d77e59a8fc
Initialising the tags and setting PG_mte_tagged flag for a page can race between multiple set_pte_at() on shared pages or setting the stage 2 pte via user_mem_abort(). Introduce a new PG_mte_lock flag as PG_arch_3 and set it before attempting page initialisation. Given that PG_mte_tagged is never cleared for a page, consider setting this flag to mean page unlocked and wait on this bit with acquire semantics if the page is locked: - try_page_mte_tagging() - lock the page for tagging, return true if it can be tagged, false if already tagged. No acquire semantics if it returns true (PG_mte_tagged not set) as there is no serialisation with a previous set_page_mte_tagged(). - set_page_mte_tagged() - set PG_mte_tagged with release semantics. The two-bit locking is based on Peter Collingbourne's idea. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Peter Collingbourne <pcc@google.com> Reviewed-by: Steven Price <steven.price@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Marc Zyngier <maz@kernel.org> Cc: Peter Collingbourne <pcc@google.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20221104011041.290951-6-pcc@google.com
41 lines
968 B
C
41 lines
968 B
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Based on arch/arm/mm/copypage.c
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*
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* Copyright (C) 2002 Deep Blue Solutions Ltd, All Rights Reserved.
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* Copyright (C) 2012 ARM Ltd.
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*/
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#include <linux/bitops.h>
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#include <linux/mm.h>
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#include <asm/page.h>
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#include <asm/cacheflush.h>
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#include <asm/cpufeature.h>
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#include <asm/mte.h>
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void copy_highpage(struct page *to, struct page *from)
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{
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void *kto = page_address(to);
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void *kfrom = page_address(from);
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copy_page(kto, kfrom);
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if (system_supports_mte() && page_mte_tagged(from)) {
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page_kasan_tag_reset(to);
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/* It's a new page, shouldn't have been tagged yet */
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WARN_ON_ONCE(!try_page_mte_tagging(to));
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mte_copy_page_tags(kto, kfrom);
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set_page_mte_tagged(to);
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}
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}
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EXPORT_SYMBOL(copy_highpage);
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void copy_user_highpage(struct page *to, struct page *from,
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unsigned long vaddr, struct vm_area_struct *vma)
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{
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copy_highpage(to, from);
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flush_dcache_page(to);
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}
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EXPORT_SYMBOL_GPL(copy_user_highpage);
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