linux-kernel - Re: Kernel V5.7-rc1 doesn't boot (EFI?)

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Message-ID: <CAHk-=wi-s0mmLAVg-aSmNU55=cE8ES7mC=Mc3Wn62P8W9VjY-A@mail.gmail.com>
Date:   Tue, 14 Apr 2020 11:27:04 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Jörg Otte <jrg.otte@...il.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Kernel V5.7-rc1 doesn't boot (EFI?)

On Tue, Apr 14, 2020 at 3:50 AM Ard Biesheuvel <ardb@...nel.org> wrote:
>
> [*] GRUB on x86 turns out not to zero initialize BSS when it invokes
> the EFI stub as a PE/COFF executable

The fix seems to be to put all globals in the .data section, even if
they don't have initializers.

That seems very fragile. Very easy to forget to not declare some
static variable with __efistub_global.

Could we not make the EFI stub code zero out the BSS itself? Perhaps
setting a warning flag (for a later printout) if it wasn't already
zero, so that people could point fingers are buggy loaders..

             Linus