From: Greg Stark <gsstark@mit.edu>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Wright <chrisw@osdl.org>,
Linus Torvalds <torvalds@osdl.org>,
Rik van Riel <riel@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] prevent NULL mmap in topdown model
Date: 29 May 2005 17:16:33 -0400 [thread overview]
Message-ID: <87u0klybpq.fsf@stark.xeocode.com> (raw)
In-Reply-To: <1116490511.6027.25.camel@laptopd505.fenrus.org>
Arjan van de Ven <arjan@infradead.org> writes:
> On Wed, 2005-05-18 at 23:46 -0700, Chris Wright wrote:
>
> sure. Making it *impossible* to mmap that page is bad. People should be
> able to do that if they really want to, just doing it if they don't ask
> for it is bad.
>
> There are plenty of reasons people may want that page mmaped, one of
> them being that the compiler can then do more speculative loads around
> null pointer checks. Not saying it's a brilliant idea always, but making
> such things impossible makes no sense.
More realistically, iirc either Wine or dosemu, i forget which, actually has
to map page 0 to work properly.
--
greg
WARNING: multiple messages have this Message-ID (diff)
From: Greg Stark <gsstark@mit.edu>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Wright <chrisw@osdl.org>,
Linus Torvalds <torvalds@osdl.org>,
Rik van Riel <riel@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] prevent NULL mmap in topdown model
Date: 29 May 2005 17:16:33 -0400 [thread overview]
Message-ID: <87u0klybpq.fsf@stark.xeocode.com> (raw)
In-Reply-To: <1116490511.6027.25.camel@laptopd505.fenrus.org>
Arjan van de Ven <arjan@infradead.org> writes:
> On Wed, 2005-05-18 at 23:46 -0700, Chris Wright wrote:
>
> sure. Making it *impossible* to mmap that page is bad. People should be
> able to do that if they really want to, just doing it if they don't ask
> for it is bad.
>
> There are plenty of reasons people may want that page mmaped, one of
> them being that the compiler can then do more speculative loads around
> null pointer checks. Not saying it's a brilliant idea always, but making
> such things impossible makes no sense.
More realistically, iirc either Wine or dosemu, i forget which, actually has
to map page 0 to work properly.
--
greg
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next prev parent reply other threads:[~2005-05-29 21:16 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-18 19:57 [PATCH] prevent NULL mmap in topdown model Rik van Riel
2005-05-18 19:57 ` Rik van Riel
2005-05-18 20:38 ` Arjan van de Ven
2005-05-18 20:38 ` Arjan van de Ven
2005-05-18 21:16 ` Rik van Riel
2005-05-18 21:16 ` Rik van Riel
2005-05-18 22:41 ` Linus Torvalds
2005-05-18 22:41 ` Linus Torvalds
2005-05-18 22:39 ` Linus Torvalds
2005-05-18 22:39 ` Linus Torvalds
2005-05-19 2:25 ` Rik van Riel
2005-05-19 2:25 ` Rik van Riel
2005-05-19 2:47 ` Linus Torvalds
2005-05-19 2:47 ` Linus Torvalds
2005-05-19 6:46 ` Chris Wright
2005-05-19 6:46 ` Chris Wright
2005-05-19 8:15 ` Arjan van de Ven
2005-05-19 8:15 ` Arjan van de Ven
2005-05-19 8:23 ` Chris Wright
2005-05-19 8:23 ` Chris Wright
2005-05-29 21:16 ` Greg Stark [this message]
2005-05-29 21:16 ` Greg Stark
2005-05-31 16:56 ` Chris Wright
2005-05-31 16:56 ` Chris Wright
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