[PATCH] ARM: fix set_tls for !CONFIG_KUSER_HELPERS

[Joachim Eastwood]

On 29 September 2014 11:03, Will Deacon <will.deacon at arm.com> wrote:
> On Sat, Sep 27, 2014 at 11:30:26AM +0100, Joachim Eastwood wrote:
>> 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>
>
> Out of interest, which M4 board are you using to run Linux?

I am using Embedded Artists' LPC4357 Developer's Kit.
http://www.embeddedartists.com/products/kits/lpc4357_kit.php

>Are they generally available?
They have a webshop so you should be able to buy one. Seems to be out
of stock now, though.

I have a github repo with all my code for LPC4357 here:
https://github.com/manabian/linux-lpc


regards
Joachim Eastwood