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, 10 insertions, 0 deletions

diff --git a/arch/um/Kconfig.debug b/arch/um/Kconfig.debug
index 8fce5e536b0f..85c86edd1e67 100644
--- a/arch/um/Kconfig.debug
+++ b/arch/um/Kconfig.debug
@@ -37,4 +37,14 @@ config DEBUG_STACK_USAGE
           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