE);
}
break;
case ND_INS_SALC:
if (GET_FLAG(Context, NDR_RFLAG_CF))
{
ShemuX86SetGprValue(Context, NDR_AL, 1, 0xFF, ND_FALSE);
}
else
{
ShemuX86SetGprValue(Context, NDR_AL, 1, 0x00, ND_FALSE);
}
break;
case ND_INS_NOP:
if (sled)
{
Context->NopCount++;
}
break;
case ND_INS_WAIT:
break;
case ND_INS_CBW:
case ND_INS_CWDE:
case ND_INS_CDQE:
GET_OP(Context, 1, &src);
dst.Size = src.Size * 2;
dst.Value.Qwords[0] = ND_SIGN_EX(src.Size, src.Value.Qwords[0]);
SET_OP(Context, 0, &dst);
break;
case ND_INS_CWD:
case ND_INS_CDQ:
case ND_INS_CQO:
GET_OP(Context, 1, &src);
dst.Size = src.Size;
if (ND_GET_SIGN(src.Size, src.Value.Qwords[0]))
{
dst.Value.Qwords[0] = 0xFFFFFFFFFFFFFFFF;
}
else
{
dst.Value.Qwords[0] = 0;
}
SET_OP(Context, 0, &dst);
break;
case ND_INS_BSWAP:
GET_OP(Context, 0, &src);
dst.Size = src.Size;
switch (src.Size)
{
case 2:
// Although undefined, when executing BSWAP with 16 bit operands, the result is set to 0.
dst.Value.Words[0] = 0;
break;
case 4:
dst.Value.Bytes[3] = src.Value.Bytes[0];
dst.Value.Bytes[2] = src.Value.Bytes[1];
dst.Value.Bytes[1] = src.Value.Bytes[2];
dst.Value.Bytes[0] = src.Value.Bytes[3];
break;
case 8:
dst.Value.Bytes[7] = src.Value.Bytes[0];
dst.Value.Bytes[6] = src.Value.Bytes[1];
dst.Value.Bytes[5] = src.Value.Bytes[2];
dst.Value.Bytes[4] = src.Value.Bytes[3];
dst.Value.Bytes[3] = src.Value.Bytes[4];
dst.Value.Bytes[2] = src.Value.Bytes[5];
dst.Value.Bytes[1] = src.Value.Bytes[6];
dst.Value.Bytes[0] = src.Value.Bytes[7];
default:
break;
}
SET_OP(Context, 0, &dst);
break;
case ND_INS_BSF:
case ND_INS_BSR:
// No APX form.
GET_OP(Context, 1, &src);
if (src.Value.Qwords[0] == 0)
{
SET_FLAG(Context, NDR_RFLAG_ZF, 1);
}
else
{
SET_FLAG(Context, NDR_RFLAG_ZF, 0);
dst.Size = src.Size;
dst.Value.Qwords[0] = ShemuX86CountZeroBits(src.Value.Qwords[0],
src.Size,
Context->Arch.X86.Instruction.Instruction == ND_INS_BSF);
if (Context->Arch.X86.Instruction.Instruction == ND_INS_BSR)
{
dst.Value.Qwords[0] = src.Size * 8ULL - dst.Value.Qwords[0] - 1;
}
SET_OP(Context, 0, &dst);
}
break;
case ND_INS_POPCNT:
// No {ND} form.
GET_OP(Context, 1, &src);
dst.Size = src.Size;
dst.Value.Qwords[0] = 0;
for (ND_UINT32 bit = 0; bit < src.Size * 8; bit++)
{
if (ND_GET_BIT(bit, src.Value.Qwords[0]))
{
dst.Value.Qwords[0]++;
}
}
SET_FLAG(Context, NDR_RFLAG_OF, 0);
SET_FLAG(Context, NDR_RFLAG_SF, 0);
SET_FLAG(Context, NDR_RFLAG_ZF, 0);
SET_FLAG(Context, NDR_RFLAG_CF, 0);
SET_FLAG(Context, NDR_RFLAG_PF, 0);
SET_FLAG(Context, NDR_RFLAG_ZF, src.Value.Qwords[0] == 0 ? 1 : 0);
SET_OP(Context, 0, &dst);
break;
case ND_INS_LZCNT:
case ND_INS_TZCNT:
// No {ND} form.
GET_OP(Context, 1, &src);
dst.Size = src.Size;
dst.Value.Qwords[0] = ShemuX86CountZeroBits(src.Value.Qwords[0],
src.Size,
Context->Arch.X86.Instruction.Instruction == ND_INS_TZCNT);
// Set CF.
if (dst.Value.Qwords[0] == src.Size * 8ULL)
{
SET_FLAG(Context, NDR_RFLAG_CF, 1);
}
else
{
SET_FLAG(Context, NDR_RFLAG_CF, 0);
}
// Set ZF.
if (dst.Value.Qwords[0] == 0)
{
SET_FLAG(Context, NDR_RFLAG_ZF, 1);
}
else
{
SET_FLAG(Context, NDR_RFLAG_ZF, 0);
}
// Set the result.
SET_OP(Context, 0, &dst);
break;
case ND_INS_SHLD:
case ND_INS_SHRD:
{
SHEMU_VALUE cnt = { 0 };
GET_OP(Context, hasNd ? 1 : 0, &dst);
GET_OP(Context, hasNd ? 2 : 1, &src);
GET_OP(Context, hasNd ? 3 : 2, &cnt);
res.Size = dst.Size;
if (dst.Size == 8)
{
cnt.Value.Qwords[0] &= 0x3f;
}
else
{
cnt.Value.Qwords[0] &= 0x1f;
}
if (cnt.Value.Qwords[0] == 0)
{
// 0-shift, destination & flags are not affected.
}
else if (cnt.Value.Qwords[0] > dst.Size * 8ull)
{
// Shift count larger that operand size, destination & flags are undefined. Store 0 in destination.
SET_OP(Context, 0, &res);
}
else
{
// Positive shift, count less than operand size.
if (ND_INS_SHLD == Context->Arch.X86.Instruction.Instruction)
{
res.Value.Qwords[0] = dst.Value.Qwords[0] << cnt.Value.Qwords[0];
res.Value.Qwords[0] |= src.Value.Qwords[0] >> (dst.Size * 8ull - cnt.Value.Qwords[0]);
SET_FLAGS(Context, res, dst, cnt, FM_SHL);
}
else
{
res.Value.Qwords[0] = dst.Value.Qwords[0] >> cnt.Value.Qwords[0];
res.Value.Qwords[0] |= src.Value.Qwords[0] << (dst.Size * 8ull - cnt.Value.Qwords[0]);
SET_FLAGS(Context, res, dst, cnt, FM_SHR);
}
SET_OP(Context, 0, &res);
}
}
break;
case ND_INS_PREFETCH:
case ND_INS_PREFETCHE:
case ND_INS_PREFETCHM:
case ND_INS_PREFETCHNTA:
case ND_INS_PREFETCHT0:
case ND_INS_PREFETCHT1:
case ND_INS_PREFETCHT2:
case ND_INS_PREFETCHW:
case ND_INS_PREFETCHWT1:
// Act as NOPs, they're just hints to the hardware prefetchers.
break;
case ND_INS_ENDBR:
// Acts as a NOP, it's just a hint to the decoder.
break;
case ND_INS_LFENCE:
case ND_INS_SFENCE:
case ND_INS_MFENCE:
// Nothing can be done for them, really.
break;
case ND_INS_CPUID:
// OK; EAX, EBX, ECX and EDX are modified, which also zeroes the high 32 bit.
ShemuX86SetGprValue(Context, NDR_RAX, 8, 0, ND_FALSE);
ShemuX86SetGprValue(Context, NDR_RCX, 8, 0, ND_FALSE);
ShemuX86SetGprValue(Context, NDR_RDX, 8, 0, ND_FALSE);
ShemuX86SetGprValue(Context, NDR_RBX, 8, 0, ND_FALSE);
break;
// Some basic MMX/SSE instructions supported.
case ND_INS_EMMS:
nd_memzero(Context->Arch.X86.MmxRegisters, sizeof(Context->Arch.X86.MmxRegisters));
break;
case ND_INS_MOVD:
case ND_INS_MOVQ:
case ND_INS_MOVDQU:
case ND_INS_MOVDQA:
// If the source size is less than the destination size, the upper bits will be zero.
// Note that we don't really care about #GP on unaligned MOVDQA accesses...
GET_OP(Context, 1, &src);
SET_OP(Context, 0, &src);
break;
case ND_INS_PUNPCKLBW:
GET_OP(Context, 0, &dst);
GET_OP(Context, 1, &src);
if (dst.Size == 8)
{
// Operating on MMX register.
dst.Value.Bytes[7] = src.Value.Bytes[3];
dst.Value.Bytes[6] = dst.Value.Bytes[3];
dst.Value.Bytes[5] = src.Value.Bytes[2];
dst.Value.Bytes[4] = dst.Value.Bytes[2];
dst.Value.Bytes[3] = src.Value.Bytes[1];
dst.Value.Bytes[2] = dst.Value.Bytes[1];
dst.Value.Bytes[1] = src.Value.Bytes[0];
}
else
{
// Operating on XMM register.
dst.Value.Bytes[15] = src.Value.Bytes[7];
dst.Value.Bytes[14] = dst.Value.Bytes[7];
dst.Value.Bytes[13] = src.Value.Bytes[6];
dst.Value.Bytes[12] = dst.Value.Bytes[6];
dst.Value.Bytes[11] = src.Value.Bytes[5];
dst.Value.Bytes[10] = dst.Value.Bytes[5];
dst.Value.Bytes[9] = src.Value.Bytes[4];
dst.Value.Bytes[8] = dst.Value.Bytes[4];
dst.Value.Bytes[7] = src.Value.Bytes[3];
dst.Value.Bytes[6] = dst.Value.Bytes[3];
dst.Value.Bytes[5] = src.Value.Bytes[2];
dst.Value.Bytes[4] = dst.Value.Bytes[2];
dst.Value.Bytes[3] = src.Value.Bytes[1];
dst.Value.Bytes[2] = dst.Value.Bytes[1];
dst.Value.Bytes[1] = src.Value.Bytes[0];
}
SET_OP(Context, 0, &dst);
break;
case ND_INS_PXOR:
GET_OP(Context, 0, &dst);
GET_OP(Context, 1, &src);
for (i = 0; i < dst.Size; i++)
{
dst.Value.Bytes[i] ^= src.Value.Bytes[i];
}
SET_OP(Context, 0, &dst);
break;
// Some basic AVX/AVX2 instructions support.
case ND_INS_VMOVD:
case ND_INS_VMOVQ:
case ND_INS_VMOVDQU:
case ND_INS_VMOVDQA:
GET_OP(Context, 1, &src);
SET_OP(Context, 0, &src);
break;
case ND_INS_VPBROADCASTB:
case ND_INS_VPBROADCASTW:
case ND_INS_VPBROADCASTD:
case ND_INS_VPBROADCASTQ:
GET_OP(Context, 1, &src);
dst.Size = Context->Arch.X86.Instruction.Operands[0].Size;
for (i = 0; i < dst.Size / src.Size; i++)
{
switch (src.Size)
{
case 1:
dst.Value.Bytes[i] = src.Value.Bytes[0];
break;
case 2:
dst.Value.Words[i] = src.Value.Words[0];
break;
case 4:
dst.Value.Dwords[i] = src.Value.Dwords[0];
break;
default:
dst.Value.Qwords[i] = src.Value.Qwords[0];
break;
}
}
SET_OP(Context, 0, &dst);
break;
case ND_INS_VPXOR:
GET_OP(Context, 1, &dst);
GET_OP(Context, 2, &src);
for (i = 0; i < dst.Size; i++)
{
dst.Value.Bytes[i] ^= src.Value.Bytes[i];
}
SET_OP(Context, 0, &dst);
break;
// Software interrupt/SYSCALL/SYSENTER.
case ND_INS_INT:
if ((Context->Arch.X86.Instruction.Immediate1 == 0x80 ||
Context->Arch.X86.Instruction.Immediate1 == 0x2E) &&
Context->Arch.X86.Registers.RegRax < 0x1000)
{
Context->Flags |= SHEMU_FLAG_SYSCALL;
}
// Fall through
case ND_INS_INT1:
case ND_INS_INT3:
case ND_INS_INTO:
stop = ND_TRUE;
break;
case ND_INS_SYSCALL:
case ND_INS_SYSENTER:
if (Context->Arch.X86.Registers.RegRax < 0x1000)
{
Context->Flags |= SHEMU_FLAG_SYSCALL;
}
stop = ND_TRUE;
break;
// Some basic privileged instructions supported, specific to kernel-mode shellcodes.
case ND_INS_SWAPGS:
if (Context->Arch.X86.Ring != 0)
{
return SHEMU_ABORT_NO_PRIVILEGE;
}
Context->Flags |= SHEMU_FLAG_SWAPGS;
stop = ND_TRUE;
break;
case ND_INS_RDMSR:
if (Context->Arch.X86.Ring != 0)
{
return SHEMU_ABORT_NO_PRIVILEGE;
}
// Fetch ECX value.
GET_OP(Context, 2, &src);
if ((src.Value.Dwords[0] == 0xC0000082 && ND_CODE_64 == Context->Arch.X86.Mode) ||
(src.Value.Dwords[0] == 0x00000176 && ND_CODE_32 == Context->Arch.X86.Mode))
{
Context->Flags |= SHEMU_FLAG_SYSCALL_MSR_READ;
}
stop = ND_TRUE;
break;
case ND_INS_WRMSR:
if (Context->Arch.X86.Ring != 0)
{
return SHEMU_ABORT_NO_PRIVILEGE;
}
// Fetch ECX value.
GET_OP(Context, 2, &src);
if ((src.Value.Dwords[0] == 0xC0000082 && ND_CODE_64 == Context->Arch.X86.Mode) ||
(src.Value.Dwords[0] == 0x00000176 && ND_CODE_32 == Context->Arch.X86.Mode))
{
Context->Flags |= SHEMU_FLAG_SYSCALL_MSR_WRITE;
}
stop = ND_TRUE;
break;
case ND_INS_SIDT:
if (Context->Arch.X86.Ring == 0)
{
// Flag this only in ring0, as we treat the SHEMU_FLAG_SIDT as a ring0 specific indicator - it can be
// used to locate the kernel image.
Context->Flags |= SHEMU_FLAG_SIDT;
}
stop = ND_TRUE;
break;
#if defined(ND_ARCH_X64) || defined(ND_ARCH_X86)
case ND_INS_AESIMC:
case ND_INS_AESDEC:
case ND_INS_AESDECLAST:
{
__m128i val, key;
// Make sure AES support is present, and we can emulate AES decryption using AES instructions.
if (0 == (Context->Options & SHEMU_OPT_SUPPORT_AES))
{
break;
}
GET_OP(Context, 0, &dst);
GET_OP(Context, 1, &src);
shemu_memcpy(&val, &dst, 16);
shemu_memcpy(&key, &src, 16);
if (Context->Arch.X86.Instruction.Instruction == ND_INS_AESDEC)
{
val = _mm_aesdec_si128(val, key);
}
else if (Context->Arch.X86.Instruction.Instruction == ND_INS_AESDECLAST)
{
val = _mm_aesdeclast_si128(val, key);
}
else if (Context->Arch.X86.Instruction.Instruction == ND_INS_AESIMC)
{
val = _mm_aesimc_si128(key);
}
shemu_memcpy(&dst, &val, 16);
SET_OP(Context, 0, &dst);
break;
}
#endif
case ND_INS_RDTSC:
src.Size = 4;
// Set EAX to lower 32 bits.
src.Value.Dwords[0] = tsc & 0xFFFFFFFF;
SET_OP(Context, 0, &src);
// Set EDX to upper 32 bits.
src.Value.Dwords[0] = tsc >> 32;
SET_OP(Context, 1, &src);
break;
case ND_INS_RDFSBASE:
case ND_INS_RDGSBASE:
src.Size = Context->Arch.X86.Instruction.Operands[0].Size;
src.Value.Qwords[0] = Context->TibBase;
SET_OP(Context, 0, &src);
break;
case ND_INS_UD0:
case ND_INS_UD1:
case ND_INS_UD2:
stop = ND_TRUE;
break;
default:
return SHEMU_ABORT_INSTRUX_NOT_SUPPORTED;
break;
}
}
// Minimum percent of the instructions were NOPs => consider we have a NOP sled. Note that we get here only if
// the maximum number of instructions has been emulated successfully; if the emulation is aborted for any reason,
// this code will have no effect.
if ((Context->InstructionsCount >= Context->MaxInstructionsCount / 2) &&
(Context->NopCount >= Context->InstructionsCount * Context->NopThreshold / 100))
{
Context->Flags |= SHEMU_FLAG_NOP_SLED;
}
return SHEMU_SUCCESS;
}
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