CoInitialize浅析一

大家都知道程序中若要使用COM组件则必需要先调用CoInitialize，该函数主要是用来初始化COM执行环境。但这个函数的作用域是以线程为单位还是以进程为单位呢？或许大家已经通过測试程序摸索出答案，没错，是以线程为单位。今天我们就略微再深入一下，通过分析CoInitialize的详细实现来印证我们的想法。

我们先来看看CoInitialize的汇编

769B2A24                 mov     edi, edi

769B2A26                 push    ebp

769B2A27                 mov     ebp, esp

769B2A29                 push    2               ; dwCoInit

769B2A2B                 push    [ebp+8] ; pvReserved

769B2A2E                 call   _CoInitializeEx@8 ; CoInitializeEx(x,x)

769B2A33                 pop     ebp

769B2A34                 retn    4

能够看到，当中的实现还是比較简单的，它仅仅是简单地调用了CoInitializeEx，将第二个參数设置为2，即COINIT_APARTMENTTHREADED。我们再来看看CoInitializeEx的实现

769AEF5B                 mov     edi, edi

769AEF5D                 push    ebp

769AEF5E                 mov     ebp, esp

769AEF60                 push    ecx

769AEF61                 push    ebx

769AEF62                 mov     ebx, [ebp+0C]

769AEF65                 mov     eax, ebx

769AEF67                 and    eax, 0Eh      ; 检查參数是否正确，眼下第二个參数仅仅用了一个字节

769AEF6A                 cmp     eax, ebx

769AEF6C                 jnz     loc_76A0B8C7

769AEF72                 push    edi

769AEF73                 xor     edi, edi

769AEF75                 cmp     [ebp+8], edi       ; 推断第一个參数是否为NULL

769AEF78                 jnz     loc_76A0B8D1

769AEF7E

769AEF7Eloc_769AEF7E:

769AEF7E                 call    ?IsRunningInRPCSS@@YGHXZ ;IsRunningInRPCSS(void)

769AEF83                 test    eax, eax                                                          ;推断当前进程是否是RPCSS

769AEF85                 jnz     loc_76A0B8ED                                             ;假设是（即返回非0）则返回“灾难性故障”的错误

769AEF8B                 mov     eax, large fs:18h

769AEF91                 mov     eax, [eax+0F80h]

769AEF97                 cmp     eax, edi

769AEF99                 mov     [ebp+8], eax

769AEF9C                 jz      loc_769ADF26                                              ; 推断当前线程中的struct tagSOleTlsData结构体是否分配，若未分配则进行分配

769AEFA2

769AEFA2loc_769AEFA2:

769AEFA2                 push    esi

769AEFA3                 push    edi             ; __int32

769AEFA4                 push    ebx             ; unsigned __int32

769AEFA5                 xor     esi, esi

769AEFA7                 inc     esi

769AEFA8                 push    esi             ; int

769AEFA9                 push    esi             ; int

769AEFAA                 call    ?NotifyInitializeSpies@@YGJHHKJ@Z ;NotifyInitializeSpies(int,int,ulong,long)

769AEFAF                 call    ?IsThreadInNTA@@YGHXZ ; IsThreadInNTA(void)

769AEFB4                 test    eax, eax

769AEFB6                 jnz     loc_769DAFAD                                            ; 假设是 则返回“无法在设置线程模式后对其加以更改。”的错误

769AEFBC                 mov     eax, [ebp+8]

769AEFBF                 mov     ecx, [eax+0Ch]

769AEFC2                 test    ch, 10h                                                          ;推断标识第4位（从第0位開始）是否置位

769AEFC5                 jnz     loc_769D9D20                                              ; server出现意外情况。

769AEFCB                 mov     edx, ebx

769AEFCD                 and     edx, 2

769AEFD0                 mov     [ebp-4], edx                                 

769AEFD3                 jz      short loc_769AEFDE                      ; 非COINIT_APARTMENTTHREADED模式

769AEFD5                 test    ch, 1                                                                    ;推断标识第0位是否置位

769AEFD8                 jnz     loc_769DAFAD                                            ; 返回“无法在设置线程模式后对其加以更改。”的错误

769AEFDE

769AEFDEloc_769AEFDE:

769AEFDE                 cmp     edx, edi                                                            

769AEFE0                 jz      loc_769DAFA5                                             ; 非COINIT_APARTMENTTHREADED模式

769AEFE6

769AEFE6loc_769AEFE6:

769AEFE6                 test    bl, 8

769AEFE9                 jnz     loc_76A0B901                                              ;第二个參数中COINIT_SPEED_OVER_MEMORY标识位被设置，即为单线程套件

769AEFEF

769AEFEFloc_769AEFEF:

769AEFEF                 add     eax, 18h

769AEFF2                 inc     dword ptr [eax]                               ; tagSOleTlsData.dwReserved1[0]++;

769AEFF4                 cmp     [eax], esi                                                    

769AEFF6                 jnz     loc_769ADBF9                                             ; 推断tagSOleTlsData.dwReserved1[0]==1?

769AEFFC                 test    edx, edx

769AEFFE                 mov     ebx, offset?gMTAInitLock@@3VCOleStaticMutexSem@@A ; COleStaticMutexSem gMTAInitLock

769AF003                 jz      loc_769DAFF2                                              ; 第二个參数未设置COINIT_APARTMENTTHREADED标识，即为多线程套件

769AF009

769AF009loc_769AF009:

769AF009                 mov     esi, offset?g_mxsSingleThreadOle@@3VCOleStaticMutexSem@@A ; COleStaticMutexSemg_mxsSingleThreadOle

769AF00E                 mov     ecx, esi

769AF010                 call    ?Request@COleStaticMutexSem@@QAEXXZ ;COleStaticMutexSem::Request(void)

769AF015                 push    [ebp+0C]

769AF018                 lea     eax, [ebp+8]

769AF01B                 push    eax

769AF01C                 call    ?wCoInitializeEx@@YGJAAVCOleTls@@K@Z ;wCoInitializeEx(COleTls &,ulong)  调用wCoInitializeEx

769AF021                 mov     ecx, esi

769AF023                 mov     edi, eax

769AF025                 call    ?Release@COleStaticMutexSem@@QAEXXZ ;COleStaticMutexSem::Release(void)

769AF02A                 test    edi, edi

769AF02C                 jl      loc_76A0B90C

769AF032

769AF032loc_769AF032:

769AF032                 cmp     [ebp-4], 0         

769AF036                 jz      loc_769DB004                   ; 第二个參数未设置COINIT_APARTMENTTHREADED标识，即为多线程套件

769AF03C

769AF03C loc_769AF03C:                           ; CODE XREF:CoInitializeEx(x,x)+2C0B6j

769AF03C                xor     esi, esi

769AF03E                 inc     esi

769AF03F

769AF03F loc_769AF03F:

769AF03F                 push    edi             ; __int32

769AF040                 push    [ebp+0C]  ; unsigned__int32

769AF043                 push    0              ; int

769AF045                 push    esi             ; int

769AF046                 call    ?NotifyInitializeSpies@@YGJHHKJ@Z ;NotifyInitializeSpies(int,int,ulong,long)

769AF04B                 pop     esi

769AF04C

769AF04C loc_769AF04C:

769AF04C                 pop     edi

769AF04D

769AF04Dloc_769AF04D:

769AF04D                 pop     ebx

769AF04E                 leave

769AF04F                 retn    8

当中有几点请注意：

1、在第一个參数为非空时，该函数会推断当前进程是否为EXCEL；

2、该函数也会推断当前进程是否为RPCSS，该进程的用途请大家另行查阅；检查进程是否为RPCSS的方法主要是：先推断当前进程是否有加载Windows文件夹下\\system32\\rpcss.dll，假设未加载则当前进程不是RPCSS；若加载了，则获取该DLL中名为WhichService的导出函数，假设未找到该函数也觉得当前进程是RPCSS；若找到，并该函数的返回值大于等于0，且作为该函数參数的指针所指向的值为2则当前进程不是RPCSS，否则当前进程即为RPCSS。

3、每一个线程的TEB结构向后偏移0x0F80的地方存放struct tagSOleTlsData的指针，该结构的声明例如以下：

typedef structtagSOleTlsData

{

    void *pvReserved0[2];

    DWORD dwReserved0[3];

    void *pvReserved1[1];

    DWORD dwReserved1[3];

    void *pvReserved2[4];

    DWORD dwReserved2[1];

    void *pCurrentCtx;

} SOleTlsData;

该结构中存放了当前线程有关COM的环境信息，这个结构体中各个域的定义微软貌似没有公开。线程启动后，在没有该线程调用CoInitialize或CoInitializeEx之前，该指针为空。第一次调用上述函数后，为该线程从堆上分配该结构的内存并将其指针保存至TEB+0x0F80处。

4、我们注意到，全部对struct tagSOleTlsData内容的改动都未进行相互排斥保护，这是由于全部对该结构的改动操作都在当前线程内部进行，因此也就不存在多线程同步的问题；而对于一些全局信息的改动则都进行了保护。