{B,C}LFS State of Things (was Re: SVN-20070706: ...)

Bryan Kadzban bryan at kadzban.is-a-geek.net
Sat Jul 21 05:49:40 PDT 2007


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Luca wrote:
> Grub-0.9x is old Grub legacy and no-more maintained.

According to their site, it is maintained, just no new features are
being added.  (Though I'm not sure what sense of the word "maintained"
they're using then... but whatever.  Presumably it just means they'd
still fix bugs if there are any.)

> Grub-1.x is new one [...] I tried it only x86 but there was a similar
> discussion in Debian for x86-64 arch support.

Here's where I'm a bit confused.  Why should grub need to switch the
processor into long mode?  For one, the kernel already does that --
IIRC, Linux expects to start in real mode.  (I'm not sure if there are
any provisions to start in protected mode, for grub2, or not.  I'm
pretty sure grub2 switches into protected mode, so if that's true and it
works, then there probably is some protocol to make it work.)

But for two, isn't 4G of virtual address space way more than enough for
grub to do whatever it needs to do?  I mean, all it has to do is load up
a file or two off the host FS and jump to an address inside the memory
image of one of the files.  That's not nearly complicated enough to
require more than 4G of memory.

In short, I'm not sure the bootloader needs to be 64-bit.

Now I can see making the grub shell (and other programs on the host) be
64-bit.  Even if that's way overkill IMO too, it would be necessary if
you're trying to do a pure64 system (because you won't have the 32-bit
ld.so).  Is that all that's being discussed when people talk about
"x86-64 arch support"?

(Not that a pure64 system is all that useful if you need -- or want --
to use Flash, but that's a different issue.)

In any case, I had planned on doing some grub2 testing today, so
hopefully I'll be able to get it to work.  I really do need to make and
test a bootable floppy first, though.  :-)
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