um: add earlyprintk support

User Mode Linux can also benefit from earlyprintk.  UML's earlyprintk
writes kernel messages directly to stdout.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/arch/um/kernel/early_printk.c b/arch/um/kernel/early_printk.c
new file mode 100644
index 000000000000..ec649bf72f68
--- /dev/null
+++ b/arch/um/kernel/early_printk.c
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/console.h>
+#include <linux/init.h>
+#include "os.h"
+
+static void early_console_write(struct console *con, const char *s, unsigned int n)
+{
+	um_early_printk(s, n);
+}
+
+static struct console early_console = {
+	.name = "earlycon",
+	.write = early_console_write,
+	.flags = CON_BOOT,
+	.index = -1,
+};
+
+static int __init setup_early_printk(char *buf)
+{
+	register_console(&early_console);
+
+	return 0;
+}
+
+early_param("earlyprintk", setup_early_printk);