| Message ID | 1415045178-4673-1-git-send-email-nathan_lynch@mentor.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Nov 03, 2014 at 02:06:18PM -0600, Nathan Lynch wrote: > 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 minor nit: Usual syntax here is: Fixes: fbfb872f5f41 ("ARM: 8148/1: flush ...") > and it's part of the s-o-b area, so no empty line > 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> Thanks Uwe
On 11/04/2014 02:03 AM, Uwe Kleine-König wrote: > On Mon, Nov 03, 2014 at 02:06:18PM -0600, Nathan Lynch wrote: >> >> Prevent CONFIG_MMU=n configurations from enabling >> CONFIG_KUSER_HELPERS. >> >> Fixes: fbfb872f5f41 ARM: 8148/1: flush TLS and thumbee register state during exec > minor nit: Usual syntax here is: > > Fixes: fbfb872f5f41 ("ARM: 8148/1: flush ...") > >> > and it's part of the s-o-b area, so no empty line Indeed, will fix before sending to the patch tracker. > >> 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> Thanks.
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index ae69809a9e47..7eb94e6fc376 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.
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> Cc: stable@vger.kernel.org --- arch/arm/mm/Kconfig | 1 + 1 file changed, 1 insertion(+)