linux-kernel - RE: [PATCH V3 2/5] efi: Introduce __efi

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Date:   Tue, 4 Sep 2018 22:25:11 +0000
From:   "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>
To:     "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
CC:     "Neri, Ricardo" <ricardo.neri@...el.com>,
        "matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>,
        Al Stone <astone@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: RE: [PATCH V3 2/5] efi: Introduce __efi_init attribute

Hi Boris and Ard,

> Buggy firmware could illegally access some efi regions even after the kernel has
> assumed control of the platform. When
> "CONFIG_EFI_WARN_ON_ILLEGAL_ACCESS" is enabled, the efi page fault
> handler will detect and recover from these illegal accesses.
> efi_md_typeattr_format() and memory_type_name are used by the efi page
> fault handler to print information about memory descriptor that was illegally
> accessed. As the page fault handler is present during/after kernel boot it doesn't
> have an __init attribute, but
> efi_md_typeattr_format() has it and thus during kernel build, "WARNING:
> modpost: Found * section mismatch(es)" build warning is observed. To fix it,
> remove __init attribute for efi_md_typeattr_format().
> 
> In order to not keep efi_md_typeattr_format() and memory_type_name
> needlessly when "CONFIG_EFI_WARN_ON_ILLEGAL_ACCESS" is not selected,
> add a new __efi_init attribute whose value changes based on whether the config
> option is selected or not.

In previous versions (i.e. up to V2), where we handled EFI_BOOT_SERVICES_<CODE/DATA> 
regions differently, it made sense to have a separate attribute like __efi_init because many 
function definitions were modified. From V3, do you think it's still OK to have __efi_init or 
should I just remove __init attribute (and not have __efi_init) for efi_md_typeattr_format() 
and memory_type_name because we are just modifying two.

Regards,
Sai