Input: implement SysRq as a separate input handler

Instead of keeping SysRq support inside of legacy keyboard driver split
it out into a separate input handler (filter). This stops most SysRq input
events from leaking into evdev clients (some events, such as first SysRq
scancode - not keycode - event, are still leaked into both legacy keyboard
and evdev).

[martinez.javier@gmail.com: fix compile error when CONFIG_MAGIC_SYSRQ is
 not defined]
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 22 insertions, 1 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8686b0f5fc12..ce724a0dd0bb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -163,6 +163,27 @@ static int proc_taint(struct ctl_table *table, int write,
                                void __user *buffer, size_t *lenp, loff_t *ppos);
 #endif
 
+#ifdef CONFIG_MAGIC_SYSRQ
+static int __sysrq_enabled; /* Note: sysrq code ises it's own private copy */
+
+static int sysrq_sysctl_handler(ctl_table *table, int write,
+                                void __user *buffer, size_t *lenp,
+                                loff_t *ppos)
+{
+        int error;
+
+        error = proc_dointvec(table, write, buffer, lenp, ppos);
+        if (error)
+                return error;
+
+        if (write)
+                sysrq_toggle_support(__sysrq_enabled);
+
+        return 0;
+}
+
+#endif
+
 static struct ctl_table root_table[];
 static struct ctl_table_root sysctl_table_root;
 static struct ctl_table_header root_table_header = {
@@ -567,7 +588,7 @@ static struct ctl_table kern_table[] = {
                 .data           = &__sysrq_enabled,
                 .maxlen         = sizeof (int),
                 .mode           = 0644,
-                .proc_handler   = proc_dointvec,
+                .proc_handler   = sysrq_sysctl_handler,
         },
 #endif
 #ifdef CONFIG_PROC_SYSCTL