linux-kernel - Re: [PATCH] mm/vma: Append unlikely() while testing VMA access permissions

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: <CAMuHMdXMSTLevTH1gkM8B53LtRUQ80o=t+W27z0QT-dNKkkYgQ@mail.gmail.com>
Date:   Mon, 24 Feb 2020 11:09:52 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     Linux MM <linux-mm@...ck.org>, Guo Ren <guoren@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paulburton@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        linux-mips@...r.kernel.org, linux-csky@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/vma: Append unlikely() while testing VMA access permissions

Hi Anshuman,

Thanks for your patch!

On Mon, Feb 24, 2020 at 7:22 AM Anshuman Khandual
<anshuman.khandual@....com> wrote:
> It is unlikely that an inaccessible VMA without required permission flags
> will get a page fault. Hence lets just append unlikely() directive to such

Why? Isn't it the idea that you get a page fault when the page is not
accessible?

> checks in order to improve performance while also standardizing it across
> various platforms.

Does it make a difference to add these? Have you benchmarked this?
https://lwn.net/Articles/420019/

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds