linux-kernel - Re: [PATCH v8 1/6] arch: enable relative relocations for arm64, power and x86

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Message-ID: <CA+55aFxcB+5oB_hL83EASOJQrVRCrzT9iS+2+XtEUToG6VHiqA@mail.gmail.com>
Date:   Sun, 11 Mar 2018 13:20:24 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Will Deacon <will.deacon@....com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thomas Garnier <thgarnie@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Russell King <linux@...linux.org.uk>,
        Paul Mackerras <paulus@...ba.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Petr Mladek <pmladek@...e.com>, Ingo Molnar <mingo@...hat.com>,
        James Morris <james.l.morris@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nicolas Pitre <nico@...aro.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Jessica Yu <jeyu@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH v8 1/6] arch: enable relative relocations for arm64, power
 and x86

On Sun, Mar 11, 2018 at 5:38 AM, Ard Biesheuvel
<ard.biesheuvel@...aro.org> wrote:
> Before updating certain subsystems to use place relative 32-bit
> relocations in special sections, to save space and reduce the
> number of absolute relocations that need to be processed at runtime
> by relocatable kernels, introduce the Kconfig symbol and define it
> for some architectures that should be able to support and benefit
> from it.

Are there actually architectures hat _don't_ support those relative
32-bit relocations? That really feels pretty fundamental.

I would have expected all of them to do it - is your selection of
arm64/powerpc/x86 perhaps more about "I have tested these" than about
anything else?

Because I'd almost prefer to just do the switch-over unconditionally
if that is at all possible?

             Linus