Propose for Several Dump types

Jun Su csujun at
Tue Dec 21 18:09:44 PST 2004

On Fri, 17 Dec 2004 11:21:39 -0500 (EST), Andrew Gallatin
<gallatin at> wrote:
> 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..
My current draft idea is to traverse the vm_map structure. Then I can
find out the vm_object list. Then dump those memory regions. I don't
understand VM much. In this area, I need input from our VM guru...

> Thanks,
> Drew
-- Jun Su

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