Propose for Several Dump types

[Andrew Gallatin]

Jun Su writes:

 > Kernel-Only Dump
 > ==============
 > We now can use /dev/kmem as the core file. If we can generate a dump file with
 > the same information with it, then we can enable kernel-only dump with
 > very limit code changes.
 > 
 > 1. Change KVM library to support a new type of file that only contains
 > kernel memory.
 > 2. Change kernel side to write only kernel memory when dumping.
 > 3. Change dumpon utility to do the right checking on the partiction size.

I think the kernel-only dump is an excellent idea.  But I'm confused
as to how you would do it.

To me, it seems like the most obvious way to do this would be walking
the kernel's vm maps.  But that does not work on 64-bit platforms which
have a direct 1-1 physical/virtual address mapping.  So how do you
quickly distinguish kernel memory from user memory in the dump
routine?  I'm probably missing something simple..

Thanks,

Drew