arm64: mte: Tags-aware aware memcmp_pages() implementation (4d1a8a2d) · Commits · 戴 / test

When the Memory Tagging Extension is enabled, two pages are identical only if both their data and tags are identical. Make the generic memcmp_pages() a __weak function and add an arm64-specific implementation which returns non-zero if any of the two pages contain valid MTE tags (PG_mte_tagged set). There isn't much benefit in comparing the tags of two pages since these are normally used for heap allocations and likely to differ anyway. Co-developed-by:

Vincenzo Frascino <vincenzo.frascino@arm.com> Signed-off-by:

Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org>

arch/arm64/kernel/mte.c

+26 −0

Original line number	Diff line number	Diff line
		@@ -5,6 +5,7 @@

		#include <linux/bitops.h>
		#include <linux/mm.h>
		#include <linux/string.h>
		#include <linux/thread_info.h>

		#include <asm/cpufeature.h>
		@@ -23,6 +24,31 @@ void mte_sync_tags(pte_t *ptep, pte_t pte)
		}
		}

		int memcmp_pages(struct page page1, struct page page2)
		{
		char addr1, addr2;
		int ret;

		addr1 = page_address(page1);
		addr2 = page_address(page2);
		ret = memcmp(addr1, addr2, PAGE_SIZE);

		if (!system_supports_mte() \|\| ret)
		return ret;

		/*
		* If the page content is identical but at least one of the pages is
		* tagged, return non-zero to avoid KSM merging. If only one of the
		* pages is tagged, set_pte_at() may zero or change the tags of the
		* other page via mte_sync_tags().
		*/
		if (test_bit(PG_mte_tagged, &page1->flags) \|\|
		test_bit(PG_mte_tagged, &page2->flags))
		return addr1 != addr2;

		return ret;
		}

		void flush_mte_state(void)
		{
		if (!system_supports_mte())

mm/util.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -957,7 +957,7 @@ out:
		return res;
		}

		int memcmp_pages(struct page page1, struct page page2)
		int __weak memcmp_pages(struct page page1, struct page page2)
		{
		char addr1, addr2;
		int ret;

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