ZFI – Zero-cost and safe interface to UEFI firmware

ZFI is a Rust crate for writing a UEFI application with the following goals:

• Provides base APIs that are almost identical to the UEFI specifications.
• Provides additional APIs that build on top of the base APIs.
• Base APIs are zero-cost abstraction over UEFI API.
• Safe and easy to use.
• Work on stable Rust.

ZFI supports only single-thread environment, which is the same as UEFI specifications.

Example

#![no_std]
#![no_main]

use alloc::boxed::Box;
use zfi::{pause, println, DebugFile, Image, Status, SystemTable};

extern crate alloc;

#[no_mangle]
extern "efiapi" fn efi_main(image: &'static Image, st: &'static SystemTable) -> Status {
    // This is the only place you need to use unsafe. This must be done immediately after landing
    // here.
    unsafe {
        zfi::init(
            image,
            st,
            Some(|| Box::new(DebugFile::next_to_image("log").unwrap())),
        )
    };

    // Any EFI_HANDLE will be represents by a reference to a Rust type (e.g. image here is a type of
    // Image). Each type that represents EFI_HANDLE provides the methods to access any protocols it
    // is capable for (e.g. you can do image.proto() here to get an EFI_LOADED_IMAGE_PROTOCOL from
    // it). You can download the UEFI specifications for free here: https://uefi.org/specifications
    println!("Hello, world!");
    pause();

    Status::SUCCESS
}

#[cfg(not(test))]
#[panic_handler]
fn panic_handler(info: &core::panic::PanicInfo) -> ! {
    zfi::eprintln!("{info}");
    loop {}
}

#[cfg(not(test))]
#[global_allocator]
static ALLOCATOR: zfi::PoolAllocator = zfi:PoolAllocator;

You can use zfi::main macro if you prefer a less boilerplate:

#![no_std]
#![no_main]

use zfi::{pause, println, Status};

// zfi::main will not enable the debug writer by default. See its documentation to see how to enable
// the debug writer.
#[zfi::main]
fn main() -> Status {
    // Use Image::current() to get the image handle.
    println!("Hello, world!");
    pause();

    Status::SUCCESS
}

To build the above example you need to add a UEFI target to Rust:

rustup target add x86_64-unknown-uefi

Then build with the following command:

cargo build --target x86_64-unknown-uefi

You can grab the EFI file in target/x86_64-unknown-uefi/debug and boot it on a compatible machine.

Integration Testing

ZFI provide zfi-testing crate to help you write the integration tests. This crate must be added as a development dependency, not a standard dependency. You need to install the following tools before you can run the integration tests that use zfi-testing:

• QEMU
• OVMF

Once ready create zfi.toml in the root of your package (the same location as Cargo.toml) with the following content:

[qemu.RUST_TARGET]
bin = "QEMU_BIN"
firmware = "OVMF_CODE"
nvram = "OVMF_VARS"

This file should not commit to the version control because it is specific to your machine. Replace the following placeholders with the appropriate value:

• RUST_TARGET: name of Rust target you want to run on the QEMU (e.g. x86_64-unknown-uefi).
• QEMU_BIN: path to the QEMU binary to run your tests. The binary must have the same CPU type as RUST_TARGET. You don't need to specify a full path if the binary can be found in the PATH environment variable (e.g. qemu-system-x86_64).
• OVMF_CODE: path to OVMF_CODE.fd from OVMF. File must have the same CPU type as RUST_TARGET (e.g. /usr/share/edk2/x64/OVMF_CODE.fd).
• OVMF_VARS: path to OVMF_VARS.fd from OVMF. File must have the same CPU type as RUST_TARGET (e.g. /usr/share/edk2/x64/OVMF_VARS.fd).

Example:

[qemu.aarch64-unknown-uefi]
bin = "qemu-system-aarch64"
firmware = "/usr/share/AAVMF/AAVMF_CODE.fd"
nvram = "/usr/share/AAVMF/AAVMF_VARS.fd"

[qemu.i686-unknown-uefi]
bin = "qemu-system-i386"
firmware = "/usr/share/edk2/ia32/OVMF_CODE.fd"
nvram = "/usr/share/edk2/ia32/OVMF_VARS.fd"

[qemu.x86_64-unknown-uefi]
bin = "qemu-system-x86_64"
firmware = "/usr/share/edk2/x64/OVMF_CODE.fd"
nvram = "/usr/share/edk2/x64/OVMF_VARS.fd"

Writing Tests

To write an integration test to run on QEMU, put zfi_testing::qemu attribute to your integration test:

use zfi_testing::qemu;

#[test]
#[qemu]
fn proto() {
    use zfi::{str, Image, PathBuf};

    let proto = Image::current().proto();
    let mut path = PathBuf::new();

    if cfg!(target_arch = "x86_64") {
        path.push_media_file_path(str!(r"\EFI\BOOT\BOOTX64.EFI"));
    } else {
        todo!("path for non-x86-64");
    }

    assert_eq!(proto.device().file_system().is_some(), true);
    assert_eq!(*proto.file_path(), path);
}

The code in the function that has zfi_testing::qemu attribute will run on the QEMU. This test can be run in the same way as normal integration tests:

cargo test

Keep in mind that you need to put everything your test needed in the same function because what qemu attribute does is moving your function body into efi_main and run it on QEMU.

Known Issues

• Any panic (including assertion failed) in your integration test will be show as src/main.rs:L:C. This is a limitation on stable Rust for now.
• rust-analyzer not report any syntax error. The reason is because qemu attribute replace the whole function body, which mean what rust-analyzer see when running syntax check is the replaced function, not the origial function. Right now there is no way to check if our proc macro being run by rust-analyzer until this issue has been resolved.

Breaking Changes

0.1 to 0.2

• Path is changed from sized type to unsized type. Any code that cast Path to a raw pointer need to update otherwise you will get a fat pointer, which is Rust specific. You can get a pointer to EFI_DEVICE_PATH_PROTOCOL via Path::as_bytes().
• FileInfo is changed from sized type to unsized type in the same way as Path.
• File::info() now return Box<FileInfo> instead of Owned<FileInfo> when success.
• The second parameter of Owned::new() is changed to Dtor.

License

MIT