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

#include <asm-generic/4level-fixup.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 <asm/bug.h>
#include <asm/processor.h>
#include <linux/threads.h>

struct vm_area_struct; /* forward declaration (include/linux/mm.h) */
struct mm_struct;

extern pgd_t swapper_pg_dir[] __attribute__ ((aligned (4096)));
extern void paging_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	22
# define PGDIR_SHIFT	22
#else /* __s390x__ */
# define PMD_SHIFT	21
# define PGDIR_SHIFT	31
#endif /* __s390x__ */

#define PMD_SIZE        (1UL << PMD_SHIFT)
#define PMD_MASK        (~(PMD_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
 */
#ifndef __s390x__
# define PTRS_PER_PTE    1024
# define PTRS_PER_PMD    1
# define PTRS_PER_PGD    512
#else /* __s390x__ */
# define PTRS_PER_PTE    512
# define PTRS_PER_PMD    1024
# define PTRS_PER_PGD    2048
#endif /* __s390x__ */

#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 pgd_ERROR(e) \
	printk("%s:%d: bad pgd %p.\n", __FILE__, __LINE__, (void *) pgd_val(e))

#ifndef __ASSEMBLY__
/*
 * 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
 * any out-of-bounds memory accesses will hopefully be caught.
 * The vmalloc() routines leaves a hole of 4kB between each vmalloced
 * area for the same reason. ;)
 */
#define VMALLOC_OFFSET  (8*1024*1024)
#define VMALLOC_START   (((unsigned long) high_memory + VMALLOC_OFFSET) \
			 & ~(VMALLOC_OFFSET-1))
#ifndef __s390x__
# define VMALLOC_END     (0x7fffffffL)
#else /* __s390x__ */
# define VMALLOC_END     (0x40000000000L)
#endif /* __s390x__ */


/*
 * 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 lenght
 *
 * 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                     */
#define _PAGE_INVALID   0x400          /* HW invalid                       */

/* Mask and six different types of pages. */
#define _PAGE_TYPE_MASK		0x601
#define _PAGE_TYPE_EMPTY	0x400
#define _PAGE_TYPE_NONE		0x401
#define _PAGE_TYPE_SWAP		0x600
#define _PAGE_TYPE_FILE		0x601
#define _PAGE_TYPE_RO		0x200
#define _PAGE_TYPE_RW		0x000

#ifndef __s390x__

/* Bits in the segment table entry */
#define _PAGE_TABLE_LEN 0xf            /* only full page-tables            */
#define _PAGE_TABLE_COM 0x10           /* common page-table                */
#define _PAGE_TABLE_INV 0x20           /* invalid page-table               */
#define _SEG_PRESENT    0x001          /* Software (overlap with PTL)      */

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

#define _USER_SEG_TABLE_LEN    0x7f    /* user-segment-table up to 2 GB    */
#define _KERNEL_SEG_TABLE_LEN  0x7f    /* kernel-segment-table up to 2 GB  */

/*
 * User and Kernel pagetables are identical
 */
#define _PAGE_TABLE	_PAGE_TABLE_LEN
#define _KERNPG_TABLE	_PAGE_TABLE_LEN

/*
 * The Kernel segment-tables includes the User segment-table
 */

#define _SEGMENT_TABLE	(_USER_SEG_TABLE_LEN|0x80000000|0x100)
#define _KERNSEG_TABLE	_KERNEL_SEG_TABLE_LEN

#define USER_STD_MASK	0x00000080UL

#else /* __s390x__ */

/* Bits in the segment table entry */
#define _PMD_ENTRY_INV   0x20          /* invalid segment table entry      */
#define _PMD_ENTRY       0x00        

/* Bits in the region third table entry */
#define _PGD_ENTRY_INV   0x20          /* invalid region table entry       */
#define _PGD_ENTRY       0x07

/*
 * User and kernel page directory
 */
#define _REGION_THIRD       0x4
#define _REGION_THIRD_LEN   0x3 
#define _REGION_TABLE       (_REGION_THIRD|_REGION_THIRD_LEN|0x40|0x100)
#define _KERN_REGION_TABLE  (_REGION_THIRD|_REGION_THIRD_LEN)

#define USER_STD_MASK           0x0000000000000080UL

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

#endif /* __s390x__ */

/*
 * 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_KERNEL	PAGE_RW
#define PAGE_COPY	PAGE_RO

/*
 * The S390 can't do page protection for execute, and considers that the
 * same are read. Also, write permissions imply read permissions. This is
 * the closest we can get..
 */
         /*xwr*/
#define __P000	PAGE_NONE
#define __P001	PAGE_RO
#define __P010	PAGE_RO
#define __P011	PAGE_RO
#define __P100	PAGE_RO
#define __P101	PAGE_RO
#define __P110	PAGE_RO
#define __P111	PAGE_RO

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

/*
 * 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(pte_t *pteptr, pte_t pteval)
{
	*pteptr = pteval;
}
#define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)

/*
 * 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 pmd_present(pmd_t pmd) { return pmd_val(pmd) & _SEG_PRESENT; }
static inline int pmd_none(pmd_t pmd)    { return pmd_val(pmd) & _PAGE_TABLE_INV; }
static inline int pmd_bad(pmd_t pmd)
{
	return (pmd_val(pmd) & (~PAGE_MASK & ~_PAGE_TABLE_INV)) != _PAGE_TABLE;
}

#else /* __s390x__ */

static inline int pgd_present(pgd_t pgd)
{
	return (pgd_val(pgd) & ~PAGE_MASK) == _PGD_ENTRY;
}

static inline int pgd_none(pgd_t pgd)
{
	return pgd_val(pgd) & _PGD_ENTRY_INV;
}

static inline int pgd_bad(pgd_t pgd)
{
	return (pgd_val(pgd) & (~PAGE_MASK & ~_PGD_ENTRY_INV)) != _PGD_ENTRY;
}

static inline int pmd_present(pmd_t pmd)
{
	return (pmd_val(pmd) & ~PAGE_MASK) == _PMD_ENTRY;
}

static inline int pmd_none(pmd_t pmd)
{
	return pmd_val(pmd) & _PMD_ENTRY_INV;
}

static inline int pmd_bad(pmd_t pmd)
{
	return (pmd_val(pmd) & (~PAGE_MASK & ~_PMD_ENTRY_INV)) != _PMD_ENTRY;
}

#endif /* __s390x__ */

static inline int pte_none(pte_t pte)
{
	return (pte_val(pte) & _PAGE_TYPE_MASK) == _PAGE_TYPE_EMPTY;
}

static inline int pte_present(pte_t pte)
{
	return !(pte_val(pte) & _PAGE_INVALID) ||
		(pte_val(pte) & _PAGE_TYPE_MASK) == _PAGE_TYPE_NONE;
}

static inline int pte_file(pte_t pte)
{
	return (pte_val(pte) & _PAGE_TYPE_MASK) == _PAGE_TYPE_FILE;
}

#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;
}

static inline int pte_read(pte_t pte)
{
	/* All pages are readable since we don't use the fetch
	 * protection bit in the storage key.
	 */
	return 1;
}

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

#ifndef __s390x__

static inline void pgd_clear(pgd_t * pgdp)      { }

static inline void pmd_clear(pmd_t * pmdp)
{
	pmd_val(pmdp[0]) = _PAGE_TABLE_INV;
	pmd_val(pmdp[1]) = _PAGE_TABLE_INV;
	pmd_val(pmdp[2]) = _PAGE_TABLE_INV;
	pmd_val(pmdp[3]) = _PAGE_TABLE_INV;
}

#else /* __s390x__ */

static inline void pgd_clear(pgd_t * pgdp)
{
	pgd_val(*pgdp) = _PGD_ENTRY_INV | _PGD_ENTRY;
}

static inline void pmd_clear(pmd_t * pmdp)
{
	pmd_val(*pmdp) = _PMD_ENTRY_INV | _PMD_ENTRY;
	pmd_val1(*pmdp) = _PMD_ENTRY_INV | _PMD_ENTRY;
}

#endif /* __s390x__ */

static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
{
	pte_val(*ptep) = _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;
}

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

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 ptep_test_and_clear_young(vma, address, ptep);
}

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

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

static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
{
	pte_t pte = *ptep;
	pte_clear(mm, addr, ptep);
	return pte;
}

static inline void __ptep_ipte(unsigned long address, pte_t *ptep)
{
	if (!(pte_val(*ptep) & _PAGE_INVALID)) {
#ifndef __s390x__
		/* S390 has 1mb segments, we are emulating 4MB segments */
		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 pte_t
ptep_clear_flush(struct vm_area_struct *vma,
		 unsigned long address, pte_t *ptep)
{
	pte_t pte = *ptep;

	__ptep_ipte(address, ptep);
	return pte;
}

static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
{
	pte_t old_pte = *ptep;
	set_pte_at(mm, addr, ptep, pte_wrprotect(old_pte));
}

static inline void
ptep_establish(struct vm_area_struct *vma, 
	       unsigned long address, pte_t *ptep,
	       pte_t entry)
{
	ptep_clear_flush(vma, address, ptep);
	set_pte(ptep, entry);
}

#define ptep_set_access_flags(__vma, __address, __ptep, __entry, __dirty) \
	ptep_establish(__vma, __address, __ptep, __entry)

/*
 * 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 page_test_and_clear_dirty(_page)				  \
({									  \
	struct page *__page = (_page);					  \
	unsigned long __physpage = __pa((__page-mem_map) << PAGE_SHIFT);  \
	int __skey = page_get_storage_key(__physpage);			  \
	if (__skey & _PAGE_CHANGED)					  \
		page_set_storage_key(__physpage, __skey & ~_PAGE_CHANGED);\
	(__skey & _PAGE_CHANGED);					  \
})

/*
 * Test and clear referenced bit in storage key.
 */
#define page_test_and_clear_young(page)					\
({									\
	struct page *__page = (page);					\
	unsigned long __physpage = __pa((__page-mem_map) << PAGE_SHIFT);\
	int __ccode;							\
	asm volatile(							\
		"	rrbe	0,%1\n"					\
		"	ipm	%0\n"					\
		"	srl	%0,28\n"				\
		: "=d" (__ccode) : "a" (__physpage) : "cc");		\
	(__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;
}

#define mk_pte(pg, pgprot)                                                \
({                                                                        \
	struct page *__page = (pg);                                       \
	pgprot_t __pgprot = (pgprot);					  \
	unsigned long __physpage = __pa((__page-mem_map) << PAGE_SHIFT);  \
	pte_t __pte = mk_pte_phys(__physpage, __pgprot);                  \
	__pte;                                                            \
})

#define pfn_pte(pfn, pgprot)                                              \
({                                                                        \
	pgprot_t __pgprot = (pgprot);					  \
	unsigned long __physpage = __pa((pfn) << PAGE_SHIFT);             \
	pte_t __pte = mk_pte_phys(__physpage, __pgprot);                  \
	__pte;                                                            \
})

#ifdef __s390x__

#define pfn_pmd(pfn, pgprot)                                              \
({                                                                        \
	pgprot_t __pgprot = (pgprot);                                     \
	unsigned long __physpage = __pa((pfn) << PAGE_SHIFT);             \
	pmd_t __pmd = __pmd(__physpage + pgprot_val(__pgprot));           \
	__pmd;                                                            \
})

#endif /* __s390x__ */

#define pte_pfn(x) (pte_val(x) >> PAGE_SHIFT)
#define pte_page(x) pfn_to_page(pte_pfn(x))

#define pmd_page_vaddr(pmd) (pmd_val(pmd) & PAGE_MASK)

#define pmd_page(pmd) (mem_map+(pmd_val(pmd) >> PAGE_SHIFT))

#define pgd_page_vaddr(pgd) (pgd_val(pgd) & PAGE_MASK)

#define pgd_page(pgd) (mem_map+(pgd_val(pgd) >> PAGE_SHIFT))

/* to find an entry in a page-table-directory */
#define pgd_index(address) (((address) >> PGDIR_SHIFT) & (PTRS_PER_PGD-1))
#define pgd_offset(mm, address) ((mm)->pgd+pgd_index(address))

/* to find an entry in a kernel page-table-directory */
#define pgd_offset_k(address) pgd_offset(&init_mm, address)

#ifndef __s390x__

/* Find an entry in the second-level page table.. */
static inline pmd_t * pmd_offset(pgd_t * dir, unsigned long address)
{
        return (pmd_t *) dir;
}

#else /* __s390x__ */

/* Find an entry in the second-level page table.. */
#define pmd_index(address) (((address) >> PMD_SHIFT) & (PTRS_PER_PMD-1))
#define pmd_offset(dir,addr) \
	((pmd_t *) pgd_page_vaddr(*(dir)) + pmd_index(addr))

#endif /* __s390x__ */

/* Find an entry in the third-level page table.. */
#define pte_index(address) (((address) >> PAGE_SHIFT) & (PTRS_PER_PTE-1))
#define pte_offset_kernel(pmd, address) \
	((pte_t *) pmd_page_vaddr(*(pmd)) + pte_index(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)

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

#define __HAVE_ARCH_PTEP_ESTABLISH
#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
#define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_DIRTY
#define __HAVE_ARCH_PTEP_CLEAR_DIRTY_FLUSH
#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
#define __HAVE_ARCH_PTEP_CLEAR_FLUSH
#define __HAVE_ARCH_PTEP_SET_WRPROTECT
#define __HAVE_ARCH_PTE_SAME
#define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY
#define __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG
#include <asm-generic/pgtable.h>

#endif /* _S390_PAGE_H */