linux-kernel - [PATCH 3/4] arm64: Move the zero page to rodata

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Message-ID: <20260119164747.1402434-9-ardb+git@google.com>
Date: Mon, 19 Jan 2026 17:47:51 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org, will@...nel.org, 
	catalin.marinas@....com, mark.rutland@....com, 
	Ard Biesheuvel <ardb@...nel.org>, Ryan Roberts <ryan.roberts@....com>, 
	Liz Prucka <lizprucka@...gle.com>, Seth Jenkins <sethjenkins@...gle.com>, 
	Kees Cook <kees@...nel.org>, linux-hardening@...r.kernel.org
Subject: [PATCH 3/4] arm64: Move the zero page to rodata

From: Ard Biesheuvel <ardb@...nel.org>

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 <ardb@...nel.org>
---
 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