linux-kernel - Re: [PATCH 3/9] efi/x86: Move efi stub globals from .bss to .data

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Message-ID: <20200411010340.GA1612878@rani.riverdale.lan>
Date:   Fri, 10 Apr 2020 21:03:40 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Brian Gerst <brgerst@...il.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...e.de>,
        Colin Ian King <colin.king@...onical.com>,
        Gary Lin <glin@...e.com>, Jiri Slaby <jslaby@...e.cz>,
        Sergey Shatunov <me@...k.pw>, Takashi Iwai <tiwai@...e.de>
Subject: Re: [PATCH 3/9] efi/x86: Move efi stub globals from .bss to .data

On Fri, Apr 10, 2020 at 08:03:15PM +0200, Ard Biesheuvel wrote:
> > >
> > > We'll still need .data.efistub for the .data pieces, but that is a
> > > separate issue.
> >
> > You can avoid that by using an archive specification like above. i.e.
> > adding
> >         drivers/firmware/efi/libstub/lib.a:(.data .data.*)
> > to the .init.data output section will pull in just the .data input
> > sections from the EFI stub into the .init.data section.
> 
> Sure. But the ARM decompressor linker script currently discards .data
> before this point in the linker script, and relies on this as a safety
> net to ensure that no new .data items get added to the decompressor
> binary (which runs after the stub)

You should be able to use EXCLUDE_FILE to skip discarding the .data
section from libstub. That also supports the archive: syntax according
to the docs though I haven't tried it.