From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id 23BE22802F9 for ; Thu, 16 Jul 2015 11:30:22 -0400 (EDT) Received: by pactm7 with SMTP id tm7so44833210pac.2 for ; Thu, 16 Jul 2015 08:30:21 -0700 (PDT) Received: from mailout2.w1.samsung.com (mailout2.w1.samsung.com. [210.118.77.12]) by mx.google.com with ESMTPS id v11si3900137pas.231.2015.07.16.08.30.20 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 16 Jul 2015 08:30:21 -0700 (PDT) Received: from eucpsbgm1.samsung.com (unknown [203.254.199.244]) by mailout2.w1.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0NRL00MGL72GR240@mailout2.w1.samsung.com> for linux-mm@kvack.org; Thu, 16 Jul 2015 16:30:16 +0100 (BST) Message-id: <55A7CE03.301@samsung.com> Date: Thu, 16 Jul 2015 18:30:11 +0300 From: Andrey Ryabinin MIME-version: 1.0 Subject: Re: [PATCH v2 5/5] arm64: add KASan support References: <1431698344-28054-1-git-send-email-a.ryabinin@samsung.com> <1431698344-28054-6-git-send-email-a.ryabinin@samsung.com> <20150708154803.GE6944@e104818-lin.cambridge.arm.com> <559FFCA7.4060008@samsung.com> <20150714150445.GH13555@e104818-lin.cambridge.arm.com> <55A61FF8.9000603@samsung.com> <20150715163732.GF20186@e104818-lin.cambridge.arm.com> In-reply-to: <20150715163732.GF20186@e104818-lin.cambridge.arm.com> Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Catalin Marinas Cc: Arnd Bergmann , linux-mm@kvack.org, Will Deacon , linux-kernel@vger.kernel.org, David Keitel , Alexander Potapenko , linux-arm-kernel@lists.infradead.org, Andrew Morton , Dmitry Vyukov On 07/15/2015 07:37 PM, Catalin Marinas wrote: > Ok, so simply taking the call out of the loop won't work unless we > conditionally define these functions (wouldn't be too bad since we have > some #if CONFIG_PGTABLE_LEVELS already introduced by this patch but it > would be nicer without). > > Anyway, I think we can keep the current iterations but exit early if > !pud_none() because it means we already populated it (reworked to match > other such patterns throughout the kernel with pgd_populate called from > the pud function; and untested): > > void kasan_early_pmd_populate(pud_t *pud, unsigned long addr, unsigned long end) > { > pmd_t *pmd; > unsigned long next; > > if (pud_none(*pud)) > pud_populate(&init_mm, pud, kasan_zero_pmd); > > pmd = pmd_offset(pud, addr); > do { > next = pmd_addr_end(addr, end); > kasan_early_pte_populate(pmd, addr, next); > } while (pmd++, addr = next, addr != end && pmd_none(*pmd)); > } > > void kasan_early_pud_populate(pgd_t *pgd, unsigned long addr, unsigned long end) > { > pud_t *pud; > unsigned long next; > > if (pgd_none(*pgd)) > pgd_populate(&init_mm, pgd, kasan_zero_pud); > > pud = pud_offset(pgd, addr); > do { > next = pud_addr_end(addr, end); > kasan_early_pmd_populate(pud, addr, next); > } while (pud++, addr = next, addr != end && pud_none(*pud)); > } > > Given that we check pud_none() after the first iterations, it covers the > lower levels if needed. > I think this may work, if pud_none(*pud) will be replaced with !pud_val(*pud). We can't use pud_none() because with 2-level page tables it's always false, so we will never go down to pmd level where swapper_pg_dir populated. But you gave me another idea how we could use p?d_none() and avoid rewriting table entries: void kasan_early_pmd_populate(unsigned long start, unsigned long end, pte_t *pte) { unsigned long addr = start; long next; do { pgd_t *pgd = pgd_offset_k(addr); pud_t *pud = pud_offset(pgd, addr); pmd_t *pmd = pmd_offset(pud, addr); if (!pmd_none(*pmd)) break; pmd_populate_kernel(&init_mm, pmd, pte); next = pgd_addr_end(addr, end); next = pud_addr_end(addr, next) next = pmd_addr_end(addr, next); } while(addr = next, addr != end); } void kasan_early_pud_populate(unsigned long start, unsigned long end, pmd_t *pmd) { unsigned long addr = start; long next; do { pgd_t *pgd = pgd_offset_k(addr); pud_t *pud = pud_offset(pgd, addr); if (!pud_none(*pud)) break; pud_populate(&init_mm, pud, pmd); next = pud_addr_end(addr, pgd_addr_end(addr, end)); } while(addr = next, addr != end); } void kasan_early_pgd_populate(...) { //something similar to above .... } static void __init kasan_map_early_shadow(void) { kasan_early_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, kasan_zero_pud); kasan_early_pud_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, kasan_zero_pmd); kasan_early_pmd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, kasan_zero_pte); kasan_early_pte_populate(); } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org