sysctl: Enable PARISC "unaligned-trap" to be used cross-arch

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 <vgupta@synopsys.com>
Acked-by: Helge Deller <deller@gmx.de>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>

3 files changed, 14 insertions, 0 deletions

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index b77feffbadea..8c7609539717 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 be8b7f55312d..01180da49add 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1232,6 +1232,14 @@ config SYSCTL_EXCEPTION_TRACE
         help
           Enable support for /proc/sys/debug/exception-trace.
 
+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 c88878db491e..878b4c41cfb7 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -157,6 +157,9 @@ extern int sysctl_tsb_ratio;
 
 #ifdef __hppa__
 extern int pwrsw_enabled;
+#endif
+
+#ifdef CONFIG_SYSCTL_ARCH_UNALIGN_ALLOW
 extern int unaligned_enabled;
 #endif
 
@@ -545,6 +548,8 @@ 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,