pbatard/EfiFs

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 https://efi.akeo.ie

Requirements

• Visual Studio 2026 (Windows), MinGW (Windows), gcc (Linux) or EDK2 (Linux).
• 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)

Compilation

Common

• Fetch the git submodules with git submodule init and git submodule update.
  NOTE This only works if you cloned the directory using git.
• Apply 0001-GRUB-fixes.patch to the grub\ subdirectory. This applies the changes that are required for successful compilation of GRUB.

Visual Studio

• Open the solution file and hit F5 to compile and debug the default driver.

gcc (non EDK2)

• 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, aa64, riscv64 or loongarch64 (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-gnueabi- or aarch64-linux-gnu-. e.g. make ARCH=aa64 CROSS_COMPILE=aarch64-linux-gnu-

EDK2 (Linux only)

• Open an elevated command prompt and create a symbolic link called EfiFsPkg, inside your EDK2 directory, to the EfiFs source.
• From a command prompt, set Grub to target the platform you are compiling for by invoking ./set_grub_cpu.sh <arch> where <arch> is one of ia32, x64, aarch64, riscv64 or loongarch64. Note that you MUST invoke the set_grub_cpu.sh script every time you switch target.
• After having invoked ``edksetup.sh` run something like:

  build -a X64 -b RELEASE -t GCC -p EfiFsPkg/EfiFsPkg.dsc
  

  NB: To build an individual driver, such as NTFS, you can also use something like:

  build -a X64 -b RELEASE -t GCC -p EfiFsPkg/EfiFsPkg.dsc -m EfiFsPkg/EfiFsPkg/Ntfs.inf
  

Testing

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

Additional Notes

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

Note however that some files (the non grub_#### sources under ./src/) are licensed under GPLv2+ rather than GPLv3+ and that, just like the GPLv3+ sources, we took great care of ensuring that we are fully compliant with any licensing or relicensing matters, so that they can legally be reused into GPLv2+ works.

Bonus: Commands to compile EfiFs using EDK2 on a vanilla Debian GNU/Linux 10.x

sudo apt install nasm uuid-dev gcc-multilib gcc-aarch64-linux-gnu gcc-arm-linux-gnueabi gcc-riscv64-linux-gnu
git clone --recurse-submodules https://github.com/tianocore/edk2.git
cd edk2
make -C BaseTools
git clone --recurse-submodules https://github.com/pbatard/EfiFs.git EfiFsPkg
cd EfiFsPkg/grub
git apply ../0001-GRUB-fixes.patch
cd -
export GCC_ARM_PREFIX=arm-linux-gnueabi-
export GCC_AARCH64_PREFIX=aarch64-linux-gnu-
export GCC_RISCV64_PREFIX=riscv64-linux-gnu-
source edksetup.sh --reconfig
./EfiFsPkg/set_grub_cpu.sh X64
build -a X64 -b RELEASE -t GCC -p EfiFsPkg/EfiFsPkg.dsc
./EfiFsPkg/set_grub_cpu.sh IA32
build -a IA32 -b RELEASE -t GCC -p EfiFsPkg/EfiFsPkg.dsc
./EfiFsPkg/set_grub_cpu.sh AARCH64
build -a AARCH64 -b RELEASE -t GCC -p EfiFsPkg/EfiFsPkg.dsc
./EfiFsPkg/set_grub_cpu.sh RISCV64
build -a RISCV64 -b RELEASE -t GCC -p EfiFsPkg/EfiFsPkg.dsc