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(p200300cbc710ff001a06080f733ae8c6.dip0.t-ipconnect.de. [2003:cb:c710:ff00:1a06:80f:733a:e8c6]) by smtp.gmail.com with ESMTPSA id i1-20020adff301000000b002f28de9f73bsm15275419wro.55.2023.06.13.05.26.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Jun 2023 05:26:55 -0700 (PDT) Message-ID: <497e571e-e4de-7634-7da6-683599a4bbba@redhat.com> Date: Tue, 13 Jun 2023 14:26:53 +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 01/42] mm: Rename arch pte_mkwrite()'s to pte_mkwrite_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-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, Michal Simek , Dinh Nguyen , linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, Linus Torvalds References: <20230613001108.3040476-1-rick.p.edgecombe@intel.com> <20230613001108.3040476-2-rick.p.edgecombe@intel.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230613001108.3040476-2-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: 8bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 1F96620019 X-Stat-Signature: ofqts4gjhxcozkaxae58ny5fesdysi69 X-HE-Tag: 1686659219-850022 X-HE-Meta: U2FsdGVkX18iFy7gjqwxPCRpP8t7iuVAAoP0Jt2x695HosHdvpvq1hk9+IgC9znhB/vW4O0OWR29PIBTjwJkIRTNkBz6ctQrE1jV78E1FNynbsjy+K8wjl+NC//JyZFcTQjey3EGDzvPVwR2/yRG/M00syFXJ9TbfOlr7a1akC+AMZjx1+LaHL7rspiyIIdjr+hYUMj/ZNi1UOKATbaFfHO+1zWs1yYA8ugIm0/49SLhn7kf3hO7CxHucCyL9Q7iYn6pfpGEVEbU6QkApnH1MiFNvPYY8H9ZndSQHs3RxTdtNbM4d6tgu21dqoUBNMM8IIrGV0Nxt+CGyWQ6A7ReBxlPxKlpkOWHm9U8r0vdkzG8yynFZlmvIypjEc0IJMbhl92BB49qiYktf96cvDBXJrXftDohivGceQk3LbP2Vw+OwDRoOYU6jAQnQyDPqVYzkCNvCDSC1r6T9pJOJ2TWMpif0M4pNyypPdVlH+Ju+haERGo32a97adhZPw54Pa8h4iG36rXcpEd8HkBDCGfCM+Ons5ZXMG5K7C6QqNoXp6H7qhuea0yu+f8LdkITR/EhEcSwwDJX5DqrQoJnEM0L7IAd1bCYm+SmC9i7ZZr0xVM9nJ6BDzuOvmtiY76abN07fyjQXeLwXeK8vBsHSGNPuLrwynYxE8zdAdhFX/6SKcYkRztPTfhLmIKyT2x/zd2/kYvAMSjYiKVso9ox7a5qjLB8kVBPRQEef+36pzJ/P1tFUczl2gkpIzq3K8kYRmQFKhMIt+vp2EQMuFkTN1rBzH6AUmMFYs1KSHquCf54d9YaBLGrcxBu5xbnt/ULESBDR2dxHXZ0UuZBgHfd5y5Mk+gyRyW5Y98FvHldZmM0Y+sWDUUNnq2txc6ao2F96uY30sIa+J7RHlifHv7MBbuvdczNHTsiP6j4Yod76RZ11+Q/PFSYuTAQqG7thlmS8A9ucPwPVjPJFs+q85iU4aq LtZBfdYV 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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. > > Start the process by renaming pte_mkwrite() to pte_mkwrite_novma() and > adding the pte_mkwrite() wrapper in linux/pgtable.h. Apply the same > pattern for pmd_mkwrite(). Since not all archs have a pmd_mkwrite_novma(), > create a new arch config HAS_HUGE_PAGE that can be used to tell if > pmd_mkwrite() should be defined. Otherwise in the !HAS_HUGE_PAGE cases the > compiler would not be able to find pmd_mkwrite_novma(). > > No functional change. > > Cc: linux-doc@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: linux-alpha@vger.kernel.org > Cc: linux-snps-arc@lists.infradead.org > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-csky@vger.kernel.org > Cc: linux-hexagon@vger.kernel.org > Cc: linux-ia64@vger.kernel.org > Cc: loongarch@lists.linux.dev > Cc: linux-m68k@lists.linux-m68k.org > Cc: Michal Simek > Cc: Dinh Nguyen > Cc: linux-mips@vger.kernel.org > Cc: openrisc@lists.librecores.org > Cc: linux-parisc@vger.kernel.org > Cc: linuxppc-dev@lists.ozlabs.org > Cc: linux-riscv@lists.infradead.org > Cc: linux-s390@vger.kernel.org > Cc: linux-sh@vger.kernel.org > Cc: sparclinux@vger.kernel.org > Cc: linux-um@lists.infradead.org > Cc: linux-arch@vger.kernel.org > Cc: linux-mm@kvack.org > Suggested-by: Linus Torvalds > Signed-off-by: Rick Edgecombe > Link: https://lore.kernel.org/lkml/CAHk-=wiZjSu7c9sFYZb3q04108stgHff2wfbokGCCgW7riz+8Q@mail.gmail.com/ > --- > Hi Non-x86 Arch’s, > > x86 has a feature that allows for the creation of a special type of > writable memory (shadow stack) that is only writable in limited specific > ways. Previously, changes were proposed to core MM code to teach it to > decide when to create normally writable memory or the special shadow stack > writable memory, but David Hildenbrand suggested[0] to change > pXX_mkwrite() to take a VMA, so awareness of shadow stack memory can be > moved into x86 code. Later Linus suggested a less error-prone way[1] to go > about this after the first attempt had a bug. > > Since pXX_mkwrite() is defined in every arch, it requires some tree-wide > changes. So that is why you are seeing some patches out of a big x86 > series pop up in your arch mailing list. There is no functional change. > After this refactor, the shadow stack series goes on to use the arch > helpers to push arch memory details inside arch/x86 and other arch's > with upcoming shadow stack features. > > Testing was just 0-day build testing. > > Hopefully that is enough context. Thanks! > > [0] https://lore.kernel.org/lkml/0e29a2d0-08d8-bcd6-ff26-4bea0e4037b0@redhat.com/ > [1] https://lore.kernel.org/lkml/CAHk-=wiZjSu7c9sFYZb3q04108stgHff2wfbokGCCgW7riz+8Q@mail.gmail.com/ > --- Acked-by: David Hildenbrand -- Cheers, David / dhildenb