From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Mon, 29 Sep 2014 10:03:13 +0100 Subject: [PATCH] ARM: fix set_tls for !CONFIG_KUSER_HELPERS In-Reply-To: References: <1411775208-14280-1-git-send-email-nathan_lynch@mentor.com> Message-ID: <20140929090313.GA20303@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sat, Sep 27, 2014 at 11:30:26AM +0100, Joachim Eastwood wrote: > On 27 September 2014 01:46, Nathan Lynch 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 > > Fixes: fbfb872f5f41 ARM: 8148/1: flush TLS and thumbee register state during exec > > Cc: stable at vger.kernel.org > > Signed-off-by: Nathan Lynch > > --- > > Works for me. > > Tested-by: Joachim Eastwood Out of interest, which M4 board are you using to run Linux? Are they generally available? Will