Linux Virtualization - May 2018 - [PATCH v3 09/27] x86/acpi: Adapt assembly for PIE support

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?
> 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.
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: Digital signature
URL:
<http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20180524/a32427da/attachment.sig>

On Thu, May 24, 2018 at 4:03 AM Pavel Machek <pavel at ucw.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.

> > 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.


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



-- 
Thomas

On Thu 2018-05-24 09:35:42, Thomas Garnier wrote:
> On Thu, May 24, 2018 at 4:03 AM Pavel Machek <pavel at ucw.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,
							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
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: Digital signature
URL:
<http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20180525/959806e5/attachment-0001.sig>