Hello,
I'm trying to understand the boot process of a 64-bit kernel but i'm
having some trouble.
The comments in
http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/i86pc/dboot/dboot_grub.s
state that
"The multiboot header has to be at the start of the file
The 32 bit kernel is ELF32, so the MB header is mostly ignored.
The 64 bit kernel is ELF64, so we get grub to load the entire
ELF file into memory and trick it into jumping into this code.
The trick is done by a binary utility run after unix is linked,
that rewrites the mb_header."
So, in order to load a 64 bit kernel, grub first loads the 32-bit dboot
program. But, from what i understand, dboot is a part of the elf64
kernel. How does grub starts loading the dboot program? The above
comments say that grub loads the whole 64-bit kernel. How does this
happen since grub cannot load elf64 images?
The comments also mention a trick which involves extract64() from
http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/tools/elfextract/elfextract.c.
However i am totally confused about the function of this procedure and
what exactly it rewrites.
Please excuse me for writing so much. I hope you can help me.
Thank you in advance for any replies.
Regards,
Constantine
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