Re: [PATCH] build 32-bit Linux loader as `linux', rename legacy loader to `linux16'

[Robert Millan <rmh@aybabtu.com>]

On Tue, Mar 31, 2009 at 01:06:25AM +0900, Yoshinori K. Okuji wrote:
> I don't know any reliable way. Some candidates:
> 
> - The ramdisk max value. On 32-bit, initrd may not be loaded onto over 2GB. 
> This is hard to change in Linux, so we can expect that this will not change. 
> On 64-bit, currently, the max is 4GB-1. It is likely that this value will not 
> change, but who knows.

This could be possible, but doesn't sound very reliable.

> - The long mode panic message. This exists only for x86_64. But the message 
> might change some day.

Actually, it seems to have changed recently.  Doesn't seem too reliable
either.

> - Otherwise, we could probe some opcodes and see if 64-bit opcodes are used. 
> This would be error-prone.

Same here :-(

However, this is not as large a problem as it seems.  Most users install GRUB
to disk through their distribution, which already provides the right Linux
builds in /boot.  It could be a problem with removable media, but:

  - It's easy to solve this when you have a "cpuid" command and know what
    each of the files you put in the CD is.  This also allows for a more
    user-friendly error message than a Linux panic.

  - GRUB is rarely used there anyway (most GNU/Linux distros opt for
    isolinux)

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."