另一个过程中的断点处理 [英] Breakpoint handling in another process

问题描述

按照读取eax寄存器中给出的建议，我使用winapi编写了一个简单的调试器. 我的目标是每次在另一个线程中执行汇编指令后，都要读取eax寄存器. 它正在运行，我设法在另一个过程中放置​​了一个硬件断点.

Following advices given in Read eax register , I wrote a simple debugger using winapi. My objective is to read the eax register each time after an assembly instruction is executed in another thread. It is working and I managed to put an hardware breakpoint in another process.

当断点到达调试对象线程内部时，就会出现问题，我可以按预期读取eax寄存器，但是我仍然找不到任何方法来恢复线程的执行.

The problem arise when the breakpoint is reach inside the debuggee thread, I can read the eax register as intended, but I still couldn't find any way to resume the thread's execution.

我的代码:

 int _tmain(int argc, _TCHAR* argv[])
 {
 // Finding Window
HWND window = FindWindow(0, _T("Test"));
if( window == 0 )
{
    printf("Process not found!\n");
    return 0;
}

DWORD_PTR pID = 0;
GetWindowThreadProcessId(window, &pID);


// Get Handle
//HANDLE _handle = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pID);

DWORD_PTR eax = 0;
DWORD_PTR address = 0xC31E1B; // address of the instruction after the call for hardware breakpoint

DebugActiveProcess(pID); // PID of target process

// Avoid killing app on exit
DebugSetProcessKillOnExit(false);

// get thread ID of the main thread in process
DWORD_PTR dwThreadID = GetProcessThreadID(pID);

// gain access to the thread
HANDLE hThread = OpenThread(THREAD_ALL_ACCESS, FALSE, dwThreadID);

SetDebugPrivilege(true);

//ctx.Dr6=0;           //clear debug status register (only bits 0-3 of dr6 are cleared by processor)

CONTEXT ctx = {0};
ctx.ContextFlags = CONTEXT_DEBUG_REGISTERS | CONTEXT_INTEGER;
ctx.Dr0 = address;
ctx.Dr7 = 0x00000001;


// hThread with enough permissions
SetThreadContext(hThread, &ctx); 

DEBUG_EVENT dbgEvent;
while (true)
{
    if (WaitForDebugEvent(&dbgEvent, INFINITE) == 0)
        break;

    if (dbgEvent.dwDebugEventCode == EXCEPTION_DEBUG_EVENT &&
        dbgEvent.u.Exception.ExceptionRecord.ExceptionCode == EXCEPTION_SINGLE_STEP) // EXCEPTION_BREAKPOINT
    {
        if (dbgEvent.u.Exception.ExceptionRecord.ExceptionAddress == (LPVOID)address)
        {
            GetThreadContext(hThread, &ctx);
            eax = ctx.Eax; // eax get
            std::cout<<eax<<"\n";
            // Resume execution
            ctx.Eip = address + 0x3;
            SetThreadContext(hThread, &ctx);
        }

    }

    ContinueDebugEvent(dbgEvent.dwProcessId, dbgEvent.dwThreadId, DBG_CONTINUE);
}
return 0;
}

感谢帮助！

推荐答案

由此而来:整个逻辑应该如下:

1. 添加断点.
2. 触发它后，您将删除断点并在EFLAGS(0x100)中设置一个单步"标志
3. 下次调用循环时，您将重新启用硬件断点.

因此，您的while循环应如下所示:

So your while-loop should be like this:

while (true)
{
    if (WaitForDebugEvent(&dbgEvent, INFINITE) == 0)
        break;

    if (dbgEvent.dwDebugEventCode == EXCEPTION_DEBUG_EVENT &&
        dbgEvent.u.Exception.ExceptionRecord.ExceptionCode == EXCEPTION_SINGLE_STEP) // EXCEPTION_BREAKPOINT
    {
        CONTEXT newCtx = {0};
        newCtx.ContextFlags = CONTEXT_ALL;
        GetThreadContext(hThread, &newCtx);
        if (dbgEvent.u.Exception.ExceptionRecord.ExceptionAddress == (LPVOID)address)
        {
            newCtx.Dr0 = newCtx.Dr6 = newCtx.Dr7 = 0;
            newCtx.EFlags |= (1 << 8);
        }else{
            newCtx.Dr0 = address;
            newCtx.Dr7 = 0x00000001;
            newCtx.EFlags &= ~(1 << 8);
        }
        SetThreadContext(hThread, &newCtx);
    }
    ContinueDebugEvent(dbgEvent.dwProcessId, dbgEvent.dwThreadId, DBG_CONTINUE);
}

这篇关于另一个过程中的断点处理的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！