linux-kernel - Re: [PATCH] mm/mincore: allow for making sys

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Date:   Sun, 6 Jan 2019 11:33:36 +0000
From:   Kevin Easton <kevin@...rana.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Masatake YAMATO <yamato@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org
Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged

On Sat, Jan 05, 2019 at 01:54:03PM -0800, Linus Torvalds wrote:
> On Sat, Jan 5, 2019 at 12:43 PM Jiri Kosina <jikos@...nel.org> wrote:
> >
> > > Who actually _uses_ mincore()? That's probably the best guide to what
> > > we should do. Maybe they open the file read-only even if they are the
> > > owner, and we really should look at file ownership instead.
> >
> > Yeah, well
> >
> >         https://codesearch.debian.net/search?q=mincore
> >
> > is a bit too much mess to get some idea quickly I am afraid.

> Anyway, the Debian code search just results in mostly non-present
> stuff. It's sad that google code search is no more. It was great for
> exactly these kinds of questions.

If you select the "Group search results by Debian source package"
option on the search results page it makes it a lot easier to skim
through.

It looks to me like Firefox is expecting mincore() not to fail on
libraries that it has mapped:

https://sources.debian.org/src/firefox-esr/60.4.0esr-1/mozglue/linker/BaseElf.cpp/?hl=98#L98

    - Kevin
> 
> The mono runtime seems to have some mono_pages_not_faulted() function,
> but I don't know if people use it for file mappings, and I couldn't
> find any interesting users of it.
> 
> I didn't find anything that seems to really care, but I gave up after
> a few pages of really boring stuff.
> 
>                     Linus
> 
>