Eric W. Biederman wrote:
>> Gujin seems to have a near-zero user community, so if they have to rev
>> their code it wouldn't be a big deal (the author keeps trying to push
>> some crack-smoking "Gujin native" patches into the kernel, too),
>> breaking ELILO would hurt anyone using Intel Macs.
>>
>
> I'm thinking we just make the code start.
> startup_32:
> movl %cs, %eax
> testl $3, %eax
> jnz 1f
>
I'm not really happy about using this as a way to distinguish paravirt
from non-paravirt in general. At some point we're going to be running
paravirt kernels in ring0 within a VT/SVM container - but they'll still
be completely paravirtualized kernels.
I think a better approach is to just do it purely based on the boot
params platform field. Ie, something along the lines of:
if (boot_params.version < new_enough)
goto native_boot;
else {
for (int i = 0; i < nplatforms; i++)
if (boot_params.platform == platforms[i].id)
goto *platforms[i].startup
panic();
}
> But that won't work if we want to support relocatability.
> Because we can't load a gdt if we don't know where we are.
>
> To find out where we are we need %ss and %ds, at which point
> we might as well assume we have %es to.
>
Yes, we won't make it far without ss and ds, and while we could avoid
string instructions, you'd have to be a pretty short-sighted bootloader
author to set ss and ds without also setting es.
> So be it then. The next rev of the boot protocol gets to be partially
> incompatible, and we just assume that %cs, %ds, %es, %ss meet our
> basic requirements. I'm pretty certain from what I saw only Gujin
> is going to suffer :(
>
I missed what Gujin does wrong here?
J
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