Re: /proc/config idea

[Brian Gerst <bgerst@didntduck.org>]

Jeremy Jackson wrote:
> 
> Ian Soboroff wrote:
> 
> > [sorry this doesn't have proper References: headers, i read the list
> > off the hypermail archive.]
> >
> > there was some discussion of whether the kernel should emit a
> > /proc/config or some such for purposes of bug reporting, but that
> > seems to be a lot of bloat.
> >
> > instead, why not try to point to a canonical location for a config
> > copy (we already basically do this with ksymoops and System.map), and
> > instead have a /proc/config-hash which emits a (precomputed) MD5 hash
> > of the .config file it was compiled with?
> >
> > this way, you could check possible configs (Debian for example likes
> > to stash a copy in /boot, like System.map) and also know if they were
> 
> Yes, I like this.  I do this manually, it allows reproducability, and
> incremental
> modifications, tracing how that kernel on that problem system was made...
> 
> I think the ultimate would be to put all of .config (gzipped?) in a new ELF
> section without the Loadable attribute...  I wish System.map was the same.
> The you're guaranteed you know how a kernel on disk was configured.
> 
> To correlate a running kernel to one on disk (vmlinuz) you have LILO...
> it appends an environment variable to the kernel command line with
> the name of the file it booted.  This is not infallable, since LILO maps
> disk sectors, only using the filesystem at map install time.
> 
> Permaps an md5sum of the .text ELF section would conclusively
> link the in-core kernel with an on-disk vmlinuz?  Shouldn't be hard
> to do with objcopy and /proc/kmem?

Except that the bootable kernel (bzImage, at least on x86) is not in ELF
format.  It is a compressed binary image.  The vmlinux file is ELF, but
you run into the same issue of correlating the file with the running
kernel.

--

				Brian Gerst