某些页面上的ReadProcessMemory失败(GetLastError()= 299)

Question

我尝试读取进程的所有提交页面(Win7-64).在大多数页面上它可以工作,但几页失败.我无法解释原因.这是我的测试程序(编译x32,在Win7-64中测试):

#include <windows.h>

void main()
{
    HANDLE hProc = OpenProcess(PROCESS_VM_READ | PROCESS_QUERY_INFORMATION,FALSE,GetCurrentProcessId());

    SYSTEM_INFO si;
    ZeroMemory(&si,sizeof(SYSTEM_INFO));
    GetSystemInfo(&si);

    char* buf = new char[si.dwPageSize];

    for (unsigned i = 0; i < 0x7fff0; i++)
    {
        void* baseOffs = (void*) (i * si.dwPageSize);
        MEMORY_BASIC_INFORMATION mbi;
        ZeroMemory(&mbi,sizeof(MEMORY_BASIC_INFORMATION));

        if (VirtualQueryEx(hProc, baseOffs, &mbi, sizeof(MEMORY_BASIC_INFORMATION)) == 0)
        {
            MessageBox(NULL, TEXT("VirtualQueryEx failed"),TEXT(""),MB_OK);
        }

        if (mbi.State == MEM_COMMIT)
        {
            SIZE_T numByteWritten = 0;
            if(ReadProcessMemory(hProc, baseOffs,buf,si.dwPageSize,&numByteWritten) == FALSE)
                OutputDebugString(TEXT("bad\n")); //GetLastError()==ERROR_PARTIALLY_READ; numByteWritten == 0;
            else
                OutputDebugString(TEXT("good\n"));

        }
    }

    delete[] buf;
}

我厌倦了查看失败页面的MEMORY_BASIC_INFORMATION,但我没有发现任何奇怪的东西.失败页面的数量也因运行而异(平均约为5).什么阻止我阅读这些页面？我是否需要调整进程令牌中的某些权限？

Answer 1

确定了一些调试和有趣的事情:所有失败的页面都设置了保护位PAGE_GUARD(参见MSDN doc).在我解释文档时,您无法使用ReadProcessMemory读取这些页面.

if(ReadProcessMemory(hProc, baseOffs,buf,si.dwPageSize,&numByteWritten) == FALSE) {
    assert(mbi.Protect & 0x100);
    OutputDebugString(TEXT("bad\n")); //GetLastError()==ERROR_PARTIALLY_READ; numByteWritten == 0; 
}
else {
    assert(!(mbi.Protect & 0x100));
    OutputDebugString(TEXT("good\n")); 
}