Examining Page Tables in Kernel Crash Dumps (amd64)

[Arlie Stephens]

I'm chasing a bug in an elderly, customized freebsd kernel that appears to
result in corrupted page tables.  

kgdb is not cooperating when I attempt to look at addresses of kernel
page tables. I've replicated that part on an elderly stock freebsd
system, running freebsd 8.4. , and it looks to me like it's probably
getting that limitation from libkvm.  

Obviously I don't expect community help with an ancient freebsd
issue... particularly one probably caused by our own customizations.

But given the tool chain changes upstream, I don't expect testing with
whatever kgdb has turned into there to be very relevant ;-(

So far, the only way I know to get a look at kernel page table
contents in FreeBSD is on live systems with ddb. 

I would like to know whether there are any tools I haven't noticed for
dealing with page tables in crash dumps - or, for that matter, whether
kgdb is supposed to be able to display the kernel's recursive page
tables. 

Failing that, I may just have to write one ;-)  (Or figure out how to
chase my problem on live systems.) 

-- 
Arlie

(Arlie Stephens					arlie at worldash.org)