Re: multiboot2: variable data size

["bibo,mao" <bibo.mao@intel.com>]

Johan Rydberg wrote:
> "bibo,mao" <bibo.mao@intel.com> writes:
> 
>  > 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.
> 
> My opinion is that bzImages should be avoided on EFI platforms, or the
> decompress-code in Linux has to be rewritten. 
bzImage supporting mainly is to be compliant with legacy bios, user need
not care for detailed bootloader procedure, user always installs linux
kernel with command "make install" which will generate bzImage format.
Now on some platform there are two kinds of bios: efi bios and legacy
bios, if bzImage is supported then one kernel image can run two kinds
of bios.
> 
> It took me a good couple of hours of debugging to find out that Linux
> simply ignores the memory layout and assumes that low memory is free
> to use as it likes.
current decompress-code with bzImage possibly touches low memory at
0x1000--0x9000, or decompress-code needs to be rewritten, or put mode
switching code below 0x1000.

thanks
bibo,mao
> 
> ~j
> 
> 
> 
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