unit FpDbgCpuX86;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, DbgIntfBaseTypes, FpDbgClasses, FpdMemoryTools,
  FpDbgDwarfCFI, FpDbgDwarfDataClasses, FpDbgDisasX86;

type

  { TDbgStackUnwinderX86FramePointer }

  TDbgStackUnwinderX86FramePointer = class(TDbgStackUnwinderX86Base)
  private
    FLastFrameBaseIncreased: Boolean;
    FCodeReadErrCnt: integer;
  public
    procedure InitForThread(AThread: TDbgThread); override;
    function Unwind(AFrameIndex: integer; var CodePointer, StackPointer,
      FrameBasePointer: TDBGPtr; ACurrentFrame: TDbgCallstackEntry; out
      ANewFrame: TDbgCallstackEntry): TTDbgStackUnwindResult; override;
  end;

  { TDbgStackUnwinderX86DwarfCfi }

  TDbgStackUnwinderX86DwarfCfi = class(TDbgStackUnwinderX86Base)
  // Maybe have TDbgStackUnwinderX86Base as delegate instead of base
  private
  public
    //procedure InitForThread(AThread: TDbgThread); override;
    function Unwind(AFrameIndex: integer; var CodePointer, StackPointer,
      FrameBasePointer: TDBGPtr; ACurrentFrame: TDbgCallstackEntry; out
      ANewFrame: TDbgCallstackEntry): TTDbgStackUnwindResult; override;
  end;

  { TDbgStackUnwinderX86MultiMethod }

  TDbgStackUnwinderX86MultiMethod = class(TDbgStackUnwinderX86Base)
  // Base is for GetTopFrame // Alternatively forward to any of the sub-unwinder
  private
    FDwarfUnwinder: TDbgStackUnwinderX86DwarfCfi;
    FFrameUnwinder: TDbgStackUnwinderX86FramePointer;
    FAsmUnwinder: TDbgStackUnwinderIntelDisAssembler;
  public
    constructor Create(AProcess: TDbgProcess);
    destructor Destroy; override;
    procedure InitForThread(AThread: TDbgThread); override;
    function Unwind(AFrameIndex: integer; var CodePointer, StackPointer,
      FrameBasePointer: TDBGPtr; ACurrentFrame: TDbgCallstackEntry; out
      ANewFrame: TDbgCallstackEntry): TTDbgStackUnwindResult; override;
  end;

implementation

{ TDbgStackUnwinderX86FramePointer }

procedure TDbgStackUnwinderX86FramePointer.InitForThread(AThread: TDbgThread);
begin
  inherited InitForThread(AThread);
  FLastFrameBaseIncreased := True;
  FCodeReadErrCnt := 0;
end;

function TDbgStackUnwinderX86FramePointer.Unwind(AFrameIndex: integer;
  var CodePointer, StackPointer, FrameBasePointer: TDBGPtr;
  ACurrentFrame: TDbgCallstackEntry; out ANewFrame: TDbgCallstackEntry
  ): TTDbgStackUnwindResult;
var
  OutSideFrame: Boolean;
  Dummy: QWord;
  LastFrameBase: TDBGPtr;
  NewRes: TTDbgStackUnwindResult;
begin
  ANewFrame := nil;
  Result := suFailed;
  NewRes := suSuccess;

  if StackPointer = 0 then
    exit;
  if not FLastFrameBaseIncreased then
    exit;

  OutSideFrame := False;
  LastFrameBase := FrameBasePointer;

  if not Process.Disassembler.GetFunctionFrameInfo(CodePointer, OutSideFrame) then begin
    if Process.Disassembler.LastErrorWasMemReadErr then begin
      inc(FCodeReadErrCnt);
      if FCodeReadErrCnt > 5 then // If the code cannot be read the stack pointer is wrong.
        exit;
      if AFrameIndex <= 1 then
        OutSideFrame := True; // Maybe after "TProc(nil)();" call, then no frame could have been set up
    end;
  end;
  if (not OutSideFrame) {and (AFrameIndex = 1)} and (ACurrentFrame.ProcSymbol <> nil) then begin
    // the frame must be outside frame, if it is at entrypoint / needed for exceptions
    OutSideFrame := CodePointer = LocToAddrOrNil(ACurrentFrame.ProcSymbol.Address);
  end;

  if OutSideFrame then begin
    if not Process.ReadData(StackPointer, AddressSize, CodePointer) or (CodePointer = 0) then
      exit;

    if (not Process.ReadData(CodePointer, 1, Dummy) or (CodePointer = 0)) then begin
      OutSideFrame := False;
      NewRes := suGuessed;
    end
    else begin
      {$PUSH}{$R-}{$Q-}
      StackPointer := StackPointer + 1 * AddressSize; // After popping return-addr from "StackPointer"
      if LastFrameBase > 0 then
        LastFrameBase := LastFrameBase - 1; // Make the loop think thas LastFrameBase was smaller
      {$POP}
      // last stack has no frame
      //ACurrentFrame.RegisterValueList.DbgRegisterAutoCreate[nBP].SetValue(0, '0',AddressSize, BP);
    end;
  end;

  if not OutSideFrame then begin
    {$PUSH}{$R-}{$Q-}
    StackPointer := FrameBasePointer + 2 * AddressSize; // After popping return-addr from "FrameBasePointer + AddressSize"
    {$POP}
    if not Process.ReadData(FrameBasePointer + AddressSize, AddressSize, CodePointer) or (CodePointer = 0) then
      exit;
    if not Process.ReadData(FrameBasePointer, AddressSize, FrameBasePointer) then
      exit;
  end;

  FLastFrameBaseIncreased := (FrameBasePointer <> 0) and (FrameBasePointer > LastFrameBase);
  if not FLastFrameBaseIncreased then
    NewRes := suGuessed;


  ANewFrame := TDbgCallstackEntry.create(Thread, AFrameIndex, FrameBasePointer, CodePointer);
  ANewFrame.RegisterValueList.DbgRegisterAutoCreate[FNameIP].SetValue(CodePointer, IntToStr(CodePointer),AddressSize, FDwarfNumIP);
  ANewFrame.RegisterValueList.DbgRegisterAutoCreate[FNameBP].SetValue(FrameBasePointer, IntToStr(FrameBasePointer),AddressSize, FDwarfNumBP);
  ANewFrame.RegisterValueList.DbgRegisterAutoCreate[FNameSP].SetValue(StackPointer, IntToStr(StackPointer),AddressSize, FDwarfNumSP);
  FCodeReadErrCnt := 0;
  Result := NewRes;
end;

{ TDbgStackUnwinderX86DwarfCfi }

function TDbgStackUnwinderX86DwarfCfi.Unwind(AFrameIndex: integer;
  var CodePointer, StackPointer, FrameBasePointer: TDBGPtr;
  ACurrentFrame: TDbgCallstackEntry; out ANewFrame: TDbgCallstackEntry
  ): TTDbgStackUnwindResult;
var
  PrevStmtAddressOffs: Integer;
  Row: TDwarfCallFrameInformationRow;
  CIE: TDwarfCIE;
  CU: TDwarfCompilationUnit;
  StackReg, FrameReg: TDbgRegisterValue;
begin
  ANewFrame := nil;
  Result := suFailed;

  PrevStmtAddressOffs := 1;
  if AFrameIndex <= 1 then
    PrevStmtAddressOffs := 0;

  {$PUSH}{$R-}{$Q-}
  if (Process.DbgInfo as TFpDwarfInfo).FindCallFrameInfo(CodePointer - PrevStmtAddressOffs, CIE, Row) and
     TDwarfCallFrameInformation.TryObtainNextCallFrame(
       ACurrentFrame, CIE, AddressSize, AFrameIndex, Thread, Row, Process, ANewFrame
     )
  {$POP}
  then begin
    if not Assigned(ANewFrame) then begin
      CU := (Process.DbgInfo as TFpDwarfInfo).CompilationUnitForAddr(CodePointer);
      if (CU = nil) or (CU.DwarfSymbolClassMap = nil) or (not CU.DwarfSymbolClassMap.IgnoreCfiStackEnd) then begin
        // Done.
        Result := suFailedAtEOS;
        exit;
      end;
    end
    else begin
      Result := suSuccess;
      CodePointer := ANewFrame.AnAddress;
      StackReg := ANewFrame.RegisterValueList.FindRegisterByDwarfIndex(FDwarfNumSP);
      FrameReg := ANewFrame.RegisterValueList.FindRegisterByDwarfIndex(FDwarfNumBP);
      StackPointer     := 0;
      FrameBasePointer := 0;
      if (StackReg <> nil) and (FrameReg <> nil) then begin
        StackPointer     := StackReg.NumValue;
        FrameBasePointer := FrameReg.NumValue;
      end;
    end;
  end;

end;

{ TDbgStackUnwinderX86MultiMethod }

constructor TDbgStackUnwinderX86MultiMethod.Create(AProcess: TDbgProcess);
begin
  FDwarfUnwinder := TDbgStackUnwinderX86DwarfCfi.Create(AProcess);
  FFrameUnwinder := TDbgStackUnwinderX86FramePointer.Create(AProcess);
  FAsmUnwinder   := TDbgStackUnwinderIntelDisAssembler.Create(AProcess);
  inherited Create(AProcess);
end;

destructor TDbgStackUnwinderX86MultiMethod.Destroy;
begin
  inherited Destroy;
  FDwarfUnwinder.Free;
  FFrameUnwinder.Free;
  FAsmUnwinder.Free;
end;

procedure TDbgStackUnwinderX86MultiMethod.InitForThread(AThread: TDbgThread);
begin
  inherited InitForThread(AThread);
  FDwarfUnwinder.InitForThread(AThread);
  FFrameUnwinder.InitForThread(AThread);
  FAsmUnwinder.InitForThread(AThread);
end;

function TDbgStackUnwinderX86MultiMethod.Unwind(AFrameIndex: integer;
  var CodePointer, StackPointer, FrameBasePointer: TDBGPtr;
  ACurrentFrame: TDbgCallstackEntry; out ANewFrame: TDbgCallstackEntry
  ): TTDbgStackUnwindResult;
var
  OrigCodePointer, OrigFrameBasePointer, OrigStackPointer: TDBGPtr;
  CodePointer2, FrameBasePointer2, StackPointer2: TDBGPtr;
  ANewFrame2: TDbgCallstackEntry;
  ResAsm: TTDbgStackUnwindResult;
begin
  OrigCodePointer      := CodePointer;
  OrigFrameBasePointer := FrameBasePointer;
  OrigStackPointer     := StackPointer;

  Result := FDwarfUnwinder.Unwind(AFrameIndex,
    CodePointer, StackPointer, FrameBasePointer, ACurrentFrame, ANewFrame);

  if (Result = suSuccess) then begin
    FFrameUnwinder.FLastFrameBaseIncreased := True;
    if Process.Disassembler.IsAfterCallInstruction(CodePointer) then
      exit;
  end;
  if Result = suFailedAtEOS then
    exit;

  // Get Asm unwind
  CodePointer2      := OrigCodePointer;
  FrameBasePointer2 := OrigFrameBasePointer;
  StackPointer2     := OrigStackPointer;
  ResAsm := FAsmUnwinder.Unwind(AFrameIndex,
      CodePointer2, StackPointer2, FrameBasePointer2, ACurrentFrame, ANewFrame2);

  if (ResAsm = suSuccess) then begin
    // prefer Asm result over DwarfCfi
    FFrameUnwinder.FLastFrameBaseIncreased := True;
    if Process.Disassembler.IsAfterCallInstruction(CodePointer2) then begin
      ANewFrame.Free;
      CodePointer      := CodePointer2;
      FrameBasePointer := FrameBasePointer2;
      StackPointer     := StackPointer2;
      ANewFrame        := ANewFrame2;
      Result := suSuccess;
      exit;
    end;
  end;


  if (ResAsm in [suSuccess, suGuessed]) and
     (Result in [suSuccess, suGuessed]) and
     (CodePointer = CodePointer2) and (StackPointer = StackPointer2) and (FrameBasePointer = FrameBasePointer2)
  then begin
    // Both results where unsure => but both equal
    FFrameUnwinder.FLastFrameBaseIncreased := True;
    ANewFrame2.Free;
    Result := suSuccess;
    exit;
  end;


  ANewFrame.Free;
  // get frame-unwind
  CodePointer      := OrigCodePointer;
  FrameBasePointer := OrigFrameBasePointer;
  StackPointer     := OrigStackPointer;
  Result := FFrameUnwinder.Unwind(AFrameIndex,
      CodePointer, StackPointer, FrameBasePointer, ACurrentFrame, ANewFrame);

  if (Result = suSuccess) then begin
    if Process.Disassembler.IsAfterCallInstruction(CodePointer2) then
      exit;
  end;

  if (ResAsm in [suSuccess, suGuessed]) then begin
    ANewFrame.Free;
    CodePointer      := CodePointer2;
    FrameBasePointer := FrameBasePointer2;
    StackPointer     := StackPointer2;
    ANewFrame        := ANewFrame2;
    Result := suSuccess;
    exit;
  end;


end;

end.