delphi - 如何在 EExternal 异常期间获取 EXCEPTION_POINTERS？

Question

我如何获得EXCEPTION_POINTERS ，即两者:

• PEXCEPTION_RECORD和
• PCONTEXT

EExternal期间的数据异常？

背景

当 Windows 抛出异常时，它会传递 PEXCEPTION_POINTERS ;指向异常信息的指针:

typedef struct _EXCEPTION_POINTERS {
   PEXCEPTION_RECORD ExceptionRecord;
   PCONTEXT          ContextRecord;
} EXCEPTION_POINTERS, *PEXCEPTION_POINTERS;

当 Delphi 向我抛出 EExternal 时异常(exception)，它只包含一半的信息，PEXCEPTION_RECORD仅:

EExternal = class(Exception)
public
  ExceptionRecord: PExceptionRecord;
end;

如何，在EExternal期间异常(exception)，我两者都可以吗？

用法示例

我正在尝试使用 MiniDumpWriteDump 编写小型转储来自 Delphi 的函数。

该函数有一些可选参数:

function MiniDumpWriteDump(
    hProcess: THandle; //A handle to the process for which the information is to be generated.
    ProcessID: DWORD; //The identifier of the process for which the information is to be generated.
    hFile: THandle; //A handle to the file in which the information is to be written.
    DumpType: MINIDUMP_TYPE; //The type of information to be generated.
    {in, optional}ExceptionParam: PMinidumpExceptionInformation; //A pointer to a MINIDUMP_EXCEPTION_INFORMATION structure describing the client exception that caused the minidump to be generated.
    {in, optional}UserStreamParam: PMinidumpUserStreamInformation;
    {in, optional}CallbackParam: PMinidumpCallbackInformation): Boolean;

在基本级别上，我可以省略三个可选参数:

MiniDumpWriteDump(
    GetCurrentProcess(), 
    GetCurrentProcessId(),
    hFileHandle,
    nil,  //PMinidumpExceptionInformation
    nil,
    nil);

并且成功了。缺点是小型转储缺少异常信息。该信息(可选)使用第四个 miniExceptionInfo 参数传递:

TMinidumpExceptionInformation = record
    ThreadId: DWORD;
    ExceptionPointers: PExceptionPointers;
    ClientPointers: BOOL;
end;
PMinidumpExceptionInformation = ^TMinidumpExceptionInformation;

这很好，但我需要一种方法来访问 EXCEPTION_POINTERS 发生异常时由 Windows 提供。

TExceptionPointers结构体包含两个成员:

EXCEPTION_POINTERS = record
   ExceptionRecord : PExceptionRecord;
   ContextRecord : PContext;
end;

我知道德尔福的EExternal异常是所有“Windows”异常的基础，它包含所需的PExceptionRecord :

EExternal = class(Exception)
public
  ExceptionRecord: PExceptionRecord;
end;

但它不包含关联的 ContextRecord 。

不是 PEXCEPTION_RECORD足够好了吗？

如果我尝试通过 EXCEPTION_POINTERS至MiniDumpWriteDump ，离开ContextRecord无:

procedure TDataModule1.ApplicationEvents1Exception(Sender: TObject; E: Exception);
var
   ei: TExceptionPointers;
begin
   if (E is EExternal) then
   begin
      ei.ExceptionRecord := EExternal(E).ExceptionRecord;
      ei.ContextRecord := nil;
      GenerateDump(@ei);
   end;

   ...
end;

function GenerateDump(exceptionInfo: PExceptionPointers): Boolean;
var
   miniEI: TMinidumpExceptionInformation;
begin
   ...

   miniEI.ThreadID := GetCurrentThreadID();
   miniEI.ExceptionPointers := exceptionInfo;
   miniEI.ClientPointers := True;

   MiniDumpWriteDump(
       GetCurrentProcess(), 
       GetCurrentProcessId(),
       hFileHandle,
       @miniEI,  //PMinidumpExceptionInformation
       nil,
       nil);
end;

然后该函数失败并出现错误 0x8007021B

Only part of a ReadProcessMemory or WriteProcessMemory request was completed

怎么样 SetUnhandledExceptionFilter ？

Why don't you just use SetUnhandledExceptionFilter and get the pointer you need?

SetUnhandledExceptionFilter(@DebugHelpExceptionFilter);

function DebugHelpExceptionFilter(const ExceptionInfo: TExceptionPointers): Longint; stdcall;
begin
   GenerateDump(@ExceptionInfo);
   Result := 1;  //1 = EXCEPTION_EXECUTE_HANDLER
end;

问题在于，未过滤异常处理程序仅在异常未过滤时才会启动。因为这是 Delphi，并且因为我处理异常:

procedure DataModule1.ApplicationEvents1Exception(Sender: TObject; E: Exception);
var
    ei: TExceptionPointers;
begin
    if (E is EExternal) then
    begin
       //If it's EXCEPTION_IN_PAGE_ERROR then we have to terminate *now*
       if EExternal(E).ExceptionRecord.ExceptionCode = EXCEPTION_IN_PAGE_ERROR then
       begin
           ExitProcess(1);
           Exit;
       end;

       //Write minidump
       ...
    end;

    {$IFDEF SaveExceptionsToDatabase}
    SaveExceptionToDatabase(Sender, E);
    {$ENDIF}

    {$IFDEF ShowExceptionForm}
    ShowExceptionForm(Sender, E);
    {$ENDIF}
end;

应用程序不会，我也不希望它因 WER 错误而终止。

我如何获得EXCEPTION_POINTERS在EExternal期间？

注意:您可以忽略背景之后的所有内容。它是不必要的填充物，旨在让我看起来更聪明。

先发制人的尖酸刻薄的 Heffernan 评论:你应该停止使用 Delphi 5。

奖励阅读

• MSDN: Crash Dump Analysis (Windows) (如何调用MiniDumpWriteDump的详细示例)
• CodeProject: Post-Mortem Debugging Your Application with Minidumps and Visual Studio .NET (一般性谈论概念、优点以及如何生成和使用小型转储)
• Stackoverflow: How to create minidump for my process when it crashes? (小型垃圾场世界的初步介绍)
• Stackoverflow: Can one prevent Microsoft Error Reporting for a single app? (在 Delphi 中设置未过滤的处理程序)

Answer 1

由于 Delphi RTL 不直接公开上下文指针，而仅提取异常指针并在系统内部执行此操作，因此解决方案将在某种程度上特定于您正在使用的 Delphi 版本。

自从我安装 Delphi 5 以来已经有一段时间了，但我确实有 Delphi 2007，并且我相信 Delphi 5 和 Delphi 2007 之间的概念到目前为止基本上保持不变。

考虑到这一点，下面是如何在 Delphi 2007 中完成此操作的示例:

program Sample;

{$APPTYPE CONSOLE}

uses
  Windows,
  SysUtils;


var
  SaveGetExceptionObject : function(P: PExceptionRecord):Exception;

// we show just the content of the general purpose registers in this example
procedure DumpContext(Context: PContext);
begin
  writeln('eip:', IntToHex(Context.Eip, 8));
  writeln('eax:', IntToHex(Context.Eax, 8));
  writeln('ebx:', IntToHex(Context.Ebx, 8));
  writeln('ecx:', IntToHex(Context.Ecx, 8));
  writeln('edx:', IntToHex(Context.Edx, 8));
  writeln('esi:', IntToHex(Context.Esi, 8));
  writeln('edi:', IntToHex(Context.Edi, 8));
  writeln('ebp:', IntToHex(Context.Ebp, 8));
  writeln('esp:', IntToHex(Context.Esp, 8));
end;

// Below, we redirect the ExceptObjProc ptr to point to here
// When control reaches here we locate the context ptr on
// stack, call the dump procedure, and then call the original ptr
function HookGetExceptionObject(P: PExceptionRecord):Exception;
var
  Context: PContext;
begin
  asm
    // This +44 value is likely to differ on a Delphi 5 setup, but probably
    // not by a lot. To figure out what value you should use, set a
    // break-point here, then look in the stack in the CPU window for the
    // P argument value on stack, and the Context pointer should be 8 bytes
    // (2 entries) above that on stack.
    // Note also that the 44 is sensitive to compiler switches, calling
    // conventions, and so on.
    mov eax, [esp+44]
    mov Context, eax
  end;
  DumpContext(Context);
  Result := SaveGetExceptionObject(P);
end;

var
  dvd, dvs, res: double; // used to force a div-by-zero error
begin
  dvd := 1; dvs := 0;
  SaveGetExceptionObject := ExceptObjProc;
  ExceptObjProc := @HookGetExceptionObject;
  try
    asm
      // this is just for register context verification
      // - don't do this in production
      mov esi, $BADF00D5;
    end;
    // cause a crash
    res := dvd / dvs;
    writeln(res);
  except
    on E:Exception do begin
      Writeln(E.Classname, ': ', E.Message);
      Readln;
    end;
  end;
end.