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Shutemov" To: Yu-cheng Yu 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 , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang , "Kirill A . Shutemov" Subject: Re: [PATCH v24 15/30] x86/mm: Update maybe_mkwrite() for shadow stack Message-ID: <20210409151623.ffydw3ckzbl7qboo@box.shutemov.name> References: <20210401221104.31584-1-yu-cheng.yu@intel.com> <20210401221104.31584-16-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210401221104.31584-16-yu-cheng.yu@intel.com> X-Stat-Signature: y63jcnc5yskh1tm89hjsjc47cnt6mgh6 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 7E7FA6000114 Received-SPF: none (shutemov.name>: No applicable sender policy available) receiver=imf09; identity=mailfrom; envelope-from=""; helo=mail-lf1-f47.google.com; client-ip=209.85.167.47 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617981383-748627 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 Thu, Apr 01, 2021 at 03:10:49PM -0700, Yu-cheng Yu wrote: > When serving a page fault, maybe_mkwrite() makes a PTE writable if its vma > has VM_WRITE. > > A shadow stack vma has VM_SHADOW_STACK. Its PTEs have _PAGE_DIRTY, but not > _PAGE_WRITE. In fork(), _PAGE_DIRTY is cleared to cause copy-on-write, > and in the page fault handler, _PAGE_DIRTY is restored and the shadow stack > page is writable again. > > Introduce an x86 version of maybe_mkwrite(), which sets proper PTE bits > according to VM flags. > > Apply the same changes to maybe_pmd_mkwrite(). > > Signed-off-by: Yu-cheng Yu > Cc: Kees Cook > Cc: Kirill A. Shutemov > --- > v24: > - Instead of doing arch_maybe_mkwrite(), overwrite maybe*_mkwrite() with x86 > versions. > - Change VM_SHSTK to VM_SHADOW_STACK. > > arch/x86/include/asm/pgtable.h | 8 ++++++++ > arch/x86/mm/pgtable.c | 20 ++++++++++++++++++++ > include/linux/mm.h | 2 ++ > mm/huge_memory.c | 2 ++ > 4 files changed, 32 insertions(+) > > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h > index 46d9394b884f..51cdf14488b7 100644 > --- a/arch/x86/include/asm/pgtable.h > +++ b/arch/x86/include/asm/pgtable.h > @@ -1686,6 +1686,14 @@ static inline bool arch_faults_on_old_pte(void) > return false; > } > > +#define maybe_mkwrite maybe_mkwrite > +extern pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma); > + > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +#define maybe_pmd_mkwrite maybe_pmd_mkwrite > +extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma); > +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ Move it next to other THP-depended stuff. Otherwise looks good to me: Reviewed-by: Kirill A. Shutemov -- Kirill A. Shutemov