Kexec command line length

[Neil Horman]

On Tue, Jan 29, 2008 at 07:17:01PM +0100, Bernhard Walle wrote:
> * Vivek Goyal <vgoyal at redhat.com> [2008-01-29 16:41]:
> > 
> > I think 2048 command line support came much later. I think it came between
> > version 2.05 and 2.06 (But somebody needs to dive into archive to verify).
> > Because command line size could go beyond 256, we introduced cmdline_size
> > parameter in version 2.06 to let a boot loader know.
> 
> Large command line support was added with
> 
>     cca97de1184f6000d22b4106d47687b31cca1fa3
>     v2.6.20-1929-gcca97de
> 
> which means that it was merged 2.6.21.
> 
> > What Bernanrd seems to be talking about a small window where boot protocol
> > was 2.05 but supported command line size was still 2048.
> 
> 2.05 was added with
> 
>     be274eeaf20b4c7155242645d5e2c48b023e609b
>     v2.6.19-1394-gbe274ee
> 
> which means that it was merged 2.6.20. But it got implemented for i386
> only that time, so x86_64 still had the 2.04 version.
> 
> The command line length in the boot protocol was added with
> 
>     8f9aeca7a081d81c4c9862be1e04f15b5ab5461f
>     v2.6.21-1864-g8f9aeca
> 
> which menas that it was merged 2.6.22.
> 
> > if (protocol version > 2.06)
> > 	error user depending on cmdline_size;
> > else if (protocol version > 2.05 && protocol version < 2.06)
> > 	warn on cmdline being more than 256. We don't know for sure.
> > else
> > 	error out if cmdline is greater than 256
> 
> The problem is 2.6.21: It had on x86_64 2.04 boot protocol but
> 2048 command line size. I just verified this via the tarball. :(
> 
> Maybe it could be implemented with versions ...
> 

Ugh.  Ok, on the bright side we only need to worry about this for bzImage files,
since we generate the header for elf files, and we can just force the header we
generate to be version 2.06 and fill it out appropriately.  For bzImage files, I
think in do_bzImage_load we can just check both our arch and the boot protocol
version for the appropriate value.  I'm testing a patch currenly and will post
shortly.

Neil

> 
>         Bernhard

-- 
/****************************************************
 * Neil Horman <nhorman at tuxdriver.com>
 * Software Engineer, Red Hat
 ****************************************************/