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

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Date:   Fri, 18 Aug 2017 07:33:13 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     "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

On 18 August 2017 at 07:29, Sergey Senozhatsky
<sergey.senozhatsky.work@...il.com> wrote:
> 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.
>

That is good to hear. Thanks.