linux-kernel - Re: [RFC 1/3] x86/vdso: create vdso file, use it for mapping

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Message-ID: <fdc408f7-f5c1-3c00-e344-d7c2ae1da652@virtuozzo.com>
Date:   Mon, 29 Aug 2016 12:50:42 +0300
From:   Dmitry Safonov <dsafonov@...tuozzo.com>
To:     Andy Lutomirski <luto@...capital.net>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [RFC 1/3] x86/vdso: create vdso file, use it for mapping

On 08/29/2016 12:28 PM, Andy Lutomirski wrote:
> On Thu, Aug 25, 2016 at 8:21 AM, Dmitry Safonov <dsafonov@...tuozzo.com> wrote:
>> I added here a new in-kernel fs with ramfs-like options.
>> Created vdso file in this fs (yet for testing, only 64-bit vdso).
>> Mapped this file to process's mm on setup_additional_pages.
>> Just for testing purpose it's done only for specific UID.
>
> I'm wondering whether all this code could be easily moved into the
> core special mapping helpers so that all special mappings get the same
> benefit.  We could embed a struct file * (or struct inode or whatever)
> in special_mapping if needed.

Hmm, yes, I guess. The only thing -- we'll still need per-arch changes
to initialize those files on booting. But that looks like the proper
generic place to move this code.

> Also, could this be simplified to use anon_inode?
>
> (I'm not a VFS expert at all, so I could be way off base.)

Well, I'll try to do the second version with anon_inode.

Thanks,
              Dmitry