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Date: Fri, 8 Dec 2023 12:41:31 -0600
From: "Madhavan T. Venkataraman" <>
To: Peter Zijlstra <>
Cc: Mickaël Salaün <>,
 Borislav Petkov <>, Dave Hansen <>,
 "H . Peter Anvin" <>, Ingo Molnar <>,
 Kees Cook <>, Paolo Bonzini <>,
 Sean Christopherson <>, Thomas Gleixner
 <>, Vitaly Kuznetsov <>,
 Wanpeng Li <>, Alexander Graf <>,
 Chao Peng <>,
 "Edgecombe, Rick P" <>,
 Forrest Yuan Yu <>, James Gowans <>,
 James Morris <>,
 John Andersen <>,
 Marian Rotariu <>,
 Mihai Donțu <>,
 Nicușor Cîțu <>,
 Thara Gopinath <>,
 Trilok Soni <>, Wei Liu <>,
 Will Deacon <>, Yu Zhang <>,
 Zahra Tarkhani <>,
 Ștefan Șicleru <>,,,,,,,,,,
Subject: Re: [RFC PATCH v2 17/19] heki: x86: Update permissions counters
 during text patching

On 12/6/23 12:51, Peter Zijlstra wrote:
> On Wed, Dec 06, 2023 at 10:37:33AM -0600, Madhavan T. Venkataraman wrote:
>> On 11/30/23 05:33, Peter Zijlstra wrote:
>>> On Wed, Nov 29, 2023 at 03:07:15PM -0600, Madhavan T. Venkataraman wrote:
>>>> Kernel Lockdown
>>>> ---------------
>>>> But, we must provide at least some security in V2. Otherwise, it is useless.
>>>> So, we have implemented what we call a kernel lockdown. At the end of kernel
>>>> boot, Heki establishes permissions in the extended page table as mentioned
>>>> before. Also, it adds an immutable attribute for kernel text and kernel RO data.
>>>> Beyond that point, guest requests that attempt to modify permissions on any of
>>>> the immutable pages will be denied.
>>>> This means that features like FTrace and KProbes will not work on kernel text
>>>> in V2. This is a temporary limitation. Once authentication is in place, the
>>>> limitation will go away.
>>> So either you're saying your patch 17 / text_poke is broken (so why
>>> include it ?!?) or your statement above is incorrect. Pick one.
>> It has been included so that people can be aware of the changes.
>> I will remove the text_poke() changes from the patchset and send it later when
>> I have some authentication in place. It will make sense then.
> If you know its broken then fucking say so in the Changelog instead of
> wasting everybody's time.. OMG.

It is not broken. It addresses one part of the problem. The other part is WIP.

I am preparing a detailed response to your comments. I ask you to be patient until then. In fact, I would appreciate your input/suggestions on some problems we are trying to solve in this context. I will mention them in my response.


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