Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965341AbbHKPl0 (ORCPT ); Tue, 11 Aug 2015 11:41:26 -0400 Received: from foss.arm.com ([217.140.101.70]:54088 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965062AbbHKPlY (ORCPT ); Tue, 11 Aug 2015 11:41:24 -0400 Date: Tue, 11 Aug 2015 16:41:18 +0100 From: Catalin Marinas To: Andrey Ryabinin Cc: Will Deacon , linux-arm-kernel@lists.infradead.org, Yury , Alexey Klimov , Arnd Bergmann , linux-mm@kvack.org, Linus Walleij , x86@kernel.org, linux-kernel@vger.kernel.org, David Keitel , Alexander Potapenko , "Aneesh Kumar K.V" , "H. Peter Anvin" , Andrew Morton , Ingo Molnar , Thomas Gleixner , Dmitry Vyukov Subject: Re: [PATCH v5 2/6] x86/kasan, mm: introduce generic kasan_populate_zero_shadow() Message-ID: <20150811154117.GH23307@e104818-lin.cambridge.arm.com> References: <1439259499-13913-1-git-send-email-ryabinin.a.a@gmail.com> <1439259499-13913-3-git-send-email-ryabinin.a.a@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1439259499-13913-3-git-send-email-ryabinin.a.a@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2003 Lines: 64 On Tue, Aug 11, 2015 at 05:18:15AM +0300, Andrey Ryabinin wrote: > --- /dev/null > +++ b/mm/kasan/kasan_init.c [...] > +#if CONFIG_PGTABLE_LEVELS > 3 > +pud_t kasan_zero_pud[PTRS_PER_PUD] __page_aligned_bss; > +#endif > +#if CONFIG_PGTABLE_LEVELS > 2 > +pmd_t kasan_zero_pmd[PTRS_PER_PMD] __page_aligned_bss; > +#endif > +pte_t kasan_zero_pte[PTRS_PER_PTE] __page_aligned_bss; Is there any problem if you don't add the #ifs here? Wouldn't the linker remove them if they are not used? Original hunk copied here for easy comparison: > -static int __init zero_pte_populate(pmd_t *pmd, unsigned long addr, > - unsigned long end) > -{ > - pte_t *pte = pte_offset_kernel(pmd, addr); > - > - while (addr + PAGE_SIZE <= end) { > - WARN_ON(!pte_none(*pte)); > - set_pte(pte, __pte(__pa_nodebug(kasan_zero_page) > - | __PAGE_KERNEL_RO)); > - addr += PAGE_SIZE; > - pte = pte_offset_kernel(pmd, addr); > - } > - return 0; > -} [...] > +static void __init zero_pte_populate(pmd_t *pmd, unsigned long addr, > + unsigned long end) > +{ > + pte_t *pte = pte_offset_kernel(pmd, addr); > + pte_t zero_pte; > + > + zero_pte = pfn_pte(PFN_DOWN(__pa(kasan_zero_page)), PAGE_KERNEL); > + zero_pte = pte_wrprotect(zero_pte); > + > + while (addr + PAGE_SIZE <= end) { > + set_pte_at(&init_mm, addr, pte, zero_pte); > + addr += PAGE_SIZE; > + pte = pte_offset_kernel(pmd, addr); > + } > +} I think there are some differences with the original x86 code. The first one is the use of __pa_nodebug, does it cause any problems if CONFIG_DEBUG_VIRTUAL is enabled? The second is the use of a read-only attribute when mapping kasan_zero_page on x86. Can it cope with a writable mapping? If there are no issues, it should be documented in the commit log. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/