arch/xtensa/include/asm/pgtable.h - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * include/asm-xtensa/pgtable.h
  *
  * Copyright (C) 2001 - 2013 Tensilica Inc.
  */

 #ifndef _XTENSA_PGTABLE_H
 #define _XTENSA_PGTABLE_H

 #include <asm/page.h>
 #include <asm/kmem_layout.h>
 #include <asm-generic/pgtable-nopmd.h>

 /*
  * We only use two ring levels, user and kernel space.
  */

 #ifdef CONFIG_MMU
 #define USER_RING		1	/* user ring level */
 #else
 #define USER_RING		0
 #endif
 #define KERNEL_RING		0	/* kernel ring level */

 /*
  * The Xtensa architecture port of Linux has a two-level page table system,
  * i.e. the logical three-level Linux page table layout is folded.
  * Each task has the following memory page tables:
  *
  *   PGD table (page directory), ie. 3rd-level page table:
  *	One page (4 kB) of 1024 (PTRS_PER_PGD) pointers to PTE tables
  *	(Architectures that don't have the PMD folded point to the PMD tables)
  *
  *	The pointer to the PGD table for a given task can be retrieved from
  *	the task structure (struct task_struct*) t, e.g. current():
  *	  (t->mm ? t->mm : t->active_mm)->pgd
  *
  *   PMD tables (page middle-directory), ie. 2nd-level page tables:
  *	Absent for the Xtensa architecture (folded, PTRS_PER_PMD == 1).
  *
  *   PTE tables (page table entry), ie. 1st-level page tables:
  *	One page (4 kB) of 1024 (PTRS_PER_PTE) PTEs with a special PTE
  *	invalid_pte_table for absent mappings.
  *
  * The individual pages are 4 kB big with special pages for the empty_zero_page.
  */

 #define PGDIR_SHIFT	22
 #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
 #define PGDIR_MASK	(~(PGDIR_SIZE-1))

 /*
  * Entries per page directory level: we use two-level, so
  * we don't really have any PMD directory physically.
  */
 #define PTRS_PER_PTE		1024
 #define PTRS_PER_PTE_SHIFT	10
 #define PTRS_PER_PGD		1024
 #define PGD_ORDER		0
 #define USER_PTRS_PER_PGD	(TASK_SIZE/PGDIR_SIZE)
 #define FIRST_USER_ADDRESS	0UL
 #define FIRST_USER_PGD_NR	(FIRST_USER_ADDRESS >> PGDIR_SHIFT)

 #ifdef CONFIG_MMU
 /*
  * Virtual memory area. We keep a distance to other memory regions to be
  * on the safe side. We also use this area for cache aliasing.
  */
 #define VMALLOC_START		(XCHAL_KSEG_CACHED_VADDR - 0x10000000)
 #define VMALLOC_END		(VMALLOC_START + 0x07FEFFFF)
 #define TLBTEMP_BASE_1		(VMALLOC_END + 1)
 #define TLBTEMP_BASE_2		(TLBTEMP_BASE_1 + DCACHE_WAY_SIZE)
 #if 2 * DCACHE_WAY_SIZE > ICACHE_WAY_SIZE
 #define TLBTEMP_SIZE		(2 * DCACHE_WAY_SIZE)
 #else
 #define TLBTEMP_SIZE		ICACHE_WAY_SIZE
 #endif

 #else

 #define VMALLOC_START		__XTENSA_UL_CONST(0)
 #define VMALLOC_END		__XTENSA_UL_CONST(0xffffffff)

 #endif

 /*
  * For the Xtensa architecture, the PTE layout is as follows:
  *
  *		31------12  11  10-9   8-6  5-4  3-2  1-0
  *		+-----------------------------------------+
  *		|           |   Software   |   HARDWARE   |
  *		|    PPN    |          ADW | RI |Attribute|
  *		+-----------------------------------------+
  *   pte_none	|             MBZ          | 01 | 11 | 00 |
  *		+-----------------------------------------+
  *   present	|    PPN    | 0 | 00 | ADW | RI | CA | wx |
  *		+- - - - - - - - - - - - - - - - - - - - -+
  *   (PAGE_NONE)|    PPN    | 0 | 00 | ADW | 01 | 11 | 11 |
  *		+-----------------------------------------+
  *   swap	|     index     |   type   | 01 | 11 | 00 |
  *		+-----------------------------------------+
  *
  * For T1050 hardware and earlier the layout differs for present and (PAGE_NONE)
  *		+-----------------------------------------+
  *   present	|    PPN    | 0 | 00 | ADW | RI | CA | w1 |
  *		+-----------------------------------------+
  *   (PAGE_NONE)|    PPN    | 0 | 00 | ADW | 01 | 01 | 00 |
  *		+-----------------------------------------+
  *
  *  Legend:
  *   PPN        Physical Page Number
  *   ADW	software: accessed (young) / dirty / writable
  *   RI         ring (0=privileged, 1=user, 2 and 3 are unused)
  *   CA		cache attribute: 00 bypass, 01 writeback, 10 writethrough
  *		(11 is invalid and used to mark pages that are not present)
  *   w		page is writable (hw)
  *   x		page is executable (hw)
  *   index      swap offset / PAGE_SIZE (bit 11-31: 21 bits -> 8 GB)
  *		(note that the index is always non-zero)
  *   type       swap type (5 bits -> 32 types)
  *
  *  Notes:
  *   - (PROT_NONE) is a special case of 'present' but causes an exception for
  *     any access (read, write, and execute).
  *   - 'multihit-exception' has the highest priority of all MMU exceptions,
  *     so the ring must be set to 'RING_USER' even for 'non-present' pages.
  *   - on older hardware, the exectuable flag was not supported and
  *     used as a 'valid' flag, so it needs to be always set.
  *   - we need to keep track of certain flags in software (dirty and young)
  *     to do this, we use write exceptions and have a separate software w-flag.
  *   - attribute value 1101 (and 1111 on T1050 and earlier) is reserved
  */

 #define _PAGE_ATTRIB_MASK	0xf

 #define _PAGE_HW_EXEC		(1<<0)	/* hardware: page is executable */
 #define _PAGE_HW_WRITE		(1<<1)	/* hardware: page is writable */

 #define _PAGE_CA_BYPASS		(0<<2)	/* bypass, non-speculative */
 #define _PAGE_CA_WB		(1<<2)	/* write-back */
 #define _PAGE_CA_WT		(2<<2)	/* write-through */
 #define _PAGE_CA_MASK		(3<<2)
 #define _PAGE_CA_INVALID	(3<<2)

 /* We use invalid attribute values to distinguish special pte entries */
 #if XCHAL_HW_VERSION_MAJOR < 2000
 #define _PAGE_HW_VALID		0x01	/* older HW needed this bit set */
 #define _PAGE_NONE		0x04
 #else
 #define _PAGE_HW_VALID		0x00
 #define _PAGE_NONE		0x0f
 #endif

 #define _PAGE_USER		(1<<4)	/* user access (ring=1) */

 /* Software */
 #define _PAGE_WRITABLE_BIT	6
 #define _PAGE_WRITABLE		(1<<6)	/* software: page writable */
 #define _PAGE_DIRTY		(1<<7)	/* software: page dirty */
 #define _PAGE_ACCESSED		(1<<8)	/* software: page accessed (read) */

 #ifdef CONFIG_MMU

 #define _PAGE_CHG_MASK	   (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY)
 #define _PAGE_PRESENT	   (_PAGE_HW_VALID | _PAGE_CA_WB | _PAGE_ACCESSED)

 #define PAGE_NONE	   __pgprot(_PAGE_NONE | _PAGE_USER)
 #define PAGE_COPY	   __pgprot(_PAGE_PRESENT | _PAGE_USER)
 #define PAGE_COPY_EXEC	   __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_HW_EXEC)
 #define PAGE_READONLY	   __pgprot(_PAGE_PRESENT | _PAGE_USER)
 #define PAGE_READONLY_EXEC __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_HW_EXEC)
 #define PAGE_SHARED	   __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_WRITABLE)
 #define PAGE_SHARED_EXEC \
 	__pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_WRITABLE | _PAGE_HW_EXEC)
 #define PAGE_KERNEL	   __pgprot(_PAGE_PRESENT | _PAGE_HW_WRITE)
 #define PAGE_KERNEL_RO	   __pgprot(_PAGE_PRESENT)
 #define PAGE_KERNEL_EXEC   __pgprot(_PAGE_PRESENT|_PAGE_HW_WRITE|_PAGE_HW_EXEC)

 #if (DCACHE_WAY_SIZE > PAGE_SIZE)
 # define _PAGE_DIRECTORY   (_PAGE_HW_VALID | _PAGE_ACCESSED | _PAGE_CA_BYPASS)
 #else
 # define _PAGE_DIRECTORY   (_PAGE_HW_VALID | _PAGE_ACCESSED | _PAGE_CA_WB)
 #endif

 #else /* no mmu */

 # define _PAGE_CHG_MASK  (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY)
 # define PAGE_NONE       __pgprot(0)
 # define PAGE_SHARED     __pgprot(0)
 # define PAGE_COPY       __pgprot(0)
 # define PAGE_READONLY   __pgprot(0)
 # define PAGE_KERNEL     __pgprot(0)

 #endif

 /*
  * On certain configurations of Xtensa MMUs (eg. the initial Linux config),
  * the MMU can't do page protection for execute, and considers that the same as
  * read.  Also, write permissions may imply read permissions.
  * What follows is the closest we can get by reasonable means..
  * See linux/mm/mmap.c for protection_map[] array that uses these definitions.
  */
 #define __P000	PAGE_NONE		/* private --- */
 #define __P001	PAGE_READONLY		/* private --r */
 #define __P010	PAGE_COPY		/* private -w- */
 #define __P011	PAGE_COPY		/* private -wr */
 #define __P100	PAGE_READONLY_EXEC	/* private x-- */
 #define __P101	PAGE_READONLY_EXEC	/* private x-r */
 #define __P110	PAGE_COPY_EXEC		/* private xw- */
 #define __P111	PAGE_COPY_EXEC		/* private xwr */

 #define __S000	PAGE_NONE		/* shared  --- */
 #define __S001	PAGE_READONLY		/* shared  --r */
 #define __S010	PAGE_SHARED		/* shared  -w- */
 #define __S011	PAGE_SHARED		/* shared  -wr */
 #define __S100	PAGE_READONLY_EXEC	/* shared  x-- */
 #define __S101	PAGE_READONLY_EXEC	/* shared  x-r */
 #define __S110	PAGE_SHARED_EXEC	/* shared  xw- */
 #define __S111	PAGE_SHARED_EXEC	/* shared  xwr */

 #ifndef __ASSEMBLY__

 #define pte_ERROR(e) \
 	printk("%s:%d: bad pte %08lx.\n", __FILE__, __LINE__, pte_val(e))
 #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);
 #else
 # define swapper_pg_dir NULL
 static inline void paging_init(void) { }
 #endif

 /*
  * The pmd contains the kernel virtual address of the pte page.
  */
 #define pmd_page_vaddr(pmd) ((unsigned long)(pmd_val(pmd) & PAGE_MASK))
 #define pmd_page(pmd) virt_to_page(pmd_val(pmd))

 /*
  * pte status.
  */
 # define pte_none(pte)	 (pte_val(pte) == (_PAGE_CA_INVALID | _PAGE_USER))
 #if XCHAL_HW_VERSION_MAJOR < 2000
 # define pte_present(pte) ((pte_val(pte) & _PAGE_CA_MASK) != _PAGE_CA_INVALID)
 #else
 # define pte_present(pte)						\
 	(((pte_val(pte) & _PAGE_CA_MASK) != _PAGE_CA_INVALID)		\
 	 || ((pte_val(pte) & _PAGE_ATTRIB_MASK) == _PAGE_NONE))
 #endif
 #define pte_clear(mm,addr,ptep)						\
 	do { update_pte(ptep, __pte(_PAGE_CA_INVALID | _PAGE_USER)); } while (0)

 #define pmd_none(pmd)	 (!pmd_val(pmd))
 #define pmd_present(pmd) (pmd_val(pmd) & PAGE_MASK)
 #define pmd_bad(pmd)	 (pmd_val(pmd) & ~PAGE_MASK)
 #define pmd_clear(pmdp)	 do { set_pmd(pmdp, __pmd(0)); } while (0)

 static inline int pte_write(pte_t pte) { return pte_val(pte) & _PAGE_WRITABLE; }
 static inline int pte_dirty(pte_t pte) { return pte_val(pte) & _PAGE_DIRTY; }
 static inline int pte_young(pte_t pte) { return pte_val(pte) & _PAGE_ACCESSED; }

 static inline pte_t pte_wrprotect(pte_t pte)
 	{ pte_val(pte) &= ~(_PAGE_WRITABLE | _PAGE_HW_WRITE); return pte; }
 static inline pte_t pte_mkclean(pte_t pte)
 	{ pte_val(pte) &= ~(_PAGE_DIRTY | _PAGE_HW_WRITE); return pte; }
 static inline pte_t pte_mkold(pte_t pte)
 	{ pte_val(pte) &= ~_PAGE_ACCESSED; return pte; }
 static inline pte_t pte_mkdirty(pte_t pte)
 	{ pte_val(pte) |= _PAGE_DIRTY; return pte; }
 static inline pte_t pte_mkyoung(pte_t pte)
 	{ pte_val(pte) |= _PAGE_ACCESSED; return pte; }
 static inline pte_t pte_mkwrite(pte_t pte)
 	{ pte_val(pte) |= _PAGE_WRITABLE; return pte; }

 #define pgprot_noncached(prot) (__pgprot(pgprot_val(prot) & ~_PAGE_CA_MASK))

 /*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
  */

 #define pte_pfn(pte)		(pte_val(pte) >> PAGE_SHIFT)
 #define pte_same(a,b)		(pte_val(a) == pte_val(b))
 #define pte_page(x)		pfn_to_page(pte_pfn(x))
 #define pfn_pte(pfn, prot)	__pte(((pfn) << PAGE_SHIFT) | pgprot_val(prot))
 #define mk_pte(page, prot)	pfn_pte(page_to_pfn(page), prot)

 static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 {
 	return __pte((pte_val(pte) & _PAGE_CHG_MASK) | pgprot_val(newprot));
 }

 /*
  * Certain architectures need to do special things when pte's
  * within a page table are directly modified.  Thus, the following
  * hook is made available.
  */
 static inline void update_pte(pte_t *ptep, pte_t pteval)
 {
 	*ptep = pteval;
 #if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
 	__asm__ __volatile__ ("dhwb %0, 0" :: "a" (ptep));
 #endif

 }

 struct mm_struct;

 static inline void
 set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pteval)
 {
 	update_pte(ptep, pteval);
 }

 static inline void set_pte(pte_t *ptep, pte_t pteval)
 {
 	update_pte(ptep, pteval);
 }

 static inline void
 set_pmd(pmd_t *pmdp, pmd_t pmdval)
 {
 	*pmdp = pmdval;
 }

 struct vm_area_struct;

 static inline int
 ptep_test_and_clear_young(struct vm_area_struct *vma, unsigned long addr,
 			  pte_t *ptep)
 {
 	pte_t pte = *ptep;
 	if (!pte_young(pte))
 		return 0;
 	update_pte(ptep, pte_mkold(pte));
 	return 1;
 }

 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_set_wrprotect(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 {
 	pte_t pte = *ptep;
 	update_pte(ptep, pte_wrprotect(pte));
 }

 /*
  * Encode and decode a swap and file entry.
  */
 #define SWP_TYPE_BITS		5
 #define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS)

 #define __swp_type(entry)	(((entry).val >> 6) & 0x1f)
 #define __swp_offset(entry)	((entry).val >> 11)
 #define __swp_entry(type,offs)	\
 	((swp_entry_t){((type) << 6) | ((offs) << 11) | \
 	 _PAGE_CA_INVALID | _PAGE_USER})
 #define __pte_to_swp_entry(pte)	((swp_entry_t) { pte_val(pte) })
 #define __swp_entry_to_pte(x)	((pte_t) { (x).val })

 #endif /*  !defined (__ASSEMBLY__) */


 #ifdef __ASSEMBLY__

 /* Assembly macro _PGD_INDEX is the same as C pgd_index(unsigned long),
  *                _PGD_OFFSET as C pgd_offset(struct mm_struct*, unsigned long),
  *                _PMD_OFFSET as C pmd_offset(pgd_t*, unsigned long)
  *                _PTE_OFFSET as C pte_offset(pmd_t*, unsigned long)
  *
  * Note: We require an additional temporary register which can be the same as
  *       the register that holds the address.
  *
  * ((pte_t*) ((unsigned long)(pmd_val(*pmd) & PAGE_MASK)) + pte_index(addr))
  *
  */
 #define _PGD_INDEX(rt,rs)	extui	rt, rs, PGDIR_SHIFT, 32-PGDIR_SHIFT
 #define _PTE_INDEX(rt,rs)	extui	rt, rs, PAGE_SHIFT, PTRS_PER_PTE_SHIFT

 #define _PGD_OFFSET(mm,adr,tmp)		l32i	mm, mm, MM_PGD;		\
 					_PGD_INDEX(tmp, adr);		\
 					addx4	mm, tmp, mm

 #define _PTE_OFFSET(pmd,adr,tmp)	_PTE_INDEX(tmp, adr);		\
 					srli	pmd, pmd, PAGE_SHIFT;	\
 					slli	pmd, pmd, PAGE_SHIFT;	\
 					addx4	pmd, tmp, pmd

 #else

 #define kern_addr_valid(addr)	(1)

 extern  void update_mmu_cache(struct vm_area_struct * vma,
 			      unsigned long address, pte_t *ptep);

 typedef pte_t *pte_addr_t;

 #endif /* !defined (__ASSEMBLY__) */

 #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
 #define __HAVE_ARCH_PTEP_GET_AND_CLEAR
 #define __HAVE_ARCH_PTEP_SET_WRPROTECT
 #define __HAVE_ARCH_PTEP_MKDIRTY
 #define __HAVE_ARCH_PTE_SAME
 /* We provide our own get_unmapped_area to cope with
  * SHM area cache aliasing for userland.
  */
 #define HAVE_ARCH_UNMAPPED_AREA

 #endif /* _XTENSA_PGTABLE_H */
	/* SPDX-License-Identifier: GPL-2.0-only */
	/*
	* include/asm-xtensa/pgtable.h
	*
	* Copyright (C) 2001 - 2013 Tensilica Inc.
	*/

	#ifndef _XTENSA_PGTABLE_H
	#define _XTENSA_PGTABLE_H

	#include <asm/page.h>
	#include <asm/kmem_layout.h>
	#include <asm-generic/pgtable-nopmd.h>

	/*
	* We only use two ring levels, user and kernel space.
	*/

	#ifdef CONFIG_MMU
	#define USER_RING 1 /* user ring level */
	#else
	#define USER_RING 0
	#endif
	#define KERNEL_RING 0 /* kernel ring level */

	/*
	* The Xtensa architecture port of Linux has a two-level page table system,
	* i.e. the logical three-level Linux page table layout is folded.
	* Each task has the following memory page tables:
	*
	* PGD table (page directory), ie. 3rd-level page table:
	* One page (4 kB) of 1024 (PTRS_PER_PGD) pointers to PTE tables
	* (Architectures that don't have the PMD folded point to the PMD tables)
	*
	* The pointer to the PGD table for a given task can be retrieved from
	* the task structure (struct task_struct*) t, e.g. current():
	* (t->mm ? t->mm : t->active_mm)->pgd
	*
	* PMD tables (page middle-directory), ie. 2nd-level page tables:
	* Absent for the Xtensa architecture (folded, PTRS_PER_PMD == 1).
	*
	* PTE tables (page table entry), ie. 1st-level page tables:
	* One page (4 kB) of 1024 (PTRS_PER_PTE) PTEs with a special PTE
	* invalid_pte_table for absent mappings.
	*
	* The individual pages are 4 kB big with special pages for the empty_zero_page.
	*/

	#define PGDIR_SHIFT 22
	#define PGDIR_SIZE (1UL << PGDIR_SHIFT)
	#define PGDIR_MASK (~(PGDIR_SIZE-1))

	/*
	* Entries per page directory level: we use two-level, so
	* we don't really have any PMD directory physically.
	*/
	#define PTRS_PER_PTE 1024
	#define PTRS_PER_PTE_SHIFT 10
	#define PTRS_PER_PGD 1024
	#define PGD_ORDER 0
	#define USER_PTRS_PER_PGD (TASK_SIZE/PGDIR_SIZE)
	#define FIRST_USER_ADDRESS 0UL
	#define FIRST_USER_PGD_NR (FIRST_USER_ADDRESS >> PGDIR_SHIFT)

	#ifdef CONFIG_MMU
	/*
	* Virtual memory area. We keep a distance to other memory regions to be
	* on the safe side. We also use this area for cache aliasing.
	*/
	#define VMALLOC_START (XCHAL_KSEG_CACHED_VADDR - 0x10000000)
	#define VMALLOC_END (VMALLOC_START + 0x07FEFFFF)
	#define TLBTEMP_BASE_1 (VMALLOC_END + 1)
	#define TLBTEMP_BASE_2 (TLBTEMP_BASE_1 + DCACHE_WAY_SIZE)
	#if 2 * DCACHE_WAY_SIZE > ICACHE_WAY_SIZE
	#define TLBTEMP_SIZE (2 * DCACHE_WAY_SIZE)
	#else
	#define TLBTEMP_SIZE ICACHE_WAY_SIZE
	#endif

	#else

	#define VMALLOC_START __XTENSA_UL_CONST(0)
	#define VMALLOC_END __XTENSA_UL_CONST(0xffffffff)

	#endif

	/*
	* For the Xtensa architecture, the PTE layout is as follows:
	*
	* 31------12 11 10-9 8-6 5-4 3-2 1-0
	* +-----------------------------------------+
	* \| \| Software \| HARDWARE \|
	* \| PPN \| ADW \| RI \|Attribute\|
	* +-----------------------------------------+
	* pte_none \| MBZ \| 01 \| 11 \| 00 \|
	* +-----------------------------------------+
	* present \| PPN \| 0 \| 00 \| ADW \| RI \| CA \| wx \|
	* +- - - - - - - - - - - - - - - - - - - - -+
	* (PAGE_NONE)\| PPN \| 0 \| 00 \| ADW \| 01 \| 11 \| 11 \|
	* +-----------------------------------------+
	* swap \| index \| type \| 01 \| 11 \| 00 \|
	* +-----------------------------------------+
	*
	* For T1050 hardware and earlier the layout differs for present and (PAGE_NONE)
	* +-----------------------------------------+
	* present \| PPN \| 0 \| 00 \| ADW \| RI \| CA \| w1 \|
	* +-----------------------------------------+
	* (PAGE_NONE)\| PPN \| 0 \| 00 \| ADW \| 01 \| 01 \| 00 \|
	* +-----------------------------------------+
	*
	* Legend:
	* PPN Physical Page Number
	* ADW software: accessed (young) / dirty / writable
	* RI ring (0=privileged, 1=user, 2 and 3 are unused)
	* CA cache attribute: 00 bypass, 01 writeback, 10 writethrough
	* (11 is invalid and used to mark pages that are not present)
	* w page is writable (hw)
	* x page is executable (hw)
	* index swap offset / PAGE_SIZE (bit 11-31: 21 bits -> 8 GB)
	* (note that the index is always non-zero)
	* type swap type (5 bits -> 32 types)
	*
	* Notes:
	* - (PROT_NONE) is a special case of 'present' but causes an exception for
	* any access (read, write, and execute).
	* - 'multihit-exception' has the highest priority of all MMU exceptions,
	* so the ring must be set to 'RING_USER' even for 'non-present' pages.
	* - on older hardware, the exectuable flag was not supported and
	* used as a 'valid' flag, so it needs to be always set.
	* - we need to keep track of certain flags in software (dirty and young)
	* to do this, we use write exceptions and have a separate software w-flag.
	* - attribute value 1101 (and 1111 on T1050 and earlier) is reserved
	*/

	#define _PAGE_ATTRIB_MASK 0xf

	#define _PAGE_HW_EXEC (1<<0) /* hardware: page is executable */
	#define _PAGE_HW_WRITE (1<<1) /* hardware: page is writable */

	#define _PAGE_CA_BYPASS (0<<2) /* bypass, non-speculative */
	#define _PAGE_CA_WB (1<<2) /* write-back */
	#define _PAGE_CA_WT (2<<2) /* write-through */
	#define _PAGE_CA_MASK (3<<2)
	#define _PAGE_CA_INVALID (3<<2)

	/* We use invalid attribute values to distinguish special pte entries */
	#if XCHAL_HW_VERSION_MAJOR < 2000
	#define _PAGE_HW_VALID 0x01 /* older HW needed this bit set */
	#define _PAGE_NONE 0x04
	#else
	#define _PAGE_HW_VALID 0x00
	#define _PAGE_NONE 0x0f
	#endif

	#define _PAGE_USER (1<<4) /* user access (ring=1) */

	/* Software */
	#define _PAGE_WRITABLE_BIT 6
	#define _PAGE_WRITABLE (1<<6) /* software: page writable */
	#define _PAGE_DIRTY (1<<7) /* software: page dirty */
	#define _PAGE_ACCESSED (1<<8) /* software: page accessed (read) */

	#ifdef CONFIG_MMU

	#define _PAGE_CHG_MASK (PAGE_MASK \| _PAGE_ACCESSED \| _PAGE_DIRTY)
	#define _PAGE_PRESENT (_PAGE_HW_VALID \| _PAGE_CA_WB \| _PAGE_ACCESSED)

	#define PAGE_NONE __pgprot(_PAGE_NONE \| _PAGE_USER)
	#define PAGE_COPY __pgprot(_PAGE_PRESENT \| _PAGE_USER)
	#define PAGE_COPY_EXEC __pgprot(_PAGE_PRESENT \| _PAGE_USER \| _PAGE_HW_EXEC)
	#define PAGE_READONLY __pgprot(_PAGE_PRESENT \| _PAGE_USER)
	#define PAGE_READONLY_EXEC __pgprot(_PAGE_PRESENT \| _PAGE_USER \| _PAGE_HW_EXEC)
	#define PAGE_SHARED __pgprot(_PAGE_PRESENT \| _PAGE_USER \| _PAGE_WRITABLE)
	#define PAGE_SHARED_EXEC \
	__pgprot(_PAGE_PRESENT \| _PAGE_USER \| _PAGE_WRITABLE \| _PAGE_HW_EXEC)
	#define PAGE_KERNEL __pgprot(_PAGE_PRESENT \| _PAGE_HW_WRITE)
	#define PAGE_KERNEL_RO __pgprot(_PAGE_PRESENT)
	#define PAGE_KERNEL_EXEC __pgprot(_PAGE_PRESENT\|_PAGE_HW_WRITE\|_PAGE_HW_EXEC)

	#if (DCACHE_WAY_SIZE > PAGE_SIZE)
	# define _PAGE_DIRECTORY (_PAGE_HW_VALID \| _PAGE_ACCESSED \| _PAGE_CA_BYPASS)
	#else
	# define _PAGE_DIRECTORY (_PAGE_HW_VALID \| _PAGE_ACCESSED \| _PAGE_CA_WB)
	#endif

	#else /* no mmu */

	# define _PAGE_CHG_MASK (PAGE_MASK \| _PAGE_ACCESSED \| _PAGE_DIRTY)
	# define PAGE_NONE __pgprot(0)
	# define PAGE_SHARED __pgprot(0)
	# define PAGE_COPY __pgprot(0)
	# define PAGE_READONLY __pgprot(0)
	# define PAGE_KERNEL __pgprot(0)

	#endif

	/*
	* On certain configurations of Xtensa MMUs (eg. the initial Linux config),
	* the MMU can't do page protection for execute, and considers that the same as
	* read. Also, write permissions may imply read permissions.
	* What follows is the closest we can get by reasonable means..
	* See linux/mm/mmap.c for protection_map[] array that uses these definitions.
	*/
	#define __P000 PAGE_NONE /* private --- */
	#define __P001 PAGE_READONLY /* private --r */
	#define __P010 PAGE_COPY /* private -w- */
	#define __P011 PAGE_COPY /* private -wr */
	#define __P100 PAGE_READONLY_EXEC /* private x-- */
	#define __P101 PAGE_READONLY_EXEC /* private x-r */
	#define __P110 PAGE_COPY_EXEC /* private xw- */
	#define __P111 PAGE_COPY_EXEC /* private xwr */

	#define __S000 PAGE_NONE /* shared --- */
	#define __S001 PAGE_READONLY /* shared --r */
	#define __S010 PAGE_SHARED /* shared -w- */
	#define __S011 PAGE_SHARED /* shared -wr */
	#define __S100 PAGE_READONLY_EXEC /* shared x-- */
	#define __S101 PAGE_READONLY_EXEC /* shared x-r */
	#define __S110 PAGE_SHARED_EXEC /* shared xw- */
	#define __S111 PAGE_SHARED_EXEC /* shared xwr */

	#ifndef __ASSEMBLY__

	#define pte_ERROR(e) \
	printk("%s:%d: bad pte %08lx.\n", __FILE__, __LINE__, pte_val(e))
	#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);
	#else
	# define swapper_pg_dir NULL
	static inline void paging_init(void) { }
	#endif

	/*
	* The pmd contains the kernel virtual address of the pte page.
	*/
	#define pmd_page_vaddr(pmd) ((unsigned long)(pmd_val(pmd) & PAGE_MASK))
	#define pmd_page(pmd) virt_to_page(pmd_val(pmd))

	/*
	* pte status.
	*/
	# define pte_none(pte) (pte_val(pte) == (_PAGE_CA_INVALID \| _PAGE_USER))
	#if XCHAL_HW_VERSION_MAJOR < 2000
	# define pte_present(pte) ((pte_val(pte) & _PAGE_CA_MASK) != _PAGE_CA_INVALID)
	#else
	# define pte_present(pte) \
	(((pte_val(pte) & _PAGE_CA_MASK) != _PAGE_CA_INVALID) \
	\|\| ((pte_val(pte) & _PAGE_ATTRIB_MASK) == _PAGE_NONE))
	#endif
	#define pte_clear(mm,addr,ptep) \
	do { update_pte(ptep, __pte(_PAGE_CA_INVALID \| _PAGE_USER)); } while (0)

	#define pmd_none(pmd) (!pmd_val(pmd))
	#define pmd_present(pmd) (pmd_val(pmd) & PAGE_MASK)
	#define pmd_bad(pmd) (pmd_val(pmd) & ~PAGE_MASK)
	#define pmd_clear(pmdp) do { set_pmd(pmdp, __pmd(0)); } while (0)

	static inline int pte_write(pte_t pte) { return pte_val(pte) & _PAGE_WRITABLE; }
	static inline int pte_dirty(pte_t pte) { return pte_val(pte) & _PAGE_DIRTY; }
	static inline int pte_young(pte_t pte) { return pte_val(pte) & _PAGE_ACCESSED; }

	static inline pte_t pte_wrprotect(pte_t pte)
	{ pte_val(pte) &= ~(_PAGE_WRITABLE \| _PAGE_HW_WRITE); return pte; }
	static inline pte_t pte_mkclean(pte_t pte)
	{ pte_val(pte) &= ~(_PAGE_DIRTY \| _PAGE_HW_WRITE); return pte; }
	static inline pte_t pte_mkold(pte_t pte)
	{ pte_val(pte) &= ~_PAGE_ACCESSED; return pte; }
	static inline pte_t pte_mkdirty(pte_t pte)
	{ pte_val(pte) \|= _PAGE_DIRTY; return pte; }
	static inline pte_t pte_mkyoung(pte_t pte)
	{ pte_val(pte) \|= _PAGE_ACCESSED; return pte; }
	static inline pte_t pte_mkwrite(pte_t pte)
	{ pte_val(pte) \|= _PAGE_WRITABLE; return pte; }

	#define pgprot_noncached(prot) (__pgprot(pgprot_val(prot) & ~_PAGE_CA_MASK))

	/*
	* Conversion functions: convert a page and protection to a page entry,
	* and a page entry and page directory to the page they refer to.
	*/

	#define pte_pfn(pte) (pte_val(pte) >> PAGE_SHIFT)
	#define pte_same(a,b) (pte_val(a) == pte_val(b))
	#define pte_page(x) pfn_to_page(pte_pfn(x))
	#define pfn_pte(pfn, prot) __pte(((pfn) << PAGE_SHIFT) \| pgprot_val(prot))
	#define mk_pte(page, prot) pfn_pte(page_to_pfn(page), prot)

	static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
	{
	return __pte((pte_val(pte) & _PAGE_CHG_MASK) \| pgprot_val(newprot));
	}

	/*
	* Certain architectures need to do special things when pte's
	* within a page table are directly modified. Thus, the following
	* hook is made available.
	*/
	static inline void update_pte(pte_t *ptep, pte_t pteval)
	{
	*ptep = pteval;
	#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
	__asm__ __volatile__ ("dhwb %0, 0" :: "a" (ptep));
	#endif

	}

	struct mm_struct;

	static inline void
	set_pte_at(struct mm_struct mm, unsigned long addr, pte_t ptep, pte_t pteval)
	{
	update_pte(ptep, pteval);
	}

	static inline void set_pte(pte_t *ptep, pte_t pteval)
	{
	update_pte(ptep, pteval);
	}

	static inline void
	set_pmd(pmd_t *pmdp, pmd_t pmdval)
	{
	*pmdp = pmdval;
	}

	struct vm_area_struct;

	static inline int
	ptep_test_and_clear_young(struct vm_area_struct *vma, unsigned long addr,
	pte_t *ptep)
	{
	pte_t pte = *ptep;
	if (!pte_young(pte))
	return 0;
	update_pte(ptep, pte_mkold(pte));
	return 1;
	}

	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_set_wrprotect(struct mm_struct mm, unsigned long addr, pte_t ptep)
	{
	pte_t pte = *ptep;
	update_pte(ptep, pte_wrprotect(pte));
	}

	/*
	* Encode and decode a swap and file entry.
	*/
	#define SWP_TYPE_BITS 5
	#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS)

	#define __swp_type(entry) (((entry).val >> 6) & 0x1f)
	#define __swp_offset(entry) ((entry).val >> 11)
	#define __swp_entry(type,offs) \
	((swp_entry_t){((type) << 6) \| ((offs) << 11) \| \
	_PAGE_CA_INVALID \| _PAGE_USER})
	#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
	#define __swp_entry_to_pte(x) ((pte_t) { (x).val })

	#endif /* !defined (__ASSEMBLY__) */


	#ifdef __ASSEMBLY__

	/* Assembly macro _PGD_INDEX is the same as C pgd_index(unsigned long),
	* _PGD_OFFSET as C pgd_offset(struct mm_struct*, unsigned long),
	* _PMD_OFFSET as C pmd_offset(pgd_t*, unsigned long)
	* _PTE_OFFSET as C pte_offset(pmd_t*, unsigned long)
	*
	* Note: We require an additional temporary register which can be the same as
	* the register that holds the address.
	*
	* ((pte_t) ((unsigned long)(pmd_val(pmd) & PAGE_MASK)) + pte_index(addr))
	*
	*/
	#define _PGD_INDEX(rt,rs) extui rt, rs, PGDIR_SHIFT, 32-PGDIR_SHIFT
	#define _PTE_INDEX(rt,rs) extui rt, rs, PAGE_SHIFT, PTRS_PER_PTE_SHIFT

	#define _PGD_OFFSET(mm,adr,tmp) l32i mm, mm, MM_PGD; \
	_PGD_INDEX(tmp, adr); \
	addx4 mm, tmp, mm

	#define _PTE_OFFSET(pmd,adr,tmp) _PTE_INDEX(tmp, adr); \
	srli pmd, pmd, PAGE_SHIFT; \
	slli pmd, pmd, PAGE_SHIFT; \
	addx4 pmd, tmp, pmd

	#else

	#define kern_addr_valid(addr) (1)

	extern void update_mmu_cache(struct vm_area_struct * vma,
	unsigned long address, pte_t *ptep);

	typedef pte_t *pte_addr_t;

	#endif /* !defined (__ASSEMBLY__) */

	#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
	#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
	#define __HAVE_ARCH_PTEP_SET_WRPROTECT
	#define __HAVE_ARCH_PTEP_MKDIRTY
	#define __HAVE_ARCH_PTE_SAME
	/* We provide our own get_unmapped_area to cope with
	* SHM area cache aliasing for userland.
	*/
	#define HAVE_ARCH_UNMAPPED_AREA

	#endif /* _XTENSA_PGTABLE_H */