linux-kernel - Re: [PATCH] x86/power/64: Do not refer to __PAGE

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Message-ID: <20160805103713.GA8106@amd>
Date:	Fri, 5 Aug 2016 12:37:13 +0200
From:	Pavel Machek <pavel@...x.de>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Thomas Garnier <thgarnie@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Kees Cook <keescook@...omium.org>,
	Yinghai Lu <yinghai@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] x86/power/64: Do not refer to __PAGE_OFFSET from
 assembly code

On Wed 2016-08-03 01:19:26, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> When CONFIG_RANDOMIZE_MEMORY is set on x86-64, __PAGE_OFFSET becomes
> a variable and using it as a symbol in the image memory restoration
> assembly code under core_restore_code is not correct any more.

On a related note... we should really have page_offset variable in
such case, and use that -- having __FOO_BAR not being a constant is
ugly/confusing/dangerous.

> To avoid that problem, modify set_up_temporary_mappings() to compute
> the physical address of the temporary page tables and store it in
> temp_level4_pgt, so that the value of that variable is ready to be
> written into CR3.  Then, the assembly code doesn't have to worry
> about converting that value into a physical address and things work
> regardless of whether or not CONFIG_RANDOMIZE_MEMORY is set.
> 
> Reported-and-tested-by: Thomas Garnier <thgarnie@...gle.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Acked-by: Pavel Machek <pavel@....cz>

Is similar patch needed for i386?

Best regards,
								Pavel


-- 
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