Easily create UEFI applications using Visual Studio 2015

As pointed out before, Visual Studio is now essentially free for all development, and its solid IDE of course makes is very desirable as the environment to use to develop UEFI applications on Windows.

Now, you might have read that, short of using the oh-so-daunting EDK2, and the intricate voodoo magic you'll have to spend days on, to make it play nice with the Visual Studio IDE, there is no salvation in the UEFI world. However, this couldn't be further from the truth.

Enters UEFI:SIMPLE.

The thing is, Visual Studio can already compile EFI applications without having to rely on any external tools, and even if you want an EDK2 like environment, with the common EFI API calls that it provides, you can totally do away with the super heavy installation and setup of the EDK, and instead use the lightweight and straightforward GNU-EFI library, that provides about the same level of functionality (as far as building standalone EFI applications or drivers are concerned, which is what we are interested in).

So really, if you want to craft an EFI application in no time at all, all you need to do is:

1. Install Visual Studio 2015, which is totally free and which, no matter who you work for or what restrictions your corporate IT department tries to impose, you are 100% legally entitled to when it comes to trying to compile and test UEFI:SIMPLE.
2. As suggested by the Visual Studio installer, install a git client such as msys-git (or TortoiseGit + msys-git). Now, you're going to wonder why, with git support being an integral part of Visual Studio 2015, we actually need an external client, but one problem is that Microsoft decided to strip their embedded git client of critical functionality, such as git submodule support, which we'll need.
3. Because you'd be a fool not to want to test your EFI application or driver in a virtual environment, and, thanks to QEMU, this is so exceedingly simple to achieve that UEFI:SIMPLE will do it for you, you should download and install QEMU, preferably the 64 bit version (you can find a 64 bit qemu installer here), and preferably to its default of C:\Program Files\qemu.
4. Clone the UEFI:SIMPLE git project, using the URI https://github.com/pbatard/uefi-simple.git. For this part, you can either use the embedded git client from Visual Studio or your external client.
5. Now, using your external git client, navigate to your uefi-simple directory and issue the following commands:
   

   git submodule init
   git submodule update

   This will fetch the gnu-efi library source, which we rely on to build our application.
6. Open the solution file in Visual Studio and just click the "Local Windows Debugger" button to both compile and run our "Hello, World"-type application in QEMU.
   Through its debug.vbs script, which can be found under the "Resource File" category, the UEFI:SIMPLE solution will take of setting everything up for you, including downloading the OVMF UEFI firmware for QEMU.
   Note that if you didn't install QEMU into C:\Program Files\qemu\ you will need to edit debug.vbs to modify the path.
7. Finally, because the UEFI:SIMPLE source is public domain, you can now use it as a starting point to build your own UEFI application, whilst relying on the standard EFI API calls that one expects, and, more importantly, with an easy way to test your module at your fingertips.

Oh and I should point out that UEFI:SIMPLE also has ARM support, and can also be compiled on Linux, or using MinGW if you don't want to use Visual Studio on Windows. Also, if you want real-life examples of fully fledged UEFI applications, that were built using UEFI:SIMPLE as their starting point, you should look no further than efifs, a project that builds whole slew of EFI file system drivers, or UEFI:NTFS, which allows seamless EFI boot of NTFS partition.