ExRegisterHost.c

NTSTATUS ExRegisterHost(_Out_ PHOST_LIST_ENTRY ExtensionHost, _In_ ULONG Unused, _In_ PHOST_INFORMATION HostInformation)
{
	NTSTATUS Status = STATUS_SUCCESS;

	// Allocate memory for a new HOST_LIST_ENTRY
	PHOST_LIST_ENTRY p = ExAllocatePoolWithTag(HostInformation->PoolType, 0x60, 'HExE');
	if (p == nullptr)
	{
		return STATUS_INSUFFICIENT_RESOURCES;
	}

	//
	// Initialize a new HOST_LIST_ENTRY 
	//
	p->Flags &= 0xFE;
	p->RefCount = 1;
	p->FunctionTable = 0;
	p->ExtensionId = HostInformation->ExtensionId;
	p->ExtensionVersion = HostInformation->ExtensionVersion;
	p->hostInterface = HostInformation->hostInterface;
	p->FunctionAddress = HostInformation->FunctionAddress;
	p->ArgForFunction = HostInformation->ArgForFunction;			
	p->Lock = 0; 			
	p->RundownRef = 0;		

	// Search for an existing listEntry with the same version and id.
	PHOST_LIST_ENTRY listEntry = ExpFindHost(HostInformation->ExtensionId, HostInformation->ExtensionVersion);
	if (listEntry)
	{
		Status = STATUS_OBJECT_NAME_COLLISION;
		ExpDereferenceHost(p);
		ExpDereferenceHost(listEntry);
	}
	else
	{
		// Insert the new HOST_LIST_ENTRY to the end of ExpHostList.
		if ( *lastHostListEntry != &firstHostListEntry )
		{
	      	    __fastfail();
		}

		firstHostListEntry->Prev = &p;
		p->Next = firstHostListEntry;
		lastHostListEntry = p;

		ExtensionHost = p;
	}
	
	return Status;
}