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Commit 5ada918b authored by Bernhard Walle's avatar Bernhard Walle Committed by Linus Torvalds
Browse files

vt: introduce and use vt_kmsg_redirect() function 



The kernel offers with TIOCL_GETKMSGREDIRECT ioctl() the possibility to
redirect the kernel messages to a specific console.

However, since it's not possible to switch to the kernel message console
after a panic(), it would be nice if the kernel would print the panic
message on the current console.

This patch series adds a new interface to access the global kmsg_redirect
variable by a function to be able to use it in code where
CONFIG_VT_CONSOLE is not set (kernel/panic.c).

This patch:

Instead of using and exporting a global value kmsg_redirect, introduce a
function vt_kmsg_redirect() that both can set and return the console where
messages are printed.

Change all users of kmsg_redirect (the VT code itself and kernel/power.c)
to the new interface.

The main advantage is that vt_kmsg_redirect() can also be used when
CONFIG_VT_CONSOLE is not set.

Signed-off-by: default avatarBernhard Walle <bernhard@bwalle.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c95d1e53

drivers/char/vt.c

+37 −6
Original line number Diff line number Diff line
@@ -184,12 +184,10 @@ 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,

 * kmsg_redirect is the console for kernel messages,

 */

int fg_console;

int last_console;

int want_console = -1;

int kmsg_redirect;



/*

 * For each existing display, we have a pointer to console currently visible
@@ -2434,6 +2432,37 @@ struct tty_driver *console_driver; 


#ifdef CONFIG_VT_CONSOLE



/**

 * vt_kmsg_redirect() - Sets/gets the kernel message console

 * @new:	The new virtual terminal number or -1 if the console should stay

 * 		unchanged

 *

 * By default, the kernel messages are always printed on the current virtual

 * console. However, the user may modify that default with the

 * TIOCL_SETKMSGREDIRECT ioctl call.

 *

 * This function sets the kernel message console to be @new. It returns the old

 * virtual console number. The virtual terminal number 0 (both as parameter and

 * return value) means no redirection (i.e. always printed on the currently

 * active console).

 *

 * The parameter -1 means that only the current console is returned, but the

 * value is not modified. You may use the macro vt_get_kmsg_redirect() in that

 * case to make the code more understandable.

 *

 * When the kernel is compiled without CONFIG_VT_CONSOLE, this function ignores

 * the parameter and always returns 0.

 */

int vt_kmsg_redirect(int new)

{

	static int kmsg_con;



	if (new != -1)

		return xchg(&kmsg_con, new);

	else

		return kmsg_con;

}



/*

 *	Console on virtual terminal

 *
@@ -2448,6 +2477,7 @@ static void vt_console_print(struct console *co, const char *b, unsigned count) 
	const ushort *start;

	ushort cnt = 0;

	ushort myx;

	int kmsg_console;



	/* console busy or not yet initialized */

	if (!printable)
@@ -2455,8 +2485,9 @@ static void vt_console_print(struct console *co, const char *b, unsigned count) 
	if (!spin_trylock(&printing_lock))

		return;



	if (kmsg_redirect && vc_cons_allocated(kmsg_redirect - 1))

		vc = vc_cons[kmsg_redirect - 1].d;

	kmsg_console = vt_get_kmsg_redirect();

	if (kmsg_console && vc_cons_allocated(kmsg_console - 1))

		vc = vc_cons[kmsg_console - 1].d;



	/* read `x' only after setting currcons properly (otherwise

	   the `x' macro will read the x of the foreground console). */
@@ -2613,7 +2644,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg) 
			ret = set_vesa_blanking(p);

			break;

		case TIOCL_GETKMSGREDIRECT:

			data = kmsg_redirect;

			data = vt_get_kmsg_redirect();

			ret = __put_user(data, p);

			break;

		case TIOCL_SETKMSGREDIRECT:
@@ -2623,7 +2654,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg) 
				if (get_user(data, p+1))

					ret = -EFAULT;

				else

					kmsg_redirect = data;

					vt_kmsg_redirect(data);

			}

			break;

		case TIOCL_GETFGCONSOLE:

include/linux/tty.h

+0 −2
Original line number Diff line number Diff line
@@ -350,8 +350,6 @@ extern void tty_write_flush(struct tty_struct *); 


extern struct ktermios tty_std_termios;



extern int kmsg_redirect;



extern void console_init(void);

extern int vcs_init(void);

include/linux/vt.h

+15 −0
Original line number Diff line number Diff line
@@ -84,4 +84,19 @@ struct vt_setactivate { 


#define VT_SETACTIVATE	0x560F	/* Activate and set the mode of a console */



#ifdef CONFIG_VT_CONSOLE



extern int vt_kmsg_redirect(int new);



#else



static inline int vt_kmsg_redirect(int new)

{

	return 0;

}



#endif



#define vt_get_kmsg_redirect() vt_kmsg_redirect(-1)



#endif /* _LINUX_VT_H */

kernel/power/console.c

+3 −4
Original line number Diff line number Diff line
@@ -6,7 +6,7 @@ 


#include <linux/vt_kern.h>

#include <linux/kbd_kern.h>

#include <linux/console.h>

#include <linux/vt.h>

#include <linux/module.h>

#include "power.h"
@@ -21,8 +21,7 @@ int pm_prepare_console(void) 
	if (orig_fgconsole < 0)

		return 1;



	orig_kmsg = kmsg_redirect;

	kmsg_redirect = SUSPEND_CONSOLE;

	orig_kmsg = vt_kmsg_redirect(SUSPEND_CONSOLE);

	return 0;

}
@@ -30,7 +29,7 @@ void pm_restore_console(void) 
{

	if (orig_fgconsole >= 0) {

		vt_move_to_console(orig_fgconsole, 0);

		kmsg_redirect = orig_kmsg;

		vt_kmsg_redirect(orig_kmsg);

	}

}

#endif