linux-kernel - Re: [PATCH] arm64: prevent regressions in compressed kernel image size when upgrading to binutils 2.27

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Message-ID: <CAKwvOdmZgzBneocuhhLs5YRwZv3JUvnSJSPi5pFCZbrkdNzc5w@mail.gmail.com>
Date:   Thu, 26 Oct 2017 14:23:39 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Siqi Lin <siqilin@...gle.com>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Jiri Kosina <jikos@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Will Deacon <will.deacon@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>, Wei Wang <wvw@...gle.com>,
        Gopinath Elanchezhian <gelanchezhian@...gle.com>,
        spentyala@...gle.com, Rahul Chaudhry <rahulchaudhry@...gle.com>,
        Stephen Hines <srhines@...gle.com>
Subject: Re: [PATCH] arm64: prevent regressions in compressed kernel image
 size when upgrading to binutils 2.27

On Thu, Oct 26, 2017 at 2:17 PM, Siqi Lin <siqilin@...gle.com> wrote:
> I'm OK with sticking with the <2.27 binutils behavior. The gzip data is:

That's what this patch does; goes back to the <2.27 behavior for 2.27+.

> binutils 2.25:
> Image 41467904
> Image.gz 13395151
> binutils 2.27:
> Image 41467392
> Image.gz 14114953
>
> gzipped kernel increased by 0.69 MiB.

That's without this patch applied?  With it applied, what are the
stats (for gzip)?

> The one special case I see is !CONFIG_RELOCATABLE and compression is
> used, where there's a tradeoff between compressed image size and the
> benefit of dynamic relocs.

if !CONFIG_RELOCATABLE, then this patch (well v2 which will use
CONFIG_RELOCATABLE rather than CONFIG_RANDOMIZE_BASE) doesn't do
anything.