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Commit b45cfba4 authored by Jesse Barnes's avatar Jesse Barnes Committed by Jason Wessel
Browse files

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: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: default avatarJason Wessel <jason.wessel@windriver.com>
CC: David Airlie <airlied@linux.ie>
CC: Andrew Morton <akpm@linux-foundation.org>
parent 3fa43aba

drivers/char/vt.c

+61 −0
Original line number Diff line number Diff line
@@ -187,10 +187,15 @@ static DECLARE_WORK(console_work, console_callback); 
 * 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
@@ -3413,6 +3418,62 @@ int con_is_bound(const struct consw *csw) 
}

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

include/linux/console.h

+13 −0
Original line number Diff line number Diff line
@@ -55,6 +55,16 @@ struct consw { 
	void	(*con_invert_region)(struct vc_data *, u16 *, int);

	u16    *(*con_screen_pos)(struct vc_data *, int);

	unsigned long (*con_getxy)(struct vc_data *, unsigned long, int *, int *);

	/*

	 * Prepare the console for the debugger.  This includes, but is not

	 * limited to, unblanking the console, loading an appropriate

	 * palette, and allowing debugger generated output.

	 */

	int	(*con_debug_enter)(struct vc_data *);

	/*

	 * Restore the console to its pre-debug state as closely as possible.

	 */

	int	(*con_debug_leave)(struct vc_data *);

};



extern const struct consw *conswitchp;
@@ -69,6 +79,9 @@ int register_con_driver(const struct consw *csw, int first, int last); 
int unregister_con_driver(const struct consw *csw);

int take_over_console(const struct consw *sw, int first, int last, int deflt);

void give_up_console(const struct consw *sw);

int con_debug_enter(struct vc_data *vc);

int con_debug_leave(void);



/* scroll */

#define SM_UP       (1)

#define SM_DOWN     (2)