From: Dan Williams <dan.j.williams@intel.com>
To: Baoquan He <bhe@redhat.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 10:24:46 -0800 [thread overview]
Message-ID: <CAPcyv4jTsUD25OGW2iwF1V7i2CTF_-+e4CsTw8NQXXVE8QhsYw@mail.gmail.com> (raw)
In-Reply-To: <20170103083137.GA15788@x1>
On Tue, Jan 3, 2017 at 12:31 AM, Baoquan He <bhe@redhat.com> wrote:
> 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.
You're right, this is supposed to be for memmap=nn!ss cases which
defines reserved persistent memory ranges, not memmap=nn@ss which
defines usable memory.
We need to fix mem_avoid_memmap() to only skip memmap= statements that
specify reserved memory.
next prev parent reply other threads:[~2017-01-03 18:24 UTC|newest]
Thread overview: 13+ 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 8:47 ` Ingo Molnar
2016-11-22 17:26 ` Dan Williams
2016-11-22 18:54 ` Kees Cook
2016-11-22 19:01 ` Dan Williams
2016-11-22 22:37 ` Kees Cook
2016-11-24 0:04 ` Dave Chinner
2016-11-24 19:30 ` Dan Williams
2017-01-03 8:31 ` Baoquan He
2017-01-03 16:27 ` Ross Zwisler
2017-01-03 18:24 ` Dan Williams [this message]
2017-01-03 20:15 ` Dave Jiang
2017-01-04 1:57 ` Baoquan He
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