[PATCH v3 01/13] arm64: Move the zero page to rodata

Ard Biesheuvel
2026-03-20T15:00:00Z

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 <ryan.roberts@arm.com>
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 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