kern/62658: loader/kernel answer to `boot -a' ignored when comconsole is configured

[Dmitry Morozovsky]

>Number:         62658
>Category:       kern
>Synopsis:       loader/kernel answer to `boot -a' ignored when comconsole is configured
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Feb 10 11:20:14 PST 2004
>Closed-Date:
>Last-Modified:
>Originator:     Dmitry Morozovsky
>Release:        FreeBSD 4-STABLE i386
>Organization:
Cronyx Plus LLC (RiNet ISP)
>Environment:
System: FreeBSD 4-STABLE 


>Description:

FreeBSD loader/kernel refuses to set up the emergency root device when asked to, if
the console is configured as comconsole:

[loader prompt] boot -a -s
...
...
ad0: 7339MB <QUANTUM FIREBALL EL7.6A> [15907/15/63] at ata0-master UDMA33

Manual root filesystem specification:
  <fstype>:<device>  Mount <device> using filesystem <fstype>
                       eg. ufs:/dev/da0s1a
  ?                  List valid disk boot devices
  <empty line>       Abort manual input

mountroot> ufs:/dev/ad0s1e
Mounting root from ufs:/dev/ad0s1a

Look at the two last lines. Input asked at vfs_mountroot_ask() has not been
used, possibly because kern/vfs_conf.c:gets() dit not actually read the input
from comconsole. However, I'm not kernel hacker and looking at kern/tty_cons.c
scares me a bit :)

yar@ confirmed this bug also exists in -current

>How-To-Repeat:
configure comconsole, such as `echo -h >/boot.config'
reboot
enter any path to root partition but configured, or simple `?'
watch for kernel mounting default root partition

>Fix:

None for the moment, sorry.

Possible workaround (at least for 4-stable):

set vfs.root.mountfrom="/dev/DEVICE-TO-MAKE-ROOT"

at loader prompt before `boot'
>Release-Note:
>Audit-Trail:
>Unformatted: