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

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Message-ID: <ddb667ef-efd1-40f5-832d-9017f6bbbec5@arm.com>
Date: Fri, 23 Jan 2026 12:13:23 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Ard Biesheuvel <ardb+git@...gle.com>, 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: Re: [PATCH 3/4] arm64: Move the zero page to rodata



On 19/01/26 10:17 PM, Ard Biesheuvel wrote:
> 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);

A small nit - could this be the first patch in the series here ? Becasue it is
not related to other three patches.

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>