[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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>>
> 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