Re: [PATCH] omap: iommu: disallow mapping NULL address

Laurent Pinchart
2011-03-07T21:19:48Z

Hi David,

On Monday 07 March 2011 20:41:21 David Cohen wrote:
> On Mon, Mar 7, 2011 at 9:25 PM, Guzman Lugo, Fernando wrote:
> > On Mon, Mar 7, 2011 at 1:19 PM, David Cohen wrote:
> >> On Mon, Mar 7, 2011 at 9:17 PM, Guzman Lugo, Fernando wrote:
> >>> On Mon, Mar 7, 2011 at 7:10 AM, Michael Jones wrote:
> >>>> From e7dbe4c4b64eb114f9b0804d6af3a3ca0e78acc8 Mon Sep 17 00:00:00 2001
> >>>> From: Michael Jones <michael.jones@matrix-vision.de>
> >>>> Date: Mon, 7 Mar 2011 13:36:15 +0100
> >>>> Subject: [PATCH] omap: iommu: disallow mapping NULL address
> >>>>
> >>>> commit c7f4ab26e3bcdaeb3e19ec658e3ad9092f1a6ceb allowed mapping
> >>>> the NULL address if da_start==0. Force da_start to exclude the
> >>>> first page.
> >>>
> >>> what about devices that uses page 0? ipu after reset always starts
> >>> from 0x00000000 how could we map that address??
> >>
> >> from 0x0? The driver sees da == 0 as error. May I ask you why do you
> >> want it?
> >
> > unlike DSP that you can load a register with the addres the DSP will
> > boot, IPU core always starts from address 0x00000000, so if you take
> > IPU out of reset it will try to access address 0x0 if not map it,
> > there will be a mmu fault.
>
> Hm. Looks like the iommu should not restrict any da. The valid da
> range should rely only on pdata.
> Michael, what about just update ISP's da_start on omap-iommu.c file?
> Set it to 0x1000.

What about patching the OMAP3 ISP driver to use a non-zero value (maybe -1) as
an invalid/freed pointer ?

--
Regards,

Laurent Pinchart