arm32 insecure W+X mapping

[Tim Harvey]

On Mon, Sep 20, 2021 at 9:22 AM Russell King (Oracle)
<linux at armlinux.org.uk> wrote:
>
> On Wed, Sep 15, 2021 at 06:44:56AM -0300, Fabio Estevam wrote:
> > Not sure if this is related or not to the following behavior that I am seeing.
> >
> > On 5.15-rc1 I see the following on an imx6dl based board:
> >
> > [    0.123336] imx6q_suspend_init: failed to find ocram device!
>
> Looking at the platforms I currently have, two imx6q which booted 5.13
> do not have this problem, but one imx6dl that booted 5.14 does seem to
> spit out this message.
>
> What I do notice is that in the 5.14 case, /proc/iomem reports that the
> ocram device does exist:
>
> 00900000-0091ffff : 900000.sram sram at 900000
>
> so I'm suspecting an init ordering issue.
>
> It looks on the face of it to be a regression between 5.13 and 5.14.
> I'm guessing that the sram device isn't being probed early enough.
> Maybe some of the initialisation/device model debug options can
> identify what changed?
>

Here's what I see on both imx6dl and imx6q with both CONFIG_DEBUG_WX
and CONFIG_SUSPEND enabled:
5.13: 'Checked W+X mappings: FAILED, 1 W+X pages found' on both imx6q and imx6dl
5.14: No W+X failure on either board.... so something different for sure
5.15-rc2: same as 5.14

So my results differ from yours but showed that something has been
fixed vs regressed. I'll bisect and see if I can figure out when my
original issue I reported here went away.

Tim