Crash on ARM: 8148/1 flush TLS and thumbee register

[Nathan Lynch]

On 11/02/2014 04:14 PM, Russell King - ARM Linux wrote:
> On Sun, Nov 02, 2014 at 11:03:14PM +0100, Stefan Agner wrote:
>> Hi all,
>>
>> While working on Vybrid (vf610) Cortex-M4 support I also hit this crash
>> observed by Joachim:
>>
>> ...
>> Freeing unused kernel memory: 16K (8800a000 - 8800e000)
>>
>> Unhandled exception: IPSR = 00000005 LR = fffffff1
>> CPU: 0 PID: 1 Comm: swapper Not tainted 3.18.0-rc1-00041-ga30465a #216
>> task: 8b838000 ti: 8b82a000 task.ti: 8b82a000
>> PC is at flush_thread+0x32/0x40
>> LR is at flush_thread+0x21/0x40
>> pc : [<8f00157a>]    lr : [<8f001569>]    psr: 4100000b
>> sp : 8b82be20  ip : 00000000  fp : 8b83c000
>> r10: 00000001  r9 : 88018c84  r8 : 8bb85000
>> r7 : 8b838000  r6 : 00000000  r5 : 8bb77400  r4 : 8b82a000
>> r3 : ffff0ff0  r2 : 8b82a000  r1 : 00000000  r0 : 88020354
>> xPSR: 4100000b
>> CPU: 0 PID: 1 Comm: swapper Not tainted 3.18.0-rc1-00041-ga30465a #216
>> [<8f002bc1>] (unwind_backtrace) from [<8f002033>] (show_stack+0xb/0xc)
>> [<8f002033>] (show_stack) from [<8f00265b>] (__invalid_entry+0x4b/0x4c)
>>
>> Can reproduce it on 3.18-rc1, as well as 3.17.
> 
> Hmm, I think KUSER_HELPERS needs to depend on MMU.  Nathan?

Yes.  I'll send a patch today.