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>
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2 changed files with 6 additions and 9 deletions
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@ -30,11 +30,7 @@ static int __init do_linuxrc(void * shell)
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extern char * envp_init[];
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sys_close(old_fd);sys_close(root_fd);
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sys_close(0);sys_close(1);sys_close(2);
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sys_setsid();
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(void) sys_open("/dev/console",O_RDWR,0);
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(void) sys_dup(0);
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(void) sys_dup(0);
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return kernel_execve(shell, argv, envp_init);
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}
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11
init/main.c
11
init/main.c
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@ -806,11 +806,6 @@ static noinline int init_post(void)
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system_state = SYSTEM_RUNNING;
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numa_default_policy();
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if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
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printk(KERN_WARNING "Warning: unable to open an initial console.\n");
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(void) sys_dup(0);
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(void) sys_dup(0);
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current->signal->flags |= SIGNAL_UNKILLABLE;
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@ -873,6 +868,12 @@ static int __init kernel_init(void * unused)
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do_basic_setup();
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/* Open the /dev/console on the rootfs, this should never fail */
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if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
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printk(KERN_WARNING "Warning: unable to open an initial console.\n");
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(void) sys_dup(0);
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(void) sys_dup(0);
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/*
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* check if there is an early userspace init. If yes, let it do all
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* the work
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