linux-kernel - Re: Execute in place

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Message-Id: <200705030812.38347.rgetz@blackfin.uclinux.org>
Date:	Thu, 3 May 2007 08:12:38 -0400
From:	Robin Getz <rgetz@...ckfin.uclinux.org>
To:	"Hugh Dickins" <hugh@...itas.com>
Cc:	"Phillip Susi" <psusi@....rr.com>,
	"Linux-kernel" <linux-kernel@...r.kernel.org>
Subject: Re: Execute in place

On Wed 2 May 2007 10:04, Hugh Dickins pondered:
> 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
>

Depends on if it is a noMMU or MMU platform.

Since noMMU platforms can't re-arrange non-contiguous blocks (which appears in 
a read/write ext2 file system) we need to use a read only romfs which 
applications are guaranteed to be contiguous by design.

I don't think the noMMU case is documented in xip.txt

-Robin
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