linux-kernel - Re: [Resend][PATCH] x86/power/64: Always create temporary identity mapping correctly

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Date:	Thu, 11 Aug 2016 02:35:48 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Jiri Kosina <jikos@...nel.org>,
	Thomas Garnier <thgarnie@...gle.com>
Cc:	Borislav Petkov <bp@...e.de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Kees Cook <keescook@...omium.org>, Pavel Machek <pavel@....cz>,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [Resend][PATCH] x86/power/64: Always create temporary identity
 mapping correctly

On Wed, Aug 10, 2016 at 11:59 PM, Jiri Kosina <jikos@...nel.org> wrote:
> On Wed, 10 Aug 2016, Rafael J. Wysocki wrote:
>
>> So I used your .config to generate one for my test machine and with
>> that I can reproduce.
>
> Was that the config I've sent, or did Boris provide one as well? Which one
> are you able to reproduce with please?

It's the Boris' one.

Moreover, I have found the options that make the difference: unsetting
CONFIG_PROVE_LOCKING and CONFIG_DEBUG_LOCK_ALLOC (which also will
unset CONFIG_LOCKDEP AFAICS) in it makes hibernation work again with
CONFIG_RANDOMIZE_MEMORY set and with the $subject patch applied.

Unbelievable, but that's what I'm seeing.

Now, that leads to a few questions:

- How does lockdep change the picture so it matters for hibernation?
- Why is hibernation the only piece that's affected?
- Why is RANDOMIZE_MEMORY necessary to make this breakage show up?

Thomas, any ideas?

Thanks,
Rafael