linux-kernel - Re: [PATCH v2 0/4] x86/boot: Remove runtime relocations from compressed kernel

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Message-ID: <20200526153636.GD2190602@rani.riverdale.lan>
Date:   Tue, 26 May 2020 11:36:36 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Sedat Dilek <sedat.dilek@...il.com>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Ard Biesheuvel <ardb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Fangrui Song <maskray@...gle.com>,
        Dmitry Golovin <dima@...ovin.in>,
        Clang-Built-Linux ML <clang-built-linux@...glegroups.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/4] x86/boot: Remove runtime relocations from
 compressed kernel

On Tue, May 26, 2020 at 04:50:38PM +0200, Sedat Dilek wrote:
> On Tue, May 26, 2020 at 4:47 PM Arvind Sankar <nivedita@...m.mit.edu> wrote:
> >
> > On Tue, May 26, 2020 at 02:44:29PM +0200, Sedat Dilek wrote:
> > >
> > > Are those diffs correct when using "x86/boot: Correct relocation
> > > destination on old linkers"?
> > >
> >
> > It looks ok, but that patch (and even marking the other symbols .hidden)
> > should be unnecessary after this series.
> 
> You mean _bss, _ebss and _end?
> 
> - Sedat -

Yes. Those .hidden markings are there to ensure that when relocations
are generated (as they are currently), they're generated as
R_386_RELATIVE (which uses B+A calculation, with A being the link-time
virtual address of the symbol, and stored in the relocation field)
rather than R_386_32 (which uses S+A calculation, and so doesn't work
without runtime processing). After this patchset there aren't any
relocations, so while the .hidden markings won't hurt, they won't be
necessary either.