init: Open /dev/console from rootfs

To avoid potential problems with an empty /dev open /dev/console
from rootfs instead of waiting to mount our root filesystem and
mounting it there.   This effectively guarantees that there will
be a device node, and it won't be on a filesystem that we will
ever unmount, so there are no issues with leaving /dev/console
open and pinning the filesystem.

This is actually more effective than automatically mounting
devtmpfs on /dev because it removes removes the occasionally
problematic assumption that /dev/console exists from the boot
code.

With this patch I was able to throw busybox on my /boot partition
(which has no /dev directory) and boot into userspace without
problems.

The only possible negative consequence I can think of is that
someone out there deliberately used did not use a character device
that is major 5 minor 2 for /dev/console.  Does anyone know of a
situation in which that could make sense?

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 0 insertions, 4 deletions

diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index 614241b5200c..2b108538d0d9 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -30,11 +30,7 @@ static int __init do_linuxrc(void * shell)
 	extern char * envp_init[];
 
 	sys_close(old_fd);sys_close(root_fd);
-	sys_close(0);sys_close(1);sys_close(2);
 	sys_setsid();
-	(void) sys_open("/dev/console",O_RDWR,0);
-	(void) sys_dup(0);
-	(void) sys_dup(0);
 	return kernel_execve(shell, argv, envp_init);
 }