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Subject: Re: [PATCH 06/17] prmem: test cases for memory protection
References: <20181023213504.28905-1-igor.stoppa@huawei.com>
 <20181023213504.28905-7-igor.stoppa@huawei.com>
 <a6c74bb1-bd0c-ed8a-1dd3-b04f2e3c78d4@infradead.org>
From: Igor Stoppa <igor.stoppa@gmail.com>
Message-ID: <00461c0a-a214-1984-5614-c7a4a2a7ff83@gmail.com>
Date: Wed, 24 Oct 2018 17:24:03 +0300
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To: Randy Dunlap <rdunlap@infradead.org>, Mimi Zohar <zohar@linux.vnet.ibm.com>, Kees Cook <keescook@chromium.org>, Matthew Wilcox <willy@infradead.org>, Dave Chinner <david@fromorbit.com>, James Morris <jmorris@namei.org>, Michal Hocko <mhocko@kernel.org>, kernel-hardening@lists.openwall.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org
Cc: igor.stoppa@huawei.com, Dave Hansen <dave.hansen@linux.intel.com>, Jonathan Corbet <corbet@lwn.net>, Laura Abbott <labbott@redhat.com>, Vlastimil Babka <vbabka@suse.cz>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Pavel Tatashin <pasha.tatashin@oracle.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org

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