Re: Does anything ever enter through startup_64 in head_64.S?

[David Howells]

Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> wrote:

> > Does anything ever enter the kernel through startup_64 in head_64.S?[*]  Do
> > all 64-bit mode entries always enter through one of the EFI entry points?
>  
> Which head_64.S? There are two ;-)
> 
> Assuming you mean startup_64 in boot/compressed/head_64.S, then the
> answer is "yes". 64-bit BIOS boot loaders will jump there.

Sorry, yes, that one.

> I'm fairly sure it's possible to boot that way on EFI too, you just
> lose some of the newer functionality that is dependent on the EFI boot
> stub. But I don't remember the last time I tried it.
> 
> In general, we've always tried to maintain backwards compat, but you
> don't get the new features without switching to the EFI entry points.
> 
> Whether or not any distros are still using the old 0x200 entry point
> for EFI is a good question, though.

I think I have to assume that there might be.

David