linux-kernel - Re: [PATCH v9 0/5] x86/KASLR: Add parameter kaslr_boot

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Date:   Thu, 29 Mar 2018 09:47:04 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     Ingo Molnar <mingo@...nel.org>, Baoquan He <bhe@...hat.com>,
        Chao Fan <fanc.fnst@...fujitsu.com>, <keescook@...omium.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <hpa@...or.com>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <yasu.isimatu@...il.com>,
        <indou.takao@...fujitsu.com>, <lcapitulino@...hat.com>
Subject: Re: [PATCH v9 0/5] x86/KASLR: Add parameter
 kaslr_boot_mem=nn[KMG]@ss[KMG]

Hi Ingo, Kees, Baoquan and Chao

At 03/12/2018 06:57 PM, Ingo Molnar wrote:
[...]
> So there's apparently a mis-design here:
> 
>   - KASLR needs to be done very early on during bootup: - it's not realistic to
>     expect KASLR to be done with a booted up kernel, because pointers to various
>     KASLR-ed objects are already widely spread out in memory.
> 
>   - But for some unfathomable reason the memory hotplug attribute of memory
>     regions is not part of the regular memory map but part of late-init ACPI data
>     structures.
> 
> The right solution would be _not_ to fudge the KASLR location, but to provide the
> memory hotplug information to early code, preferably via the primary memory map.
> KASLR can then make use of it and avoid those regions, just like it avoids other
> memory regions already.
> 
> In addition to that hardware makers (including virtualized hardware) should also
> fix their systems to provide memory hotplug information to early code.
> 

Yes, but before this, can we fix this problem by the following patch 
which has been sent and reviewed by Kees before[1]. its solution is:

   Extend movable_node option to restrict kernel to be randomized in
   immovable nodes by adding a parameter. this parameter sets up
   the boundaries between the home nodes and other nodes.

My reason is here:

   - What we really want to solve is the KASLR breaks *physical Node
     hotplug*, Keep the decompressed kernel in an immovable node is
     enough.

   - AFAICS, there are not too many systems where physical Node hotplug
     actually works in practice, and there mush be one node called *home
     node* which is immovable for storing basic information.

   - the node in modern systems could have double-digit gigabytes memory,
     It can completely satisfy the operation of KASLR.

So, Just restrict kernel to be randomized in the home node, and ignore
other nodes when kernel has the *movable_node* option in the command
line.

Thoughts? may I rebase and resend the patch?

[1] https://lkml.org/lkml/2017/8/3/401

Thanks,

	dou