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

[Uwe Kleine-König]

On Sun, Nov 02, 2014 at 10:14:01PM +0000, 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?
On Cortex-M3 and M4 addresses that start with 0xf....... cannot be RAM.
So as long as the address is fixed there it won't work on ARMv7-M.

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
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