windbg - 如何从 DLL 的堆标记中受益？

Question

我如何使用 GFlags 设置并从中受益 Enable heap tagging by DLL ?

我知道如何激活进程的设置，但我在 !heap -t 的输出中没有找到有用的信息在 WinDbg 中。我期待这样的输出:

0:000> !heap -t
Index   Address   Allocated by 
1:      005c0000  MyDll.dll
2:      006b0000  AnotherDll.dll

这样我就可以确定哪个堆是由哪个 DLL 创建的，然后例如确定内存泄漏的来源。

这是对术语“DLL 堆标记”的误解还是我需要更多命令才能获得所需的结果？

到目前为止我的研究:

我在谷歌上搜索了有关此主题的教程，但找不到详细说明

我阅读了 WinDbg 的 .hh !heap但它也没有详细解释。标签仅用于 !heap -b

Answer 1

又是一个很晚的答案

受益于 HeapTagging you need to create a tag首先在您的代码中。
据我所知(最多 xp-sp3)有 no Documented APIS to Create a tag
(从那时起我就没有处理过堆，所以我不知道 os > vista 中的最新 api 对堆管理器进行了重写，因此我在下面发布的许多 ^^^features^^^ 可能已得到纠正或改进或删除了错误)

在 xp-sp3 中，您可以使用未记录的 RtlCreateTagHeap为 Process Heap 创建一个新标签或 Private Heap
创建 tha 标签后，您需要设置全局标志 8000 | 800

htg - Enable heap tagging
htd - Enable heap tagging by DLL

和 theoratically all allocs and frees must get tagged .

但是 practically only allocations > 512 kB gets tagged在 xp-sp3 中使用这些基本步骤

它要么是一个错误，要么是一个将标记限制为分配和释放 > 512 kB 的功能 HeapAlloc goes through ZwAllocateVirtualMemory如果在 32 位进程中分配 > 512 kB refer HeapCreate / HeapAlloc Documentation in msdn
并作为 debuging aid您可以 patch ntdll.dll在 the fly to enable tagging为 all Allocations and frees .

下面是一个示例代码，演示了标记以及如何在 windbg 中查看所有内容

使用 cl /Zi /analyze /W4 <src> /link /RELEASE 编译

使用 windbg 执行应用程序并使用 !heap * -t 观看标记命令

#include <windows.h>
#include <stdio.h>

//heaptags are kinda broken or they are intentionally 
//given only to allocations > 512 kb // allocation > 512 kb
//go through VirtualAlloc Route for Heap created with maxsize 
//set to 0 uncomment ALLOCSIZE 0xfdfd2 and recompile to watch 
// tagging increase by 100% with ALLOCSIZE  0xfdfd1 only 50 allocs 
// and frees that are > 512 kB will be tagged these magic numbers 
// are related to comment in HeapCreate Documentation that state 
// slightly less than 512 kB will be allocated for 32 bit process 
// tagging can be dramatically increased by patching ntdll when 
// stopped on system breakpoint patch 7c94b8a4 (xpsp3 ntdll.dll) 
// use the below command in windbg for finding the offset of pattern
// command must be in single line no line breaks
// .foreach /pS 4 /ps 4 ( place  { !grep -i -e call -c 
// "# call*RtlpUpdateTagEntry 7c900000 l?20000" } ) { ub place }
// the instruction we are searching to patch is 
//7c94b8a1 81e3ff0fffff    and     ebx,0FFFF0FFFh 
// patch 0f to 00 at system breakpoint with eb 7c94b8a1+3 00 

#define BUFFERSIZE 100
#define ALLOCSIZE  0xfdfd1
//#define ALLOCSIZE  0xfdfd2

typedef int ( __stdcall *g_RtlCreateTagHeap) ( 
    HANDLE hHeap ,
    void * unknown, 
    wchar_t * BaseString, 
    wchar_t * TagString 
    );

void HeapTagwithHeapAllocPrivate()
{
    PCHAR pch[BUFFERSIZE] = {};
    HANDLE hHeap    = 0;
    ULONG tag1      = 0;
    ULONG tag2      = 0;
    ULONG tag3      = 0;
    ULONG tag4      = 0;
    ULONG tag5      = 0;
    g_RtlCreateTagHeap RtlCreateTagHeap = 0;
    HMODULE hMod = LoadLibrary("ntdll.dll");
    if(hMod)
    {
        RtlCreateTagHeap = (g_RtlCreateTagHeap) 
            GetProcAddress( hMod,"RtlCreateTagHeap");
    }
    if (hHeap == 0)
    {
        hHeap = HeapCreate(0,0,0);
        if (RtlCreateTagHeap != NULL)
        {
            tag1 = RtlCreateTagHeap (hHeap,0,L"HeapTag!",L"MyTag1");
            tag2 = RtlCreateTagHeap (hHeap,0,L"HeapTag!",L"MyTag2"); 
            tag3 = RtlCreateTagHeap (hHeap,0,L"HeapTag!",L"MyTag3");
            tag4 = RtlCreateTagHeap (hHeap,0,L"HeapTag!",L"MyTag4");
        }
    }
    HANDLE DefHeap = GetProcessHeap();
    if ( (RtlCreateTagHeap != NULL)  && (DefHeap != NULL ))
    {
        tag5 = RtlCreateTagHeap (DefHeap,0,L"HeapTag!",L"MyTag5");
        for ( int i = 0; i < BUFFERSIZE ; i++ )
        {
            pch[i]= (PCHAR) HeapAlloc( DefHeap,HEAP_ZERO_MEMORY| tag5, 1 );
            HeapFree(DefHeap,NULL,pch[i]);
        }

    }
    if(hHeap)
    {
        for ( int i = 0; i < BUFFERSIZE ; i++ )
        {
            pch[i]= (PCHAR) HeapAlloc( hHeap,HEAP_ZERO_MEMORY| tag1, 1 );
            //lets leak all allocs patch ntdll to see the tagging details
            //HeapFree(hHeap,NULL,pch[i]);
        }
        for ( int i = 0; i < BUFFERSIZE ; i++ )
        {
            pch[i]= (PCHAR) HeapAlloc( hHeap,HEAP_ZERO_MEMORY| tag2, 100 );
            // lets leak 40% allocs patch ntdll to see the tagging details
            if(i >= 40)
                HeapFree(hHeap,NULL,pch[i]);
        }
        // slightly less than 512 kb no tagging
        for ( int i = 0; i < BUFFERSIZE / 2 ; i++ ) 
        {
            pch[i]= (PCHAR) HeapAlloc( 
                hHeap,HEAP_ZERO_MEMORY| tag3, ALLOCSIZE / 2 );
        }
        // > 512 kb  default tagging 
        for ( int i = BUFFERSIZE / 2; i < BUFFERSIZE ; i++ ) 
        {
            pch[i]= (PCHAR) HeapAlloc( 
                hHeap,HEAP_ZERO_MEMORY | tag4 ,ALLOCSIZE );
        }
        for (int i =0 ; i < BUFFERSIZE ; i++)
        {
            HeapFree(hHeap,NULL,pch[i]);
        }
    }
}
void _cdecl main()
{
    HeapTagwithHeapAllocPrivate();
}

编译后的exe将与windbg一起运行，如下所示

DEFAULT 执行和检查
**只有 50 个标签可见，所有标签都 > 512 kB 分配

cdb -c "g;!heap * -t;q"newheaptag.exe | grep 标签**

heaptag:\>cdb -c "g;!heap * -t;q" newheaptag.exe | grep Tag
 Tag  Name                   Allocs    Frees   Diff  Allocated
 Tag  Name                   Allocs    Frees   Diff  Allocated
 Tag  Name                   Allocs    Frees   Diff  Allocated
0004: HeapTag!MyTag4             50       50      0        0

在系统断点上修补 ntdll 应该使所有标签可见

eb = 写字节
修补并在带有标签的退出检查堆上运行 exe
cdb -c "eb 7c94b8a1+3 00;g;!heap * -t;q"newheaptag.exe | grep 标签

heaptag:\>cdb -c "eb 7c94b8a1+3 00;g;!heap * -t;q" newheaptag.exe | grep Tag
 Tag  Name                   Allocs    Frees   Diff  Allocated
0012: HeapTag!MyTag5            100      100      0        0  <-our tag in process heap
 Tag  Name                   Allocs    Frees   Diff  Allocated
 Tag  Name                   Allocs    Frees   Diff  Allocated
0001: HeapTag!MyTag1            100        0    100     3200  <--- leak all
0002: HeapTag!MyTag2            100       60     40     5120  <--- leak 40 %
0003: HeapTag!MyTag3             50       50      0        0  <--- clean < 512 kB
0004: HeapTag!MyTag4             50       50      0        0  <----clean > 512 kB