linux-kernel - Re: [PATCH v2 04/15] x86, kaslr: get kaslr

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Message-ID: <CAE9FiQVt8Bi==r7pPhSOcSTmmpkjZ4c7O6iphbzFkgbugzKbqw@mail.gmail.com>
Date:	Fri, 6 Mar 2015 11:50:54 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Borislav Petkov <bp@...e.de>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Matt Fleming <matt.fleming@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
	Baoquan He <bhe@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v2 04/15] x86, kaslr: get kaslr_enabled back correctly

On Fri, Mar 6, 2015 at 5:33 AM, Borislav Petkov <bp@...e.de> wrote:

>
> "However, the setup_data linked list and thus the element which contains
> kaslr_enabled is chained together using physical addresses. At the
> time when we access it in the kernel proper, we're already running
> with paging enabled and therefore must access it through its virtual
> address."
>
> That's it, now how hard was to explain it that way?

No, I don't think your change log is right.

Actually the old code is using address as value.

if the old code would be like:

kaslr_enabled = (bool)(*(unsigned char *)(pa_data + sizeof(struct setup_data)));

then your change log would be good, but the old code is

kaslr_enabled = (bool)(pa_data + sizeof(struct setup_data));
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