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Peter Anvin" , Thomas Gleixner , Ingo Molnar , 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 , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, 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, szabolcs.nagy@arm.com, torvalds@linux-foundation.org, broonie@kernel.org Subject: Re: [PATCH v9 03/42] mm: Make pte_mkwrite() take a VMA Message-ID: <20230613074245.GQ52412@kernel.org> References: <20230613001108.3040476-1-rick.p.edgecombe@intel.com> <20230613001108.3040476-4-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230613001108.3040476-4-rick.p.edgecombe@intel.com> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C11E240014 X-Stat-Signature: 468uzms33pzqppmdnu1qeadmeyqhuh3r X-HE-Tag: 1686642206-787210 X-HE-Meta: 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 /1Vb6CP+ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jun 12, 2023 at 05:10:29PM -0700, Rick Edgecombe wrote: > The x86 Shadow stack 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 unusual properties is that shadow stack memory is writable, > but only in limited ways. These limits are applied via a specific PTE > bit combination. Nevertheless, the memory is writable, and core mm code > will need to apply the writable permissions in the typical paths that > call pte_mkwrite(). Future patches will make pte_mkwrite() take a VMA, so > that the x86 implementation of it can know whether to create regular > writable memory or shadow stack memory. Nit: ^ mappings? > But there are a couple of challenges to this. Modifying the signatures of > each arch pte_mkwrite() implementation would be error prone because some > are generated with macros and would need to be re-implemented. Also, some > pte_mkwrite() callers operate on kernel memory without a VMA. > > So this can be done in a three step process. First pte_mkwrite() can be > renamed to pte_mkwrite_novma() in each arch, with a generic pte_mkwrite() > added that just calls pte_mkwrite_novma(). Next callers without a VMA can > be moved to pte_mkwrite_novma(). And lastly, pte_mkwrite() and all callers > can be changed to take/pass a VMA. > > In a previous patches, pte_mkwrite() was renamed pte_mkwrite_novma() and > callers that don't have a VMA were changed to use pte_mkwrite_novma(). So Maybe This is the third step so pte_mkwrite() was renamed to pte_mkwrite_novma() and ... > now change pte_mkwrite() to take a VMA and change the remaining callers to > pass a VMA. Apply the same changes for pmd_mkwrite(). > > No functional change. > > Suggested-by: David Hildenbrand > Signed-off-by: Rick Edgecombe Reviewed-by: Mike Rapoport (IBM)