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

[Alex Ionescu]

Hartmut Birr wrote:

>   Royce Mitchell III schrieb:
>
> >   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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> >  Ros-dev(a)reactos.com
> >  http://reactos.com:8080/mailman/listinfo/ros-dev
> >  
>  Hi,
>
>  I think your patch will never work. There are used some offsets which 
>  based on the '/3GB' switch and other ones are hard coded by 
>  KERNEL_BASE. IMHO, the boot code should not search for the '/3GB' 
>  option. The kernel base address must be send by freeldr.  
I agree...

>   The boot code must not contain any KERNEL_BASE value.
> I've add your 
>  patch to my source tree. On the smp machine, ros reboots in the very 
>  early boot phase. It is before the call to _main.
>
>  - Hartmut 
I think freeldr shoudl be modified to PE load the boot drivers and 
ntoskrnl, instead of just memory dumping. This should remove most of the 
bss hacks which use kernel_base, and the rest should use whatever 
freeldr pushes on the loader_block. For now, we were simply testing some 
things, and Royce's patch still helps a lot.

>  
>  
Best regards,
Alex Ionescu