efivars

[FMDF]

On Wed, 22 Sep 2021, 08:22 Ruben Safir, <ruben at mrbrklyn.com> wrote:

> What is this for?
>
> efivarfs on /sys/firmware/efi/efivars type efivarfs
>
> why would the OS need to know anything about the UEFI
> boot loader once it is up and running?
>

I think you are still making confusion: UEFI bootloaders and UEFI are two
different entities.

UEFI bootloaders (like Grub2) serve the purpose to locate, pass kernel
options  and platform information to the kernel that themselves are going
to boot.

Instead the UEFI is an interface between the running OS and the platform
firmware.

UEFI defines two types of services: boot services and runtime services.

After booting is done, via UEFI boot services and eventually UEFI
bootloaders, the OS does not need anymore the bootloader and the UEFI boot
services.

Instead the OS needs UEFI runtime services to talk to the platform
firmware. For example, if OS cannot talk to the platform via UEFI, it
cannot even shutdown the system (obviously there is much more than simply
shutting down). How can an OS know that you've attached a plug and play
device if it cannot talk to the platform firmware?

Fabio


>
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