On Tue, 24 Apr 2001, Gunther Schadow wrote:
> Hi,
>
> trying to use the ipfilter suite with PicoBSD poses problems. Ipfstat
> uses /kernel and /dev/kmem to read the filter statistics and this seems
> not available on PicoBSD. Sure this is because the PicoBSD kernel is
> without any symbols and is gzipped, and is not even in the root file
> system. There are all good reasons why this is so (even if PicoBSD is
> used from a flash ROM instead of a floppy.) But could one not make
> kernel and kmem available anyway using the kernfs virtual file system?
> I could imagine that we need not absolutely strip the kernel from its
> symbol table. We could still gzip the kernel. Given that the kernel
> is loaded into physical memory, could it not be accessible from there
> to the kernfs virtual file system? Or mapped into the mfs root file
> system? How hard would it be?
>
> There are a number of system tools that use kernel and kmem, moving
*********
"a rapidly decreasing number"...
> all of them to something like sps and vm etc. would be a lot of
> repetitive work, there should be a more fundamental solution...
>
> Any thoughts?
> -Gunther
Well, the general trend in FreeBSD kernel development is to phase out all
/dev/kmem access, even when wrapped with libkvm calls, using sysctl(9)
instead. Groping through kernel memory is Bad. Sysctl(9) presents
consistent, safe, and well-defined interface.
The utilities like vm, ns, and others are in fact now much closer to the
standard utilities, because recently most (if not all) kvm_* calls in the
latter have been replaced with sysctl calls.
So, the fundamental solution is to move everything that needs to access
from user-space any internal kernel data structures either to a device or
a sysctl.
Consequently, my POV on this is: if ipfilter uses /dev/kmem, then it
should be fixed.
Andrzej
// ----------------------------------------------------------------
// Andrzej Bialecki <abial@webgiro.com>, Chief System Architect
// WebGiro AB, Sweden (http://www.webgiro.com)
// ----------------------------------------------------------------
// <abial@freebsd.org> FreeBSD developer (http://www.freebsd.org)
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