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

H. Peter Anvin
2011-06-01T15:45:31Z

On 05/31/2011 11:18 PM, Ingo Molnar wrote:
>>
>> 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)

But it would have depended on the target hardware! That's the problem.

>
> 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.
>

Well, yes; and I don't think the randomization. is a signifiant problem.

> 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?

No, because I don't think Grub is fixed in any of its flavors.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.