linux-kernel - Re: [PATCH] ARM: OMAP2+: Add support for thumb mode on DT booted N900

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Date:	Wed, 5 Feb 2014 18:17:29 +0100
From:	Sebastian Reichel <sre@...ian.org>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Tony Lindgren <tony@...mide.com>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, freemangordon@....bg
Subject: Re: [PATCH] ARM: OMAP2+: Add support for thumb mode on DT booted N900

Hi,

On Wed, Feb 05, 2014 at 05:38:54PM +0100, Pali Rohár wrote:
> > I assumed, that the workaround is not needed for this device type.
> 
> That rx51 secure call must not be called on non secure devices (e.g.
> qemu), because it cause kernel crash. So I thought that kernel should
> write something like secure call is disabled on that device types.
> Kernel code for errata 430973 will update ibe bit for non secure
> devices.

Do you see any advantage in having that message?

> > I just added the warning for missing CONFIG_ARM_ERRATA_430973,
> > because its very likely a misconfigured kernel.
> 
> Yes, it can be misconfigured kernel, but if you do not have any thumb
> binary (like stock Maemo 5 system), then it is safe and OK.

I think running this kernel may also be a potential security
problem. If I understand it right the ARM core is left in an
unstable state when you run Thumb code, so this may result in
funny effects in the kernel?

-- Sebastian

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