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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 , 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, Yu-cheng Yu Subject: Re: [PATCH v4 11/39] x86/mm: Update pte_modify for _PAGE_COW Message-ID: References: <20221203003606.6838-1-rick.p.edgecombe@intel.com> <20221203003606.6838-12-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20221203003606.6838-12-rick.p.edgecombe@intel.com> X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 052BD120009 X-Stat-Signature: 4id6q48nog96jbsznyzsnu5m76gs4mnn X-HE-Tag: 1672141338-462624 X-HE-Meta: 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 +HJRBF5/ sQqp7 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 Fri, Dec 02, 2022 at 04:35:38PM -0800, Rick Edgecombe wrote: > static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) > { > + pteval_t _page_chg_mask_no_dirty = _PAGE_CHG_MASK & ~_PAGE_DIRTY; > pteval_t val = pte_val(pte), oldval = val; > + pte_t pte_result; > > /* > * Chop off the NX bit (if present), and add the NX portion of > * the newprot (if present): > */ > - val &= _PAGE_CHG_MASK; > - val |= check_pgprot(newprot) & ~_PAGE_CHG_MASK; > + val &= _page_chg_mask_no_dirty; > + val |= check_pgprot(newprot) & ~_page_chg_mask_no_dirty; > val = flip_protnone_guard(oldval, val, PTE_PFN_MASK); > - return __pte(val); > + > + pte_result = __pte(val); > + > + /* > + * Dirty bit is not preserved above so it can be done Just for my own understanding: are you saying here that flip_protnone_guard() might end up setting _PAGE_DIRTY in val... > + * in a special way for the shadow stack case, where it > + * needs to set _PAGE_COW. pte_mkcow() will do this in > + * the case of shadow stack. > + */ > + if (pte_dirty(pte_result)) > + pte_result = pte_mkcow(pte_result); ... and in that case we need to turn it into a _PAGE_COW setting? Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette