linux-kernel - Re: [PATCH 06/17] prmem: test cases for memory protection

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Date:   Wed, 24 Oct 2018 17:24:03 +0300
From:   Igor Stoppa <igor.stoppa@...il.com>
To:     Randy Dunlap <rdunlap@...radead.org>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        Dave Chinner <david@...morbit.com>,
        James Morris <jmorris@...ei.org>,
        Michal Hocko <mhocko@...nel.org>,
        kernel-hardening@...ts.openwall.com,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Cc:     igor.stoppa@...wei.com, Dave Hansen <dave.hansen@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Laura Abbott <labbott@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pavel Tatashin <pasha.tatashin@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/17] prmem: test cases for memory protection

Hi,

On 24/10/18 06:27, Randy Dunlap wrote:

> a. It seems backwards (or upside down) to have a test case select a feature (PRMEM)
> instead of depending on that feature.
> 
> b. Since PRMEM depends on MMU (in patch 04/17), the "select" here could try to
> enabled PRMEM even when MMU is not enabled.
> 
> Changing this to "depends on PRMEM" would solve both of these issues.

The weird dependency you pointed out is partially caused by the 
incompleteness of PRMEM.

What I have in mind is to have a fallback version of it for systems 
without MMU capable of write protection.
Possibly defaulting to kvmalloc.
In that case there would not be any need for a configuration option.

> c. Don't use "default n".  That is already the default.

ok

--
igor