Date: Sat, 3 Feb 1996 14:40:22 -0500 (EST) From: "Marc G. Fournier" <scrappy@ki.net> To: hackers@freebsd.org Subject: How to use DDB to debug a boottime panic? Message-ID: <Pine.BSF.3.91.960203143227.10739D-100000@ki.net>
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Hi... In order to debug a panic problem with a -stable kernel, I've been asked by a gentleman in Germany to send him the values of "scbus" & "scbus->adapter_link" from before and after the function scsi_attachdevs() is called. Now, I don't have a clue on how to do this using DDB, and since there is about 5-6 hours difference between here and Germany (ie. I'm probably in bed while he's awake, or at least not around), the back and forth exchange on what I need to do in DDB is going to be slow :( So, I ask here...how do I use DDB? I've read through the man page for DDB, and got absolutely no where with it. The panic occurs right after the probe to the ncr0 device, and I'm not getting a core dump that I can use gdb against, so am stuck with only being able to use DDB. From the man page, I had assumed that doing something like: print $scbus would work, at least giving me the value of it *at* panic time, but I get something like "unknown variable/symbol", so that's wrong. On top of that, I somehow need to step back to get the value before the call to scsi_attachdevs(), but...'step -1' doesn't do that either :( If found the GDB examples in the FAQ (or handbook) to be enough to get me stepping through the kernel and getting the data that was requested, but have yet to find a similar example for DDB. So...help? How do I get the information that is being requested of me? Or is it not possible to get this without getting a core dump first? Thanks... Marc G. Fournier | POP Mail Telnet Acct DNS Hosting System | WWW Services Database Services | Knowledge, Administrator | | Information and scrappy@ki.net | WWW: http://www.ki.net | Communications, Inc
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