Date: Sat, 02 Mar 1996 00:59:04 -0800 From: David Greenman <davidg@Root.COM> To: Paul Traina <pst@shockwave.com> Cc: questions@freebsd.org, hackers@freebsd.org Subject: Re: using ddb to debug a double-panic? Message-ID: <199603020859.AAA13750@Root.COM> In-Reply-To: Your message of "Fri, 01 Mar 1996 13:53:27 PST." <199603012153.NAA00721@precipice.shockwave.com>
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>Is there a simple sequence I can type into ddb to switch stack pointers and >frames so I can do a "where" to see where I was when the first panic occured? I thought about writing some extensions to "trace" to allow it to apply a (operator supplied) 'stack offset' that would be used to adjust the pushed FPs (for precisely the purpose of what you're requesting above). ...but I haven't gotten around to this yet. For now, I just use 'curpcb' to find the stack that [might] have been in use at the time of the double fault, and then munge around in the stack manually (yes, I know, yuck). Of course if there was no process running at the time, you'll want to look at tmpstk instead. This code definately code use some work - I just wanted to catch the case in the first place so that machines didn't just "wedge"...and then have at least a snowball's chance of figuring out the cause. I'm not happy with the way that the double fault TSS currently works (using IdlePTD, etc), but I haven't had any time to implement it better. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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