nrdmn / uefi-examples

UEFI examples in Zig

UEFI examples in Zig

This repo contains examples about how to use Zig to build UEFI apps.

Recommended reading order:

1. hello
2. protocols
3. events
4. memory
5. exit_boot_services
6. efivars
7. hii (TODO)

How to build and run.

Run zig build in any of the subdirectories to build. Then you can copy the output file to a FAT32 formatted device to efi/boot/bootx64.efi. Alternatively you can use QEMU with qemu-system-x86_64 -bios /usr/share/edk2-ovmf/OVMF_CODE.fd -hdd fat:rw:. -serial stdio.

FAQ

How much stack space do I get?

At least 128 KiB before calling exitBootServices(). After calling exitBootServices() you have to provide at least 4 KiB.

Why does my computer reboot after 5 minutes?

By default, your firmware's watchdog reboots your system after 5 minutes if your application does not call exitBootServices(). You can disable the watchdog timer using boot_services.setWatchdogTimer(0, 0, 0, null).

Where do I get more information?

Read the spec. It's really well written.

Further reading

• https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_final.pdf
• https://www.intel.com/content/dam/doc/guide/efi-driver-writers-v1-10-guide.pdf
• Beyond BIOS: Developing with the Unified Extensible Firmware Interface