Re: [PATCH] i386 boot loader IDs

["H. Peter Anvin" <hpa@zytor.com>]

Eric W. Biederman wrote:
> 
> I suspect /sbin/kexec could use one.  But I don't have the faintest
> what you could do with the information after the kernel came up.
> 

Sounds incorrect, unless you're generating the zeropage information.

> I don't think enhancing the bootloader numeric parameter is the
> right way to go.  Currently the value is a single byte with the low
> nibble reserved for version number information.  With the
> values already assigned we have 7 left.  
> 
> If we assign a new value each for the bootloaders I know of that don't
> yet have values assigned: pxelinux, isolinux, filo, /sbin/kexec,
> redboot the pool of numbers is nearly exhausted.  With the addition of
> bootloaders I can't recall or have not been written yet we will
> quickly exhaust the pool of numbers.

pxelinux, isolinux and extlinux are syslinux derivatives (0x32, 0x33 and 
0x34 respectively.)  filo and redboot probably could use them, though.

> Even if using this mechanism is needed for supporting existing
> bootloaders I suggest it be deprecated in favor of a kernel command
> line option.  A command line option would be easier to maintain
> being string based.  It would be portable to architectures besides
> x86.  And it requires no additional code to implement, as you
> can already read /proc/cmdline.

Unfortunately the command line is very squeezed.  With the newer 
protocol we can probably support longer command lines, though.

It's a significant boot loader change, though.  In the short term it's 
definitely desirable to be able to read it.

	-hpa