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Fri, 20 Mar 2026 07:59:58 -0700 (PDT) Date: Fri, 20 Mar 2026 15:59:36 +0100 In-Reply-To: <20260320145934.2349881-15-ardb+git@google.com> Mime-Version: 1.0 References: <20260320145934.2349881-15-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=1378; i=ardb@kernel.org; h=from:subject; bh=RibIB1GLYG+hdvnhodqrMTwRdLcWjhU+FIfxTN8QGOE=; b=owGbwMvMwCVmkMcZplerG8N4Wi2JIXNvwg0NRZfn2x1sFK1v1Pz9rqZ67tSf5pz7BSbbI45lq r6JCj/SUcrCIMbFICumyCIw+++7nacnStU6z5KFmcPKBDKEgYtTACYSe4Lhf4av44tX7XM2z5jP tiQteavvlcf7rP4+8/f/HWmS78DCrcjwT7fZMPfNT6PIiPcsKSeFWxb9ELqz5sr8wg1Z953NNuz 9zAcA X-Mailer: git-send-email 2.53.0.959.g497ff81fa9-goog Message-ID: <20260320145934.2349881-16-ardb+git@google.com> Subject: [PATCH v3 01/13] 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 , Anshuman Khandual , 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-20260320_080001_830155_62F2552A X-CRM114-Status: GOOD ( 11.56 ) 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. Combine it with reserved_pg_dir, which lives in the read-only region of the kernel, and already serves a similar purpose. Reviewed-by: Ryan Roberts Signed-off-by: Ard Biesheuvel --- arch/arm64/kernel/vmlinux.lds.S | 1 + arch/arm64/mm/mmu.c | 3 +-- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 2964aad0362e..2d021a576e50 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -229,6 +229,7 @@ SECTIONS #endif reserved_pg_dir = .; + empty_zero_page = .; . += PAGE_SIZE; swapper_pg_dir = .; diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index a6a00accf4f9..795743913ce5 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -66,9 +66,8 @@ 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. + * and COW. Defined in the linker script. */ -unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss; EXPORT_SYMBOL(empty_zero_page); static DEFINE_SPINLOCK(swapper_pgdir_lock); -- 2.53.0.959.g497ff81fa9-goog