Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751484AbdCYQgc (ORCPT ); Sat, 25 Mar 2017 12:36:32 -0400 Received: from forward4o.cmail.yandex.net ([37.9.109.248]:36749 "EHLO forward4o.cmail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751400AbdCYQg3 (ORCPT ); Sat, 25 Mar 2017 12:36:29 -0400 X-Greylist: delayed 5844 seconds by postgrey-1.27 at vger.kernel.org; Sat, 25 Mar 2017 12:35:03 EDT Authentication-Results: smtp3j.mail.yandex.net; dkim=pass header.i=@yandex.ru X-Yandex-Suid-Status: 1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0,1 0 Subject: Re: [PATCH] hibernation: on 32-bit x86, disabled in favor of KASLR To: "Rafael J. Wysocki" , Yu Chen References: <20170323002701.GA90470@beast> <58D3CC61.8080609@yandex.ru> Cc: Kees Cook , "Rafael J. Wysocki" , Pavel Machek , "open list:DOCUMENTATION" , Linux PM , Linux Kernel Mailing List , "H. Peter Anvin" , Thomas Gleixner From: Evgenii Shatokhin Message-ID: <58D6849B.1090106@yandex.ru> Date: Sat, 25 Mar 2017 17:54:19 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2722 Lines: 76 On 23.03.2017 18:30, Rafael J. Wysocki wrote: > On Thu, Mar 23, 2017 at 2:23 PM, Evgenii Shatokhin > wrote: >> On 23.03.2017 03:27, Kees Cook wrote: >>> >>> This is a modified revert of commit 65fe935dd238 ("x86/KASLR, x86/power: >>> Remove x86 hibernation restrictions"), since it appears that 32-bit >>> hibernation still can't support KASLR. 64-bit is fine. Since people have >>> been running with KASLR by default on 32-bit since v4.8, this disables >>> hibernation (with a warning). Booting with "nokaslr" will disable KASLR >>> and enable hibernation. >>> >>> Reported-by: Evgenii Shatokhin >>> Signed-off-by: Kees Cook >>> Cc: stable@vger.kernel.org # v4.8+ >> >> >> The patch does not work as intended on my system, unfortunately. >> >> I tried the mainline kernel v4.11-rc3 and added this patch. With "nokaslr" >> in the kernel command line, the system fails to hibernate. It complains this >> way in the log: >> >> <...> >> kernel: PM: writing image. >> kernel: PM: Cannot find swap device, try swapon -a. >> kernel: PM: Cannot get swap writer >> kernel: PM: Basic memory bitmaps freed >> kernel: Restarting tasks ... done. >> systemd[1]: Time has been changed >> systemd[3948]: Time has been changed >> systemd[14825]: Time has been changed >> systemd[1]: systemd-hibernate.service: main process exited, code=exited, >> status=1/FAILURE >> systemd[1]: Failed to start Hibernate. >> <...> >> >> The swap device (swap file, actually) is available, however: >> ------------- >> # swapon -s >> Filename Type Size Used Priority >> /swap file 6297596 0 -1 >> ------------- >> >> I built the same kernel without this patch then, added "nokaslr" in the >> kernel command line again, and the system hibernates and resumes fine. > > With the patch applied and "nokaslr" in the kernel command line, what > shows up when you do > > $ cat /sys/power/state > > ? freeze standby mem disk However, I think now that the patch itself is OK. I experimented with the patched kernel a bit more and found that hibernate does work when I place "nokaslr" before "resume=xxx resume_offset=xxx" in the kernel command line and does not work when I place "nokaslr" after these options. So I guess there is an issue with parsing of the kernel command line somewhere (dracut scripts? systemd? I do not know). If resume= or resume_offset= were corrupted, that might have been the reason why the system could not find the swap file when hibernating. Anyway, that issue is clearly unrelated to this patch and the patch itself works OK for me. Thanks a lot! Tested-by: Evgenii Shatokhin Regards, Evgenii