EFI FileSystem drivers
C Visual Basic Makefile Other
Latest commit e6540ed Dec 28, 2016 @pbatard version 1.1
* Update GRUB to latest


efifs - EFI File System Drivers

This is a GPLv3+ implementation of standalone EFI File System drivers, based on the GRUB 2.0 read-only drivers.

For additional info as well as precompiled drivers, see http://efi.akeo.ie


  • Visual Studio 2015 or MinGW/gcc
  • A git client able to initialize/update submodules
  • QEMU v2.7 or later if debugging with Visual Studio (NB: You can find QEMU Windows binaries here)


  • [Common] Fetch the git submodules with git submodule init and git submodule update.
  • [Common] Apply the included f2fs patch to the grub\ subdirectory. This adds F2FS support, which is not yet included in GRUB2.
  • [Visual Studio] Apply the other patches to the grub\ subdirectory. If you are using Clang/C2 you can apply the first patch only. If you are using MSVC, then you must apply both patches.
  • [Visual Studio] Open the solution file and hit F5 to compile and debug the default driver.
  • [gcc] Run make in the top directory. If needed you can also issue something like make ARCH=<arch> CROSS_COMPILE=<tuple> where <arch> is one of ia32, x64, arm or aa64 (the official UEFI abbreviations for an arch, as used in /efi/boot/boot[ARCH].efi) and tuple is the one for your cross-compiler, such as arm-linux-gnueabihf-. e.g. make ARCH=aa64 CROSS_COMPILE=aarch64-linux-gnu-


If QEMU is installed, the Visual Studio solution will set up and test the drivers using QEMU (by also downloading a sample image for each target file system).
Note however that VS debugging expects a 64-bit version of QEMU to be installed in C:\Program Files\qemu\ (which you can download here).
If that is not the case, you should edit .msvc\debug.vbs accordingly.

For testing outside of Visual Studio, make sure you have at least one disk with a target partition using the target filesystem, that is not being handled by other EFI filesystem drivers.
Then boot into the EFI shell and run the following:

  • load fs0:\<fs_name>_<arch>.efi or wherever your driver was copied
  • map -r this should make a new fs# available, eg fs2:
  • You should now be able to navigate and access content (in read-only mode)
  • For logging output, set the FS_LOGGING shell variable to 1 or more
  • To unload use the drivers command, then unload with the driver ID

Visual Studio and ARM support

To enable ARM compilation in Visual Studio 2015, you must perform the following:

  • Make sure Visual Studio is fully closed.
  • Navigate to C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V140\Platforms\ARM and remove the read-only attribute on Platform.Common.props.
  • With a text editor running with Administrative privileges open:
    C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V140\Platforms\ARM\Platform.Common.props.
  • Under the <PropertyGroup> section add the following:


This is a pure GPLv3+ implementation of EFI drivers. Great care was taken not to use non GPLv3 compatible sources, such as rEFInd's fsw_efi (GPLv2 only) or Intel's FAT driver (requires an extra copyright notice).