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[209.85.166.177]) by smtp.gmail.com with ESMTPSA id z10-20020a056638000a00b004091d72f62dsm3267301jao.85.2023.06.13.00.25.33 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Jun 2023 00:25:33 -0700 (PDT) Received: by mail-il1-f177.google.com with SMTP id e9e14a558f8ab-33e517e5f99so22477195ab.2 for ; Tue, 13 Jun 2023 00:25:33 -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 Cc: 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, david@redhat.com, debug@rivosinc.com, szabolcs.nagy@arm.com, torvalds@linux-foundation.org, broonie@kernel.org, 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 2F216A0008 X-Stat-Signature: 47dx1w3btetcypg4tj6ud8hgy5gni8st X-Rspam-User: X-HE-Tag: 1686641134-67111 X-HE-Meta: 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 CyhoLe+W 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 4HgpDZco fVy3h6QYoLGkSkrdmgDyjMvMWLu70TFP 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 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