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ARM: 8198/1: make kuser helpers depend on MMU

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The kuser helpers page is not set up on non-MMU systems, so it does
not make sense to allow CONFIG_KUSER_HELPERS to be enabled when
CONFIG_MMU=n.  Allowing it to be set on !MMU results in an oops in
set_tls (used in execve and the arm_syscall trap handler):

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)

As best I can tell this issue existed for the set_tls ARM syscall
before commit fbfb872f5f "ARM: 8148/1: flush TLS and thumbee
register state during exec" consolidated the TLS manipulation code
into the set_tls helper function, but now that we're using it to flush
register state during execve, !MMU users encounter the oops at the
first exec.

Prevent CONFIG_MMU=n configurations from enabling
CONFIG_KUSER_HELPERS.

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

Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Reported-by: Stefan Agner <stefan@agner.ch>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Nathan Lynch 2014-11-10 23:46:27 +01:00 committed by Russell King
parent 238962ac71
commit 08b964ff3c
1 changed files with 1 additions and 0 deletions
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arch/arm/mm/Kconfig
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@ -798,6 +798,7 @@ config NEED_KUSER_HELPERS
config KUSER_HELPERS
bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
depends on MMU
default y
help
Warning: disabling this option may break user programs.