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Wed, 03 Jun 2026 09:11:22 -0700 (PDT) Date: Wed, 3 Jun 2026 18:09:53 +0200 In-Reply-To: <20260603160949.3372482-6-ardb+git@google.com> Mime-Version: 1.0 References: <20260603160949.3372482-6-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=1037; i=ardb@kernel.org; h=from:subject; bh=SJHawBMrvWNXo+6oa7fD+p3VxoLw7RWBCVzA/QDwCOg=; b=owGbwMvMwCVmkMcZplerG8N4Wi2JIUsh8FLd1w3h24XNTyeYGLFxHm72u+/DcGNVcbKX3jXWH UnCv092lLIwiHExyIopsgjM/vtu5+mJUrXOs2Rh5rAygQxh4OIUgIn01TIyvHN4t/fK3iV7N0yb H3rcwJP5rHPc4/MJQYtmbpwYdK+Ut4vhr+SPVTMyHFw14pUUEyfzzTXYGGSy5frpGwsWtSz5UpT uwAEA X-Mailer: git-send-email 2.54.0.1013.g208068f2d8-goog Message-ID: <20260603160949.3372482-9-ardb+git@google.com> Subject: [PATCH 3/4] arm64: mte: Disregard the zero page explicitly for manipulating tags From: Ard Biesheuvel To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, maz@kernel.org, Ard Biesheuvel , Kevin Brodsky , Mark Brown Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260603_091125_030459_FE44E53A X-CRM114-Status: GOOD ( 12.03 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Ard Biesheuvel The zero page is conceptually immutable, and will be moved into .rodata to prevent inadvertent corruption. Prepare the MTE code for this, by ensuring that the zero page is never taken into account for tag manipulation, given that those actions will no longer be permitted on the read-only alias of .rodata in the linear map. Signed-off-by: Ard Biesheuvel --- arch/arm64/include/asm/mte.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h index 7f7b97e09996..093b34944aee 100644 --- a/arch/arm64/include/asm/mte.h +++ b/arch/arm64/include/asm/mte.h @@ -80,6 +80,11 @@ static inline bool page_mte_tagged(struct page *page) */ static inline bool try_page_mte_tagging(struct page *page) { + extern struct page *__zero_page; + + if (page == __zero_page) + return false; + VM_WARN_ON_ONCE(folio_test_hugetlb(page_folio(page))); if (!test_and_set_bit(PG_mte_lock, &page->flags.f)) -- 2.54.0.1013.g208068f2d8-goog