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SubjectRe: [PATCH] binfmt_elf: fix PIE load with randomization disabled
On Mon, 9 Dec 2013, H.J. Lu wrote:

> >> No, please don't do that. Normally, PIE has zero load address and kernel
> >> can load it anywhere. There are multiple reasons why PIE has non-zero
> >> load address. Saying you need to load a program above 4GB under x86-64,
> >> you can't do that with normal dynamic executable. PIE with non-zero load
> >> address is the only way to do that on x86-64.
> >
> > Hmm, so if it's because of 4G PT_LOAD limit, how about at least adding
>
> Yes.
>
> > randomized offset to the supplied vaddr?
>
> Yes, people who build PIE with non-zero vaddr can use
> randomized vaddr.

I don't follow you here. Do you suggest compile-time randomzation?

> > PT_LOAD being non-zero causing randomization to be turned off seems like
> > quite unexpected behavior to me, with a great potential to cause a lot of
> > confusion.
> >
>
> There should be no difference between dynamic executable and PIE
> with non-zero vaddr when choosing where to load them.

Could you please elaborate why do you think this statement is true?

Thanks,

--
Jiri Kosina
SUSE Labs


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