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SubjectRe: [PATCH] ARM: reinsert ARCH_MULTI_V4 Kconfig option
On Fri, Dec 13, 2013 at 11:51:09AM +0100, Jonas Jensen wrote:
> On 13 December 2013 10:56, Russell King - ARM Linux
> <linux@arm.linux.org.uk> wrote:
> > So, having these symbols enabled (provided the right ones for FA526 are
> > also enabled) makes no difference. So I don't buy your explanation.
>
> The explanation is indeed false, CPU_FA526 and CPU_ARM920T get along just fine.
> That's not where the problem is.
>
> Panic goes away after removing CONFIG_ARM_THUMB=y.
>
> I assume this is what should happen on processors without thumb?

I see what's causing this: the kuser helpers are using "bx lr" to return
which will be undefined on non-Thumb CPUs. We generally cope fine with
non-Thumb CPUs, conditionalising where necessary on HWCAP_THUMB or the
T bit in the PSR being set.

However, it looks like the kuser helpers got missed. As a check, please
look at arch/arm/kernel/entry-armv.S, find the line with:

.macro usr_ret, reg

and ensure that the mov pc, \reg case always gets used. Please report
back.

Thanks.


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