Re: [RFC][PATCH] Randomize kernel base address on boot

Ingo Molnar
2011-06-01T06:19:08Z

* H. Peter Anvin <hpa@zytor.com> wrote:

> On 05/31/2011 01:27 PM, Ingo Molnar wrote:
> >
> >> Other than that, Ingo's idea at least have the merit that it would
> >> break only older bootloaders doing things wrong.
> >
> > I'm wondering, why would it break older bootloaders? It's just a
> > slightly larger than usual kernel image, nothing is visible to the
> > bootloader.
> >
>
> Older boot loaders did not know how big the kernel image was,
> therefore had no way to avoid memory space collision. That is
> fixed in boot protocol 2.10.

But i loaded really large kernel images way back 10 years ago on
various systems and never had any problems until the default
allyesconfig hit a ~40 MB kernel image size limit ;-)

(which limit was in the kernel, not in the bootloader)

So yes, a large kernel image "can" be an issue with old bootloaders
in some situations on weird machines but we don't really "break" them
via randomization, they were broken and fragile in some situations to
begin with.

It's fixed in any distro that cares and which would use our (not even
released) kernel that might one day have randomization.

Is that a fair summary of the bootloader situation?

Thanks,

Ingo