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Mon, 19 Jan 2026 08:56:22 -0800 (PST) Date: Mon, 19 Jan 2026 17:47:51 +0100 In-Reply-To: <20260119164747.1402434-6-ardb+git@google.com> Mime-Version: 1.0 References: <20260119164747.1402434-6-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=912; i=ardb@kernel.org; h=from:subject; bh=ntHgf/B5rJ53w9Bpw1t4lvz9osH4/R661+iGUCVVrMg=; b=kA0DAAoWMG4JVi59LVwByyZiAGluYDWjUrFAokWqtXDSeMp+fXT75fRWyZSWbI99Ms6WNd75g 4h1BAAWCgAdFiEEEJv97rnLkRp9Q5odMG4JVi59LVwFAmluYDUACgkQMG4JVi59LVxCrgD/Z9M5 i4NwfvsUUSXv+UZafROf6v5ISFsyVqAdG/yUKToBAI84KHD/NB176E35kaZByGlx6nYy+/owAfj bvWNO+8YO X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog Message-ID: <20260119164747.1402434-9-ardb+git@google.com> Subject: [PATCH 3/4] arm64: Move the zero page to rodata From: Ard Biesheuvel To: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, Ard Biesheuvel , Ryan Roberts , Liz Prucka , Seth Jenkins , Kees Cook , linux-hardening@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260119_085624_284865_BF22333C X-CRM114-Status: GOOD ( 11.42 ) 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 should contain only zero bytes, and so mapping it read-write is unnecessary. Move it to __ro_after_init instead. Signed-off-by: Ard Biesheuvel --- arch/arm64/mm/mmu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 2a18637ecc15..d978b07ab7b8 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -68,7 +68,8 @@ long __section(".mmuoff.data.write") __early_cpu_boot_status; * Empty_zero_page is a special page that is used for zero-initialized data * and COW. */ -unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss; +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] + __ro_after_init __aligned(PAGE_SIZE); EXPORT_SYMBOL(empty_zero_page); static DEFINE_SPINLOCK(swapper_pgdir_lock); -- 2.52.0.457.g6b5491de43-goog