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From: Baoquan He <bhe@redhat.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Kees Cook <keescook@chromium.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
	X86 ML <x86@kernel.org>, david <david@fromorbit.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	dyoung@redhat.com, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] x86: fix kaslr and memmap collision
Date: Tue, 3 Jan 2017 16:31:37 +0800	[thread overview]
Message-ID: <20170103083137.GA15788@x1> (raw)
In-Reply-To: <CAPcyv4i+2NxdTc1xzVL+KQs8hLfUhbpGX3zstO_b=RY3hCy64w@mail.gmail.com>

Hi Dan,

On 11/22/16 at 09:26am, Dan Williams wrote:
> [ replying for Dave since he's offline today and tomorrow ]
> 
> On Tue, Nov 22, 2016 at 12:47 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Dave Jiang <dave.jiang@intel.com> wrote:
> >
> >> CONFIG_RANDOMIZE_BASE relocates the kernel to a random base address.
> >> However it does not take into account the memmap= parameter passed in from
> >> the kernel commandline.
> >
> > memmap= parameters are often used as a list.
> >
> >> [...] This results in the kernel sometimes being put in the middle of the user
> >> memmap. [...]
> >
> > What does this mean? If memmap= is used to re-define the memory map then the
> > kernel getting in the middle of a RAM area is what we want, isn't it? What we
> > don't want is for the kernel to get into reserved areas, right?
> 
> Right, this is about teaching kaslr to not land the kernel in newly
> defined reserved regions that were not marked reserved in the initial
> e820 map from platform firmware.

If only tell kaslr to not land kernel in newly defined reserved regions,
memory added by "memmap=nn[KMG]@ss[KMG]" should not be avoided since
it's usable memory. Kernel randomized into this region is also what we
want. Not sure if I understand it right.

Thanks
Baoquan
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WARNING: multiple messages have this Message-ID (diff)
From: Baoquan He <bhe@redhat.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>, Dave Jiang <dave.jiang@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	X86 ML <x86@kernel.org>, david <david@fromorbit.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
	Kees Cook <keescook@chromium.org>,
	dyoung@redhat.com
Subject: Re: [PATCH] x86: fix kaslr and memmap collision
Date: Tue, 3 Jan 2017 16:31:37 +0800	[thread overview]
Message-ID: <20170103083137.GA15788@x1> (raw)
In-Reply-To: <CAPcyv4i+2NxdTc1xzVL+KQs8hLfUhbpGX3zstO_b=RY3hCy64w@mail.gmail.com>

Hi Dan,

On 11/22/16 at 09:26am, Dan Williams wrote:
> [ replying for Dave since he's offline today and tomorrow ]
> 
> On Tue, Nov 22, 2016 at 12:47 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Dave Jiang <dave.jiang@intel.com> wrote:
> >
> >> CONFIG_RANDOMIZE_BASE relocates the kernel to a random base address.
> >> However it does not take into account the memmap= parameter passed in from
> >> the kernel commandline.
> >
> > memmap= parameters are often used as a list.
> >
> >> [...] This results in the kernel sometimes being put in the middle of the user
> >> memmap. [...]
> >
> > What does this mean? If memmap= is used to re-define the memory map then the
> > kernel getting in the middle of a RAM area is what we want, isn't it? What we
> > don't want is for the kernel to get into reserved areas, right?
> 
> Right, this is about teaching kaslr to not land the kernel in newly
> defined reserved regions that were not marked reserved in the initial
> e820 map from platform firmware.

If only tell kaslr to not land kernel in newly defined reserved regions,
memory added by "memmap=nn[KMG]@ss[KMG]" should not be avoided since
it's usable memory. Kernel randomized into this region is also what we
want. Not sure if I understand it right.

Thanks
Baoquan

  parent reply	other threads:[~2017-01-03  8:31 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-22  0:22 [PATCH] x86: fix kaslr and memmap collision Dave Jiang
2016-11-22  0:22 ` Dave Jiang
2016-11-22  8:47 ` Ingo Molnar
2016-11-22  8:47   ` Ingo Molnar
2016-11-22 17:26   ` Dan Williams
2016-11-22 17:26     ` Dan Williams
2016-11-22 18:54     ` Kees Cook
2016-11-22 18:54       ` Kees Cook
2016-11-22 19:01       ` Dan Williams
2016-11-22 19:01         ` Dan Williams
2016-11-22 22:37         ` Kees Cook
2016-11-22 22:37           ` Kees Cook
2016-11-24  0:04         ` Dave Chinner
2016-11-24  0:04           ` Dave Chinner
2016-11-24 19:30           ` Dan Williams
2016-11-24 19:30             ` Dan Williams
2017-01-03  8:31     ` Baoquan He [this message]
2017-01-03  8:31       ` Baoquan He
2017-01-03 16:27       ` Ross Zwisler
2017-01-03 16:27         ` Ross Zwisler
2017-01-03 18:24       ` Dan Williams
2017-01-03 18:24         ` Dan Williams
2017-01-03 20:15         ` Dave Jiang
2017-01-03 20:15           ` Dave Jiang
2017-01-04  1:57           ` Baoquan He
2017-01-04  1:57             ` Baoquan He

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