Message-ID: <63f28901.170a0220.7090.af7b@mx.google.com>
Date:   Sun, 19 Feb 2023 12:39:28 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc:     x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@kernel.org>,
        Balbir Singh <bsingharora@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Eugene Syromiatnikov <esyr@redhat.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H . J . Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Weijiang Yang <weijiang.yang@intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        John Allen <john.allen@amd.com>, kcc@google.com,
        eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com,
        dethoma@microsoft.com, akpm@linux-foundation.org,
        Andrew.Cooper3@citrix.com, christina.schimpe@intel.com,
        david@redhat.com, debug@rivosinc.com, linux-s390@vger.kernel.org
Subject: Re: [PATCH v6 12/41] s390/mm: Introduce pmd_mkwrite_kernel()
References: <20230218211433.26859-1-rick.p.edgecombe@intel.com>
 <20230218211433.26859-13-rick.p.edgecombe@intel.com>
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In-Reply-To: <20230218211433.26859-13-rick.p.edgecombe@intel.com>
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On Sat, Feb 18, 2023 at 01:14:04PM -0800, Rick Edgecombe wrote:
> The x86 Control-flow Enforcement Technology (CET) feature includes a new
> type of memory called shadow stack. This shadow stack memory has some
> unusual properties, which requires some core mm changes to function
> properly.
> 
> One of these changes is to allow for pmd_mkwrite() to create different
> types of writable memory (the existing conventionally writable type and
> also the new shadow stack type). Future patches will convert pmd_mkwrite()
> to take a VMA in order to facilitate this, however there are places in the
> kernel where pmd_mkwrite() is called outside of the context of a VMA.
> These are for kernel memory. So create a new variant called
> pmd_mkwrite_kernel() and switch the kernel users over to it. Have
> pmd_mkwrite() and pmd_mkwrite_kernel() be the same for now. Future patches
> will introduce changes to make pmd_mkwrite() take a VMA.
> 
> Only do this for architectures that need it because they call pmd_mkwrite()
> in arch code without an associated VMA. Since it will only currently be
> used in arch code, so do not include it in arch_pgtable_helpers.rst.
> 
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-s390@vger.kernel.org
> Cc: linux-arch@vger.kernel.org
> Cc: linux-mm@kvack.org
> Tested-by: Pengfei Xu <pengfei.xu@intel.com>
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>

Yup, 1:1 refactor.

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook