linux-kernel - Re: [PATCH] [ARM] Use AT() in the linker script to create correct program headers

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Message-ID: <20121008102413.GC2302@linaro.org>
Date:	Mon, 8 Oct 2012 11:24:13 +0100
From:	Dave Martin <dave.martin@...aro.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] [ARM] Use AT() in the linker script to create correct
 program headers

On Fri, Oct 05, 2012 at 09:45:00AM +0100, Russell King - ARM Linux wrote:
> On Mon, Oct 01, 2012 at 10:06:39AM -0600, Jason Gunthorpe wrote:
> > On Mon, Oct 01, 2012 at 04:39:53PM +0100, Dave Martin wrote:
> > > >   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
> > > >   LOAD           0x008000 0xc0008000 0x00008000 0x372244 0x3a4310 RWE 0x8000
> > > 
> > > Not related directly to your patch, but I wonder why we don't we see
> > > separate r-x and rw- segments?
> > 
> > I think this is because the sections are not aligned when the
> > protections change, and the sections are not sorted by protection
> > type.
> 
> They aren't sorted by protection type, they're ordered according to what's
> required for the kernel - which is to have the init sections together as
> one complete block so that it can be freed, and to place all of the kernel
> text as close to the beginning of the image as possible.

Ah, right.

Partly this came from some side speculation about whether we could do
things like privileged read-only permissions on newer CPUs, for preventing
unintended or undesired writes to the kernel's code or read-only data.

There would be various things to solve in order to make that work, so I
guess there's no great urgency for it right now.

Cheers
---Dave
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