/efi-power

Simple UEFI programs for powering/rebooting

Primary LanguageMakefileMIT LicenseMIT

Poweroff & Reset from UEFI

systemd-boot does not have built in entries for powering off/reseting from the menu. This provides two simple UEFI programs for performing those actions. Original code from arch-wiki, but I made the makefile made more robust and packaged it for nix.

Testing

Cross compilation utilizes nixpkgs. Just change the cross system with Nix and the efi image will cross compile.

Tested on the following using qemu:

x86-64

x86_64-unknown-linux-gnu

$ cp $OVMF_DIR/OVMF.fd ./qemu/ovmf.fd
$ make/nix build
$ cp XXX.efi root/XXX.efi
$ qemu-system-x86_64 \
    -bios qemu/ovmf.fd \
    -drive format=raw,file=fat:rw:root \
    -net none \
    -nographic

aarch64

Help from: http://cdn.kernel.org/pub/linux/kernel/people/will/docs/qemu/qemu-arm64-howto.html

aarch64-unknown-linux-gnu

$ truncate -s 64m efi-aarch.img
$ truncate -s 64m varstore.img
$ dd if=$OVMF_DIR/QEMU_EFI.fd of=efi-aarch.img conv=notrunc
$ make/nix build
$ cp XXX.efi root/XXX.efi
$ qemu-system-aarch64 -M virt -cpu cortex-a57 \
    -drive file=qemu/efi-aarch.img,if=pflash,format=raw,readonly=true \
    -drive file=qemu/varstore.img,if=pflash,format=raw \
    -net none -nographic \
    -drive format=raw,file=fat:rw:root

arm

armv7l-unknown-linux-gnueabihf

Same as above.

$ truncate -s 64m efi-aarch.img
$ truncate -s 64m varstore.img
$ dd if=$OVMF_DIR/QEMU_EFI.fd of=efi-arm.img conv=notrunc
$ make/nix build
$ cp XXX.efi root/XXX.efi
$ qemu-system-arm -M virt -cpu cortex-a7 \
    -drive file=qemu/efi-arm.img,if=pflash,format=raw,readonly=true \
    -drive file=qemu/varstore.img,if=pflash,format=raw \
    -net none -nographic \
    -drive format=raw,file=fat:rw:root

Automated Testing

See boot tests for inspiration:

https://github.com/NixOS/nixpkgs/blob/master/nixos/tests/boot.nix

UEFI Development Resources

OSDev GNU-EFI

  • How to develop UEFI applications
  • Calling conventions
    • x86-64 uses microsoft ABI for interaction with firmware
    • All else uses c decltype
    • EFIAPI is just a preprocessor for choosing when to use a different abi
      • do not use on efi_main as that is always a cdecltype from gnu-efi
      • Not entirely sure why so many examples have it set (bad makefiles is my guess)
      • Set by CPPFLAGS += -DGNU_EFI_USE_MS_ABI -maccumulate-outgoing-args on x86-64 arch as ms_abi does not work without accumulate-outgoing-args
  • Non-root qemu: https://wiki.osdev.org/UEFI#Linux.2C_root_not_required

Getting started with EFI

  • Expected to be position independent (no guarantee that it will be loaded at fixed address)
  • Binary format is PE32+

Debugging with GDB

  • Provide -s -S to qemu to start gdb server
  • Call info files, file, target remote :1234, then add-symbol-file xxx.efi.debug 0xTEXT_LOCATION -s .data 0xDATA_LOCATION
    • To get data location use
      status = uefi_call_wrapper(systab->BootServices->HandleProtocol, 3, image,
                             &LoadedImageProtocol, (void **)&loaded_image);
  if (EFI_ERROR(status)) {
    Print(L"handleprotocol: %r\n", status);
  }
  Print(L"Image base: 0x%lx\n", loaded_image->ImageBase);
    • Add the offsets to the image base location