Disassembler.c File Reference

#include "pch.h"

Functions
BOOLEAN	DisassemblerShowInstructionsInVmxNonRootMode (PVOID Address, UINT32 Length, BOOLEAN Is32Bit)
	Disassembler show the instructions.
BOOLEAN	DisassemblerShowOneInstructionInVmxNonRootMode (PVOID Address, UINT64 ActualRip, BOOLEAN Is32Bit)
	Disassembler show only one instruction.
UINT32	DisassemblerLengthDisassembleEngine (PVOID Address, BOOLEAN Is32Bit)
	Disassembler length disassemble engine.
UINT32	DisassemblerLengthDisassembleEngineInVmxRootOnTargetProcess (PVOID Address, BOOLEAN Is32Bit)
	Disassembler length disassembler engine.
UINT32	DisassemblerShowOneInstructionInVmxRootMode (PVOID Address, BOOLEAN Is32Bit)
	Shows the disassembly of only one instruction.

Function Documentation

DisassemblerLengthDisassembleEngine()

UINT32 DisassemblerLengthDisassembleEngine	(	PVOID	Address,
		BOOLEAN	Is32Bit )

Disassembler length disassemble engine.

if you want to call it directly, shouldn't not be in VMX-root mode, otherwise, you can call DisassemblerLengthDisassembleEngineInVmxRootOnTargetProcess to access memory safely

Parameters

Address
Is32Bit

Returns

UINT32

{
    ZydisDecoder            Decoder;
    ZydisDecodedInstruction Instruction;
    ZydisDecodedOperand     Operands[ZYDIS_MAX_OPERAND_COUNT];
    ZyanStatus              Status;
 
    if (ZydisGetVersion() != ZYDIS_VERSION)
    {
        LogError("Err, invalid zydis version");
        return NULL_ZERO;
    }
 
    //
    // Initialize Zydis decoder
    //
    if (Is32Bit)
    {
        if (!ZYAN_SUCCESS(ZydisDecoderInit(&Decoder, ZYDIS_MACHINE_MODE_LONG_COMPAT_32, ZYDIS_STACK_WIDTH_32)))
        {
            return NULL_ZERO;
        }
    }
    else
    {
        if (!ZYAN_SUCCESS(ZydisDecoderInit(&Decoder, ZYDIS_MACHINE_MODE_LONG_64, ZYDIS_STACK_WIDTH_64)))
        {
            return NULL_ZERO;
        }
    }
 
    //
    // Start the decode loop
    //
    while ((Status = ZydisDecoderDecodeFull(&Decoder,
                                            (PVOID)((UINT64)Address),
                                            MAXIMUM_INSTR_SIZE,
                                            &Instruction,
                                            Operands)) != ZYDIS_STATUS_NO_MORE_DATA)
    {
        NT_ASSERT(ZYAN_SUCCESS(Status));
 
        if (!ZYAN_SUCCESS(Status))
        {
            //
            // Probably invalid instruction
            //
            return NULL_ZERO;
        }
 
        //
        // This is a length disassembler, so we just return the length
        //
        return Instruction.length;
    }
 
    //
    // return an error status
    //
    return NULL_ZERO;
}

DisassemblerLengthDisassembleEngineInVmxRootOnTargetProcess()

UINT32 DisassemblerLengthDisassembleEngineInVmxRootOnTargetProcess	(	PVOID	Address,
		BOOLEAN	Is32Bit )

Disassembler length disassembler engine.

Should be called in VMX-root mode

Parameters

Address
Is32Bit

Returns

UINT32

{
    BYTE   SafeMemoryToRead[MAXIMUM_INSTR_SIZE] = {0};
    UINT64 SizeOfSafeBufferToRead               = 0;
 
    //
    // Read the maximum number of instruction that is valid to be read in the
    // target address
    //
    SizeOfSafeBufferToRead = CheckAddressMaximumInstructionLength(Address);
 
    //
    // Find the current instruction
    //
    MemoryMapperReadMemorySafeOnTargetProcess((UINT64)Address,
                                              SafeMemoryToRead,
                                              SizeOfSafeBufferToRead);
 
    return DisassemblerLengthDisassembleEngine(SafeMemoryToRead, Is32Bit);
}

DisassemblerShowInstructionsInVmxNonRootMode()

BOOLEAN DisassemblerShowInstructionsInVmxNonRootMode	(	PVOID	Address,
		UINT32	Length,
		BOOLEAN	Is32Bit )

Disassembler show the instructions.

This function should not be called from VMX-root mode

Parameters

Address
Length
Is32Bit

Returns

BOOLEAN

{
    ZydisDecoder            Decoder;
    ZydisFormatter          Formatter;
    SIZE_T                  ReadOffset = 0;
    ZydisDecodedInstruction Instruction;
    ZydisDecodedOperand     Operands[ZYDIS_MAX_OPERAND_COUNT];
    ZyanStatus              Status;
    CHAR                    PrintBuffer[128];
 
    PAGED_CODE();
 
    if (ZydisGetVersion() != ZYDIS_VERSION)
    {
        LogError("Err, invalid zydis version");
        return FALSE;
    }
 
    //
    // Initialize Zydis decoder
    //
    if (Is32Bit)
    {
        if (!ZYAN_SUCCESS(ZydisDecoderInit(&Decoder, ZYDIS_MACHINE_MODE_LONG_COMPAT_32, ZYDIS_STACK_WIDTH_32)))
        {
            return FALSE;
        }
    }
    else
    {
        if (!ZYAN_SUCCESS(ZydisDecoderInit(&Decoder, ZYDIS_MACHINE_MODE_LONG_64, ZYDIS_STACK_WIDTH_64)))
        {
            return FALSE;
        }
    }
 
    //
    // Initialize Zydis formatter
    //
    if (!ZYAN_SUCCESS(ZydisFormatterInit(&Formatter, ZYDIS_FORMATTER_STYLE_INTEL)))
    {
        return FALSE;
    }
 
    //
    // Start the decode loop
    //
    while ((Status = ZydisDecoderDecodeFull(&Decoder,
                                            (PVOID)((UINT64)Address + ReadOffset),
                                            Length - ReadOffset,
                                            &Instruction,
                                            Operands)) != ZYDIS_STATUS_NO_MORE_DATA)
    {
        NT_ASSERT(ZYAN_SUCCESS(Status));
        if (!ZYAN_SUCCESS(Status))
        {
            ReadOffset++;
            continue;
        }
 
        // Format and print the instruction
        const ZyanU64 InstrAddress = (ZyanU64)((UINT64)Address + ReadOffset);
        ZydisFormatterFormatInstruction(
            &Formatter,
            &Instruction,
            Operands,
            Instruction.operand_count_visible,
            PrintBuffer,
            sizeof(PrintBuffer),
            InstrAddress,
            NULL);
 
        LogInfo("+%-4X 0x%-16llX\t\t%hs\n", (UINT32)ReadOffset, InstrAddress, PrintBuffer);
 
        ReadOffset += Instruction.length;
    }
 
    //
    // return an error status so that the driver does not have to be unloaded after running
    //
    return TRUE;
}

DisassemblerShowOneInstructionInVmxNonRootMode()

BOOLEAN DisassemblerShowOneInstructionInVmxNonRootMode	(	PVOID	Address,
		UINT64	ActualRip,
		BOOLEAN	Is32Bit )

Disassembler show only one instruction.

This function should not be directly called from VMX-root mode if the caller is sure that the target buffer is safe to be access, then it's okay

Parameters

Address
ActualRip
Is32Bit

Returns

BOOLEAN

{
    ZydisDecoder            Decoder;
    ZydisFormatter          Formatter;
    SIZE_T                  ReadOffset = 0;
    ZydisDecodedInstruction Instruction;
    ZydisDecodedOperand     Operands[ZYDIS_MAX_OPERAND_COUNT];
    ZyanStatus              Status;
    CHAR                    PrintBuffer[128];
 
    if (ZydisGetVersion() != ZYDIS_VERSION)
    {
        LogError("Err, invalid zydis version");
        return FALSE;
    }
 
    //
    // Initialize Zydis decoder
    //
    if (Is32Bit)
    {
        if (!ZYAN_SUCCESS(ZydisDecoderInit(&Decoder, ZYDIS_MACHINE_MODE_LONG_COMPAT_32, ZYDIS_STACK_WIDTH_32)))
        {
            return FALSE;
        }
    }
    else
    {
        if (!ZYAN_SUCCESS(ZydisDecoderInit(&Decoder, ZYDIS_MACHINE_MODE_LONG_64, ZYDIS_STACK_WIDTH_64)))
        {
            return FALSE;
        }
    }
 
    //
    // Initialize Zydis formatter
    //
    if (!ZYAN_SUCCESS(ZydisFormatterInit(&Formatter, ZYDIS_FORMATTER_STYLE_INTEL)))
    {
        return FALSE;
    }
 
    //
    // Start the decode loop
    //
    while ((Status = ZydisDecoderDecodeFull(&Decoder,
                                            (PVOID)((UINT64)Address + ReadOffset),
                                            MAXIMUM_INSTR_SIZE - ReadOffset,
                                            &Instruction,
                                            Operands)) != ZYDIS_STATUS_NO_MORE_DATA)
    {
        NT_ASSERT(ZYAN_SUCCESS(Status));
        if (!ZYAN_SUCCESS(Status))
        {
            ReadOffset++;
            continue;
        }
 
        // Format and print the instruction
        const ZyanU64 InstrAddress = (ZyanU64)((UINT64)ActualRip + ReadOffset);
        ZydisFormatterFormatInstruction(
            &Formatter,
            &Instruction,
            Operands,
            Instruction.operand_count_visible,
            PrintBuffer,
            sizeof(PrintBuffer),
            InstrAddress,
            NULL);
 
        // LogInfo("+%-4X 0x%-16llX\t\t%hs\n", (UINT32)ReadOffset, InstrAddress, PrintBuffer);
 
        Log("core: %x | pid: %x - tid: %x,\t %llx \t\t\t\t%hs\n",
            KeGetCurrentProcessorNumberEx(NULL),
            PsGetCurrentProcessId(),
            PsGetCurrentThreadId(),
            ActualRip,
            PrintBuffer);
 
        // ReadOffset += Instruction.length;
 
        //
        // Only one instruction is enough
        //
        break;
    }
 
    //
    // return an error status so that the driver does not have to be unloaded after running
    //
    return TRUE;
}

DisassemblerShowOneInstructionInVmxRootMode()

UINT32 DisassemblerShowOneInstructionInVmxRootMode	(	PVOID	Address,
		BOOLEAN	Is32Bit )

Shows the disassembly of only one instruction.

Should be called in VMX-root mode

Parameters

Address
Is32Bit

Returns

UINT32

{
    BYTE   SafeMemoryToRead[MAXIMUM_INSTR_SIZE] = {0};
    UINT64 SizeOfSafeBufferToRead               = 0;
 
    //
    // Read the maximum number of instruction that is valid to be read in the
    // target address
    //
    SizeOfSafeBufferToRead = CheckAddressMaximumInstructionLength(Address);
 
    //
    // Find the current instruction
    //
    MemoryMapperReadMemorySafeOnTargetProcess((UINT64)Address,
                                              SafeMemoryToRead,
                                              SizeOfSafeBufferToRead);
 
    return DisassemblerShowOneInstructionInVmxNonRootMode(SafeMemoryToRead, (UINT64)Address, Is32Bit);
}