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[209.132.180.67]) by mx.google.com with ESMTP id h7si68474180pgc.130.2019.08.13.16.03.03; Tue, 13 Aug 2019 16:03:19 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727496AbfHMXCZ (ORCPT + 99 others); Tue, 13 Aug 2019 19:02:25 -0400 Received: from mga05.intel.com ([192.55.52.43]:63294 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726155AbfHMXCY (ORCPT ); Tue, 13 Aug 2019 19:02:24 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 13 Aug 2019 16:02:23 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,382,1559545200"; d="scan'208";a="260271269" Received: from ray.jf.intel.com (HELO [10.7.201.140]) ([10.7.201.140]) by orsmga001.jf.intel.com with ESMTP; 13 Aug 2019 16:02:22 -0700 Subject: Re: [PATCH v8 11/27] x86/mm: Introduce _PAGE_DIRTY_SW To: Yu-cheng Yu , 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 , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin References: <20190813205225.12032-1-yu-cheng.yu@intel.com> <20190813205225.12032-12-yu-cheng.yu@intel.com> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; keydata= mQINBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABtEVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT6JAjgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lcuQINBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABiQIfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y Message-ID: Date: Tue, 13 Aug 2019 16:02:22 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190813205225.12032-12-yu-cheng.yu@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > +#if defined(CONFIG_X86_INTEL_SHADOW_STACK_USER) > +static inline pte_t pte_move_flags(pte_t pte, pteval_t from, pteval_t to) > +{ > + if (pte_flags(pte) & from) > + pte = pte_set_flags(pte_clear_flags(pte, from), to); > + return pte; Why is this conditional on the compile option and not a runtime check? > +} > +#else > +static inline pte_t pte_move_flags(pte_t pte, pteval_t from, pteval_t to) > +{ > + return pte; > +} > +#endif Why do we need this function? It's not mentioned in the changelog or commented. > static inline pte_t pte_mkclean(pte_t pte) > { > - return pte_clear_flags(pte, _PAGE_DIRTY); > + return pte_clear_flags(pte, _PAGE_DIRTY_BITS); > } > > static inline pte_t pte_mkold(pte_t pte) > @@ -322,6 +336,7 @@ static inline pte_t pte_mkold(pte_t pte) > > static inline pte_t pte_wrprotect(pte_t pte) > { > + pte = pte_move_flags(pte, _PAGE_DIRTY_HW, _PAGE_DIRTY_SW); > return pte_clear_flags(pte, _PAGE_RW); > } Please comment what this is doing and why. > @@ -332,9 +347,24 @@ static inline pte_t pte_mkexec(pte_t pte) > > static inline pte_t pte_mkdirty(pte_t pte) > { > + pteval_t dirty = (!IS_ENABLED(CONFIG_X86_INTEL_SHADOW_STACK_USER) || > + pte_write(pte)) ? _PAGE_DIRTY_HW:_PAGE_DIRTY_SW; This is *really* hard for me to read and parse. How about: pte_t dirty = _PAGE_DIRTY_HW; /* * When Shadow Stacks are enabled, read-only PTEs can * not have the hardware dirty bit set and must use * the software bit. */ if (IS_ENABLED(CONFIG_X86_INTEL_SHADOW_STACK_USER) && !pte_write(pte)) dirty = _PAGE_DIRTY_SW; > + return pte_set_flags(pte, dirty | _PAGE_SOFT_DIRTY); > +} > + > +#ifdef CONFIG_ARCH_HAS_SHSTK > +static inline pte_t pte_mkdirty_shstk(pte_t pte) > +{ > + pte = pte_clear_flags(pte, _PAGE_DIRTY_SW); > return pte_set_flags(pte, _PAGE_DIRTY_HW | _PAGE_SOFT_DIRTY); > } Why does the _PAGE_DIRTY_SW *HAVE* to be cleared on shstk pages? > +static inline bool pte_dirty_hw(pte_t pte) > +{ > + return pte_flags(pte) & _PAGE_DIRTY_HW; > +} > +#endif Why are these #ifdef'd? > static inline pte_t pte_mkyoung(pte_t pte) > { > return pte_set_flags(pte, _PAGE_ACCESSED); > @@ -342,6 +372,7 @@ static inline pte_t pte_mkyoung(pte_t pte) > > static inline pte_t pte_mkwrite(pte_t pte) > { > + pte = pte_move_flags(pte, _PAGE_DIRTY_SW, _PAGE_DIRTY_HW); > return pte_set_flags(pte, _PAGE_RW); > } It also isn't clear to me why this *must* move bits here. Its doubly unclear why you would need to do this on systems when shadow stacks are compiled in but disabled. Same comments for pmds and puds. > - > /* mprotect needs to preserve PAT bits when updating vm_page_prot */ > #define pgprot_modify pgprot_modify > static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) > @@ -1178,6 +1254,19 @@ static inline int pmd_write(pmd_t pmd) > return pmd_flags(pmd) & _PAGE_RW; > } > > +static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot) > +{ > + pmdval_t val = pmd_val(pmd), oldval = val; > + > + val &= _HPAGE_CHG_MASK; > + val |= check_pgprot(newprot) & ~_HPAGE_CHG_MASK; > + val = flip_protnone_guard(oldval, val, PHYSICAL_PMD_PAGE_MASK); > + if ((pmd_write(pmd) && !(pgprot_val(newprot) & _PAGE_RW))) > + return pmd_move_flags(__pmd(val), _PAGE_DIRTY_HW, > + _PAGE_DIRTY_SW); > + return __pmd(val); > +} Why was this function moved? This makes it really hard to review what you changed I'm going to stop reading this code now. It needs a lot more care and feeding to make it reviewable. Please go back, double-check your changelogs and flesh them out, then please try to make the code more readable and understandable by commenting it. Please take all of the compile-time checks and ask yourself whether they need to be or *can* be runtime checks. Consider what the overhead is of non-shadowstack systems running shadowstack-required code. Please also reconcile the supervisor XSAVE portion of your patches with the ones that Fenghua has been sending around. I've given quite a bit of feedback to improve those. Please consolidate and agree on a common set of patches with him.