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| author | Catalin Marinas <catalin.marinas@arm.com> | 2019-11-27 09:53:44 +0000 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2020-09-04 12:46:07 +0100 |
| commit | 4d1a8a2dc0f4cdc2d74491a60709e698f85daf55 (patch) | |
| tree | 86fcb21ff8feb64b59ffaf47756cb2c2353f13cb | |
| parent | 738c8780fc1fa11fb996a962a54703d0450cae59 (diff) | |
| download | linux-4d1a8a2dc0f4cdc2d74491a60709e698f85daf55.tar.bz2 | |
arm64: mte: Tags-aware aware memcmp_pages() implementation
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: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
| -rw-r--r-- | arch/arm64/kernel/mte.c | 26 | ||||
| -rw-r--r-- | mm/util.c | 2 |
2 files changed, 27 insertions, 1 deletions
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index 5bf9bbed5a25..5f54fd140610 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -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()) diff --git a/mm/util.c b/mm/util.c index 5ef378a2a038..4e21fe7eae27 100644 --- a/mm/util.c +++ b/mm/util.c @@ -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; |