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    SubjectRe: [RFC] ELF Relocatable x86 and x86_64 bzImages
    On 8/2/06, Eric W. Biederman <> wrote:
    > "Magnus Damm" <> writes:
    > > Eric, could you please list the advantages of your run-time relocation
    > > code over my incomplete relocate-in-userspace prototype posted to
    > > fastboot a few weeks ago?
    > If you watch an architecture evolve one thing you will notice is that
    > the kinds of relocations keep growing. An ever growing list of things
    > to for the bootloader to do is a pain. Especially when bootloaders
    > generally need to be as simple and as fixed as possible because bootloaders
    > are not something you generally want to update.

    I agree that updating bootloaders is something you want to avoid. I'm
    not however sure that I would call kexec-tools a bootloader...

    > Beyond that if you look at head.S the code to process the relocations
    > (after I have finished post processing them at build time) is 9 instructions.
    > Which is absolutely trivial, at least for now.

    Yeah, but the 33 patches are touching more than 9 instructions. =)

    > By keeping the bzImage processing the relocations we have kept the
    > bootloader/kernel interface simple.

    Agreed. I think your patch makes sense.

    > > One thing I know for sure is that your implementation supports bzImage
    > > while my only supports relocation of vmlinux files. Are there any
    > > other uses for relocatable bzImage except kdump?
    > I can't think of any volume users. A hypervisor that would actually report
    > the real physical addresses would be a candidate. It's a general purpose
    > facility so if it is interesting users will show up. Static
    > relocation has already found another use on x86_64.
    > There are definitely users of an ELF bzImage beyond the kdump case.
    > Anything that doesn't have a traditional 16bit BIOS on it. LinuxBIOS,
    > and Xen, and some others.
    > Not having to keep track of anything but your bzImage to boot is also
    > a serious advantage. It's the one binary to rule them all. :)

    One binary to rule them all... If that is true, is there any simple
    way then to extract vmlinux from the bzImage?


    / magnus
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