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arch, mm: consolidate empty_zero_page

Browse Source 
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>
This commit is contained in:
Mike Rapoport (Microsoft)
2026-02-11 12:31:40 +02:00
committed by Andrew Morton
parent 9a1d0c738b
commit 6215d9f447
59 changed files with 23 additions and 285 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
arch/alpha/include/asm/pgtable.h
View File

@@ -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

3
arch/arc/include/asm/pgtable.h
View File

@@ -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 */

2
arch/arc/mm/init.c
View File

@@ -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;

9
arch/arm/include/asm/pgtable.h
View File

@@ -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

7
arch/arm/mm/mmu.c
View File

@@ -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.
*/

7
arch/arm/mm/nommu.c
View File

@@ -27,13 +27,6 @@
unsigned long vectors_base;
/*
* 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);
#ifdef CONFIG_ARM_MPU
struct mpu_rgn_info mpu_rgn_info;
#endif

1
arch/arm64/include/asm/pgtable.h
View File

@@ -110,7 +110,6 @@ static inline void arch_leave_lazy_mmu_mode(void)
* 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) phys_to_page(__pa_symbol(empty_zero_page))
#define pte_ERROR(e) \

7
arch/arm64/mm/mmu.c
View File

@@ -64,13 +64,6 @@ static bool rodata_is_rw __ro_after_init = true;
*/
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;
EXPORT_SYMBOL(empty_zero_page);
static DEFINE_SPINLOCK(swapper_pgdir_lock);
static DEFINE_MUTEX(fixmap_lock);

3
arch/csky/include/asm/pgtable.h
View File

@@ -76,9 +76,6 @@
#define MAX_SWAPFILES_CHECK() \
BUILD_BUG_ON(MAX_SWAPFILES_SHIFT != 5)
extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
extern void load_pgd(unsigned long pg_dir);
extern pte_t invalid_pte_table[PTRS_PER_PTE];

3
arch/csky/mm/init.c
View File

@@ -38,9 +38,6 @@ pte_t invalid_pte_table[PTRS_PER_PTE] __page_aligned_bss;
pte_t kernel_pte_tables[PTRS_KERN_TABLE] __page_aligned_bss;
EXPORT_SYMBOL(invalid_pte_table);
unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
__page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);
void free_initmem(void)
{

6
arch/hexagon/include/asm/pgtable.h
View File

@@ -14,9 +14,6 @@
#include <asm/page.h>
#include <asm-generic/pgtable-nopmd.h>
/* A handy thing to have if one has the RAM. Declared in head.S */
extern unsigned long empty_zero_page;
/*
* The PTE model described here is that of the Hexagon Virtual Machine,
* which autonomously walks 2-level page tables. At a lower level, we
@@ -348,9 +345,6 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
return (unsigned long)__va(pmd_val(pmd) & PAGE_MASK);
}
/* ZERO_PAGE - returns the globally shared zero page */
#define ZERO_PAGE(vaddr) (virt_to_page(&empty_zero_page))
/*
* Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
* are !pte_none() && !pte_present().

5
arch/hexagon/kernel/head.S
View File

@@ -216,8 +216,3 @@ __head_s_vaddr_target:
.p2align PAGE_SHIFT
ENTRY(external_cmdline_buffer)
.fill _PAGE_SIZE,1,0
.data
.p2align PAGE_SHIFT
ENTRY(empty_zero_page)
.fill _PAGE_SIZE,1,0

1
arch/hexagon/kernel/hexagon_ksyms.c
View File

@@ -17,7 +17,6 @@ EXPORT_SYMBOL(raw_copy_to_user);
EXPORT_SYMBOL(__vmgetie);
EXPORT_SYMBOL(__vmsetie);
EXPORT_SYMBOL(__vmyield);
EXPORT_SYMBOL(empty_zero_page);
EXPORT_SYMBOL(memcpy);
EXPORT_SYMBOL(memset);

9
arch/loongarch/include/asm/pgtable.h
View File

@@ -74,15 +74,6 @@
struct mm_struct;
struct vm_area_struct;
/*
* 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)
#ifdef CONFIG_32BIT
#define VMALLOC_START (vm_map_base + PCI_IOSIZE + (2 * PAGE_SIZE))

3
arch/loongarch/mm/init.c
View File

@@ -36,9 +36,6 @@
#include <asm/pgalloc.h>
#include <asm/tlb.h>
unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);
void copy_user_highpage(struct page *to, struct page *from,
unsigned long vaddr, struct vm_area_struct *vma)
{

9
arch/m68k/include/asm/pgtable_mm.h
View File

@@ -110,15 +110,6 @@ extern unsigned long m68k_vmalloc_end;
#define VMALLOC_END KMAP_START
#endif
/* zero page used for uninitialized stuff */
extern void *empty_zero_page;
/*
* 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(empty_zero_page))
extern void kernel_set_cachemode(void *addr, unsigned long size, int cmode);
/*

7
arch/m68k/include/asm/pgtable_no.h
View File

@@ -30,13 +30,6 @@
#define swapper_pg_dir ((pgd_t *) 0)
/*
* ZERO_PAGE is a global shared page that is always zero: used
* for zero-mapped memory areas etc..
*/
extern void *empty_zero_page;
#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
/*
* All 32bit addresses are effectively valid for vmalloc...
* Sort of meaningless for non-VM targets.

9
arch/m68k/mm/init.c
View File

@@ -33,13 +33,6 @@
#include <asm/sections.h>
#include <asm/tlb.h>
/*
* ZERO_PAGE is a special page that is used for zero-initialized
* data and COW.
*/
void *empty_zero_page;
EXPORT_SYMBOL(empty_zero_page);
void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
{
max_zone_pfns[ZONE_DMA] = PFN_DOWN(memblock_end_of_DRAM());
@@ -71,8 +64,6 @@ void __init paging_init(void)
unsigned long end_mem = memory_end & PAGE_MASK;
high_memory = (void *) end_mem;
empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
}
#endif /* CONFIG_MMU */

2
arch/m68k/mm/mcfmmu.c
View File

@@ -41,8 +41,6 @@ void __init paging_init(void)
unsigned long next_pgtable;
int i;
empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
pg_dir = swapper_pg_dir;
memset(swapper_pg_dir, 0, sizeof(swapper_pg_dir));

6
arch/m68k/mm/motorola.c
View File

@@ -498,12 +498,6 @@ void __init paging_init(void)
early_memtest(min_addr, max_addr);
/*
* initialize the bad page table and bad page to point
* to a couple of allocated pages
*/
empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
/*
* Set up SFC/DFC registers
*/

2
arch/m68k/mm/sun3mmu.c
View File

@@ -43,8 +43,6 @@ void __init paging_init(void)
unsigned long bootmem_end;
unsigned long size;
empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
address = PAGE_OFFSET;
pg_dir = swapper_pg_dir;
memset (swapper_pg_dir, 0, sizeof (swapper_pg_dir));

10
arch/microblaze/include/asm/pgtable.h
View File

@@ -207,16 +207,6 @@ extern pte_t *va_to_pte(unsigned long address);
* Also, write permissions imply read permissions.
*/
#ifndef __ASSEMBLER__
/*
* ZERO_PAGE is a global shared page that is always zero: used
* for zero-mapped memory areas etc..
*/
extern unsigned long empty_zero_page[1024];
#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
#endif /* __ASSEMBLER__ */
#define pte_none(pte) ((pte_val(pte) & ~_PTE_NONE_MASK) == 0)
#define pte_present(pte) (pte_val(pte) & _PAGE_PRESENT)
#define pte_clear(mm, addr, ptep) \

4
arch/microblaze/kernel/head.S
View File

@@ -39,10 +39,6 @@
#include <asm/processor.h>
.section .data
.global empty_zero_page
.align 12
empty_zero_page:
.space PAGE_SIZE
.global swapper_pg_dir
swapper_pg_dir:
.space PAGE_SIZE

2
arch/microblaze/kernel/microblaze_ksyms.c
View File

@@ -33,8 +33,6 @@ EXPORT_SYMBOL(memcpy);
EXPORT_SYMBOL(memmove);
#endif
EXPORT_SYMBOL(empty_zero_page);
EXPORT_SYMBOL(mbc);
extern void __divsi3(void);

7
arch/nios2/include/asm/pgtable.h
View File

@@ -65,13 +65,6 @@ struct mm_struct;
#define PGDIR_SIZE (1UL << PGDIR_SHIFT)
#define PGDIR_MASK (~(PGDIR_SIZE-1))
/*
* 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))
extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
extern pte_t invalid_pte_table[PAGE_SIZE/sizeof(pte_t)];

10
arch/nios2/kernel/head.S
View File

@@ -23,16 +23,6 @@
#include <asm/asm-offsets.h>
#include <asm/asm-macros.h>
/*
* ZERO_PAGE is a special page that is used for zero-initialized
* data and COW.
*/
.data
.global empty_zero_page
.align 12
empty_zero_page:
.space PAGE_SIZE
/*
* This global variable is used as an extension to the nios'
* STATUS register to emulate a user/supervisor mode.

1
arch/nios2/kernel/nios2_ksyms.c
View File

@@ -20,7 +20,6 @@ EXPORT_SYMBOL(memmove);
/* memory management */
EXPORT_SYMBOL(empty_zero_page);
EXPORT_SYMBOL(flush_icache_range);
/*

4
arch/openrisc/include/asm/pgtable.h
View File

@@ -179,10 +179,6 @@ extern void paging_init(void);
__pgprot(_PAGE_ALL | _PAGE_SRE | _PAGE_SWE \
| _PAGE_SHARED | _PAGE_DIRTY | _PAGE_EXEC | _PAGE_CI)
/* zero page used for uninitialized stuff */
extern unsigned long empty_zero_page[2048];
#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
#define pte_none(x) (!pte_val(x))
#define pte_present(x) (pte_val(x) & _PAGE_PRESENT)
#define pte_clear(mm, addr, xp) do { pte_val(*(xp)) = 0; } while (0)

3
arch/openrisc/kernel/head.S
View File

@@ -1563,9 +1563,6 @@ _string_nl:
*/
.section .data,"aw"
.align 8192
.global empty_zero_page
empty_zero_page:
.space 8192
.global swapper_pg_dir
swapper_pg_dir:

1
arch/openrisc/kernel/or32_ksyms.c
View File

@@ -40,7 +40,6 @@ DECLARE_EXPORT(__ashldi3);
DECLARE_EXPORT(__lshrdi3);
DECLARE_EXPORT(__ucmpdi2);
EXPORT_SYMBOL(empty_zero_page);
EXPORT_SYMBOL(__copy_tofrom_user);
EXPORT_SYMBOL(__clear_user);
EXPORT_SYMBOL(memset);

3
arch/openrisc/mm/init.c
View File

@@ -188,9 +188,6 @@ void __init mem_init(void)
{
BUG_ON(!mem_map);
/* clear the zero-page */
memset((void *)empty_zero_page, 0, PAGE_SIZE);
printk("mem_init_done ...........................................\n");
mem_init_done = 1;
return;

11
arch/parisc/include/asm/pgtable.h
View File

@@ -262,17 +262,6 @@ extern pgd_t swapper_pg_dir[]; /* declared in init_task.c */
extern pte_t pg0[];
/* zero page used for uninitialized stuff */
extern unsigned long *empty_zero_page;
/*
* 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(empty_zero_page))
#define pte_none(x) (pte_val(x) == 0)
#define pte_present(x) (pte_val(x) & _PAGE_PRESENT)
#define pte_user(x) (pte_val(x) & _PAGE_USER)

6
arch/parisc/mm/init.c
View File

@@ -604,9 +604,6 @@ void __init mem_init(void)
#endif
}
unsigned long *empty_zero_page __ro_after_init;
EXPORT_SYMBOL(empty_zero_page);
/*
* pagetable_init() sets up the page tables
*
@@ -639,9 +636,6 @@ static void __init pagetable_init(void)
initrd_end - initrd_start, PAGE_KERNEL, 0);
}
#endif
empty_zero_page = memblock_alloc_or_panic(PAGE_SIZE, PAGE_SIZE);
}
static void __init gateway_init(void)

6
arch/powerpc/include/asm/pgtable.h
View File

@@ -76,12 +76,6 @@ static inline const void *pmd_page_vaddr(pmd_t pmd)
}
#define pmd_page_vaddr pmd_page_vaddr
#endif
/*
* ZERO_PAGE is a global shared page that is always zero: used
* for zero-mapped memory areas etc..
*/
extern unsigned long empty_zero_page[];
#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
extern pgd_t swapper_pg_dir[];

3
arch/powerpc/mm/mem.c
View File

@@ -38,9 +38,6 @@
unsigned long long memory_limit __initdata;
unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);
pgprot_t __phys_mem_access_prot(unsigned long pfn, unsigned long size,
pgprot_t vma_prot)
{

7
arch/riscv/include/asm/pgtable.h
View File

@@ -1284,13 +1284,6 @@ extern u64 satp_mode;
void paging_init(void);
void misc_mem_init(void);
/*
* 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))
/*
* Use set_p*_safe(), and elide TLB flushing, when confident that *no*
* TLB flush will be required as a result of the "set". For example, use

4
arch/riscv/mm/init.c
View File

@@ -69,10 +69,6 @@ unsigned long vmemmap_start_pfn __ro_after_init;
EXPORT_SYMBOL(vmemmap_start_pfn);
#endif
unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
__page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);
extern char _start[];
void *_dtb_early_va __initdata;
uintptr_t _dtb_early_pa __initdata;

8
arch/sh/include/asm/pgtable.h
View File

@@ -20,14 +20,6 @@
#ifndef __ASSEMBLER__
#include <asm/addrspace.h>
#include <asm/fixmap.h>
/*
* 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 /* !__ASSEMBLER__ */
/*

3
arch/sh/include/asm/setup.h
View File

@@ -7,7 +7,8 @@
/*
* This is set up by the setup-routine at boot-time
*/
#define PARAM ((unsigned char *)empty_zero_page)
extern unsigned char *boot_params_page;
#define PARAM boot_params_page
#define MOUNT_ROOT_RDONLY (*(unsigned long *) (PARAM+0x000))
#define RAMDISK_FLAGS (*(unsigned long *) (PARAM+0x004))

4
arch/sh/kernel/head_32.S
View File

@@ -26,7 +26,7 @@
#endif
.section .empty_zero_page, "aw"
ENTRY(empty_zero_page)
ENTRY(boot_params_page)
.long 1 /* MOUNT_ROOT_RDONLY */
.long 0 /* RAMDISK_FLAGS */
.long 0x0200 /* ORIG_ROOT_DEV */
@@ -39,7 +39,7 @@ ENTRY(empty_zero_page)
.long 0x53453f00 + 29 /* "SE?" = 29 bit */
#endif
1:
.skip PAGE_SIZE - empty_zero_page - 1b
.skip PAGE_SIZE - boot_params_page - 1b
__HEAD

1
arch/sh/kernel/sh_ksyms_32.c
View File

@@ -20,7 +20,6 @@ EXPORT_SYMBOL(csum_partial);
EXPORT_SYMBOL(csum_partial_copy_generic);
EXPORT_SYMBOL(copy_page);
EXPORT_SYMBOL(__clear_user);
EXPORT_SYMBOL(empty_zero_page);
#ifdef CONFIG_FLATMEM
/* need in pfn_valid macro */
EXPORT_SYMBOL(min_low_pfn);

1
arch/sh/mm/init.c
View File

@@ -332,7 +332,6 @@ void __init mem_init(void)
cpu_cache_init();
/* clear the zero-page */
memset(empty_zero_page, 0, PAGE_SIZE);
__flush_wback_region(empty_zero_page, PAGE_SIZE);
vsyscall_init();

8
arch/sparc/include/asm/pgtable_32.h
View File

@@ -71,14 +71,6 @@ extern unsigned long ptr_in_current_pgd;
extern unsigned long phys_base;
extern unsigned long pfn_base;
/*
* 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))
/*
* In general all page table modifications should use the V8 atomic
* swap instruction. This insures the mmu and the cpu are in sync

2
arch/sparc/include/asm/setup.h
View File

@@ -17,8 +17,6 @@ extern char reboot_command[];
*/
extern unsigned char boot_cpu_id;
extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
extern int serial_console;
static inline int con_is_present(void)
{

7
arch/sparc/kernel/head_32.S
View File

@@ -57,13 +57,6 @@ sun4e_notsup:
.align PAGE_SIZE
/* This was the only reasonable way I could think of to properly align
* these page-table data structures.
*/
.globl empty_zero_page
empty_zero_page: .skip PAGE_SIZE
EXPORT_SYMBOL(empty_zero_page)
.global root_flags
.global ram_flags
.global root_dev

4
arch/sparc/mm/init_32.c
View File

@@ -246,10 +246,6 @@ void __init arch_mm_preinit(void)
prom_halt();
}
/* Saves us work later. */
memset((void *)empty_zero_page, 0, PAGE_SIZE);
i = last_valid_pfn >> ((20 - PAGE_SHIFT) + 5);
i += 1;
sparc_valid_addr_bitmap = (unsigned long *)

11
arch/sparc/mm/init_64.c
View File

@@ -2492,6 +2492,9 @@ static void __init register_page_bootmem_info(void)
}
void __init mem_init(void)
{
phys_addr_t zero_page_pa = kern_base +
((unsigned long)&empty_zero_page[0] - KERNBASE);
/*
* Must be done after boot memory is put on freelist, because here we
* might set fields in deferred struct pages that have not yet been
@@ -2504,13 +2507,7 @@ void __init mem_init(void)
* Set up the zero page, mark it reserved, so that page count
* is not manipulated when freeing the page from user ptes.
*/
mem_map_zero = alloc_pages(GFP_KERNEL|__GFP_ZERO, 0);
if (mem_map_zero == NULL) {
prom_printf("paging_init: Cannot alloc zero page.\n");
prom_halt();
}
mark_page_reserved(mem_map_zero);
mem_map_zero = pfn_to_page(PHYS_PFN(zero_page_pa));
if (tlb_type == cheetah || tlb_type == cheetah_plus)
cheetah_ecache_flush_init();

9
arch/um/include/asm/pgtable.h
View File

@@ -34,9 +34,6 @@
extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
/* zero page used for uninitialized stuff */
extern unsigned long *empty_zero_page;
/* Just any arbitrary offset to the start of the vmalloc VM area: the
* current 8MB value just means that there will be a 8MB "hole" after the
* physical memory until the kernel virtual memory starts. That means that
@@ -74,12 +71,6 @@ extern unsigned long *empty_zero_page;
* get..
*/
/*
* 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(empty_zero_page)
#define pte_clear(mm, addr, xp) pte_set_val(*(xp), (phys_t) 0, __pgprot(_PAGE_NEEDSYNC))
#define pmd_none(x) (!((unsigned long)pmd_val(x) & ~_PAGE_NEEDSYNC))

1
arch/um/include/shared/kern_util.h
View File

@@ -38,7 +38,6 @@ extern void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs
extern void uml_pm_wake(void);
extern int start_uml(void);
extern void paging_init(void);
extern void uml_cleanup(void);
extern void do_uml_exitcalls(void);

16
arch/um/kernel/mem.c
View File

@@ -44,10 +44,6 @@ __section(".kasan_init") __used
= kasan_init;
#endif
/* allocated in paging_init, zeroed in mem_init, and unchanged thereafter */
unsigned long *empty_zero_page = NULL;
EXPORT_SYMBOL(empty_zero_page);
/*
* Initialized during boot, and readonly for initializing page tables
* afterwards
@@ -65,9 +61,6 @@ void __init arch_mm_preinit(void)
/* Safe to call after jump_label_init(). Enables KASAN. */
kasan_init_generic();
/* clear the zero-page */
memset(empty_zero_page, 0, PAGE_SIZE);
/* Map in the area just after the brk now that kmalloc is about
* to be turned on.
*/
@@ -89,15 +82,6 @@ void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
max_zone_pfns[ZONE_NORMAL] = high_physmem >> PAGE_SHIFT;
}
void __init paging_init(void)
{
empty_zero_page = (unsigned long *) memblock_alloc_low(PAGE_SIZE,
PAGE_SIZE);
if (!empty_zero_page)
panic("%s: Failed to allocate %lu bytes align=%lx\n",
__func__, PAGE_SIZE, PAGE_SIZE);
}
/*
* This can't do anything because nothing in the kernel image can be freed
* since it's not in kernel physical memory.

1
arch/um/kernel/um_arch.c
View File

@@ -413,7 +413,6 @@ void __init setup_arch(char **cmdline_p)
uml_dtb_init();
read_initrd();
paging_init();
strscpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
*cmdline_p = command_line;
setup_hostinfo(host_info, sizeof host_info);

8
arch/x86/include/asm/pgtable.h
View File

@@ -47,14 +47,6 @@ void ptdump_walk_user_pgd_level_checkwx(void);
#define debug_checkwx_user() do { } while (0)
#endif
/*
* 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)]
__visible;
#define ZERO_PAGE(vaddr) ((void)(vaddr),virt_to_page(empty_zero_page))
extern spinlock_t pgd_lock;
extern struct list_head pgd_list;

4
arch/x86/kernel/head_32.S
View File

@@ -441,10 +441,6 @@ initial_pg_fixmap:
swapper_pg_dir:
.fill 1024,4,0
.fill PTI_USER_PGD_FILL,4,0
.globl empty_zero_page
empty_zero_page:
.fill 4096,1,0
EXPORT_SYMBOL(empty_zero_page)
/*
* This starts the data section.

7
arch/x86/kernel/head_64.S
View File

@@ -684,10 +684,3 @@ SYM_PIC_ALIAS(phys_base);
EXPORT_SYMBOL(phys_base)
#include "../xen/xen-head.S"
__PAGE_ALIGNED_BSS
SYM_DATA_START_PAGE_ALIGNED(empty_zero_page)
.skip PAGE_SIZE
SYM_DATA_END(empty_zero_page)
EXPORT_SYMBOL(empty_zero_page)

4
arch/xtensa/include/asm/pgtable.h
View File

@@ -209,10 +209,6 @@
#define pgd_ERROR(e) \
printk("%s:%d: bad pgd entry %08lx.\n", __FILE__, __LINE__, pgd_val(e))
extern unsigned long empty_zero_page[1024];
#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
#ifdef CONFIG_MMU
extern pgd_t swapper_pg_dir[PAGE_SIZE/sizeof(pgd_t)];
extern void paging_init(void);

3
arch/xtensa/kernel/head.S
View File

@@ -381,6 +381,3 @@ ENTRY(swapper_pg_dir)
.fill PAGE_SIZE, 1, 0
END(swapper_pg_dir)
#endif
ENTRY(empty_zero_page)
.fill PAGE_SIZE, 1, 0
END(empty_zero_page)

2
arch/xtensa/kernel/xtensa_ksyms.c
View File

@@ -15,8 +15,6 @@
#include <linux/module.h>
#include <asm/pgtable.h>
EXPORT_SYMBOL(empty_zero_page);
unsigned int __sync_fetch_and_and_4(volatile void *p, unsigned int v)
{
BUG();

10
include/linux/pgtable.h
View File

@@ -1925,6 +1925,9 @@ static inline void pfnmap_setup_cachemode_pfn(unsigned long pfn, pgprot_t *prot)
* for different ranges in the virtual address space.
*
* zero_page_pfn identifies the first (or the only) pfn for these pages.
*
* For architectures that don't __HAVE_COLOR_ZERO_PAGE the zero page lives in
* empty_zero_page in BSS.
*/
#ifdef __HAVE_COLOR_ZERO_PAGE
static inline int is_zero_pfn(unsigned long pfn)
@@ -1951,6 +1954,13 @@ static inline unsigned long zero_pfn(unsigned long addr)
return zero_page_pfn;
}
extern uint8_t empty_zero_page[PAGE_SIZE];
#ifndef ZERO_PAGE
#define ZERO_PAGE(vaddr) ((void)(vaddr),virt_to_page(empty_zero_page))
#endif
#endif /* __HAVE_COLOR_ZERO_PAGE */
#ifdef CONFIG_MMU

5
mm/mm_init.c
View File

@@ -56,6 +56,11 @@ EXPORT_SYMBOL(high_memory);
unsigned long zero_page_pfn __ro_after_init;
EXPORT_SYMBOL(zero_page_pfn);
#ifndef __HAVE_COLOR_ZERO_PAGE
uint8_t empty_zero_page[PAGE_SIZE] __page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);
#endif
#ifdef CONFIG_DEBUG_MEMORY_INIT
int __meminitdata mminit_loglevel;