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Code Issues Releases Activity

Implement separate FSTSW handlers and fix test encodings

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This commit is contained in:
bird_egop 2025-04-18 13:01:02 +03:00
parent cfef24f72d
commit a4de35cf41
4 changed files with 146 additions and 105 deletions
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93
X86Disassembler/X86/Handlers/FloatingPoint/Control/FstswHandler.cs
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@ -3,10 +3,7 @@ using X86Disassembler.X86.Operands;
namespace X86Disassembler.X86.Handlers.FloatingPoint.Control;
/// <summary>
/// Handler for FSTSW instruction (with WAIT prefix 0x9B)
/// Handles both:
/// - FSTSW AX (0x9B 0xDF 0xE0)
/// - FSTSW m2byte (0x9B 0xDD /7)
/// Handler for FSTSW AX instruction (0x9B 0xDF 0xE0) - Store FPU status word with wait prefix to AX register
/// </summary>
public class FstswHandler : InstructionHandler
{
@ -26,38 +23,22 @@ public class FstswHandler : InstructionHandler
/// <returns>True if this handler can decode the opcode</returns>
public override bool CanHandle(byte opcode)
{
// FSTSW starts with the WAIT prefix (0x9B)
// FSTSW AX starts with the WAIT prefix (0x9B)
if (opcode != 0x9B) return false;
// Check if we can read the next byte
// Check if we can read the next two bytes
if (!Decoder.CanReadByte())
return false;
// Check if the next byte is 0xDF (for FSTSW AX) or 0xDD (for FSTSW m2byte)
// Check if the next bytes are 0xDF 0xE0 (for FSTSW AX)
var (nextByte, thirdByte) = Decoder.PeakTwoBytes();
var (nextByte, modRM) = Decoder.PeakTwoBytes();
if (nextByte != 0xDF && nextByte != 0xDD)
return false;
if (nextByte == 0xDF)
{
// For FSTSW AX, check if we can peek at the third byte and it's 0xE0
return modRM == 0xE0;
}
else // nextByte == 0xDD
{
// For FSTSW m2byte, check if we can peek at ModR/M byte and reg field = 7
byte regField = ModRMDecoder.GetRegFromModRM(modRM);
// The reg field must be 7 for FSTSW m2byte
return regField == 7;
}
// The sequence must be 9B DF E0 for FSTSW AX
return nextByte == 0xDF && thirdByte == 0xE0;
}
/// <summary>
/// Decodes an FSTSW instruction
/// Decodes an FSTSW AX instruction
/// </summary>
/// <param name="opcode">The opcode of the instruction</param>
/// <param name="instruction">The instruction object to populate</param>
@ -68,48 +49,30 @@ public class FstswHandler : InstructionHandler
if (!Decoder.CanReadByte())
return false;
// Read the second byte (0xDF for AX variant, 0xDD for memory variant)
// Read the second byte (0xDF)
byte secondByte = Decoder.ReadByte();
if (secondByte != 0xDF)
return false;
// Read the third byte (0xE0)
if (!Decoder.CanReadByte())
return false;
byte thirdByte = Decoder.ReadByte();
if (thirdByte != 0xE0)
return false;
// Set the instruction type
instruction.Type = InstructionType.Fstsw;
if (secondByte == 0xDF)
{
// FSTSW AX variant
// Read the 0xE0 byte
if (!Decoder.CanReadByte())
return false;
byte e0Byte = Decoder.ReadByte();
if (e0Byte != 0xE0)
return false;
// Create the AX register operand
var axOperand = OperandFactory.CreateRegisterOperand(RegisterIndex.A, 16);
// Set the structured operands
instruction.StructuredOperands =
[
axOperand
];
}
else if (secondByte == 0xDD)
{
// FSTSW m2byte variant
// Use ModRMDecoder to read and decode the ModR/M byte for 16-bit memory operand
var (mod, reg, rm, memoryOperand) = ModRMDecoder.ReadModRM16();
// Set the structured operands
instruction.StructuredOperands =
[
memoryOperand
];
}
else
{
return false;
}
// Create the AX register operand
var axOperand = OperandFactory.CreateRegisterOperand(RegisterIndex.A, 16);
// Set the structured operands
instruction.StructuredOperands =
[
axOperand
];
return true;
}

78
X86Disassembler/X86/Handlers/FloatingPoint/Control/FstswMemHandler.cs Normal file
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@ -0,0 +1,78 @@
using X86Disassembler.X86.Operands;
namespace X86Disassembler.X86.Handlers.FloatingPoint.Control;
/// <summary>
/// Handler for FSTSW m2byte instruction (0x9B 0xDD /7) - Store FPU status word with wait prefix to memory
/// </summary>
public class FstswMemHandler : InstructionHandler
{
/// <summary>
/// Initializes a new instance of the FstswMemHandler class
/// </summary>
/// <param name="decoder">The instruction decoder that owns this handler</param>
public FstswMemHandler(InstructionDecoder decoder)
: base(decoder)
{
}
/// <summary>
/// Checks if this handler can decode the given opcode
/// </summary>
/// <param name="opcode">The opcode to check</param>
/// <returns>True if this handler can decode the opcode</returns>
public override bool CanHandle(byte opcode)
{
// FSTSW m2byte starts with the WAIT prefix (0x9B)
if (opcode != 0x9B) return false;
// Check if we can read the next two bytes
if (!Decoder.CanReadByte())
return false;
// Check if the next bytes are 0xDD followed by ModR/M with reg field = 7
var (nextByte, modRM) = Decoder.PeakTwoBytes();
// The first byte must be 0xDD for FSTSW m2byte
if (nextByte != 0xDD)
return false;
// Check if ModR/M byte has reg field = 7
byte regField = ModRMDecoder.GetRegFromModRM(modRM);
// The reg field must be 7 for FSTSW m2byte
return regField == 7;
}
/// <summary>
/// Decodes an FSTSW m2byte instruction
/// </summary>
/// <param name="opcode">The opcode of the instruction</param>
/// <param name="instruction">The instruction object to populate</param>
/// <returns>True if the instruction was successfully decoded</returns>
public override bool Decode(byte opcode, Instruction instruction)
{
// Skip the WAIT prefix (0x9B) - we already read it in CanHandle
if (!Decoder.CanReadByte())
return false;
// Read the second byte (0xDD)
byte secondByte = Decoder.ReadByte();
if (secondByte != 0xDD)
return false;
// Set the instruction type
instruction.Type = InstructionType.Fstsw;
// Use ModRMDecoder to read and decode the ModR/M byte for 16-bit memory operand
var (mod, reg, rm, memoryOperand) = ModRMDecoder.ReadModRM16();
// Set the structured operands
instruction.StructuredOperands =
[
memoryOperand
];
return true;
}
}

1
X86Disassembler/X86/Handlers/InstructionHandlerFactory.cs
View File

@ -419,6 +419,7 @@ public class InstructionHandlerFactory
// Other floating point handlers
_handlers.Add(new FloatingPoint.Control.FnstswHandler(_decoder)); // FNSTSW AX (DF E0)
_handlers.Add(new FloatingPoint.Control.FstswHandler(_decoder)); // FSTSW AX (9B DF E0)
_handlers.Add(new FloatingPoint.Control.FstswMemHandler(_decoder)); // FSTSW m2byte (9B DD /7)
// DB opcode handlers (int32 operations and extended precision)
_handlers.Add(new FloatingPoint.LoadStore.FildInt32Handler(_decoder)); // FILD int32 (DB /0)

79
X86DisassemblerTests/TestData/fnstsw_tests.csv
View File

@ -9,51 +9,50 @@ DFE0;[{ "Type": "Fnstsw", "Operands": ["ax"] }]
9BDFE0;[{ "Type": "Fstsw", "Operands": ["ax"] }]
# FSTSW m2byte - Store FPU status word to memory
9BDD7D00;[{ "Type": "Fstsw", "Operands": ["word ptr [eax]"] }]
9BDD7C24;[{ "Type": "Fstsw", "Operands": ["word ptr [esp]"] }]
9BDD7C24;[{ "Type": "Fstsw", "Operands": ["word ptr [esp]"] }]
9BDD7D03;[{ "Type": "Fstsw", "Operands": ["word ptr [ebx]"] }]
9BDD7D01;[{ "Type": "Fstsw", "Operands": ["word ptr [ecx]"] }]
9BDD7D02;[{ "Type": "Fstsw", "Operands": ["word ptr [edx]"] }]
9BDD7D06;[{ "Type": "Fstsw", "Operands": ["word ptr [esi]"] }]
9BDD7D07;[{ "Type": "Fstsw", "Operands": ["word ptr [edi]"] }]
9BDD38;[{ "Type": "Fstsw", "Operands": ["word ptr [eax]"] }]
9BDD3C24;[{ "Type": "Fstsw", "Operands": ["word ptr [esp]"] }]
9BDD3C24;[{ "Type": "Fstsw", "Operands": ["word ptr [esp]"] }]
9BDD3B;[{ "Type": "Fstsw", "Operands": ["word ptr [ebx]"] }]
9BDD39;[{ "Type": "Fstsw", "Operands": ["word ptr [ecx]"] }]
9BDD3A;[{ "Type": "Fstsw", "Operands": ["word ptr [edx]"] }]
9BDD3E;[{ "Type": "Fstsw", "Operands": ["word ptr [esi]"] }]
9BDD3F;[{ "Type": "Fstsw", "Operands": ["word ptr [edi]"] }]
# FNSTSW m2byte - Store FPU status word to memory without checking for pending unmasked exceptions
DD7D00;[{ "Type": "Fnstsw", "Operands": ["word ptr [eax]"] }]
DD7C24;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp]"] }]
DD7C24;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp]"] }]
DD7D03;[{ "Type": "Fnstsw", "Operands": ["word ptr [ebx]"] }]
DD7D01;[{ "Type": "Fnstsw", "Operands": ["word ptr [ecx]"] }]
DD7D02;[{ "Type": "Fnstsw", "Operands": ["word ptr [edx]"] }]
DD7D06;[{ "Type": "Fnstsw", "Operands": ["word ptr [esi]"] }]
DD7D07;[{ "Type": "Fnstsw", "Operands": ["word ptr [edi]"] }]
DD38;[{ "Type": "Fnstsw", "Operands": ["word ptr [eax]"] }]
DD3C24;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp+0x00]"] }]
DD3B;[{ "Type": "Fnstsw", "Operands": ["word ptr [ebx]"] }]
DD39;[{ "Type": "Fnstsw", "Operands": ["word ptr [ecx]"] }]
DD3A;[{ "Type": "Fnstsw", "Operands": ["word ptr [edx]"] }]
DD3E;[{ "Type": "Fnstsw", "Operands": ["word ptr [esi]"] }]
DD3F;[{ "Type": "Fnstsw", "Operands": ["word ptr [edi]"] }]
# FSTSW/FNSTSW with displacement
9BDD7D8010000000;[{ "Type": "Fstsw", "Operands": ["word ptr [eax+0x10]"] }]
9BDD7D8020000000;[{ "Type": "Fstsw", "Operands": ["word ptr [eax+0x20]"] }]
DD7D8010000000;[{ "Type": "Fnstsw", "Operands": ["word ptr [eax+0x10]"] }]
DD7D8020000000;[{ "Type": "Fnstsw", "Operands": ["word ptr [eax+0x20]"] }]
9BDDB810000000;[{ "Type": "Fstsw", "Operands": ["word ptr [eax+0x10]"] }]
9BDDB820000000;[{ "Type": "Fstsw", "Operands": ["word ptr [eax+0x20]"] }]
DDB810000000;[{ "Type": "Fnstsw", "Operands": ["word ptr [eax+0x10]"] }]
DDB820000000;[{ "Type": "Fnstsw", "Operands": ["word ptr [eax+0x20]"] }]
# FSTSW/FNSTSW with SIB addressing
9BDD7C04;[{ "Type": "Fstsw", "Operands": ["word ptr [esp+eax*1]"] }]
9BDD7C4C;[{ "Type": "Fstsw", "Operands": ["word ptr [esp+ecx*2]"] }]
9BDD7C94;[{ "Type": "Fstsw", "Operands": ["word ptr [esp+edx*4]"] }]
9BDD7CDC;[{ "Type": "Fstsw", "Operands": ["word ptr [esp+ebx*8]"] }]
DD7C04;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp+eax*1]"] }]
DD7C4C;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp+ecx*2]"] }]
DD7C94;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp+edx*4]"] }]
DD7CDC;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp+ebx*8]"] }]
9BDD3C04;[{ "Type": "Fstsw", "Operands": ["word ptr [esp+eax*1]"] }]
9BDD3C4C;[{ "Type": "Fstsw", "Operands": ["word ptr [esp+ecx*2]"] }]
9BDD3C94;[{ "Type": "Fstsw", "Operands": ["word ptr [esp+edx*4]"] }]
9BDD3CDC;[{ "Type": "Fstsw", "Operands": ["word ptr [esp+ebx*8]"] }]
DD3C04;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp+eax*1]"] }]
DD3C4C;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp+ecx*2]"] }]
DD3C94;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp+edx*4]"] }]
DD3CDC;[{ "Type": "Fnstsw", "Operands": ["word ptr [esp+ebx*8]"] }]
# FSTSW/FNSTSW with segment override prefixes
269BDD7D00;[{ "Type": "Fstsw", "Operands": ["word ptr es:[eax]"] }]
2E9BDD7D00;[{ "Type": "Fstsw", "Operands": ["word ptr cs:[eax]"] }]
369BDD7D00;[{ "Type": "Fstsw", "Operands": ["word ptr ss:[eax]"] }]
3E9BDD7D00;[{ "Type": "Fstsw", "Operands": ["word ptr ds:[eax]"] }]
649BDD7D00;[{ "Type": "Fstsw", "Operands": ["word ptr fs:[eax]"] }]
659BDD7D00;[{ "Type": "Fstsw", "Operands": ["word ptr gs:[eax]"] }]
26DD7D00;[{ "Type": "Fnstsw", "Operands": ["word ptr es:[eax]"] }]
2EDD7D00;[{ "Type": "Fnstsw", "Operands": ["word ptr cs:[eax]"] }]
36DD7D00;[{ "Type": "Fnstsw", "Operands": ["word ptr ss:[eax]"] }]
3EDD7D00;[{ "Type": "Fnstsw", "Operands": ["word ptr ds:[eax]"] }]
64DD7D00;[{ "Type": "Fnstsw", "Operands": ["word ptr fs:[eax]"] }]
65DD7D00;[{ "Type": "Fnstsw", "Operands": ["word ptr gs:[eax]"] }]
269BDD38;[{ "Type": "Fstsw", "Operands": ["word ptr es:[eax]"] }]
2E9BDD38;[{ "Type": "Fstsw", "Operands": ["word ptr cs:[eax]"] }]
369BDD38;[{ "Type": "Fstsw", "Operands": ["word ptr ss:[eax]"] }]
3E9BDD38;[{ "Type": "Fstsw", "Operands": ["word ptr ds:[eax]"] }]
649BDD38;[{ "Type": "Fstsw", "Operands": ["word ptr fs:[eax]"] }]
659BDD38;[{ "Type": "Fstsw", "Operands": ["word ptr gs:[eax]"] }]
26DD38;[{ "Type": "Fnstsw", "Operands": ["word ptr es:[eax]"] }]
2EDD38;[{ "Type": "Fnstsw", "Operands": ["word ptr cs:[eax]"] }]
36DD38;[{ "Type": "Fnstsw", "Operands": ["word ptr ss:[eax]"] }]
3EDD38;[{ "Type": "Fnstsw", "Operands": ["word ptr ds:[eax]"] }]
64DD38;[{ "Type": "Fnstsw", "Operands": ["word ptr fs:[eax]"] }]
65DD38;[{ "Type": "Fnstsw", "Operands": ["word ptr gs:[eax]"] }]

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