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

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Message-ID: <CAMj1kXH7Ed6+uKWEDozu97tfiQUtXxuT5ocp7HoBpZ++T0tvuA@mail.gmail.com>
Date: Fri, 23 Jan 2026 07:44:26 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: Ard Biesheuvel <ardb+git@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, will@...nel.org, 
	catalin.marinas@....com, mark.rutland@....com, 
	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 Fri, 23 Jan 2026 at 07:43, Anshuman Khandual
<anshuman.khandual@....com> wrote:
>
>
>
> 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.
>

It is related to the other three patches: the 4th patch requires it.

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

Thanks!