linux-kernel - Re: [PATCH v2 2/2] ARM: mm: convert empty_zero

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Y1ANW9ZRRPDJxlmc@shell.armlinux.org.uk>
Date:   Wed, 19 Oct 2022 15:44:43 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Giulio Benetti <giulio.benetti@...ettiengineering.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Anshuman Khandual <anshuman.khandual@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Arnd Bergmann <arnd@...db.de>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH v2 2/2] ARM: mm: convert empty_zero_page to array for
 consistency

On Wed, Oct 19, 2022 at 12:25:03AM +0200, Giulio Benetti wrote:
> ARM architecture is the only one to have empty_zero_page to be a
> struct page pointer, while in all other implementations empty_zero_page is
> a data pointer or directly an array(the zero page itself). So let's convert
> empty_zero_page to an array for consistency and to avoid an early
> allocation+dcache flush. Being the array in .bss it will be cleared earlier
> in a more linear way(and a bit faster) way.
> 
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Giulio Benetti <giulio.benetti@...ettiengineering.com>

I'm completely against this approach. It introduces inefficiencies in
paths we don't need, and also means that the zero page is at a fixed
location relative to the kernel, neither of which I like in the
slightest.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!