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Date: Sat, 17 Aug 1996 19:33:48 -0700 (PDT)
From: Paul Traina <pst@Shockwave.COM>
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Subject: kern/1508: syscons does not protect against entering DDB when X11 screen is active
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>Number:         1508
>Category:       kern
>Synopsis:       syscons should protect against useless DDB entry
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Aug 17 19:40:03 PDT 1996
>Last-Modified:
>Originator:     Paul Traina
>Organization:
Shockwave Engineering
>Release:        FreeBSD 2.2-CURRENT i386
>Environment:

Current system with DDB in kernel.

>Description:

PCVT sets the boolean "cons_unavail" whenever it has been declared the system
console and the X11 screen is the currently active screen (actually, any time
the current screen mode is VT_PROCESS).

Syscons doesn't do this.  This means that if I enter DDB when X11 is active
(due to a trap or due to the keyboard entry sequence) the system locks down
and is totally useless.  I don't even get an honest panic. :-(

Syscons should set this flag when it is responsible for operating the console
and X11 is active, and clear this flag when operating from a non VT_PROCESS
screen.

>How-To-Repeat:

Compile kernel with DDB.
Start X
Generate a kernel debugger trap.
Kiss freebsd goodbye.

>Fix:
	
Take a peek at PCVT sources.  Look for cons_unavail.

>Audit-Trail:
>Unformatted: