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[209.85.160.51]) by smtp.gmail.com with ESMTPSA id o38-20020a05687107a600b0019e6b96f909sm6965807oap.22.2023.06.13.00.20.05 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Jun 2023 00:20:05 -0700 (PDT) Received: by mail-oa1-f51.google.com with SMTP id 586e51a60fabf-1a694ac3238so1361667fac.3 for ; Tue, 13 Jun 2023 00:20:05 -0700 (PDT) X-Received: by 2002:a25:b191:0:b0:ba8:3bc0:4d19 with SMTP id h17-20020a25b191000000b00ba83bc04d19mr680890ybj.28.1686640784641; Tue, 13 Jun 2023 00:19:44 -0700 (PDT) MIME-Version: 1.0 References: <20230613001108.3040476-1-rick.p.edgecombe@intel.com> <20230613001108.3040476-2-rick.p.edgecombe@intel.com> In-Reply-To: <20230613001108.3040476-2-rick.p.edgecombe@intel.com> From: Geert Uytterhoeven Date: Tue, 13 Jun 2023 09:19:32 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v9 01/42] mm: Rename arch pte_mkwrite()'s to pte_mkwrite_novma() To: Rick Edgecombe Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Mailman-Approved-At: Tue, 13 Jun 2023 17:35:37 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kcc@google.com, linux-ia64@vger.kernel.org, loongarch@lists.linux.dev, linux-doc@vger.kernel.org, Peter Zijlstra , Dave Hansen , david@redhat.com, eranian@google.com, Oleg Nesterov , linux-mm@kvack.org, linux-csky@vger.kernel.org, Pavel Machek , "H . Peter Anvin" , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Nadav Amit , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, dethoma@microsoft.com, Linus Torvalds , Jonathan Corbet , linux-sh@vger.kernel.org, linux-hexagon@vger.kernel.org, x86@kernel.org, Eugene Syromiatnikov , jamorris@linux.microsoft.com, szabolcs.nagy@arm.com, Ingo Molnar , linux-snps-arc@lists.infradead.org, "H . J . Lu" , Kees Cook , Arnd Bergmann , Jann Horn , linux-alp ha@vger.kernel.org, linux-um@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org, linux-m68k@lists.linux-m68k.org, broonie@kernel.org, Borislav Petkov , Andy Lutomirski , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, debug@rivosinc.com, Florian Weimer , Michal Simek , John Allen , linux-parisc@vger.kernel.org, Weijiang Yang , linux-api@vger.kernel.org, christina.schimpe@intel.com, Randy Dunlap , linux-kernel@vger.kernel.org, Cyrill Gorcunov , Dinh Nguyen , openrisc@lists.librecores.org, rppt@kernel.org, Andrew.Cooper3@citrix.com, akpm@linux-foundation.org, torvalds@linux-foundation.org, "Kirill A . Shutemov" , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Jun 13, 2023 at 2:13=E2=80=AFAM 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 requir= es > 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 caller= s > 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 th= e > 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-=3DwiZjSu7c9sFYZb3q04108stgHff2wf= bokGCCgW7riz+8Q@mail.gmail.com/ > arch/m68k/include/asm/mcf_pgtable.h | 2 +- > arch/m68k/include/asm/motorola_pgtable.h | 2 +- > arch/m68k/include/asm/sun3_pgtable.h | 2 +- Acked-by: Geert Uytterhoeven Gr{oetje,eeting}s, Geert --=20 Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k= .org In personal conversations with technical people, I call myself a hacker. Bu= t when I'm talking to journalists I just say "programmer" or something like t= hat. -- Linus Torvalds