linux-kernel - Re: [PATCH 0/5] add support for relative references in special sections

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Date:   Fri, 18 Aug 2017 15:29:57 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        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>,
        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>,
        Steven Rostedt <rostedt@...dmis.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Jessica Yu <jeyu@...nel.org>
Subject: Re: [PATCH 0/5] add support for relative references in special
 sections

Hi Ard,

On (08/18/17 07:12), Ard Biesheuvel wrote:
> Hi Sergey,
> 
> Thanks for taking a look
> 
> On 18 August 2017 at 06:56, Sergey Senozhatsky
> <sergey.senozhatsky.work@...il.com> wrote:
> > On (08/14/17 11:52), Ard Biesheuvel wrote:
> >> This adds support for emitting special sections such as initcall arrays,
> >> PCI fixups and tracepoints as relative references rather than absolute
> >> references. This reduces the size by 50% on 64-bit architectures, but
> >> more importantly, it removes the need for carrying relocation metadata
> >> for these sections in relocatables kernels (e.g., for KASLR) that need
> >> to fix up these absolute references at boot time. On arm64, this reduces
> >> the vmlinux footprint of such a reference by 8x (8 byte absolute reference
> >> + 24 byte RELA entry vs 4 byte relative reference)
> > [..]
> >
> > a side note,
> > checkpatch complaints quite a lot.
> >
[..]
> I will clean up the meaningful ones in v2, but please don't expect
> this series to be checkpatch clean: it simply doesn't deal with inline
> asm very well, and some of this code predates checkpatch by a decade,
> and I'd rather not mix up rather tricky functional changes with
> checkpatch cleanup duty.

sure. thanks.

I'm running two x86 boxes with the patch set applied, for
several days, with no issues being observed. it does save
some memory (well, several pages in my case) even on "tiny"
kernels configs.

	-ss