From ea30b6f6b9efd2e348687ddbaf5dd4d42309a0ad Mon Sep 17 00:00:00 2001
From: martin <laz.git@mfriebe.de>
Date: Mon, 20 Apr 2020 15:31:45 +0000
Subject: [PATCH] FpDebug: Detect internal forwarding jumps, and avoid stopping
 at them

git-svn-id: trunk@63033 -
---
 components/fpdebug/fpdbgclasses.pp     |  7 +++++
 components/fpdebug/fpdbgcontroller.pas | 39 ++++++++++++++++++++++++--
 components/fpdebug/fpdbgdisasx86.pp    | 31 ++++++++++++++++++++
 3 files changed, 74 insertions(+), 3 deletions(-)

diff --git a/components/fpdebug/fpdbgclasses.pp b/components/fpdebug/fpdbgclasses.pp
index cd70b1b840..d2ec94132d 100644
--- a/components/fpdebug/fpdbgclasses.pp
+++ b/components/fpdebug/fpdbgclasses.pp
@@ -405,6 +405,7 @@ type
     function IsCallInstruction: boolean; virtual;
     function IsReturnInstruction: boolean; virtual;
     function IsLeaveStackFrame: boolean; virtual;
+    function IsJumpInstruction(IncludeConditional: Boolean = True; IncludeUncoditional: Boolean = True): boolean; virtual;
     function InstructionLength: Integer; virtual;
   end;
 
@@ -1294,6 +1295,12 @@ begin
   Result := False;
 end;
 
+function TDbgAsmInstruction.IsJumpInstruction(IncludeConditional: Boolean;
+  IncludeUncoditional: Boolean): boolean;
+begin
+  Result := False;
+end;
+
 function TDbgAsmInstruction.InstructionLength: Integer;
 begin
   Result := 0;
diff --git a/components/fpdebug/fpdbgcontroller.pas b/components/fpdebug/fpdbgcontroller.pas
index 7e142cf014..3871207acb 100644
--- a/components/fpdebug/fpdbgcontroller.pas
+++ b/components/fpdebug/fpdbgcontroller.pas
@@ -79,6 +79,8 @@ type
     FIsSteppedOut: Boolean;
     FHiddenBreakpoint: TFpInternalBreakpoint;
     FHiddenBreakAddr, FHiddenBreakInstrPtr, FHiddenBreakFrameAddr, FHiddenBreakStackPtrAddr: TDBGPtr;
+    FWasAtJumpInstruction: Boolean;
+    FJumpPadCount: Integer;
     function GetIsSteppedOut: Boolean;
   protected
     function IsAtHiddenBreak: Boolean; inline;
@@ -88,6 +90,8 @@ type
     procedure SetHiddenBreak(AnAddr: TDBGPtr);
     procedure RemoveHiddenBreak;
     function CheckForCallAndSetBreak: boolean; // True, if break is newly set
+    procedure StoreWasAtJumpInstruction;
+    function  IsAtJumpPad: Boolean;
 
     procedure Init; override;
     procedure InternalContinue(AProcess: TDbgProcess; AThread: TDbgThread); virtual; abstract;
@@ -477,6 +481,22 @@ begin
     {$POP}
 end;
 
+procedure TDbgControllerHiddenBreakStepBaseCmd.StoreWasAtJumpInstruction;
+begin
+  FWasAtJumpInstruction := NextInstruction.IsJumpInstruction;
+end;
+
+function TDbgControllerHiddenBreakStepBaseCmd.IsAtJumpPad: Boolean;
+begin
+  Result := FWasAtJumpInstruction and
+            NextInstruction.IsJumpInstruction(False) and
+            not FController.FCurrentThread.IsAtStartOfLine; // TODO: check for lines with line=0
+  if Result then
+    inc(FJumpPadCount);
+  if FJumpPadCount > 2 then
+    Result := False;
+end;
+
 procedure TDbgControllerHiddenBreakStepBaseCmd.Init;
 begin
   FStoredStackPointer := FThread.GetStackPointerRegisterValue;
@@ -499,6 +519,8 @@ begin
     r := NextInstruction.IsReturnInstruction
   else
     r := False;
+
+  FWasAtJumpInstruction := False;
   InternalContinue(AProcess, AThread);
   if r and
      (FHiddenBreakpoint = nil)
@@ -621,6 +643,8 @@ begin
     end;
   end;
 
+  if FState <> siRunningStepOut then
+    StoreWasAtJumpInstruction;
   FProcess.Continue(FProcess, FThread, FState <> siRunningStepOut);
 end;
 
@@ -644,6 +668,8 @@ begin
 
   if (FState = siSteppingCurrent) then begin
     Finished := HasSteppedAwayFromOriginLine;
+    if Finished then
+      Finished := not IsAtJumpPad;
   end
   else begin
     // we stepped into
@@ -689,6 +715,9 @@ begin
   assert(FProcess=AProcess, 'TDbgControllerStepOverLineCmd.DoContinue: FProcess=AProcess');
   if (AThread = FThread) then
   CheckForCallAndSetBreak;
+
+  if FHiddenBreakpoint = nil then
+    StoreWasAtJumpInstruction;
   FProcess.Continue(FProcess, FThread, FHiddenBreakpoint = nil);
 end;
 
@@ -710,10 +739,14 @@ begin
   if IsAtOrOutOfHiddenBreakFrame then
       RemoveHiddenBreak;
 
-  if FHiddenBreakpoint <> nil then
-    Finished := False
-  else
+  if FHiddenBreakpoint <> nil then begin
+    Finished := False;
+  end
+  else begin
     Finished := HasSteppedAwayFromOriginLine;
+    if Finished then
+      Finished := not IsAtJumpPad;
+  end;
 
   if Finished then
     AnEvent := deFinishedStep
diff --git a/components/fpdebug/fpdbgdisasx86.pp b/components/fpdebug/fpdbgdisasx86.pp
index efb40f9970..42fccf982e 100644
--- a/components/fpdebug/fpdbgdisasx86.pp
+++ b/components/fpdebug/fpdbgdisasx86.pp
@@ -224,6 +224,7 @@ type
     function IsCallInstruction: boolean; override;
     function IsReturnInstruction: boolean; override;
     function IsLeaveStackFrame: boolean; override;
+    function IsJumpInstruction(IncludeConditional: Boolean = True; IncludeUncoditional: Boolean = True): boolean; override;
     function InstructionLength: Integer; override;
     function X86OpCode: TOpCode;
     property X86Instruction: TInstruction read FInstruction; // only valid after call to X86OpCode
@@ -446,6 +447,36 @@ begin
   Result := (FInstruction.OpCode = OPleave);
 end;
 
+function TX86AsmInstruction.IsJumpInstruction(IncludeConditional: Boolean;
+  IncludeUncoditional: Boolean): boolean;
+var
+  a: PByte;
+begin
+  (* Excluding
+     E1, E2  loop
+     E3   JCXZ   Jump short if eCX register is 0
+  *)
+  Result := False;
+  ReadCode;
+  if diCodeReadError in FFlags then
+    exit;
+  a := @FCodeBin[0];
+
+  if IncludeConditional and (a^ in [$70..$7F]) then
+    exit(True);
+  if IncludeConditional and (a^ = $0F) and (a[1] in [$80..$8F]) then
+    exit(True);
+
+  if IncludeUncoditional and (a^ in [$E9..$EB]) then
+    exit(True);
+
+  if IncludeUncoditional and (a^ in [$FF]) then begin
+    Disassemble;
+    exit(FInstruction.OpCode = OPjmp);
+  end;
+
+end;
+
 function TX86AsmInstruction.InstructionLength: Integer;
 begin
   Disassemble;