lion-tutorial17.htm

内有一些代码

  You can't obtain it again easily. <br>
  <b>reason</b> can be one of the four values: 
<ul>
  <li> <b>DLL_PROCESS_ATTACH</b> The DLL receives this value when it is first 
    injected into the process address space. You can use this opportunity to do 
    initialization.</li>
  <li> <b>DLL_PROCESS_DETACH</b> The DLL receives this value when it is being 
    unloaded from the process address space. You can use this opportunity to do 
    some cleanup such as deallocate memory and so on.</li>
  <li> <b>DLL_THREAD_ATTACH</b> The DLL receives this value when the process creates 
    a new thread.</li>
  <li> <b>DLL_THREAD_DETACH</b> The DLL receives this value when a thread in the 
    process is destroyed.</li>
</ul>
You return TRUE in eax if you want the DLL to go on running. If you return FALSE, 
the DLL will not be loaded. For example, if your initialization code must allocate 
some memory and it cannot do that successfully, the entrypoint function should 
return FALSE to indicate that the DLL cannot run. <br>
You can put your functions in the DLL following the entrypoint function or before 
it. But if you want them to be callable from other programs, you must put their 
names in the export list in the module definition file (.def). <br>
A DLL needs a module definition file in its developmental stage. We will take 
a look at it now. 
<p><b>LIBRARY</b>&nbsp;&nbsp; DLLSkeleton <br>
  <b>EXPORTS</b>&nbsp;&nbsp; TestFunction 
<p>Normally you must have the first line.The <b>LIBRARY</b> statement defines 
  the internal module name of the DLL. You should match it with the filename of 
  the DLL. <br>
  The <b>EXPORTS</b> statement tells the linker which functions in the DLL are 
  exported, that is, callable from other programs. In the example, we want other 
  modules to be able to call TestFunction, so we put its name in the <b>EXPORTS</b> 
  statement. <br>
  Another change is in the linker switch. You must put <b>/DLL</b> switch and 
  <b>/DEF:&lt;your def filename> </b>in your linker switches like this: 
<p><b>link /DLL /SUBSYSTEM:WINDOWS /DEF:DLLSkeleton.def /LIBPATH:c:\masm32\lib 
  DLLSkeleton.obj</b> 
<p>The assembler switches are the same, namely /c /coff /Cp. So after you link 
  the object file, you will get .dll and .lib. The .lib is the import library 
  which you can use to link to other programs that use the functions in the DLL. 
  <br>
  Next I'll show you how to use LoadLibrary to load a DLL. 
<p>;--------------------------------------------------------------------------------------------- 
  <br>
  ;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  UseDLL.asm <br>
  ;---------------------------------------------------------------------------------------------- 
  <br>
  <b>.386</b> <br>
  <b>.model flat,stdcall</b> <br>
  <b>option casemap:none</b> <br>
  <b>include \masm32\include\windows.inc</b> <br>
  <b>include \masm32\include\user32.inc</b> <br>
  <b>include \masm32\include\kernel32.inc</b> <br>
  <b>includelib \masm32\lib\kernel32.lib</b> <br>
  <b>includelib \masm32\lib\user32.lib</b> 
<p><b>.data</b> <br>
  <b>LibName db "DLLSkeleton.dll",0</b> <br>
  <b>FunctionName db "TestHello",0</b> <br>
  <b>DllNotFound db "Cannot load library",0</b> <br>
  <b>AppName db "Load Library",0</b> <br>
  <b>FunctionNotFound db "TestHello function not found",0</b> 
<p><b>.data?</b> <br>
  <b>hLib dd ?&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  ; the handle of the library (DLL)</b> <br>
  <b>TestHelloAddr dd ?&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  ; the address of the TestHello function</b> 
<p><b>.code</b> <br>
  <b>start:</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke LoadLibrary,addr LibName</b> 
  <br>
  <b>;---------------------------------------------------------------------------------------------------------</b> 
  <br>
  <b>; Call LoadLibrary with the name of the desired DLL. If the call is successful</b> 
  <br>
  <b>; it will return the handle to the library (DLL). If not, it will return 
  NULL</b> <br>
  <b>; You can pass the library handle to GetProcAddress or any function that 
  requires</b> <br>
  <b>; a library handle as a parameter.</b> <br>
  <b>;------------------------------------------------------------------------------------------------------------</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .if eax==NULL</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke MessageBox,NULL,addr DllNotFound,addr AppName,MB_OK</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .else</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  mov hLib,eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke GetProcAddress,hLib,addr FunctionName</b> <br>
  <b>;-------------------------------------------------------------------------------------------------------------</b> 
  <br>
  <b>; When you get the library handle, you pass it to GetProcAddress with the 
  address</b> <br>
  <b>; of the name of the function in that DLL you want to call. It returns the 
  address</b> <br>
  <b>; of the function if successful. Otherwise, it returns NULL</b> <br>
  <b>; Addresses of functions don't change unless you unload and reload the library.</b> 
  <br>
  <b>; So you can put them in global variables for future use.</b> <br>
  <b>;-------------------------------------------------------------------------------------------------------------</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .if eax==NULL</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke MessageBox,NULL,addr FunctionNotFound,addr AppName,MB_OK</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .else</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  mov TestHelloAddr,eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  call [TestHelloAddr]</b> <br>
  <b>;-------------------------------------------------------------------------------------------------------------</b> 
  <br>
  <b>; Next, you can call the function with a simple call with the variable containing</b> 
  <br>
  <b>; the address of the function as the operand.</b> <br>
  <b>;-------------------------------------------------------------------------------------------------------------</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke FreeLibrary,hLib</b> <br>
  <b>;-------------------------------------------------------------------------------------------------------------</b> 
  <br>
  <b>; When you don't need the library anymore, unload it with FreeLibrary.</b> 
  <br>
  <b>;-------------------------------------------------------------------------------------------------------------</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke ExitProcess,NULL</b> <br>
  <b>end start</b> 
<p>So you can see that using LoadLibrary is a little more involved but it's also 
  more flexible. 
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