Source code of Windows XP (NT5)
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// this file builds a "lib" (really just an .obj) for people who want to
// use the kernel32.dll delay-load exception handler.
#define DELAYLOAD_VERSION 0x0200
#include <windows.h>
#include <delayimp.h>
// kernel32's base hmodule
extern HANDLE BaseDllHandle;
// prototype (implemented in kernl32p.lib)
FARPROC
DelayLoadFailureHook (
LPCSTR pszDllName,
LPCSTR pszProcName
);
// people who care about being notified of dll loadlibray will override this
PfnDliHook __pfnDliNotifyHook2;
// Instead of implementing a "notify hook" (__pfnDliNotifyHook2) or a
// "failure hook" (__pfnDliFailureHook2) we are just going to up and implement
// __delayLoadHelper2 which is the stub who's fn. pointer is filled in all
// of the import tables for delayloaded entries.
//
// This will effectively bypass the linker's LoadLibrary/GetProcAddress thunk code
// as we simply duplicate it here (most of this fn. was stolen from \vc7\delayhlp.cpp)
FARPROC
WINAPI
__delayLoadHelper2(
PCImgDelayDescr pidd,
FARPROC * ppfnIATEntry
)
{
UINT iINT;
PCImgThunkData pitd;
LPCSTR pszProcName;
LPCSTR pszDllName = (LPCSTR)PFromRva(pidd->rvaDLLName, NULL);
HMODULE* phmod = (HMODULE*)PFromRva(pidd->rvaHmod, NULL);
PCImgThunkData pIAT = (PCImgThunkData)PFromRva(pidd->rvaIAT, NULL);
PCImgThunkData pINT = (PCImgThunkData)PFromRva(pidd->rvaINT, NULL);
FARPROC pfnRet = 0;
HMODULE hmod = *phmod;
// Calculate the index for the name in the import name table.
// N.B. it is ordered the same as the IAT entries so the calculation
// comes from the IAT side.
//
iINT = IndexFromPImgThunkData((PCImgThunkData)ppfnIATEntry, pIAT);
pitd = &(pINT[iINT]);
if (!IMAGE_SNAP_BY_ORDINAL(pitd->u1.Ordinal))
{
PIMAGE_IMPORT_BY_NAME pibn = (PIMAGE_IMPORT_BY_NAME)PFromRva((RVA)pitd->u1.AddressOfData, NULL);
pszProcName = pibn->Name;
}
else
{
pszProcName = MAKEINTRESOURCEA(IMAGE_ORDINAL(pitd->u1.Ordinal));
}
if (hmod == 0)
{
hmod = LoadLibraryA(pszDllName);
if (hmod != 0)
{
// Store the library handle. If it is already there, we infer
// that another thread got there first, and we need to do a
// FreeLibrary() to reduce the refcount
//
HMODULE hmodT = (HMODULE)InterlockedCompareExchangePointer((void**)phmod, (void*)hmod, NULL);
if (hmodT == NULL)
{
DelayLoadInfo dli = {0};
dli.cb = sizeof(dli);
dli.szDll = pszDllName;
dli.hmodCur = hmod;
// call the notify hook to inform them that we have successfully LoadLibrary'ed a dll.
// (we do this in case they want to free it when they unload)
if (__pfnDliNotifyHook2 != NULL)
{
__pfnDliNotifyHook2(dliNoteEndProcessing, &dli);
}
}
else
{
// some other thread beat us to loading this module, use the existing hmod
FreeLibrary(hmod);
hmod = hmodT;
}
}
}
if (hmod)
{
// Go for the procedure now.
pfnRet = GetProcAddress(hmod, pszProcName);
}
if (pfnRet == 0)
{
pfnRet = DelayLoadFailureHook(pszDllName, pszProcName);
}
*ppfnIATEntry = pfnRet;
return pfnRet;
}