linux-kernel - Re: Execute in place

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 2 May 2007 16:22:43 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Björn Steinbrink <B.Steinbrink@....de>
cc:	Phillip Susi <psusi@....rr.com>,
	Linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Execute in place

On Wed, 2 May 2007, Björn Steinbrink wrote:
> On 2007.05.02 15:04:44 +0100, Hugh Dickins wrote:
> > On Tue, 1 May 2007, Phillip Susi wrote:
> > > I seem to remember seeing some patches go by at some point that
> > > allowed one of the rom type embeded system filesystems to directly
> > > execute binaries out of the original rom memory rather than copying
> > > them to ram first, then executing from there.  I was wondering if
> > > rootfs or tmpfs support such execute in place today, or if binaries
> > > executed from there have their code segments duplicated in ram?
> > 
> > Only ext2 supports it today: see Documentation/filesystems/xip.txt
> 
> As I understand it, xip avoids the page cache copy. But tmpfs already
> lives in the page cache (or swap), so avoiding that "copy" is
> impossible. But I always expected tmpfs to implicitly due its own kind
> of xip, i.e. that it doesn't have to store its stuff in the page cache
> twice. Are you saying that this isn't true?

tmpfs doesn't store its stuff in the page cache twice: that's true,
and I didn't mean to imply otherwise.  But tmpfs doesn't contain any
support for rom memory: you'd have to copy from rom to tmpfs to use it.

Hugh