linux-kernel - Re: [PATCH 1/8] x86, kaslr: get kaslr

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Message-ID: <20150301202938.GD7748@pd.tnic>
Date:	Sun, 1 Mar 2015 21:29:38 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>, Jiri Kosina <jkosina@...e.cz>,
	Kees Cook <keescook@...omium.org>,
	Matt Fleming <matt.fleming@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	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>
Subject: Re: [PATCH 1/8] x86, kaslr: get kaslr_enabled back correctly

On Sun, Mar 01, 2015 at 12:24:08PM -0800, Yinghai Lu wrote:
> static allocation in misc.c can not be used to kernel/head_64.S stage safely.

Correct. One possibility that works is sticking it right below
LOAD_PHYSICAL_ADDR:

+static void add_kaslr_setup_data(struct boot_params *params,
+				 u8 *output, __u8 enabled)
 {
+	/*
+	 * Stick it right under LOAD_PHYSICAL_ADDR
+	 */
+	ksd = (struct setup_data *)(output - 2 * sizeof(struct setup_data));

output is LOAD_PHYSICAL_ADDR AFAICT and is the minimum kASLR considers
so right below it should work:

https://lkml.kernel.org/r/20150228105049.GA11038@pd.tnic

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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