I 'm working on a minifilter project. How can I call GetProcAddress within a minifilter program? My compiler keeps telling me "GetProcAddress undefined assume extern returning int". According to msdn, I might need to include window.h. But if I do so, many more other compiler errors occur? what should do?
There is no kernel mode equivalent of GetProcAddress.
May be you need to check, why do you need that. If you want to load and call some function of your DLL, then probably instead of DLL link it statically with your driver.
Also, you can't load any DLL in kernel mode.
If you think you really want to do this, check following articles
Calling a DLL in a Kernel-Mode Driver
Writing Kernel Mode DLLs
MmGetSystemRoutineAddress can be used for the same purpose.
Refer: https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-mmgetsystemroutineaddress
Related
I'm curious about how Dynamic Linking works on windows. Since we CAN NOT link to a directly, windows usually link your executable to a LIB file which contains the stub of functions exported by the DLL. Does this type of linking results in LoadLibrary and GetProcAddress at runtime? If not, how does the linking work internally?
The answer is maybe.
The default method is to create an Import Table, which lists all required DLL's and the functions used from there. This table is parsed directly by the OS. It will probably reuse some of the same code behind LoadLibrary for that. It most likely will not use the code from GetProcAddress but prefer to do a single bulk lookup of all necessary functions.
However there's an MSVC feature called delay-loading. With this feature, MSVC++ will not build such an import table, but insert actual LoadLibrary and GetProcAddress calls. The benefit is that these calls are made at the latest possible moment. While you don't need a particular DLL, it's not loaded. This can accelerate program start up.
I'm using MYSQL library, and libmysql.lib /.dll.
My program cannot be working without the libmysql.dll
When I'm trying to run my project without the dll I'm getting that error message.
What I'm basically want to do is to put that dll in my .exe file.
build the .exe file with that dll and make the program read it from himself.
I mean, give the program to people with that dll inside.
It is possible ?
I tried this section: embed DLL in MFC C++ EXE?
But the program still asking for the dll .. (But I do see that the size of the .exe has been changed) so that dll has been added.
But the program still asking for the libmysql.dll ..
All the point is to use it inside the .exe file..
thanks.
What you are asking for cannot be done if you statically link to the DLL at compile-time. You need to dynamically link to the DLL at run-time instead, either by explicit calls to LoadLibrary() and GetProcAddress() to access the DLL functions directly, or by utilizing your compiler's delay-load functionality (which uses LoadLibrary() and GetProcAddress() internally, but hides that fact from your code). Either way, you can then store the DLL in your EXE's resources at compile-time, then extract the resource to a temporary file at run-time and load/use it as needed (you can't use the DLL from inside the EXE's resources directly. Well, there is a way to do it, but it is a VERY complicated and advanced technique, as it requires implementing your own executable loader that basically mimics what the OS's built-in executable loader already does). When you are done using the DLL, you can unload it from memory and delete the temp file.
I'm using Code::Blocks and hate manually linking DLLs. I found the LoadLibrary() function, and am wondering if it works like a .a or .lib file would. Does this function work like that? If not, what can I do programming-wise (if anything) to link a DLL without having to link a DLL by doing the Project < Build options < Linker settings < add < ... method?
LoadLibrary loads the requested library (and all the libraries it needs) into your process' address space. In order to access any of the code/data in that library, you need to find out the code or data address in the newly loaded region of memory. You need to use GetProcAddress.
The difference between this process and adding a library during build time is that for build-time library the compiler prepares a list of locations that refer to a given function, linker puts that list into .exe, and run-time linker loads the library, does the equivalent of GetProcAddress for the function name and places the address into all locations that the compiler marked.
When you don't have this automated support, you have to declare a pointer to function, call GetProcAddress yourself, and assign the returned value to your pointer to function. You can then call the function like any other C function (note "C" part - the above process is complicated by name mangling when you use C++, so make use of extern "C")
LoadLibrary() loads a DLL at runtime. Normaly you link when you compile the EXE, and link the DLLs like a static library at this time. If you need to load libraries dynamically at runtime, you use LoadLibrary().
For example when you implement a pluginsystem, is this usefull, as you don't know the libraries beforehand.
Not how it works at all. LoadLibrary is used to load a "at compile time unknown" DLL - such as program extensions/plugins or "This DLL for SSE, that DLL for non-SSE" based on "what can the hardware do - one could also consider having a DLL per connection type to email servers or something like that, so that the email program doesn't have to "carry" all the different variants, when only one is used for any particular email address.
Further, to use a DLL that has been loaded this way, you need to use GetProcAddress to get the address of the functions in the DLL. This is very different from linking the DLL into the project at buildtime, where functions simply appear "automagically" by help of the system loader functions that load the DLL's that are added to the project at build-time.
Contrary to static or dynamic library linking, LoadLibrary doesn't make the library's symbols directly available to your program. You need to call GetProcAddress at runtime to get a pointer to the functions you want to call.
As #Devolus mentioned, this is a good way to implement plugin systems and/or to access optional components. However, since the symbols are not available to your program in a transparent way, this is not really practical for ordinary usage.
I have a Win32 program that's built with VS2008, so my code is linked with MSVCR90.DLL and MSVCP90.DLL. However, it's also running code in a DLL (which I can't modify) that's been built with VS2005 and when code in that DLL prints to the clog stream it does it via MSVCR80.DLL and MSVCP80.DLL. Here's the problem: if I re-route std::clog in my code, I only affect code built against crt 9.0 libs, code using the older crt 8.0 wont have its output re-routed. So is there a way to re-route the clog stream in a DLL built against an older CRT?
I've investigated calling GetModuleHandle() and GetProcAddress() on the older CRT DLLs and have managed to re-route the C stderr stream (via _open_osfhandle and _dup2), however the C++ clog stream still seems to be unaffected. I think I also need to call ios_base::sync_with_stdio() in the older CRT lib but I couldn't get a valid address to that function. Any help would be greatly appreciated.
Thanks.
Build a helper DLL using VS2005 - This DLL should simply export some functions to do the setup you need for VS8 runtime.
Try also freopen... but this too might need to be called in the older CRT. Eric's suggestion of a helper DLL is massive overkill though, just use GetProcAddress to get a pointer to the VC8 version.
The most effective option is to redirect the standard streams when launching the process in the first place.
Another possibility is to delay-load the helper DLL, and perform the stream redirection before loading it. That way when MSVCRT80 loads, it will attach to the redirected stream.
I've encountered a strange behavior in __declspec(dllexport) in my project.
I have a C++ project that uses classes, namespaces, try-catches and more cpp elements.
When exporting any dummy function in this DLL, no other C project will be able to load it with LoadLibrary (Getting error 'module not found').
Is it possible to load dynamically C++ dlls through C projects?
These projects are Windows Mobile projects, but they should behave the same as on regular PC win32.
I'm stuck on it and any help will be appreciated.
Thank you,
Emil.
LoadLibrary is completely oblivious to the language used to compile a module. If LoadLibrary says it can't find the module, then it's very likely the case that it really can't find it. Make sure you've specified the right file name. If you've included a drive and path, make sure they're correct, too. If you haven't included a drive or path, then make sure the file exists somewhere where LoadLibrary can find it. The places it searches are listed in Dynamic-Link Library Search Order. Also consider whether Windows Vista's directory-virtualization feature might be interfering.
Once the DLL is loaded, you may have any number of other issues in using the C++ DLL from your C code. The C++ compiler may have mangled the function names, so you'll need to provide the right names when you call GetProcAddress. The C++ code might use a different calling convention from what your C code expects, so you may need to change declarations in the C++ code, the C code, or both. If the C++ functions expect to receive pointers to classes or other C++-specific types, you'll need to change your C++ code so that its API is compatible with C. If your DLL allocates memory that the host program should free, or vice versa, you'll need to make sure that both modules can use the same memory manager.
All that is separate from the problem you're reporting, though, which is simply that the OS can't find your file. Focus on that first.
I found the problem. It was really a dependency dll problem. It was not found in the directory of the loading DLL.
Thank you all.