linux-kernel - [PATCH 5.19 112/207] um: fix default console kernel parameter

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Message-Id: <20220926100811.621399975@linuxfoundation.org>
Date:   Mon, 26 Sep 2022 12:11:41 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Thomas Meyer <thomas@...3r.de>,
        Christian Lamparter <chunkeey@...il.com>,
        Richard Weinberger <richard@....at>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.19 112/207] um: fix default console kernel parameter

From: Christian Lamparter <chunkeey@...il.com>

[ Upstream commit 782b1f70f8a8b28571949d2ba43fe88b96d75ec3 ]

OpenWrt's UML with 5.15 was producing odd errors/warnings during preinit
part of the early userspace portion:

|[    0.000000] Kernel command line: ubd0=root.img root=98:0 console=tty
|[...]
|[    0.440000] random: jshn: uninitialized urandom read (4 bytes read)
|[    0.460000] random: jshn: uninitialized urandom read (4 bytes read)
|/etc/preinit: line 47: can't create /dev/tty: No such device or address
|/etc/preinit: line 48: can't create /dev/tty: No such device or address
|/etc/preinit: line 58: can't open /dev/tty: No such device or address
|[...] repeated many times

That "/dev/tty" came from the command line (which is automatically
added if no console= parameter was specified for the uml binary).

The TLDP project tells the following about the /dev/tty:
<https://tldp.org/HOWTO/Text-Terminal-HOWTO-7.html#ss7.3>
| /dev/tty stands for the controlling terminal (if any) for the current
| process.[...]
| /dev/tty is something like a link to the actually terminal device[..]

The "(if any)" is important here, since it's possible for processes to
not have a controlling terminal.

I think this was a simple typo and the author wanted tty0 there.

CC: Thomas Meyer <thomas@...3r.de>
Fixes: d7ffac33631b ("um: stdio_console: Make preferred console")
Signed-off-by: Christian Lamparter <chunkeey@...il.com>
Signed-off-by: Richard Weinberger <richard@....at>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/um/kernel/um_arch.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index e0de60e503b9..d9e023c78f56 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -33,7 +33,7 @@
 #include "um_arch.h"
 
 #define DEFAULT_COMMAND_LINE_ROOT "root=98:0"
-#define DEFAULT_COMMAND_LINE_CONSOLE "console=tty"
+#define DEFAULT_COMMAND_LINE_CONSOLE "console=tty0"
 
 /* Changed in add_arg and setup_arch, which run before SMP is started */
 static char __initdata command_line[COMMAND_LINE_SIZE] = { 0 };
-- 
2.35.1