Re: [PATCH v2 01/10] arm64: Move the zero page to rodata

On Tue, 27 Jan 2026 at 11:04, Ryan Roberts [off-list ref] wrote:

On 27/01/2026 09:49, Ard Biesheuvel wrote:

quoted

On Tue, 27 Jan 2026 at 10:34, Ryan Roberts [off-list ref] wrote:

quoted

On 26/01/2026 09:26, Ard Biesheuvel wrote:

quoted

From: Ard Biesheuvel <ardb@kernel.org>

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.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 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 ad6133b89e7a..b2a093f5b3fc 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 = .;

Isn't there a magic macro for getting from swapper to reserved? That will need
updating?

Why? This just adds an alias to refer to the same allocation.

Oh yes, sorry I completely missed that. And you've even stated it in the commit
log...

I'm struggling to see where this gets zeroed though? I assume it must be zeroed
before the old empty_zero_page would have been so everything works fine?

It is statically zero initialized in the image.

Assuming yes, then:

Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>

Thanks!