[ros-dev] multiboot.S patch in need of review, please

[Royce Mitchell III]

I was in a strange mood and decided to try to implement something Alex 
wanted.

I've done the leg-work on this, but need someone familiar with boot-up 
and particularly smp to review this patch. I do not have access to smp, 
and do not wish to break it.

This patch implements the /3G switch from within multiboot.S, which is 
necessary in order to configure the page tables correctly.

I noticed some code in _main() that was processing a 3G switch on the 
command-line, and I can't understand how it could possibly work because 
it's not readjusting the page tables, nor does it transition to the 
0xC0000000 address space that I can see, so I don't think that code 
actually works. If it does, I'm glad to be proved wrong.

The patch I've written makes an assumption that lowmem is available when 
application processors execute the code. I can't seem to figure out how 
or where the application processor(s) actually get told to start 
executing, so I don't know if this assumption is true. However, if it's 
not true, if someone could point me to the code that inits the 
application processors, I can configure them to pass the needed info via 
%ebp or something.

Finally, I haven't actually tried booting this code. I wanted someone to 
review it first for obvious blunders, or to tell me, if necessary, that 
I've wasted my time ;)    If I'm on the right track then, when I'm 
feeling motivated enough again, I will actually try booting it.
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