Translations:EFI stub/89/en
From Gentoo Wiki
When the efistub USE flag is enabled on sys-kernel/installkernel, but the systemd USE flag is disabled. Installkernel calls uefi-mkconfig from sys-boot/uefi-mkconfig to dynamically update the UEFI configuration. If the shim EFI executable is present in the same directory as the kernel image the kernels will be chainloaded via Shim.