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Re: bcm33xx port

To: "Kevin D. Kissell" <kevink@mips.com>
Subject: Re: bcm33xx port
From: "Maciej W. Rozycki" <macro@linux-mips.org>
Date: Sun, 8 Jun 2008 21:14:06 +0100 (BST)
Cc: Luke -Jr <luke@dashjr.org>, linux-kernel <linux-kernel@vger.kernel.org>, linux-mips@linux-mips.org
In-reply-to: <484C38A6.7080503@mips.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200806072113.26433.luke@dashjr.org> <200806072332.06460.luke@dashjr.org> <Pine.LNX.4.55.0806081332560.15673@cliff.in.clinika.pl> <200806081357.02601.luke@dashjr.org> <484C38A6.7080503@mips.com>
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On Sun, 8 Jun 2008, Kevin D. Kissell wrote:

> > The RI error spits out a bunch of info, including epc which presumably 
> > points 
> > to the instruction causing the problem: ac85ffc0; this is 'sw a1,-64(a0)'
> >   
> But unless the processor itself is actually defective, there is no way that
> a  SW instruction can cause an RI exception.  Sometimes a kernel crash
> is so violent that the kernel stack frame cannot be reliably decoded by
> the crash dump code, and this would appear to be one of those cases.
> I find the address of 0xac85ffc0 to be a bit suspicious, myself.  That's
> a kseg1 (non-cacheable identity map) address for physical address
> 0x0c85ffc0, which would be legitimate (though suspicious) if you had
> 256MB of RAM, but the boot log quote you posted earlier suggests
> that you've only got 16M.  Is there really memory of some kind at
> that address?  Are you calling routines in a boot ROM from Linux?

 Well, 0xac85ffc0 is the instruction word corresponding to 'sw a1,-64(a0)'.
:)  The actual address of the failure is apparently 0x004e010c, which is
pretty much a standard location somewhere within a user executable proper.

  Maciej

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