PARISC defines /proc/sys/kernel/unaligned-trap to runtime toggle
unaligned access emulation.

The exact mechanics of enablig/disabling are still arch specific, we can
make the sysctl usable by other arches.

Signed-off-by: Vineet Gupta <vgu...@synopsys.com>
Cc: "James E.J. Bottomley" <j...@parisc-linux.org>
Cc: Helge Deller <del...@gmx.de>
Cc: "Eric W. Biederman" <ebied...@xmission.com>
Cc: Serge Hallyn <serge.hal...@canonical.com>
---
 arch/parisc/Kconfig |    1 +
 init/Kconfig        |    8 ++++++++
 kernel/sysctl.c     |    7 ++++++-
 3 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index b77feff..8c76095 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -20,6 +20,7 @@ config PARISC
        select ARCH_HAVE_NMI_SAFE_CMPXCHG
        select GENERIC_SMP_IDLE_THREAD
        select GENERIC_STRNCPY_FROM_USER
+       select SYSCTL_ARCH_UNALIGN_ALLOW
        select HAVE_MOD_ARCH_SPECIFIC
        select MODULES_USE_ELF_RELA
        select CLONE_BACKWARDS
diff --git a/init/Kconfig b/init/Kconfig
index e188f9f..e64bb18 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1240,6 +1240,14 @@ config SYSCTL_ARCH_UNALIGN_NO_WARN
          unaligned access emulation going on under the hood.
          see arch/ia64/kernel/unaligned.c for reference
 
+config SYSCTL_ARCH_UNALIGN_ALLOW
+       bool
+       help
+         Enable support for /proc/sys/kernel/unaligned-trap
+         Allows arches to define/use @unaligned_enabled to runtime toggle
+         the unaligned access emulation.
+         see arch/parisc/kernel/unaligned.c for reference
+
 config KALLSYMS
         bool "Load all symbols for debugging/ksymoops" if EXPERT
         default y
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 840fd5e..c4cd655 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -157,13 +157,16 @@ extern int sysctl_tsb_ratio;
 
 #ifdef __hppa__
 extern int pwrsw_enabled;
-extern int unaligned_enabled;
 #endif
 
 #ifdef CONFIG_IA64
 extern int unaligned_dump_stack;
 #endif
 
+#ifdef CONFIG_SYSCTL_ARCH_UNALIGN_ALLOW
+extern int unaligned_enabled;
+#endif
+
 #ifdef CONFIG_SYSCTL_ARCH_UNALIGN_NO_WARN
 extern int no_unaligned_warning;
 #endif
@@ -548,6 +551,8 @@ static struct ctl_table kern_table[] = {
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
+#endif
+#ifdef CONFIG_SYSCTL_ARCH_UNALIGN_ALLOW
        {
                .procname       = "unaligned-trap",
                .data           = &unaligned_enabled,
-- 
1.7.4.1

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