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Re: [Xen-devel] x86: PIE support and option to extend KASLR randomization

On Tue, Aug 15, 2017 at 07:20:38AM -0700, Thomas Garnier wrote:
> On Tue, Aug 15, 2017 at 12:56 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:

> > Have you considered a kernel with -mcmodel=small (or medium) instead of 
> > -fpie
> > -mcmodel=large? We can pick a random 2GB window in the (non-kernel) 
> > canonical
> > x86-64 address space to randomize the location of kernel text. The location 
> > of
> > modules can be further randomized within that 2GB window.
> -model=small/medium assume you are on the low 32-bit. It generates
> instructions where the virtual addresses have the high 32-bit to be
> zero.

That's a compiler fail, right? Because the SDM states that for "CALL
rel32" the 32bit displacement is sign extended on x86_64.

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