vt,console,kdb: implement atomic console enter/leave functions
These functions allow the kernel debugger to save and restore the
state of the system console.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
CC: David Airlie <airlied@linux.ie>
CC: Andrew Morton <akpm@linux-foundation.org>
diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 7cdb6ee..117ce99 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -187,10 +187,15 @@
* fg_console is the current virtual console,
* last_console is the last used one,
* want_console is the console we want to switch to,
+ * saved_* variants are for save/restore around kernel debugger enter/leave
*/
int fg_console;
int last_console;
int want_console = -1;
+int saved_fg_console;
+int saved_last_console;
+int saved_want_console;
+int saved_vc_mode;
/*
* For each existing display, we have a pointer to console currently visible
@@ -3414,6 +3419,62 @@
EXPORT_SYMBOL(con_is_bound);
/**
+ * con_debug_enter - prepare the console for the kernel debugger
+ * @sw: console driver
+ *
+ * Called when the console is taken over by the kernel debugger, this
+ * function needs to save the current console state, then put the console
+ * into a state suitable for the kernel debugger.
+ *
+ * RETURNS:
+ * Zero on success, nonzero if a failure occurred when trying to prepare
+ * the console for the debugger.
+ */
+int con_debug_enter(struct vc_data *vc)
+{
+ int ret = 0;
+
+ saved_fg_console = fg_console;
+ saved_last_console = last_console;
+ saved_want_console = want_console;
+ saved_vc_mode = vc->vc_mode;
+ vc->vc_mode = KD_TEXT;
+ console_blanked = 0;
+ if (vc->vc_sw->con_debug_enter)
+ ret = vc->vc_sw->con_debug_enter(vc);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(con_debug_enter);
+
+/**
+ * con_debug_leave - restore console state
+ * @sw: console driver
+ *
+ * Restore the console state to what it was before the kernel debugger
+ * was invoked.
+ *
+ * RETURNS:
+ * Zero on success, nonzero if a failure occurred when trying to restore
+ * the console.
+ */
+int con_debug_leave(void)
+{
+ struct vc_data *vc;
+ int ret = 0;
+
+ fg_console = saved_fg_console;
+ last_console = saved_last_console;
+ want_console = saved_want_console;
+ vc_cons[fg_console].d->vc_mode = saved_vc_mode;
+
+ vc = vc_cons[fg_console].d;
+ if (vc->vc_sw->con_debug_leave)
+ ret = vc->vc_sw->con_debug_leave(vc);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(con_debug_leave);
+
+/**
* register_con_driver - register console driver to console layer
* @csw: console driver
* @first: the first console to take over, minimum value is 0