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Date: Fri, 25 May 2018 10:00:04 -0700
From: Thomas Garnier <thgarnie@...gle.com>
To: Pavel Machek <pavel@....cz>
Cc: Herbert Xu <herbert@...dor.apana.org.au>, "David S . Miller" <davem@...emloft.net>, 
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Subject: Re: [PATCH v3 09/27] x86/acpi: Adapt assembly for PIE support

On Fri, May 25, 2018 at 2:14 AM Pavel Machek <pavel@....cz> wrote:

> On Thu 2018-05-24 09:35:42, Thomas Garnier wrote:
> > On Thu, May 24, 2018 at 4:03 AM Pavel Machek <pavel@....cz> wrote:
> >
> > > On Wed 2018-05-23 12:54:03, Thomas Garnier wrote:
> > > > Change the assembly code to use only relative references of symbols
for
> > the
> > > > kernel to be PIE compatible.
> > > >
> > > > Position Independent Executable (PIE) support will allow to
extended the
> > > > KASLR randomization range below the -2G memory limit.
> >
> > > What testing did this get?
> >
> > Tested boot, hibernation and performance on qemu and dedicated machine.

> Well, this is suspend, not hibernation code.

> So "sudo pm-suspend" or "echo mem > /sys/power/state" would be good
> way to test this.

Thanks, it worked. I added this to the testsuite I use for KASLR.


> Thanks,
>                                                          Pavel

> > > > diff --git a/arch/x86/kernel/acpi/wakeup_64.S
> > b/arch/x86/kernel/acpi/wakeup_64.S
> > > > index 50b8ed0317a3..472659c0f811 100644
> > > > --- a/arch/x86/kernel/acpi/wakeup_64.S
> > > > +++ b/arch/x86/kernel/acpi/wakeup_64.S
> > > > @@ -14,7 +14,7 @@
> > > >        * Hooray, we are in Long 64-bit mode (but still running in
low
> > memory)
> > > >        */
> > > >  ENTRY(wakeup_long64)
> > > > -     movq    saved_magic, %rax
> > > > +     movq    saved_magic(%rip), %rax
> > > >       movq    $0x123456789abcdef0, %rdx
> > > >       cmpq    %rdx, %rax
> > > >       jne     bogus_64_magic
> >
> > > Because, as comment says, this is rather tricky code.
> >
> > I agree, I think maintainers feedback is very important for this
patchset.


> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html



-- 
Thomas

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