From: Vivek Goyal <vgoyal@redhat.com>
To: "H. Peter Anvin" <hpa@linux.intel.com>
Cc: Kees Cook <keescook@chromium.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Richard Weinberger <richard.weinberger@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Cong Ding <dinggnu@gmail.com>, Ingo Molnar <mingo@elte.hu>,
Ingo Molnar <mingo@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Mathias Krause <minipli@googlemail.com>,
Michael Davidson <md@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Wei Yongjun <yongjun_wei@trendmicro.com.cn>,
Dave Young <dyoung@redhat.com>,
Kexec Mailing List <kexec@lists.infradead.org>,
Yinghai Lu <yinghai@kernel.org>
Subject: Re: [GIT PULL] x86/kaslr for v3.14
Date: Fri, 7 Feb 2014 11:24:09 -0500 [thread overview]
Message-ID: <20140207162408.GD6967@redhat.com> (raw)
In-Reply-To: <52F503FD.8080607@linux.intel.com>
On Fri, Feb 07, 2014 at 08:04:13AM -0800, H. Peter Anvin wrote:
> On 02/07/2014 06:49 AM, Vivek Goyal wrote:
> >
> > Hi Kees,
> >
> > Dave Young is testing kdump with kaslr enabled. He is facing some issues.
> >
> > One issue he mentioned is that when second kernel boots, it might be
> > placed in an area which is outside the reserved area for second kernel.
> >
> > We reserve a certain memory for second kernel. And modify memory map of
> > second kernel using memmap=exactmap parameter. Looks like kernel placement
> > is happening before memmap=exactmap takes effect. And that seems to be
> > the reason that second kernel can be placed outside the reserved memory.
> >
> > IOW, memmap=exactmap and kaslr don't work together. Is it possible to
> > first let memmap=exactmap take affect and then kaslr does its job. Or it
> > is too late by the time memmap=exactmap is parsed.
> >
> > As a workaround, Dave is currently using "nokaslr" command line parameter
> > for second kernel. He is still facing issues where makedumpfile segment
> > faults. He is looking into it further.
> >
> > I thought I will atleast bring up with issue of memmap=exactmap and kaslr
> > being incompatible.
> >
>
> Yes, because memmap=exactmap gets parsed too late; kaslr assumes that
> the e820 information passed to it is actually correct.
>
> Yet another cause of breakage caused by the decision on the part of
> kdump to rely on command-line options.
[CC kexec mailing list]
Ok, I think this is high time we change kexec-tools to not use
memmap=exactmap and start passing modified memory map in bootparams. I
think only concern with that change was backward compatibility of
kexec-tools with older kernels.
IIUC, only thing which will be impacted by this change is users of
saved_max_pfn which determine the highest accessible pfn in first
kernel. Some calgary IOMMU code seems to be the only user of it now.
So may be we can create a new command line option say --pass-memmap-cmdline
to kexec-tools which forces old behavior and by default we pass memmap
in bootparams.
Or create --do-not-pass-memmap-cmdline and new users will use it. Default
will be old behavior.
Thansk
Vivek
next prev parent reply other threads:[~2014-02-07 16:25 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-20 16:47 [GIT PULL] x86/kaslr for v3.14 H. Peter Anvin
2014-01-20 22:54 ` Linus Torvalds
2014-01-20 23:00 ` H. Peter Anvin
2014-01-20 23:12 ` Linus Torvalds
2014-01-20 23:13 ` H. Peter Anvin
2014-01-21 9:00 ` Peter Zijlstra
2014-01-21 14:20 ` H. Peter Anvin
2014-01-21 14:39 ` Ingo Molnar
2014-01-21 14:51 ` H. Peter Anvin
2014-01-21 14:56 ` Ingo Molnar
2014-01-21 18:37 ` Kees Cook
2014-01-21 10:27 ` Ingo Molnar
2014-01-21 13:55 ` H. Peter Anvin
2014-01-21 14:03 ` Ingo Molnar
2014-01-21 14:05 ` H. Peter Anvin
2014-01-21 14:14 ` Ingo Molnar
2014-01-21 14:17 ` H. Peter Anvin
2014-01-21 5:18 ` Kees Cook
2014-01-23 9:39 ` Pavel Machek
2014-01-26 10:16 ` Richard Weinberger
2014-01-27 5:33 ` H. Peter Anvin
2014-01-27 6:49 ` Richard Weinberger
2014-01-27 6:51 ` H. Peter Anvin
2014-01-27 7:38 ` Ingo Molnar
2014-01-27 7:43 ` Ingo Molnar
2014-01-27 7:59 ` Richard Weinberger
2014-01-30 22:07 ` Vivek Goyal
2014-01-31 16:57 ` Kees Cook
2014-02-07 14:49 ` Vivek Goyal
2014-02-07 16:04 ` H. Peter Anvin
2014-02-07 16:24 ` Vivek Goyal [this message]
2014-02-07 23:16 ` Dave Young
2014-02-07 23:20 ` H. Peter Anvin
2014-02-07 23:28 ` Dave Young
2014-02-07 19:07 ` H. Peter Anvin
2014-02-07 19:44 ` Kees Cook
2014-01-27 6:52 ` H. Peter Anvin
2014-01-27 7:34 ` Richard Weinberger
2014-01-27 17:05 ` Kees Cook
2014-01-27 17:20 ` Richard Weinberger
2014-01-27 17:24 ` Kees Cook
2014-01-28 6:28 ` Ingo Molnar
2014-01-28 8:25 ` Richard Weinberger
2014-01-28 15:55 ` H. Peter Anvin
2014-01-28 16:25 ` Richard Weinberger
2014-01-28 16:30 ` H. Peter Anvin
2014-01-28 16:51 ` Linus Torvalds
2014-01-28 17:05 ` Ingo Molnar
2014-01-28 17:12 ` Linus Torvalds
2014-01-28 17:24 ` Richard Weinberger
2014-01-28 17:35 ` Linus Torvalds
2014-01-28 17:52 ` Richard Weinberger
2014-01-28 17:56 ` Linus Torvalds
2014-01-28 18:54 ` Richard Weinberger
2014-01-28 19:48 ` Ingo Molnar
2014-01-28 20:07 ` Linus Torvalds
2014-01-28 20:15 ` Borislav Petkov
2014-01-28 20:25 ` Linus Torvalds
2014-01-28 20:28 ` Richard Weinberger
2014-01-28 20:38 ` H. Peter Anvin
2014-01-29 8:25 ` Ingo Molnar
2014-01-29 10:40 ` Borislav Petkov
2014-01-28 20:49 ` Borislav Petkov
2014-01-28 23:37 ` Borislav Petkov
2014-01-28 21:08 ` Dave Jones
2014-01-29 6:36 ` Mike Galbraith
2014-01-29 8:11 ` Ingo Molnar
2014-01-29 8:27 ` Mathias Krause
2014-01-30 9:23 ` Ingo Molnar
2014-01-30 18:15 ` Linus Torvalds
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