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(p200300cbc710ff001a06080f733ae8c6.dip0.t-ipconnect.de. [2003:cb:c710:ff00:1a06:80f:733a:e8c6]) by smtp.gmail.com with ESMTPSA id c12-20020a05600c0acc00b003f195d540d9sm14232474wmr.14.2023.06.13.05.27.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Jun 2023 05:27:25 -0700 (PDT) Message-ID: Date: Tue, 13 Jun 2023 14:27:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v9 02/42] mm: Move pte/pmd_mkwrite() callers with no VMA to _novma() To: Rick Edgecombe , x86@kernel.org, "H . 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, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, debug@rivosinc.com, szabolcs.nagy@arm.com, torvalds@linux-foundation.org, broonie@kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, xen-devel@lists.xenproject.org References: <20230613001108.3040476-1-rick.p.edgecombe@intel.com> <20230613001108.3040476-3-rick.p.edgecombe@intel.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230613001108.3040476-3-rick.p.edgecombe@intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: k9okd1n13uxyfhpijhsgod7rwrduksa6 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0B2E41A000B X-Rspam-User: X-HE-Tag: 1686659249-276983 X-HE-Meta: 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 HEV0pLNn 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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 13.06.23 02:10, 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. > > 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. > > Previous patches have done the first step, so next move the callers that > don't have a VMA to pte_mkwrite_novma(). Also do the same for > pmd_mkwrite(). This will be ok for the shadow stack feature, as these > callers are on kernel memory which will not need to be made shadow stack, > and the other architectures only currently support one type of memory > in pte_mkwrite() > > Cc: linux-doc@vger.kernel.org > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-s390@vger.kernel.org > Cc: xen-devel@lists.xenproject.org > Cc: linux-arch@vger.kernel.org > Cc: linux-mm@kvack.org > Signed-off-by: Rick Edgecombe > --- Acked-by: David Hildenbrand -- Cheers, David / dhildenb