linux-kernel - Re: [PATCH v2 3/5] mm: madvise: implement lightweight guard page mechanism

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Message-ID: <a4b7ed07-3b14-4443-aa76-77d720912cd0@lucifer.local>
Date: Mon, 21 Oct 2024 20:39:42 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: John Hubbard <jhubbard@...dia.com>
Cc: David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Matthew Wilcox <willy@...radead.org>, Vlastimil Babka <vbabka@...e.cz>,
        "Paul E . McKenney" <paulmck@...nel.org>, Jann Horn <jannh@...gle.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <muchun.song@...ux.dev>,
        Richard Henderson <richard.henderson@...aro.org>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "James E . J . Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>, Arnd Bergmann <arnd@...db.de>,
        linux-alpha@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linux-arch@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>, Christian Brauner <brauner@...nel.org>,
        linux-kselftest@...r.kernel.org,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Jeff Xu <jeffxu@...omium.org>, Christoph Hellwig <hch@...radead.org>,
        linux-api@...r.kernel.org
Subject: Re: [PATCH v2 3/5] mm: madvise: implement lightweight guard page
 mechanism

On Mon, Oct 21, 2024 at 12:25:08PM -0700, John Hubbard wrote:
> On 10/21/24 10:23 AM, David Hildenbrand wrote:
[snip]
> > > > Just to raise it here: MADV_GUARD_INSTALL / MADV_GUARD_REMOVE or sth. like
> > > > that would have been even clearer, at least to me.
>
> Yes, I think so.
>
> > >
> > > :)
> > >
> > > It still feels like poisoning to me because we're explicitly putting
> > > something in the page tables to make a range have different fault behaviour
> > > like a HW poisoning, and 'installing' suggests backing or something like
> > > this, I think that's more confusing.
> >
> > I connect "poison" to "SIGBUS" and "corrupt memory state", not to "there is nothing and there must not be anything". Thus my thinking. But again, not the end of the world, just wanted to raise it ...
>
> "Poison" is used so far for fairly distinct things, and I'd very much like
> to avoid extending its meaning to guard pages. It makes the other things
> less unique, and it misses a naming and classification opportunity.
>
> "Guard" and "guard page" are fairly unique names. That's valuable.
>
>
> thanks,
> --
> John Hubbard
>

Guys you're breaking my heart... Will you not leave me with even a remnant
of a cultural reference?? [0]

[0]:https://www.youtube.com/watch?v=_mej5wS7viw