Messages in this thread | | | Subject | Re: udev: what's up with old /dev ? | From | Zack Weinberg <> | Date | Mon, 11 Oct 2004 00:19:13 -0700 |
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Hacksaw writes: >Zack Weinberg writes: >>The very first thing init does is open /dev/console, and if it doesn't >>exist the entire boot hangs. > >This raises a question: Would it be a useful thing to make a modified init >that could run udev before it does anything else?
It wouldn't help. The opening of /dev/console actually happens inside the kernel, near the bottom of init/main.c:
if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0) printk("Warning: unable to open an initial console.\n");
(void) sys_dup(0); (void) sys_dup(0);
That's not a fatal error, but the userspace startup process does get stuck not very long afterward. (I'm not sure precisely where. It hadn't mounted filesystems read-write yet.)
Control reaches the above code after an initramfs is unpacked, so including /dev/console in an initramfs will work. I do not think it will work to invoke udevstart from an initramfs or initrd *without* also including a static /dev/console -- I'm pretty darn sure that control reaches /init in an initramfs after the above code executes. I'm not sure whether control reaches /linuxrc in an initrd before or after the above code.
Being inside the kernel at this point, it seems to me there ought to be some way to open device <5,1> without going through the filesystem, but I could not find one.
[Tangentially, I thought kernel-side syscalls had been stamped out, but there's still a __KERNEL_SYSCALLS__ #define at the top of the file and a bare execve() in run_init_process()... which does in fact get compiled to int $0x80 on my boring old x86...]
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