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Message-ID: <1466188786.34556.21.camel@freebsd.org>
Subject: Re: RPI-B 11.0-ALPHA3 r301815 panic ["when connecting via WiFi"]
From: Ian Lepore <ian@freebsd.org>
To: Keith White <kwhite@site.uottawa.ca>
Cc: Adrian Chadd <adrian.chadd@gmail.com>, freebsd-arm
 <freebsd-arm@freebsd.org>, FreeBSD Current <freebsd-current@freebsd.org>
Date: Fri, 17 Jun 2016 12:39:46 -0600
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On Fri, 2016-06-17 at 12:28 -0400, Keith White wrote:
> On Fri, 17 Jun 2016, Ian Lepore wrote:
> 
> > On Fri, 2016-06-17 at 07:52 -0700, Adrian Chadd wrote:
> > > Just disable 11n for now. ifconfig wlan0 -ht (and reassociate.)
> > > 
> > > See if it's that.
> > > 
> > > 
> > > 
> > > -adrian
> > > 
> > 
> > You can see from the crash info that it's an alignment fault:
> > 
> >  r6 =c21a4876
> >  ldmib   r6,{r1-r2}
> > 
> > An ldm instruction requires 4-byte alignment.  Now the question is
> > why
> > undefining __NO_STRICT_ALIGNMENT didn't fix the problem.  Maybe the
> > wifi code doesn't use __NO_STRICT_ALIGNMENT the same way other
> > network
> > drivers do?
> > 
> > Unfortunately the pasted info lists the nearby symbol as
> > $a.17+0x38,
> > which doesn't help find the actual code.  A stack backtrace might
> > help.
> > 
> > -- Ian
> > ...
> 
> What do I need to type at the "db> " prompt that would be useful?
> I should be able to access the RPI-B in 5 hours.
> 
> Here's the result of a "where" taken from an earlier logged session
> (different r6 value):
> 

"where" is a synonym for getting a stack backtrace, that's just what I
needed.  Now I know what's wrong, but not yet how to fix it.

-- Ian