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	<20091210135816.6325.37536.stgit@warthog.procyon.org.uk>
From: Mike Frysinger <vapier.adi@gmail.com>
Date: Mon, 14 Dec 2009 18:55:43 -0500
Message-ID: <8bd0f97a0912141555l103e4833k1ffae12f6924a9a4@mail.gmail.com>
Subject: Re: [PATCH 5/7] NOMMU: Avoiding duplicate icache flushes of shared 
	maps
To: David Howells <dhowells@redhat.com>
Cc: lethal@linux-sh.org, jie.zhang@analog.com, stefani@seibold.net,
       gerg@snapgear.com, uclinux-dev@uclinux.org,
       linux-kernel@vger.kernel.org
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On Thu, Dec 10, 2009 at 08:58, David Howells wrote:
> From: Mike Frysinger <vapier.adi@gmail.com>
>
> When working with FDPIC, there are many shared mappings of read-only code
> regions between applications (the C library, applet packages like busybox,
> etc.), but the current do_mmap_pgoff() function will issue an icache flush
> whenever a VMA is added to an MM instead of only doing it when the map is
> initially created.
>
> The flush can instead be done when a region is first mmapped PROT_EXEC.  Note
> that we may not rely on the first mapping of a region being executable - it's
> possible for it to be PROT_READ only, so we have to remember whether we've
> flushed the region or not, and then flush the entire region when a bit of it is
> made executable.
>
> However, this also affects the brk area.  That will no longer be executable.
> We can mprotect() it to PROT_EXEC on MPU-mode kernels, but for NOMMU mode
> kernels, when it increases the brk allocation, making sys_brk() flush the extra
> from the icache should suffice.  The brk area probably isn't used by NOMMU
> programs since the brk area can only use up the leavings from the stack
> allocation, where the stack allocation is larger than requested.

this works fine for me, thanks.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
-mike
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