[PATCH] ARM: fix set_tls for !CONFIG_KUSER_HELPERS

[Joachim Eastwood]

On 27 September 2014 01:46, Nathan Lynch <nathan_lynch at mentor.com> wrote:
> Joachim Eastwood reports that commit fbfb872f5f41 "ARM: 8148/1: flush
> TLS and thumbee register state during exec" causes a boot-time crash
> on a Cortex-M4 nommu system:
>
> Freeing unused kernel memory: 68K (281e5000 - 281f6000)
> Unhandled exception: IPSR = 00000005 LR = fffffff1
> CPU: 0 PID: 1 Comm: swapper Not tainted 3.17.0-rc6-00313-gd2205fa30aa7 #191
> task: 29834000 ti: 29832000 task.ti: 29832000
> PC is at flush_thread+0x2e/0x40
> LR is at flush_thread+0x21/0x40
> pc : [<2800954a>] lr : [<2800953d>] psr: 4100000b
> sp : 29833d60 ip : 00000000 fp : 00000001
> r10: 00003cf8 r9 : 29b1f000 r8 : 00000000
> r7 : 29b0bc00 r6 : 29834000 r5 : 29832000 r4 : 29832000
> r3 : ffff0ff0 r2 : 29832000 r1 : 00000000 r0 : 282121f0
> xPSR: 4100000b
> CPU: 0 PID: 1 Comm: swapper Not tainted 3.17.0-rc6-00313-gd2205fa30aa7 #191
> [<2800afa5>] (unwind_backtrace) from [<2800a327>] (show_stack+0xb/0xc)
> [<2800a327>] (show_stack) from [<2800a963>] (__invalid_entry+0x4b/0x4c)
>
> The problem is that set_tls is attempting to clear the TLS location in
> the kernel-user helper page, which isn't set up on V7M.
>
> Fix this by guarding the write to the kuser helper page with
> a CONFIG_KUSER_HELPERS ifdef.
>
> Reported-by: Joachim Eastwood <manabian at gmail.com>
> Fixes: fbfb872f5f41 ARM: 8148/1: flush TLS and thumbee register state during exec
> Cc: stable at vger.kernel.org
> Signed-off-by: Nathan Lynch <nathan_lynch at mentor.com>
> ---

Works for me.

Tested-by: Joachim Eastwood <manabian at gmail.com>

Thanks!

regards,
Joachim Eastwood