On Sun, 10 Dec 2000, Kjetil B. Thomassen wrote:

> On Sat 09 Dec, Ben Harris wrote:
> > On Sun, 3 Dec 2000, Kjetil B. Thomassen wrote:
> > 
> > > I made myself a test kernel were I added DDB and strip out some of the
> > > things I didn't think I needed. The config file has been attached to
> > > this email.
> > > 
> > > The last stuff before it hang is:
> > > root file system type: nfs
> > > init: copying out path '/sbin/init' 11
> > > 
> > > I broke into DDB with CTRL-ALT-Esc
> > 
> > Is it possible for you to try typing "x/i 0,8" at DDB here?  This will
> > dump the exception vectors, and on my system, I find that the vector at
> > 0x8 (the SWI vector) has been corrupted to "andeq r0,r0,r0" (ie all
> > zeroes).  It looks like something in the kernel is writing through a NULL
> > pointer.  That'll be fun to debug.
> 
> The vectors are not corrupted on my R140. They look fine to me.

How odd.  So they were all of the form "ldr r15, fiqhandler+0x100" etc?  
Incidentally, if you get revision 1.15 or later of
sys/arch/arm26/arm26/except.c, the kernel will check the vectors itself
every time it returns to user mode (if DIAGNOSTIC's defined).

> Yes, I got several pages of output, and I couldn't understand much of
> it. Also, the stuff in uvm_stat.c is above my head, so I think I need to
> understand more of this before I can do anything more.
>
> I used sources from some time yesterday, but it did not get any further
> than it has done before. The R140 is up and running as it has mounted
> the root directory and is answering when I ping it. The delay is around
> 5 ms.
> 
> Is there anything else I can do in DDB to try to track this down?

One possibility is to look at the UVM histories, making a note of the
timestamps of the last few entries, then type "c", wait a bit, drop back
into the debugger and re-run the history and see if any more things have
happened.  This can give you some idea of what's going on.

-- 
Ben Harris                                                   <bjh21@netbsd.org>
Portmaster, NetBSD/arm26               <URL:http://www.netbsd.org/Ports/arm26/>