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vt,console,kdb: implement atomic console enter/leave functions

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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>
This commit is contained in:
Jesse Barnes 2010-08-05 09:22:30 -05:00 committed by Jason Wessel
parent 3fa43aba08
commit b45cfba4e9
2 changed files with 74 additions and 0 deletions
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61
drivers/char/vt.c
View File

@ -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

13
include/linux/console.h
View File

@ -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)