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: Bernhard Walle <bernhard@bwalle.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/kernel/power/console.c b/kernel/power/console.c
index 5187136..218e5af 100644
--- a/kernel/power/console.c
+++ b/kernel/power/console.c
@@ -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