Commit 6215d9f4 authored Feb 11, 2026 by Mike Rapoport (Microsoft) Committed by Andrew Morton Apr 05, 2026

arch, mm: consolidate empty_zero_page

Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of
ZERO_PAGE() to 4.

Every architecture defines empty_zero_page that way or another, but for the
most of them it is always a page aligned page in BSS and most definitions
of ZERO_PAGE do virt_to_page(empty_zero_page).

Move Linus vetted x86 definition of empty_zero_page and ZERO_PAGE() to the
core MM and drop these definitions in architectures that do not implement
colored zero page (MIPS and s390).

ZERO_PAGE() remains a macro because turning it to a wrapper for a static
inline causes severe pain in header dependencies.

For the most part the change is mechanical, with these being noteworthy:

* alpha: aliased empty_zero_page with ZERO_PGE that was also used for boot
  parameters. Switching to a generic empty_zero_page removes the aliasing
  and keeps ZERO_PGE for boot parameters only
* arm64: uses __pa_symbol() in ZERO_PAGE() so that definition of
  ZERO_PAGE() is kept intact.
* m68k/parisc/um: allocated empty_zero_page from memblock,
  although they do not support zero page coloring and having it in BSS
  will work fine.
* sparc64 can have empty_zero_page in BSS rather allocate it, but it
  can't use virt_to_page() for BSS. Keep it's definition of ZERO_PAGE()
  but instead of allocating it, make mem_map_zero point to
  empty_zero_page.
* sh: used empty_zero_page for boot parameters at the very early boot.
  Rename the parameters page to boot_params_page and let sh use the generic
  empty_zero_page.
* hexagon: had an amusing comment about empty_zero_page

	/* A handy thing to have if one has the RAM. Declared in head.S */

  that unfortunately had to go :)

Link: https://lkml.kernel.org/r/20260211103141.3215197-4-rppt@kernel.org


Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Helge Deller <deller@gmx.de>		[parisc]
Tested-by: Helge Deller <deller@gmx.de>		[parisc]
Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Magnus Lindholm <linmag7@gmail.com>	[alpha]
Acked-by: Dinh Nguyen <dinguyen@kernel.org>	[nios2]
Acked-by: Andreas Larsson <andreas@gaisler.com>	[sparc]
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 9a1d0c73

arch/alpha/include/asm/pgtable.h

+0 −6

Original line number	Diff line number	Diff line
		@@ -126,12 +126,6 @@ struct vm_area_struct;
		*/
		#define pgprot_noncached(prot) (prot)

		/*
		* ZERO_PAGE is a global shared page that is always zero: used
		* for zero-mapped memory areas etc..
		*/
		#define ZERO_PAGE(vaddr) (virt_to_page(ZERO_PGE))

		/*
		* On certain platforms whose physical address space can overlap KSEG,
		* namely EV6 and above, we must re-twiddle the physaddr to restore the

arch/arc/include/asm/pgtable.h

+0 −3

Original line number	Diff line number	Diff line
		@@ -21,9 +21,6 @@

		#ifndef __ASSEMBLER__

		extern char empty_zero_page[PAGE_SIZE];
		#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))

		extern pgd_t swapper_pg_dir[] __aligned(PAGE_SIZE);

		/* to cope with aliasing VIPT cache */

arch/arc/mm/init.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -19,8 +19,6 @@
		#include <asm/arcregs.h>

		pgd_t swapper_pg_dir[PTRS_PER_PGD] __aligned(PAGE_SIZE);
		char empty_zero_page[PAGE_SIZE] __aligned(PAGE_SIZE);
		EXPORT_SYMBOL(empty_zero_page);

		static const unsigned long low_mem_start = CONFIG_LINUX_RAM_BASE;
		static unsigned long low_mem_sz;

arch/arm/include/asm/pgtable.h

+0 −9

Original line number	Diff line number	Diff line
		@@ -10,15 +10,6 @@
		#include <linux/const.h>
		#include <asm/proc-fns.h>

		#ifndef __ASSEMBLY__
		/*
		* ZERO_PAGE is a global shared page that is always zero: used
		* for zero-mapped memory areas etc..
		*/
		extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
		#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
		#endif

		#include <asm-generic/pgtable-nopud.h>

		#ifndef CONFIG_MMU

arch/arm/mm/mmu.c

+0 −7

Original line number	Diff line number	Diff line
		@@ -41,13 +41,6 @@

		extern unsigned long __atags_pointer;

		/*
		* 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;
		EXPORT_SYMBOL(empty_zero_page);

		/*
		* The pmd table for the upper-most set of pages.
		*/