mirror of https://lore.kernel.org/lkml/
 help / color / mirror / Atom feed
From: David Howells <dhowells@redhat.com>
To: "Mike Frysinger" <vapier.adi@gmail.com>
Cc: dhowells@redhat.com, "Greg Ungerer" <gerg@snapgear.com>,
	"David McCullough" <David_Mccullough@securecomputing.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"Bryan Wu" <Bryan.Wu@analog.com>,
	"Bernd Schmidt" <bernds_cb1@t-online.de>,
	"Robin Getz" <rgetz@blackfin.uclinux.org>
Subject: Re: nommu: handling anonymous mmap clearing in userspace rather than kernel
Date: Wed, 02 Apr 2008 15:20:14 +0100	[thread overview]
Message-ID: <5516.1207146014@redhat.com> (raw)
In-Reply-To: <8bd0f97a0804011434r4869fbe8t89ade12c04c97f2@mail.gmail.com>

Mike Frysinger <vapier.adi@gmail.com> wrote:

> a workaround: introduce a new no-mmu-only mmap flag MAP_UNINITIALIZE
> to signal to the kernel that it should skip the memset().  this way,
> userspace malloc() can do mmap(MAP_ANONYMOUS|MAP_UNINITIALIZE) to get
> large chunks of memory without affecting any other anonymous mmap()
> call.

I think that's reasonable for NOMMU.  It's not like the process accessing the
uninitialised memory is prevented from accessing anything it wants to anyway.

I would vote that the memset() should only be skipped if requested as there
may be programs that call mmap(MAP_ANONYMOUS) expecting the memory they're
given to be zeroed out.

David



  reply	other threads:[~2008-04-02 14:45 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-04-01 21:34 Mike Frysinger
2008-04-02 14:20 ` David Howells [this message]
2008-04-02 14:47   ` Mike Frysinger
2008-04-02 15:03     ` Bernd Schmidt
2008-04-02 15:07       ` Mike Frysinger
2008-04-03 11:06         ` Bernd Schmidt
2008-04-03 14:46           ` Mike Frysinger
2008-04-03 13:14         ` David Howells

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=5516.1207146014@redhat.com \
    --to=dhowells@redhat.com \
    --cc=Bryan.Wu@analog.com \
    --cc=David_Mccullough@securecomputing.com \
    --cc=bernds_cb1@t-online.de \
    --cc=gerg@snapgear.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=rgetz@blackfin.uclinux.org \
    --cc=vapier.adi@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
Powered by JetHome