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| author | Nathan Lynch <nathan_lynch@mentor.com> | 2014-11-10 23:46:27 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-11-21 09:23:02 -0800 |
| commit | 962febd8f207bc0908b898ad5ed3594e2341f6e7 (patch) | |
| tree | 5f2a61740235482e1663d73295d233755741f831 /arch | |
| parent | fab22a1bde15890e22aa07e86ad66ee5c82ce909 (diff) | |
| download | lwn-962febd8f207bc0908b898ad5ed3594e2341f6e7.tar.gz lwn-962febd8f207bc0908b898ad5ed3594e2341f6e7.zip | |
ARM: 8198/1: make kuser helpers depend on MMU
commit 08b964ff3c51b10aaf2e6ba639f40054c09f0f7a upstream.
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 fbfb872f5f41 "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: fbfb872f5f41 (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>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/mm/Kconfig | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index ca8ecdee47d8..e9c290c21744 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -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. |