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>

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>
Richard Weinberger · Linus Torvalds
1 parent 2525e70d49
Showing 5 changed files with 50 additions and 0 deletions Side-by-side Diff
arch/um/Kconfig.debug
arch/um/include/shared/os.h
arch/um/kernel/Makefile
arch/um/kernel/early_printk.c
arch/um/os-Linux/util.c
@@ -37,5 +37,15 @@
 	  stack seen so far.
  
 	  This option will slow down process creation and destruction somewhat.
+
+config EARLY_PRINTK
+	bool "Early printk"
+	default y
+	---help---
+	  Write kernel log output directly to stdout.
+
+	  This is useful for kernel debugging when your machine crashes very
+	  early before the console code is initialized.
+
 endmenu
@@ -244,6 +244,7 @@
 extern void setup_machinename(char *machine_out);
 extern void setup_hostinfo(char *buf, int len);
 extern void os_dump_core(void) __attribute__ ((noreturn));
+extern void um_early_printk(const char *s, unsigned int n);
  
 /* time.c */
 extern void idle_sleep(unsigned long long nsecs);
@@ -17,6 +17,7 @@
 obj-$(CONFIG_BLK_DEV_INITRD) += initrd.o
 obj-$(CONFIG_GPROF)	+= gprof_syms.o
 obj-$(CONFIG_GCOV)	+= gmon_syms.o
+obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
  
 USER_OBJS := config.o
  
+/*
+ * 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);
@@ -139,4 +139,9 @@
  
 	uml_abort();
 }
+
+void um_early_printk(const char *s, unsigned int n)
+{
+	printf("%.*s", n, s);
+}
...	...	@@ -37,5 +37,15 @@
37	37	stack seen so far.
38	38
39	39	This option will slow down process creation and destruction somewhat.
	40	+
	41	+config EARLY_PRINTK
	42	+ bool "Early printk"
	43	+ default y
	44	+ ---help---
	45	+ Write kernel log output directly to stdout.
	46	+
	47	+ This is useful for kernel debugging when your machine crashes very
	48	+ early before the console code is initialized.
	49	+
40	50	endmenu
...	...	@@ -244,6 +244,7 @@
244	244	extern void setup_machinename(char *machine_out);
245	245	extern void setup_hostinfo(char *buf, int len);
246	246	extern void os_dump_core(void) __attribute__ ((noreturn));
	247	+extern void um_early_printk(const char *s, unsigned int n);
247	248
248	249	/* time.c */
249	250	extern void idle_sleep(unsigned long long nsecs);
...	...	@@ -17,6 +17,7 @@
17	17	obj-$(CONFIG_BLK_DEV_INITRD) += initrd.o
18	18	obj-$(CONFIG_GPROF) += gprof_syms.o
19	19	obj-$(CONFIG_GCOV) += gmon_syms.o
	20	+obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
20	21
21	22	USER_OBJS := config.o
22	23
	1	+/*
	2	+ * Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
	3	+ *
	4	+ * This program is free software; you can redistribute it and/or modify
	5	+ * it under the terms of the GNU General Public License version 2 as
	6	+ * published by the Free Software Foundation.
	7	+ */
	8	+
	9	+#include <linux/kernel.h>
	10	+#include <linux/console.h>
	11	+#include <linux/init.h>
	12	+#include "os.h"
	13	+
	14	+static void early_console_write(struct console con, const char s, unsigned int n)
	15	+{
	16	+ um_early_printk(s, n);
	17	+}
	18	+
	19	+static struct console early_console = {
	20	+ .name = "earlycon",
	21	+ .write = early_console_write,
	22	+ .flags = CON_BOOT,
	23	+ .index = -1,
	24	+};
	25	+
	26	+static int __init setup_early_printk(char *buf)
	27	+{
	28	+ register_console(&early_console);
	29	+
	30	+ return 0;
	31	+}
	32	+
	33	+early_param("earlyprintk", setup_early_printk);
...	...	@@ -139,4 +139,9 @@
139	139
140	140	uml_abort();
141	141	}
	142	+
	143	+void um_early_printk(const char *s, unsigned int n)
	144	+{
	145	+ printf("%.*s", n, s);
	146	+}