最近看到了一個模擬LoadLibrary的代碼,其中有這麼一段
// === Windows NT DLL Loading (supports shared sections) ===
if(svMappingName!=NULL) {
hmapping=OpenFileMapping(FILE_MAP_WRITE,TRUE,svMappingName);
bCreated=FALSE;
}
if(hmapping==NULL) {
hmapping=CreateFileMapping(INVALID_HANDLE_VALUE,NULL,PAGE_READWRITE,0,dwImageSize+SIZE_OF_PARAMETER_BLOCK,svMappingName);
if(hmapping==NULL) return NULL;
bCreated=TRUE;
}
// Try to load file mapping view at preferred image base (not gonna happen in Win9x..sigh)
pImageBase=MapViewOfFileEx(hmapping,FILE_MAP_WRITE,0,0,0,pPreferredImageBase);
if(pImageBase==NULL) {
pImageBase=MapViewOfFileEx(hmapping,FILE_MAP_WRITE,0,0,0,NULL);
}
CloseHandle(hmapping);
if(pImageBase==NULL) return NULL;
} else {
// === Windows 9x DLL Loading (does not support shared sections) ===
pImageBase=VirtualAlloc(pPreferredImageBase,dwImageSize,MEM_COMMIT|MEM_RESERVE,PAGE_READWRITE);
if(pImageBase==NULL) {
pImageBase=VirtualAlloc(NULL,dwImageSize,MEM_COMMIT|MEM_RESERVE,PAGE_READWRITE);
if(pImageBase==NULL) return NULL;
}
bCreated=TRUE;
}
可見Windows NT和Windows 9x下面對於dll的空間分配是不一樣的,Windows NT會使用共享內存,而Windows 9x對任何DLL都會產生一個新的空間來放置.
所以同一個程序,在9x下面每次運行,模塊的地址都很不一樣,而在NT下面只要在同一個機器下面,每次運行都很可能一樣(除非模塊變化了--比如中了注入的病毒),道理就在這裏