From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f200.google.com (mail-pg1-f200.google.com [209.85.215.200]) by kanga.kvack.org (Postfix) with ESMTP id 68E3F6B522D for ; Thu, 30 Aug 2018 10:43:47 -0400 (EDT) Received: by mail-pg1-f200.google.com with SMTP id g9-v6so5141607pgc.16 for ; Thu, 30 Aug 2018 07:43:47 -0700 (PDT) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTPS id z73-v6si6610727pgd.471.2018.08.30.07.43.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 30 Aug 2018 07:43:46 -0700 (PDT) From: Yu-cheng Yu Subject: [RFC PATCH v3 14/24] mm: Handle shadow stack page fault Date: Thu, 30 Aug 2018 07:38:54 -0700 Message-Id: <20180830143904.3168-15-yu-cheng.yu@intel.com> In-Reply-To: <20180830143904.3168-1-yu-cheng.yu@intel.com> References: <20180830143904.3168-1-yu-cheng.yu@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: 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 , Cyrill Gorcunov , Dave Hansen , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , "Ravi V. Shankar" , Vedvyas Shanbhogue Cc: Yu-cheng Yu When a task does fork(), its shadow stack must be duplicated for the child. However, the child may not actually use all pages of of the copied shadow stack. This patch implements a flow that is similar to copy-on-write of an anonymous page, but for shadow stack memory. A shadow stack PTE needs to be RO and dirty. We use this dirty bit requirement to effect the copying of shadow stack pages. In copy_one_pte(), we clear the dirty bit from the shadow stack PTE. On the next shadow stack access to the PTE, a page fault occurs. At that time, we then copy/re-use the page and fix the PTE. Signed-off-by: Yu-cheng Yu --- arch/x86/mm/pgtable.c | 10 ++++++++++ include/asm-generic/pgtable.h | 7 +++++++ mm/memory.c | 3 +++ 3 files changed, 20 insertions(+) diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index e848a4811785..c63261128ac3 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -872,3 +872,13 @@ int pmd_free_pte_page(pmd_t *pmd, unsigned long addr) #endif /* CONFIG_X86_64 */ #endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */ + +#ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER +inline pte_t pte_set_vma_features(pte_t pte, struct vm_area_struct *vma) +{ + if (vma->vm_flags & VM_SHSTK) + return pte_mkdirty_shstk(pte); + else + return pte; +} +#endif /* CONFIG_X86_INTEL_SHADOW_STACK_USER */ diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index aa5271717126..558a485617cd 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -1146,6 +1146,13 @@ static inline bool pmd_dirty_hw(pmd_t pmd) { return false; } + +static inline pte_t pte_set_vma_features(pte_t pte, struct vm_area_struct *vma) +{ + return pte; +} +#else +pte_t pte_set_vma_features(pte_t pte, struct vm_area_struct *vma); #endif #endif /* _ASM_GENERIC_PGTABLE_H */ diff --git a/mm/memory.c b/mm/memory.c index c467102a5cbc..9b4e11944b5d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2462,6 +2462,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf) flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); entry = pte_mkyoung(vmf->orig_pte); entry = maybe_mkwrite(pte_mkdirty(entry), vma); + entry = pte_set_vma_features(entry, vma); if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1)) update_mmu_cache(vma, vmf->address, vmf->pte); pte_unmap_unlock(vmf->pte, vmf->ptl); @@ -2535,6 +2536,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); entry = mk_pte(new_page, vma->vm_page_prot); entry = maybe_mkwrite(pte_mkdirty(entry), vma); + entry = pte_set_vma_features(entry, vma); /* * Clear the pte entry and flush it first, before updating the * pte with the new entry. This will avoid a race condition @@ -3187,6 +3189,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) entry = mk_pte(page, vma->vm_page_prot); if (vma->vm_flags & VM_WRITE) entry = pte_mkwrite(pte_mkdirty(entry)); + entry = pte_set_vma_features(entry, vma); vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, &vmf->ptl); -- 2.17.1