include/asm-s390/pgtable.h

/*
 *  include/asm-s390/pgtable.h
 *
 *  S390 version
 *    Copyright (C) 1999,2000 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Hartmut Penner (hp@de.ibm.com)
 *               Ulrich Weigand (weigand@de.ibm.com)
 *               Martin Schwidefsky (schwidefsky@de.ibm.com)
 *
 *  Derived from "include/asm-i386/pgtable.h"
 */

#ifndef _ASM_S390_PGTABLE_H
#define _ASM_S390_PGTABLE_H

/*
 * The Linux memory management assumes a three-level page table setup. For
 * s390 31 bit we "fold" the mid level into the top-level page table, so
 * that we physically have the same two-level page table as the s390 mmu
 * expects in 31 bit mode. For s390 64 bit we use three of the five levels
 * the hardware provides (region first and region second tables are not
 * used).
 *
 * The "pgd_xxx()" functions are trivial for a folded two-level
 * setup: the pgd is never bad, and a pmd always exists (as it's folded
 * into the pgd entry)
 *
 * This file contains the functions and defines necessary to modify and use
 * the S390 page table tree.
 */
#ifndef __ASSEMBLY__
#include <linux/mm_types.h>
#include <asm/bug.h>
#include <asm/processor.h>

extern pgd_t swapper_pg_dir[] __attribute__ ((aligned (4096)));
extern void paging_init(void);
extern void vmem_map_init(void);

/*
 * The S390 doesn't have any external MMU info: the kernel page
 * tables contain all the necessary information.
 */
#define update_mmu_cache(vma, address, pte)     do { } while (0)

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

/*
 * PMD_SHIFT determines the size of the area a second-level page
 * table can map
 * PGDIR_SHIFT determines what a third-level page table entry can map
 */
#ifndef __s390x__
# define PMD_SHIFT	20
# define PUD_SHIFT	20
# define PGDIR_SHIFT	20
#else /* __s390x__ */
# define PMD_SHIFT	20
# define PUD_SHIFT	31
# define PGDIR_SHIFT	42
#endif /* __s390x__ */

#define PMD_SIZE        (1UL << PMD_SHIFT)
#define PMD_MASK        (~(PMD_SIZE-1))
#define PUD_SIZE	(1UL << PUD_SHIFT)
#define PUD_MASK	(~(PUD_SIZE-1))
#define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
#define PGDIR_MASK	(~(PGDIR_SIZE-1))

/*
 * entries per page directory level: the S390 is two-level, so
 * we don't really have any PMD directory physically.
 * for S390 segment-table entries are combined to one PGD
 * that leads to 1024 pte per pgd
 */
#define PTRS_PER_PTE	256
#ifndef __s390x__
#define PTRS_PER_PMD	1
#define PTRS_PER_PUD	1
#else /* __s390x__ */
#define PTRS_PER_PMD	2048
#define PTRS_PER_PUD	2048
#endif /* __s390x__ */
#define PTRS_PER_PGD	2048

#define FIRST_USER_ADDRESS  0

#define pte_ERROR(e) \
	printk("%s:%d: bad pte %p.\n", __FILE__, __LINE__, (void *) pte_val(e))
#define pmd_ERROR(e) \
	printk("%s:%d: bad pmd %p.\n", __FILE__, __LINE__, (void *) pmd_val(e))
#define pud_ERROR(e) \
	printk("%s:%d: bad pud %p.\n", __FILE__, __LINE__, (void *) pud_val(e))
#define pgd_ERROR(e) \
	printk("%s:%d: bad pgd %p.\n", __FILE__, __LINE__, (void *) pgd_val(e))

#ifndef __ASSEMBLY__
/*
 * The vmalloc area will always be on the topmost area of the kernel
 * mapping. We reserve 96MB (31bit) / 1GB (64bit) for vmalloc,
 * which should be enough for any sane case.
 * By putting vmalloc at the top, we maximise the gap between physical
 * memory and vmalloc to catch misplaced memory accesses. As a side
 * effect, this also makes sure that 64 bit module code cannot be used
 * as system call address.
 */
#ifndef __s390x__
#define VMALLOC_START	0x78000000UL
#define VMALLOC_END	0x7e000000UL
#define VMEM_MAP_END	0x80000000UL
#else /* __s390x__ */
#define VMALLOC_START	0x3e000000000UL
#define VMALLOC_END	0x3e040000000UL
#define VMEM_MAP_END	0x40000000000UL
#endif /* __s390x__ */

/*
 * VMEM_MAX_PHYS is the highest physical address that can be added to the 1:1
 * mapping. This needs to be calculated at compile time since the size of the
 * VMEM_MAP is static but the size of struct page can change.
 */
#define VMEM_MAX_PAGES	((VMEM_MAP_END - VMALLOC_END) / sizeof(struct page))
#define VMEM_MAX_PFN	min(VMALLOC_START >> PAGE_SHIFT, VMEM_MAX_PAGES)
#define VMEM_MAX_PHYS	((VMEM_MAX_PFN << PAGE_SHIFT) & ~((16 << 20) - 1))
#define VMEM_MAP	((struct page *) VMALLOC_END)

/*
 * A 31 bit pagetable entry of S390 has following format:
 *  |   PFRA          |    |  OS  |
 * 0                   0IP0
 * 00000000001111111111222222222233
 * 01234567890123456789012345678901
 *
 * I Page-Invalid Bit:    Page is not available for address-translation
 * P Page-Protection Bit: Store access not possible for page
 *
 * A 31 bit segmenttable entry of S390 has following format:
 *  |   P-table origin      |  |PTL
 * 0                         IC
 * 00000000001111111111222222222233
 * 01234567890123456789012345678901
 *
 * I Segment-Invalid Bit:    Segment is not available for address-translation
 * C Common-Segment Bit:     Segment is not private (PoP 3-30)
 * PTL Page-Table-Length:    Page-table length (PTL+1*16 entries -> up to 256)
 *
 * The 31 bit segmenttable origin of S390 has following format:
 *
 *  |S-table origin   |     | STL |
 * X                   **GPS
 * 00000000001111111111222222222233
 * 01234567890123456789012345678901
 *
 * X Space-Switch event:
 * G Segment-Invalid Bit:     *
 * P Private-Space Bit:       Segment is not private (PoP 3-30)
 * S Storage-Alteration:
 * STL Segment-Table-Length:  Segment-table length (STL+1*16 entries -> up to 2048)
 *
 * A 64 bit pagetable entry of S390 has following format:
 * |                     PFRA                         |0IP0|  OS  |
 * 0000000000111111111122222222223333333333444444444455555555556666
 * 0123456789012345678901234567890123456789012345678901234567890123
 *
 * I Page-Invalid Bit:    Page is not available for address-translation
 * P Page-Protection Bit: Store access not possible for page
 *
 * A 64 bit segmenttable entry of S390 has following format:
 * |        P-table origin                              |      TT
 * 0000000000111111111122222222223333333333444444444455555555556666
 * 0123456789012345678901234567890123456789012345678901234567890123
 *
 * I Segment-Invalid Bit:    Segment is not available for address-translation
 * C Common-Segment Bit:     Segment is not private (PoP 3-30)
 * P Page-Protection Bit: Store access not possible for page
 * TT Type 00
 *
 * A 64 bit region table entry of S390 has following format:
 * |        S-table origin                             |   TF  TTTL
 * 0000000000111111111122222222223333333333444444444455555555556666
 * 0123456789012345678901234567890123456789012345678901234567890123
 *
 * I Segment-Invalid Bit:    Segment is not available for address-translation
 * TT Type 01
 * TF
 * TL Table length
 *
 * The 64 bit regiontable origin of S390 has following format:
 * |      region table origon                          |       DTTL
 * 0000000000111111111122222222223333333333444444444455555555556666
 * 0123456789012345678901234567890123456789012345678901234567890123
 *
 * X Space-Switch event:
 * G Segment-Invalid Bit:  
 * P Private-Space Bit:    
 * S Storage-Alteration:
 * R Real space
 * TL Table-Length:
 *
 * A storage key has the following format:
 * | ACC |F|R|C|0|
 *  0   3 4 5 6 7
 * ACC: access key
 * F  : fetch protection bit
 * R  : referenced bit
 * C  : changed bit
 */

/* Hardware bits in the page table entry */
#define _PAGE_RO	0x200		/* HW read-only bit  */
#define _PAGE_INVALID	0x400		/* HW invalid bit    */

/* Software bits in the page table entry */
#define _PAGE_SWT	0x001		/* SW pte type bit t */
#define _PAGE_SWX	0x002		/* SW pte type bit x */

/* Six different types of pages. */
#define _PAGE_TYPE_EMPTY	0x400
#define _PAGE_TYPE_NONE		0x401
#define _PAGE_TYPE_SWAP		0x403
#define _PAGE_TYPE_FILE		0x601	/* bit 0x002 is used for offset !! */
#define _PAGE_TYPE_RO		0x200
#define _PAGE_TYPE_RW		0x000
#define _PAGE_TYPE_EX_RO	0x202
#define _PAGE_TYPE_EX_RW	0x002

/*
 * PTE type bits are rather complicated. handle_pte_fault uses pte_present,
 * pte_none and pte_file to find out the pte type WITHOUT holding the page
 * table lock. ptep_clear_flush on the other hand uses ptep_clear_flush to
 * invalidate a given pte. ipte sets the hw invalid bit and clears all tlbs
 * for the page. The page table entry is set to _PAGE_TYPE_EMPTY afterwards.
 * This change is done while holding the lock, but the intermediate step
 * of a previously valid pte with the hw invalid bit set can be observed by
 * handle_pte_fault. That makes it necessary that all valid pte types with
 * the hw invalid bit set must be distinguishable from the four pte types
 * empty, none, swap and file.
 *
 *			irxt  ipte  irxt
 * _PAGE_TYPE_EMPTY	1000   ->   1000
 * _PAGE_TYPE_NONE	1001   ->   1001
 * _PAGE_TYPE_SWAP	1011   ->   1011
 * _PAGE_TYPE_FILE	11?1   ->   11?1
 * _PAGE_TYPE_RO	0100   ->   1100
 * _PAGE_TYPE_RW	0000   ->   1000
 * _PAGE_TYPE_EX_RO	0110   ->   1110
 * _PAGE_TYPE_EX_RW	0010   ->   1010
 *
 * pte_none is true for bits combinations 1000, 1010, 1100, 1110
 * pte_present is true for bits combinations 0000, 0010, 0100, 0110, 1001
 * pte_file is true for bits combinations 1101, 1111
 * swap pte is 1011 and 0001, 0011, 0101, 0111 are invalid.
 */

#ifndef __s390x__

/* Bits in the segment table address-space-control-element */
#define _ASCE_SPACE_SWITCH	0x80000000UL	/* space switch event	    */
#define _ASCE_ORIGIN_MASK	0x7ffff000UL	/* segment table origin	    */
#define _ASCE_PRIVATE_SPACE	0x100	/* private space control	    */
#define _ASCE_ALT_EVENT		0x80	/* storage alteration event control */
#define _ASCE_TABLE_LENGTH	0x7f	/* 128 x 64 entries = 8k	    */

/* Bits in the segment table entry */
#define _SEGMENT_ENTRY_ORIGIN	0x7fffffc0UL	/* page table origin	    */
#define _SEGMENT_ENTRY_INV	0x20	/* invalid segment table entry	    */
#define _SEGMENT_ENTRY_COMMON	0x10	/* common segment bit		    */
#define _SEGMENT_ENTRY_PTL	0x0f	/* page table length		    */

#define _SEGMENT_ENTRY		(_SEGMENT_ENTRY_PTL)
#define _SEGMENT_ENTRY_EMPTY	(_SEGMENT_ENTRY_INV)

#else /* __s390x__ */

/* Bits in the segment/region table address-space-control-element */
#define _ASCE_ORIGIN		~0xfffUL/* segment table origin		    */
#define _ASCE_PRIVATE_SPACE	0x100	/* private space control	    */
#define _ASCE_ALT_EVENT		0x80	/* storage alteration event control */
#define _ASCE_SPACE_SWITCH	0x40	/* space switch event		    */
#define _ASCE_REAL_SPACE	0x20	/* real space control		    */
#define _ASCE_TYPE_MASK		0x0c	/* asce table type mask		    */
#define _ASCE_TYPE_REGION1	0x0c	/* region first table type	    */
#define _ASCE_TYPE_REGION2	0x08	/* region second table type	    */
#define _ASCE_TYPE_REGION3	0x04	/* region third table type	    */
#define _ASCE_TYPE_SEGMENT	0x00	/* segment table type		    */
#define _ASCE_TABLE_LENGTH	0x03	/* region table length		    */

/* Bits in the region table entry */
#define _REGION_ENTRY_ORIGIN	~0xfffUL/* region/segment table origin	    */
#define _REGION_ENTRY_INV	0x20	/* invalid region table entry	    */
#define _REGION_ENTRY_TYPE_MASK	0x0c	/* region/segment table type mask   */
#define _REGION_ENTRY_TYPE_R1	0x0c	/* region first table type	    */
#define _REGION_ENTRY_TYPE_R2	0x08	/* region second table type	    */
#define _REGION_ENTRY_TYPE_R3	0x04	/* region third table type	    */
#define _REGION_ENTRY_LENGTH	0x03	/* region third length		    */

#define _REGION1_ENTRY		(_REGION_ENTRY_TYPE_R1 | _REGION_ENTRY_LENGTH)
#define _REGION1_ENTRY_EMPTY	(_REGION_ENTRY_TYPE_R1 | _REGION_ENTRY_INV)
#define _REGION2_ENTRY		(_REGION_ENTRY_TYPE_R2 | _REGION_ENTRY_LENGTH)
#define _REGION2_ENTRY_EMPTY	(_REGION_ENTRY_TYPE_R2 | _REGION_ENTRY_INV)
#define _REGION3_ENTRY		(_REGION_ENTRY_TYPE_R3 | _REGION_ENTRY_LENGTH)
#define _REGION3_ENTRY_EMPTY	(_REGION_ENTRY_TYPE_R3 | _REGION_ENTRY_INV)

/* Bits in the segment table entry */
#define _SEGMENT_ENTRY_ORIGIN	~0x7ffUL/* segment table origin		    */
#define _SEGMENT_ENTRY_RO	0x200	/* page protection bit		    */
#define _SEGMENT_ENTRY_INV	0x20	/* invalid segment table entry	    */

#define _SEGMENT_ENTRY		(0)
#define _SEGMENT_ENTRY_EMPTY	(_SEGMENT_ENTRY_INV)

#endif /* __s390x__ */

/*
 * A user page table pointer has the space-switch-event bit, the
 * private-space-control bit and the storage-alteration-event-control
 * bit set. A kernel page table pointer doesn't need them.
 */
#define _ASCE_USER_BITS		(_ASCE_SPACE_SWITCH | _ASCE_PRIVATE_SPACE | \
				 _ASCE_ALT_EVENT)

/* Bits int the storage key */
#define _PAGE_CHANGED    0x02          /* HW changed bit                   */
#define _PAGE_REFERENCED 0x04          /* HW referenced bit                */

/*
 * Page protection definitions.
 */
#define PAGE_NONE	__pgprot(_PAGE_TYPE_NONE)
#define PAGE_RO		__pgprot(_PAGE_TYPE_RO)
#define PAGE_RW		__pgprot(_PAGE_TYPE_RW)
#define PAGE_EX_RO	__pgprot(_PAGE_TYPE_EX_RO)
#define PAGE_EX_RW	__pgprot(_PAGE_TYPE_EX_RW)

#define PAGE_KERNEL	PAGE_RW
#define PAGE_COPY	PAGE_RO

/*
 * Dependent on the EXEC_PROTECT option s390 can do execute protection.
 * Write permission always implies read permission. In theory with a
 * primary/secondary page table execute only can be implemented but
 * it would cost an additional bit in the pte to distinguish all the
 * different pte types. To avoid that execute permission currently
 * implies read permission as well.
 */
         /*xwr*/
#define __P000	PAGE_NONE
#define __P001	PAGE_RO
#define __P010	PAGE_RO
#define __P011	PAGE_RO
#define __P100	PAGE_EX_RO
#define __P101	PAGE_EX_RO
#define __P110	PAGE_EX_RO
#define __P111	PAGE_EX_RO

#define __S000	PAGE_NONE
#define __S001	PAGE_RO
#define __S010	PAGE_RW
#define __S011	PAGE_RW
#define __S100	PAGE_EX_RO
#define __S101	PAGE_EX_RO
#define __S110	PAGE_EX_RW
#define __S111	PAGE_EX_RW

#ifndef __s390x__
# define PxD_SHADOW_SHIFT	1
#else /* __s390x__ */
# define PxD_SHADOW_SHIFT	2
#endif /* __s390x__ */

static inline void *get_shadow_table(void *table)
{
	unsigned long addr, offset;
	struct page *page;

	addr = (unsigned long) table;
	offset = addr & ((PAGE_SIZE << PxD_SHADOW_SHIFT) - 1);
	page = virt_to_page((void *)(addr ^ offset));
	return (void *)(addr_t)(page->index ? (page->index | offset) : 0UL);
}

/*
 * Certain architectures need to do special things when PTEs
 * within a page table are directly modified.  Thus, the following
 * hook is made available.
 */
static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
			      pte_t *ptep, pte_t entry)
{
	*ptep = entry;
	if (mm->context.noexec) {
		if (!(pte_val(entry) & _PAGE_INVALID) &&
		    (pte_val(entry) & _PAGE_SWX))
			pte_val(entry) |= _PAGE_RO;
		else
			pte_val(entry) = _PAGE_TYPE_EMPTY;
		ptep[PTRS_PER_PTE] = entry;
	}
}

/*
 * pgd/pmd/pte query functions
 */
#ifndef __s390x__

static inline int pgd_present(pgd_t pgd) { return 1; }
static inline int pgd_none(pgd_t pgd)    { return 0; }
static inline int pgd_bad(pgd_t pgd)     { return 0; }

static inline int pud_present(pud_t pud) { return 1; }
static inline int pud_none(pud_t pud)	 { return 0; }
static inline int pud_bad(pud_t pud)	 { return 0; }

#else /* __s390x__ */

static inline int pgd_present(pgd_t pgd)
{
	if ((pgd_val(pgd) & _REGION_ENTRY_TYPE_MASK) < _REGION_ENTRY_TYPE_R2)
		return 1;
	return (pgd_val(pgd) & _REGION_ENTRY_ORIGIN) != 0UL;
}

static inline int pgd_none(pgd_t pgd)
{
	if ((pgd_val(pgd) & _REGION_ENTRY_TYPE_MASK) < _REGION_ENTRY_TYPE_R2)
		return 0;
	return (pgd_val(pgd) & _REGION_ENTRY_INV) != 0UL;
}

static inline int pgd_bad(pgd_t pgd)
{
	/*
	 * With dynamic page table levels the pgd can be a region table
	 * entry or a segment table entry. Check for the bit that are
	 * invalid for either table entry.
	 */
	unsigned long mask =
		~_SEGMENT_ENTRY_ORIGIN & ~_REGION_ENTRY_INV &
		~_REGION_ENTRY_TYPE_MASK & ~_REGION_ENTRY_LENGTH;
	return (pgd_val(pgd) & mask) != 0;
}

static inline int pud_present(pud_t pud)
{
	if ((pud_val(pud) & _REGION_ENTRY_TYPE_MASK) < _REGION_ENTRY_TYPE_R3)
		return 1;
	return (pud_val(pud) & _REGION_ENTRY_ORIGIN) != 0UL;
}

static inline int pud_none(pud_t pud)
{
	if ((pud_val(pud) & _REGION_ENTRY_TYPE_MASK) < _REGION_ENTRY_TYPE_R3)
		return 0;
	return (pud_val(pud) & _REGION_ENTRY_INV) != 0UL;
}

static inline int pud_bad(pud_t pud)
{
	/*
	 * With dynamic page table levels the pud can be a region table
	 * entry or a segment table entry. Check for the bit that are
	 * invalid for either table entry.
	 */
	unsigned long mask =
		~_SEGMENT_ENTRY_ORIGIN & ~_REGION_ENTRY_INV &
		~_REGION_ENTRY_TYPE_MASK & ~_REGION_ENTRY_LENGTH;
	return (pud_val(pud) & mask) != 0;
}

#endif /* __s390x__ */

static inline int pmd_present(pmd_t pmd)
{
	return (pmd_val(pmd) & _SEGMENT_ENTRY_ORIGIN) != 0UL;
}

static inline int pmd_none(pmd_t pmd)
{
	return (pmd_val(pmd) & _SEGMENT_ENTRY_INV) != 0UL;
}

static inline int pmd_bad(pmd_t pmd)
{
	unsigned long mask = ~_SEGMENT_ENTRY_ORIGIN & ~_SEGMENT_ENTRY_INV;
	return (pmd_val(pmd) & mask) != _SEGMENT_ENTRY;
}

static inline int pte_none(pte_t pte)
{
	return (pte_val(pte) & _PAGE_INVALID) && !(pte_val(pte) & _PAGE_SWT);
}

static inline int pte_present(pte_t pte)
{
	unsigned long mask = _PAGE_RO | _PAGE_INVALID | _PAGE_SWT | _PAGE_SWX;
	return (pte_val(pte) & mask) == _PAGE_TYPE_NONE ||
		(!(pte_val(pte) & _PAGE_INVALID) &&
		 !(pte_val(pte) & _PAGE_SWT));
}

static inline int pte_file(pte_t pte)
{
	unsigned long mask = _PAGE_RO | _PAGE_INVALID | _PAGE_SWT;
	return (pte_val(pte) & mask) == _PAGE_TYPE_FILE;
}

#define __HAVE_ARCH_PTE_SAME
#define pte_same(a,b)  (pte_val(a) == pte_val(b))

/*
 * query functions pte_write/pte_dirty/pte_young only work if
 * pte_present() is true. Undefined behaviour if not..
 */
static inline int pte_write(pte_t pte)
{
	return (pte_val(pte) & _PAGE_RO) == 0;
}

static inline int pte_dirty(pte_t pte)
{
	/* A pte is neither clean nor dirty on s/390. The dirty bit
	 * is in the storage key. See page_test_and_clear_dirty for
	 * details.
	 */
	return 0;
}

static inline int pte_young(pte_t pte)
{
	/* A pte is neither young nor old on s/390. The young bit
	 * is in the storage key. See page_test_and_clear_young for
	 * details.
	 */
	return 0;
}

/*
 * pgd/pmd/pte modification functions
 */

#ifndef __s390x__

#define pgd_clear(pgd)		do { } while (0)
#define pud_clear(pud)		do { } while (0)

#else /* __s390x__ */

static inline void pgd_clear_kernel(pgd_t * pgd)
{
	if ((pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R2)
		pgd_val(*pgd) = _REGION2_ENTRY_EMPTY;
}

static inline void pgd_clear(pgd_t * pgd)
{
	pgd_t *shadow = get_shadow_table(pgd);

	pgd_clear_kernel(pgd);
	if (shadow)
		pgd_clear_kernel(shadow);
}

static inline void pud_clear_kernel(pud_t *pud)
{
	if ((pud_val(*pud) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
		pud_val(*pud) = _REGION3_ENTRY_EMPTY;
}

static inline void pud_clear(pud_t *pud)
{
	pud_t *shadow = get_shadow_table(pud);

	pud_clear_kernel(pud);
	if (shadow)
		pud_clear_kernel(shadow);
}

#endif /* __s390x__ */

static inline void pmd_clear_kernel(pmd_t * pmdp)
{
	pmd_val(*pmdp) = _SEGMENT_ENTRY_EMPTY;
}

static inline void pmd_clear(pmd_t *pmd)
{
	pmd_t *shadow = get_shadow_table(pmd);

	pmd_clear_kernel(pmd);
	if (shadow)
		pmd_clear_kernel(shadow);
}

static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
{
	pte_val(*ptep) = _PAGE_TYPE_EMPTY;
	if (mm->context.noexec)
		pte_val(ptep[PTRS_PER_PTE]) = _PAGE_TYPE_EMPTY;
}

/*
 * The following pte modification functions only work if
 * pte_present() is true. Undefined behaviour if not..
 */
static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
{
	pte_val(pte) &= PAGE_MASK;
	pte_val(pte) |= pgprot_val(newprot);
	return pte;
}

static inline pte_t pte_wrprotect(pte_t pte)
{
	/* Do not clobber _PAGE_TYPE_NONE pages!  */
	if (!(pte_val(pte) & _PAGE_INVALID))
		pte_val(pte) |= _PAGE_RO;
	return pte;
}

static inline pte_t pte_mkwrite(pte_t pte)
{
	pte_val(pte) &= ~_PAGE_RO;
	return pte;
}

static inline pte_t pte_mkclean(pte_t pte)
{
	/* The only user of pte_mkclean is the fork() code.
	   We must *not* clear the *physical* page dirty bit
	   just because fork() wants to clear the dirty bit in
	   *one* of the page's mappings.  So we just do nothing. */
	return pte;
}

static inline pte_t pte_mkdirty(pte_t pte)
{
	/* We do not explicitly set the dirty bit because the
	 * sske instruction is slow. It is faster to let the
	 * next instruction set the dirty bit.
	 */
	return pte;
}

static inline pte_t pte_mkold(pte_t pte)
{
	/* S/390 doesn't keep its dirty/referenced bit in the pte.
	 * There is no point in clearing the real referenced bit.
	 */
	return pte;
}

static inline pte_t pte_mkyoung(pte_t pte)
{
	/* S/390 doesn't keep its dirty/referenced bit in the pte.
	 * There is no point in setting the real referenced bit.
	 */
	return pte;
}

#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
					    unsigned long addr, pte_t *ptep)
{
	return 0;
}

#define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
					 unsigned long address, pte_t *ptep)
{
	/* No need to flush TLB; bits are in storage key */
	return 0;
}

static inline void __ptep_ipte(unsigned long address, pte_t *ptep)
{
	if (!(pte_val(*ptep) & _PAGE_INVALID)) {
#ifndef __s390x__
		/* pto must point to the start of the segment table */
		pte_t *pto = (pte_t *) (((unsigned long) ptep) & 0x7ffffc00);
#else
		/* ipte in zarch mode can do the math */
		pte_t *pto = ptep;
#endif
		asm volatile(
			"	ipte	%2,%3"
			: "=m" (*ptep) : "m" (*ptep),
			  "a" (pto), "a" (address));
	}
	pte_val(*ptep) = _PAGE_TYPE_EMPTY;
}

static inline void ptep_invalidate(struct mm_struct *mm,
				   unsigned long address, pte_t *ptep)
{
	__ptep_ipte(address, ptep);
	if (mm->context.noexec)
		__ptep_ipte(address, ptep + PTRS_PER_PTE);
}

/*
 * This is hard to understand. ptep_get_and_clear and ptep_clear_flush
 * both clear the TLB for the unmapped pte. The reason is that
 * ptep_get_and_clear is used in common code (e.g. change_pte_range)
 * to modify an active pte. The sequence is
 *   1) ptep_get_and_clear
 *   2) set_pte_at
 *   3) flush_tlb_range
 * On s390 the tlb needs to get flushed with the modification of the pte
 * if the pte is active. The only way how this can be implemented is to
 * have ptep_get_and_clear do the tlb flush. In exchange flush_tlb_range
 * is a nop.
 */
#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
#define ptep_get_and_clear(__mm, __address, __ptep)			\
({									\
	pte_t __pte = *(__ptep);					\
	if (atomic_read(&(__mm)->mm_users) > 1 ||			\
	    (__mm) != current->active_mm)				\
		ptep_invalidate(__mm, __address, __ptep);		\
	else								\
		pte_clear((__mm), (__address), (__ptep));		\
	__pte;								\
})

#define __HAVE_ARCH_PTEP_CLEAR_FLUSH
static inline pte_t ptep_clear_flush(struct vm_area_struct *vma,
				     unsigned long address, pte_t *ptep)
{
	pte_t pte = *ptep;
	ptep_invalidate(vma->vm_mm, address, ptep);
	return pte;
}

/*
 * The batched pte unmap code uses ptep_get_and_clear_full to clear the
 * ptes. Here an optimization is possible. tlb_gather_mmu flushes all
 * tlbs of an mm if it can guarantee that the ptes of the mm_struct
 * cannot be accessed while the batched unmap is running. In this case
 * full==1 and a simple pte_clear is enough. See tlb.h.
 */
#define __HAVE_ARCH_PTEP_GET_AND_CLEAR_FULL
static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
					    unsigned long addr,
					    pte_t *ptep, int full)
{
	pte_t pte = *ptep;

	if (full)
		pte_clear(mm, addr, ptep);
	else
		ptep_invalidate(mm, addr, ptep);
	return pte;
}

#define __HAVE_ARCH_PTEP_SET_WRPROTECT
#define ptep_set_wrprotect(__mm, __addr, __ptep)			\
({									\
	pte_t __pte = *(__ptep);					\
	if (pte_write(__pte)) {						\
		if (atomic_read(&(__mm)->mm_users) > 1 ||		\
		    (__mm) != current->active_mm)			\
			ptep_invalidate(__mm, __addr, __ptep);		\
		set_pte_at(__mm, __addr, __ptep, pte_wrprotect(__pte));	\
	}								\
})

#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
#define ptep_set_access_flags(__vma, __addr, __ptep, __entry, __dirty)	\
({									\
	int __changed = !pte_same(*(__ptep), __entry);			\
	if (__changed) {						\
		ptep_invalidate((__vma)->vm_mm, __addr, __ptep);	\
		set_pte_at((__vma)->vm_mm, __addr, __ptep, __entry);	\
	}								\
	__changed;							\
})

/*
 * Test and clear dirty bit in storage key.
 * We can't clear the changed bit atomically. This is a potential
 * race against modification of the referenced bit. This function
 * should therefore only be called if it is not mapped in any
 * address space.
 */
#define __HAVE_ARCH_PAGE_TEST_DIRTY
static inline int page_test_dirty(struct page *page)
{
	return (page_get_storage_key(page_to_phys(page)) & _PAGE_CHANGED) != 0;
}

#define __HAVE_ARCH_PAGE_CLEAR_DIRTY
static inline void page_clear_dirty(struct page *page)
{
	page_set_storage_key(page_to_phys(page), PAGE_DEFAULT_KEY);
}

/*
 * Test and clear referenced bit in storage key.
 */
#define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG
static inline int page_test_and_clear_young(struct page *page)
{
	unsigned long physpage = page_to_phys(page);
	int ccode;

	asm volatile(
		"	rrbe	0,%1\n"
		"	ipm	%0\n"
		"	srl	%0,28\n"
		: "=d" (ccode) : "a" (physpage) : "cc" );
	return ccode & 2;
}

/*
 * Conversion functions: convert a page and protection to a page entry,
 * and a page entry and page directory to the page they refer to.
 */
static inline pte_t mk_pte_phys(unsigned long physpage, pgprot_t pgprot)
{
	pte_t __pte;
	pte_val(__pte) = physpage + pgprot_val(pgprot);
	return __pte;
}

static inline pte_t mk_pte(struct page *page, pgprot_t pgprot)
{
	unsigned long physpage = page_to_phys(page);

	return mk_pte_phys(physpage, pgprot);
}

#define pgd_index(address) (((address) >> PGDIR_SHIFT) & (PTRS_PER_PGD-1))
#define pud_index(address) (((address) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
#define pmd_index(address) (((address) >> PMD_SHIFT) & (PTRS_PER_PMD-1))
#define pte_index(address) (((address) >> PAGE_SHIFT) & (PTRS_PER_PTE-1))

#define pgd_offset(mm, address) ((mm)->pgd + pgd_index(address))
#define pgd_offset_k(address) pgd_offset(&init_mm, address)

#ifndef __s390x__

#define pmd_deref(pmd) (pmd_val(pmd) & _SEGMENT_ENTRY_ORIGIN)
#define pud_deref(pmd) ({ BUG(); 0UL; })
#define pgd_deref(pmd) ({ BUG(); 0UL; })

#define pud_offset(pgd, address) ((pud_t *) pgd)
#define pmd_offset(pud, address) ((pmd_t *) pud + pmd_index(address))

#else /* __s390x__ */

#define pmd_deref(pmd) (pmd_val(pmd) & _SEGMENT_ENTRY_ORIGIN)
#define pud_deref(pud) (pud_val(pud) & _REGION_ENTRY_ORIGIN)
#define pgd_deref(pgd) (pgd_val(pgd) & _REGION_ENTRY_ORIGIN)

static inline pud_t *pud_offset(pgd_t *pgd, unsigned long address)
{
	pud_t *pud = (pud_t *) pgd;
	if ((pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R2)
		pud = (pud_t *) pgd_deref(*pgd);
	return pud  + pud_index(address);
}

static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)
{
	pmd_t *pmd = (pmd_t *) pud;
	if ((pud_val(*pud) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
		pmd = (pmd_t *) pud_deref(*pud);
	return pmd + pmd_index(address);
}

#endif /* __s390x__ */

#define pfn_pte(pfn,pgprot) mk_pte_phys(__pa((pfn) << PAGE_SHIFT),(pgprot))
#define pte_pfn(x) (pte_val(x) >> PAGE_SHIFT)
#define pte_page(x) pfn_to_page(pte_pfn(x))

#define pmd_page(pmd) pfn_to_page(pmd_val(pmd) >> PAGE_SHIFT)

/* Find an entry in the lowest level page table.. */
#define pte_offset(pmd, addr) ((pte_t *) pmd_deref(*(pmd)) + pte_index(addr))
#define pte_offset_kernel(pmd, address) pte_offset(pmd,address)
#define pte_offset_map(pmd, address) pte_offset_kernel(pmd, address)
#define pte_offset_map_nested(pmd, address) pte_offset_kernel(pmd, address)
#define pte_unmap(pte) do { } while (0)
#define pte_unmap_nested(pte) do { } while (0)

/*
 * 31 bit swap entry format:
 * A page-table entry has some bits we have to treat in a special way.
 * Bits 0, 20 and bit 23 have to be zero, otherwise an specification
 * exception will occur instead of a page translation exception. The
 * specifiation exception has the bad habit not to store necessary
 * information in the lowcore.
 * Bit 21 and bit 22 are the page invalid bit and the page protection
 * bit. We set both to indicate a swapped page.
 * Bit 30 and 31 are used to distinguish the different page types. For
 * a swapped page these bits need to be zero.
 * This leaves the bits 1-19 and bits 24-29 to store type and offset.
 * We use the 5 bits from 25-29 for the type and the 20 bits from 1-19
 * plus 24 for the offset.
 * 0|     offset        |0110|o|type |00|
 * 0 0000000001111111111 2222 2 22222 33
 * 0 1234567890123456789 0123 4 56789 01
 *
 * 64 bit swap entry format:
 * A page-table entry has some bits we have to treat in a special way.
 * Bits 52 and bit 55 have to be zero, otherwise an specification
 * exception will occur instead of a page translation exception. The
 * specifiation exception has the bad habit not to store necessary
 * information in the lowcore.
 * Bit 53 and bit 54 are the page invalid bit and the page protection
 * bit. We set both to indicate a swapped page.
 * Bit 62 and 63 are used to distinguish the different page types. For
 * a swapped page these bits need to be zero.
 * This leaves the bits 0-51 and bits 56-61 to store type and offset.
 * We use the 5 bits from 57-61 for the type and the 53 bits from 0-51
 * plus 56 for the offset.
 * |                      offset                        |0110|o|type |00|
 *  0000000000111111111122222222223333333333444444444455 5555 5 55566 66
 *  0123456789012345678901234567890123456789012345678901 2345 6 78901 23
 */
#ifndef __s390x__
#define __SWP_OFFSET_MASK (~0UL >> 12)
#else
#define __SWP_OFFSET_MASK (~0UL >> 11)
#endif
static inline pte_t mk_swap_pte(unsigned long type, unsigned long offset)
{
	pte_t pte;
	offset &= __SWP_OFFSET_MASK;
	pte_val(pte) = _PAGE_TYPE_SWAP | ((type & 0x1f) << 2) |
		((offset & 1UL) << 7) | ((offset & ~1UL) << 11);
	return pte;
}

#define __swp_type(entry)	(((entry).val >> 2) & 0x1f)
#define __swp_offset(entry)	(((entry).val >> 11) | (((entry).val >> 7) & 1))
#define __swp_entry(type,offset) ((swp_entry_t) { pte_val(mk_swap_pte((type),(offset))) })

#define __pte_to_swp_entry(pte)	((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x)	((pte_t) { (x).val })

#ifndef __s390x__
# define PTE_FILE_MAX_BITS	26
#else /* __s390x__ */
# define PTE_FILE_MAX_BITS	59
#endif /* __s390x__ */

#define pte_to_pgoff(__pte) \
	((((__pte).pte >> 12) << 7) + (((__pte).pte >> 1) & 0x7f))

#define pgoff_to_pte(__off) \
	((pte_t) { ((((__off) & 0x7f) << 1) + (((__off) >> 7) << 12)) \
		   | _PAGE_TYPE_FILE })

#endif /* !__ASSEMBLY__ */

#define kern_addr_valid(addr)   (1)

extern int add_shared_memory(unsigned long start, unsigned long size);
extern int remove_shared_memory(unsigned long start, unsigned long size);

/*
 * No page table caches to initialise
 */
#define pgtable_cache_init()	do { } while (0)

#define __HAVE_ARCH_MEMMAP_INIT
extern void memmap_init(unsigned long, int, unsigned long, unsigned long);

#include <asm-generic/pgtable.h>

#endif /* _S390_PAGE_H */