Re: multiboot2: variable data size

[Yoshinori K. Okuji]

On Tuesday 28 November 2006 13:46, bibo,mao wrote:
> yes, x84_64EFI starts with 64-bit long mode and page enabled(virtual
> address equals physical address) if it is x86_64 efi bios, it is defined in
> section 2.3.4 of UEFI Specification Version 2.0.
>
> If kernel image is bzImage, x64 efi bootloader need switch to 32 bit
> protect mode(or real mode) from 64 bit long mode, and if kernel image is
> gzipped/plain format, efi bootloader can directly jump to 64-bit kernel
> entry address without mode switch.

Thanks for your detailed information. So does it mean that GRUB needs to 
provide a PE32+ application to EFI, if it is on x86_64? Or does it understand 
PE32? More information is welcome.

BTW, in the current implementation, GRUB skips real mode setup code in Linux 
and directly jumps to a protected mode entry on EFI. Can we use the same 
trick with bzImage on x86_64? Mode switching is not difficult, but if we can 
omit it, that would be much easier to implement.

Okuji