printk: ipipe: add raw console channel

diff --git a/include/linux/console.h b/include/linux/console.h
index b8920a031a3e357d71101905e3396ba245160781..6af12e994dae692c9bcf134fe2dbf5865c70d435 100644 (file)
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -133,10 +133,12 @@ static inline int con_debug_leave(void)
 #define CON_ANYTIME    (16) /* Safe to call when cpu is offline */
 #define CON_BRL                (32) /* Used for a braille device */
 #define CON_EXTENDED   (64) /* Use the extended output format a la /dev/kmsg */
+#define CON_RAW                (128) /* Supports raw write mode */
 
 struct console {
        char    name[16];
        void    (*write)(struct console *, const char *, unsigned);
+       void    (*write_raw)(struct console *, const char *, unsigned);
        int     (*read)(struct console *, char *, unsigned);
        struct tty_driver *(*device)(struct console *, int *);
        void    (*unblank)(void);

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 335926039adcfda6f9a8af97a15f9c7802d63b4a..80009812b27726e84cc7ce12b26598835e789159 100644 (file)
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -155,6 +155,17 @@ static inline void printk_nmi_enter(void) { }
 static inline void printk_nmi_exit(void) { }
 #endif /* PRINTK_NMI */
 
+#ifdef CONFIG_RAW_PRINTK
+void raw_vprintk(const char *fmt, va_list ap);
+asmlinkage __printf(1, 2)
+void raw_printk(const char *fmt, ...);
+#else
+static inline __cold
+void raw_vprintk(const char *s, va_list ap) { }
+static inline __printf(1, 2) __cold
+void raw_printk(const char *s, ...) { }
+#endif
+
 #ifdef CONFIG_PRINTK
 asmlinkage __printf(5, 0)
 int vprintk_emit(int facility, int level,

diff --git a/init/Kconfig b/init/Kconfig
index ea6e9e4c2b2a3906803a9a063aa127af287fda5d..623794011a604b968047f368f7cba50cbb80a117 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1238,6 +1238,18 @@ config PRINTK_NMI
        depends on PRINTK
        depends on HAVE_NMI
 
+config RAW_PRINTK
+       bool "Enable support for raw printk"
+       default n
+       help
+         This option enables a printk variant called raw_printk() for
+         writing all output unmodified to a raw console channel
+         immediately, without any header or preparation whatsoever,
+         usable from any context.
+
+        Unlike early_printk() console devices, raw_printk() devices
+         can live past the boot sequence.
+
 config BUG
        bool "BUG() support" if EXPERT
        default y

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 651265f21c1c567c9980243eef53329b0bd1dd75..a68f4a495c9fd73da6eedf5519d83446c7387efc 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1984,6 +1984,62 @@ asmlinkage __visible void early_printk(const char *fmt, ...)
 }
 #endif
 
+#ifdef CONFIG_RAW_PRINTK
+static struct console *raw_console;
+static IPIPE_DEFINE_RAW_SPINLOCK(raw_console_lock);
+
+void raw_vprintk(const char *fmt, va_list ap)
+{
+       unsigned long flags;
+       char buf[256];
+       int n;
+       
+       if (raw_console == NULL || console_suspended)
+               return;
+
+       n = vscnprintf(buf, sizeof(buf), fmt, ap);
+        touch_nmi_watchdog();
+       raw_spin_lock_irqsave(&raw_console_lock, flags);
+       if (raw_console)
+               raw_console->write_raw(raw_console, buf, n);
+       raw_spin_unlock_irqrestore(&raw_console_lock, flags);
+}
+
+asmlinkage __visible void raw_printk(const char *fmt, ...)
+{
+       va_list ap;
+
+       va_start(ap, fmt);
+       raw_vprintk(fmt, ap);
+       va_end(ap);
+}
+
+static inline void register_raw_console(struct console *newcon)
+{
+       if ((newcon->flags & CON_RAW) != 0 && newcon->write_raw)
+               raw_console = newcon;
+}
+
+static inline void unregister_raw_console(struct console *oldcon)
+{
+       unsigned long flags;
+
+       raw_spin_lock_irqsave(&raw_console_lock, flags);
+       if (oldcon == raw_console)
+               raw_console = NULL;
+       raw_spin_unlock_irqrestore(&raw_console_lock, flags);
+}
+
+#else
+
+static inline void register_raw_console(struct console *newcon)
+{ }
+
+static inline void unregister_raw_console(struct console *oldcon)
+{ }
+
+#endif
+
 static int __add_preferred_console(char *name, int idx, char *options,
                                   char *brl_options)
 {
@@ -2612,6 +2668,9 @@ void register_console(struct console *newcon)
                console_drivers->next = newcon;
        }
 
+       /* The latest raw console to register is current. */
+       register_raw_console(newcon);
+
        if (newcon->flags & CON_EXTENDED)
                if (!nr_ext_console_drivers++)
                        pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
@@ -2667,6 +2726,8 @@ int unregister_console(struct console *console)
                (console->flags & CON_BOOT) ? "boot" : "" ,
                console->name, console->index);
 
+       unregister_raw_console(console);
+
        res = _braille_unregister_console(console);
        if (res)
                return res;