Re: [PATCH 12/12] i386 boot: Add an ELF header to bzImage

H. Peter Anvin
2006-10-04T15:19:11Z

Eric W. Biederman wrote:
>
>> The entrypoint is going to be a major headache, since the standard kernel is
>> entered in real mode, whereas an ELF file will typically be entered in protected
>> mode, quite possibly using the C calling convention to pass the command line as
>> (argc, argv). God only knows how they're going to deal with an initrd.
>>
>> It may very well be that the ELF magic number has to be obfuscated.
>
> The entry point that is exported is the kernels protected mode entry point
> that is used after the real mode code has been run. This is to allow
> bootloaders like kexec where running the real-mode code is insane or
> impossible to be used.
>
> The calling conventions though are not changed, this is just formalizing
> something that various groups have been doing for years. Since it is
> all in the bzImage we still only have a single file format to support,
> so any bootloader that can load a standard bzImage and run the kernels
> real mode code should still do it that way but. If you can't the
> rest of the information is available.
>

Well, it doesn't help if what you end up with for some bootloader is a
nonfunctioning kernel.

-hpa