From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Rapoport Subject: Re: [PATCH v9 01/42] mm: Rename arch pte_mkwrite()'s to pte_mkwrite_novma() Date: Tue, 13 Jun 2023 10:43:47 +0300 Message-ID: <20230613074347.GR52412@kernel.org> References: <20230613001108.3040476-1-rick.p.edgecombe@intel.com> <20230613001108.3040476-2-rick.p.edgecombe@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=1I4g1L1LZVuurrGJPXbjGUxhmXBg5ha813t1LX0CXsM=; b=CBECYVa5mrB4HJ QutNMLpzCkKlc6DNrX9K7gaVdRuNBcZCIeFVtQ+psT4Qg9K+iHOeq9hTWg/QIAgPZmuOtWM71RbBq xp2xEsHubxusmYsQEBqrkgJElPlT5v5TuEeVmzax3soEmZnskv1u0yp5RyxFo0G7QZp223ACQLxUv d2F4ot2yfN9nyKL3Vmx/jUTPz1vSrq02CZlhHUnfflrH1YvqiRXnf/JnbTHyM/nOlfjU07fW8DuPc dssLK0hKEQX3Eq5wZIoYL1DZuDTLD1GDqbTimgkay7GY4V7zS8STO1wfHmtwnt5f1L9gVOXvta6xO yHTw4eCcyiA6ogNEj3Gg==; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686642270; bh=ez0I+RKRhMdZt82NML91fPb7fzRC4/NkCFA3IdK3cEg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HyA2VS9kwVTQsYOWOuof1Z4qJ92ct0+rpQ0B5SIAzOL2Mz6wp6NoYwA7DcLYOqzj9 Q8Z9RGOQt5lsRA8Nc33tC8G7SiwN9ipBSdD03bBdhpX4MycI3Vh7vOT7ypJVtsouWv 8Bsg5dlRSFLhnsq+PWCSJc5VolYLva+SeDgrT92N096TEl0/uLmsJvVPLGz9OK3/dz OYm6tEkeVT/cDyaIgk5UyxE5b/W7hyDcldGwNesOYI9EZOqwD7xGIveZKNt/lp9izm uoBjmwxoGZjGvj7XWF9lQv7iNjjhyG9sIxFni/WcE8h+xW9r48P7ifrawWGz2rEEWN FKciDs53eQHeQ== Content-Disposition: inline In-Reply-To: <20230613001108.3040476-2-rick.p.edgecombe@intel.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+glpr-linux-riscv=m.gmane-mx.org@lists.infradead.org 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 On Mon, Jun 12, 2023 at 05:10:27PM -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: ^ mapping? > 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/ Reviewed-by: Mike Rapoport (IBM) -- Sincerely yours, Mike.