From 5ada918b82399eef3afd6a71e3637697d6bd719f Mon Sep 17 00:00:00 2001 From: Bernhard Walle Date: Mon, 14 Dec 2009 18:00:43 -0800 Subject: [PATCH] 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 Cc: Alan Cox Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/char/vt.c | 43 ++++++++++++++++++++++++++++++++++++------ include/linux/tty.h | 2 -- include/linux/vt.h | 15 +++++++++++++++ kernel/power/console.c | 7 +++---- 4 files changed, 55 insertions(+), 12 deletions(-) diff --git a/drivers/char/vt.c b/drivers/char/vt.c index 1e3d728dbf7e..e43fbc66aef0 100644 --- a/drivers/char/vt.c +++ b/drivers/char/vt.c @@ -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: diff --git a/include/linux/tty.h b/include/linux/tty.h index 405a9035fe40..ef3a2947b102 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -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); diff --git a/include/linux/vt.h b/include/linux/vt.h index 7ffa11f06232..3fb9944e50a6 100644 --- a/include/linux/vt.h +++ b/include/linux/vt.h @@ -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 */ diff --git a/kernel/power/console.c b/kernel/power/console.c index 5187136fe1de..218e5af90156 100644 --- a/kernel/power/console.c +++ b/kernel/power/console.c @@ -6,7 +6,7 @@ #include #include -#include +#include #include #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 -- 2.39.5