NetBSD Problem Report #4761
Received: (qmail 12892 invoked from network); 31 Dec 1997 22:47:37 -0000
Date: Wed, 31 Dec 97 17:47:04 EST
From: davide+@cs.cmu.edu
Sender: davide+@piper.nectar.cs.cmu.edu
Reply-To: David_Eckhardt@cs.cmu.edu
To: gnats-bugs@gnats.netbsd.org
Cc: davide+@cs.cmu.edu
Subject: i386 ddb "watch" seems broken
X-Send-Pr-Version: 3.95
>Number: 4761
>Category: kern
>Synopsis: setting any watchpoint results in a fatal page fault
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: kern-bug-people
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Wed Dec 31 14:50:02 +0000 1997
>Closed-Date:
>Last-Modified: Mon Feb 28 14:56:22 +0000 2011
>Originator: David Eckhardt
>Release: 1.2
>Organization:
Carnegie Mellon University Computer Science Department
>Environment:
NetBSD 1.1, 1.2, ...?
>Description:
It seems as though setting any watchpoint with ddb somehow
destroys the machine state: I can't get anything but kernel
page faults.
>How-To-Repeat:
control-alt-escape, "watch ipstat", "c"
>Fix:
If this isn't easily fixable, disabling the command would not be
a bad idea.
>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: gnats-admin->port-i386-maintainer
Responsible-Changed-By: fair
Responsible-Changed-When: Mon Dec 28 09:55:30 PST 1998
Responsible-Changed-Why:
This PR is the responsibility of the portmaster,
not the GNATS database administrator.
State-Changed-From-To: open->feedback
State-Changed-By: fair
State-Changed-When: Thu Jan 17 12:40:16 PST 2002
State-Changed-Why:
NetBSD has been through two major releases since this PR was filed;
does the problem still occurr?
From: "Perry E. Metzger" <perry@piermont.com>
To: David_Eckhardt@cs.cmu.edu, fvdl@netbsd.org
Cc: gnats-bugs@gnats.netbsd.org, perry@piermont.com
Subject: Re: port-i386/4761
Date: 04 Apr 2003 12:05:32 -0500
> >Synopsis: setting any watchpoint results in a fatal page fault
> >Arrival-Date: Wed Dec 31 14:50:02 1997
> >Description:
> It seems as though setting any watchpoint with ddb somehow
> destroys the machine state: I can't get anything but kernel
> page faults.
> >How-To-Repeat:
> control-alt-escape, "watch ipstat", "c"
This appears to still be a problem to this day. I just tested it and
got the stated behavior.
I'm going to assign the PR to the portmaster.
Perry
State-Changed-From-To: feedback->open
State-Changed-By: perry
State-Changed-When: Fri Apr 4 09:06:08 PST 2003
State-Changed-Why:
I just tested the problem -- it still happens, five years later.
Responsible-Changed-From-To: port-i386-maintainer->fvdl
Responsible-Changed-By: perry
Responsible-Changed-When: Fri Apr 4 09:06:08 PST 2003
Responsible-Changed-Why:
Frank is the x86 portmaster.
From: "Charles M. Hannum" <abuse@spamalicious.com>
To: gnats-bugs@gnats.NetBSD.org
Cc:
Subject: Re: port-i386/4761
Date: Sat, 3 Jul 2004 21:38:54 +0000
The way watchpoints are handled is sort of doomed. db_set_watchpoints() uses
pmap_protect() to change the page to read-only, and relies on the fault path
to restore the permissions later. However, in many cases UVM does not know
about kernel pages, and so the fault fails.
Responsible-Changed-From-To: fvdl->kern-bug-people
Responsible-Changed-By: wiz@NetBSD.org
Responsible-Changed-When: Mon, 28 Feb 2011 14:56:22 +0000
Responsible-Changed-Why:
Reset responsible field for retired developer.
>Unformatted:
(Contact us)
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