[RFC][PATCH] init: Open /dev/console from rootfs
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From: Eric W. Biederman on 3 Mar 2010 03:00 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(a)xmission.com> --- init/do_mounts_initrd.c | 4 ---- init/main.c | 11 ++++++----- 2 files changed, 6 insertions(+), 9 deletions(-) diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c index 614241b..2b10853 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); } diff --git a/init/main.c b/init/main.c index 67e40fc..9ba505f 100644 --- a/init/main.c +++ b/init/main.c @@ -806,11 +806,6 @@ static noinline int init_post(void) system_state = SYSTEM_RUNNING; numa_default_policy(); - if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0) - printk(KERN_WARNING "Warning: unable to open an initial console.\n"); - - (void) sys_dup(0); - (void) sys_dup(0); current->signal->flags |= SIGNAL_UNKILLABLE; @@ -864,6 +859,12 @@ static int __init kernel_init(void * unused) do_basic_setup(); + /* Open the /dev/console on the rootfs, this should never fail */ + if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0) + printk(KERN_WARNING "Warning: unable to open an initial console.\n"); + + (void) sys_dup(0); + (void) sys_dup(0); /* * check if there is an early userspace init. If yes, let it do all * the work -- 1.6.5.2.143.g8cc62 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |