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ARM: 8178/1: fix set_tls for !CONFIG_KUSER_HELPERS

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Joachim Eastwood reports that commit fbfb872f5f "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.

Fixes: fbfb872f5f ARM: 8148/1: flush TLS and thumbee register state during exec

Reported-by: Joachim Eastwood <manabian@gmail.com>
Tested-by: Joachim Eastwood <manabian@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Nathan Lynch 2014-09-29 19:11:36 +01:00 committed by Russell King
parent ebc77251a4
commit 9cc6d9e5da
1 changed files with 2 additions and 0 deletions
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2
arch/arm/include/asm/tls.h
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@ -81,6 +81,7 @@ static inline void set_tls(unsigned long val)
asm("mcr p15, 0, %0, c13, c0, 3"
: : "r" (val));
} else {
#ifdef CONFIG_KUSER_HELPERS
/*
* User space must never try to access this
* directly. Expect your app to break
@ -89,6 +90,7 @@ static inline void set_tls(unsigned long val)
* entry-armv.S for details)
*/
*((unsigned int *)0xffff0ff0) = val;
#endif
}
}