linux/include/asm-arm/pgtable.h

/*
 *  linux/include/asm-arm/pgtable.h
 *
 *  Copyright (C) 1995-2002 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#ifndef _ASMARM_PGTABLE_H
#define _ASMARM_PGTABLE_H

#include <asm-generic/4level-fixup.h>
#include <asm/proc-fns.h>

#ifndef CONFIG_MMU

#include "pgtable-nommu.h"

#else

#include <asm/memory.h>
#include <asm/arch/vmalloc.h>
#include <asm/pgtable-hwdef.h>

/*
 * 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. ;)
 *
 * Note that platforms may override VMALLOC_START, but they must provide
 * VMALLOC_END.  VMALLOC_END defines the (exclusive) limit of this space,
 * which may not overlap IO space.
 */
#ifndef VMALLOC_START
#define VMALLOC_OFFSET		(8*1024*1024)
#define VMALLOC_START		(((unsigned long)high_memory + VMALLOC_OFFSET) & ~(VMALLOC_OFFSET-1))
#endif

/*
 * Hardware-wise, we have a two level page table structure, where the first
 * level has 4096 entries, and the second level has 256 entries.  Each entry
 * is one 32-bit word.  Most of the bits in the second level entry are used
 * by hardware, and there aren't any "accessed" and "dirty" bits.
 *
 * Linux on the other hand has a three level page table structure, which can
 * be wrapped to fit a two level page table structure easily - using the PGD
 * and PTE only.  However, Linux also expects one "PTE" table per page, and
 * at least a "dirty" bit.
 *
 * Therefore, we tweak the implementation slightly - we tell Linux that we
 * have 2048 entries in the first level, each of which is 8 bytes (iow, two
 * hardware pointers to the second level.)  The second level contains two
 * hardware PTE tables arranged contiguously, followed by Linux versions
 * which contain the state information Linux needs.  We, therefore, end up
 * with 512 entries in the "PTE" level.
 *
 * This leads to the page tables having the following layout:
 *
 *    pgd             pte
 * |        |
 * +--------+ +0
 * |        |-----> +------------+ +0
 * +- - - - + +4    |  h/w pt 0  |
 * |        |-----> +------------+ +1024
 * +--------+ +8    |  h/w pt 1  |
 * |        |       +------------+ +2048
 * +- - - - +       | Linux pt 0 |
 * |        |       +------------+ +3072
 * +--------+       | Linux pt 1 |
 * |        |       +------------+ +4096
 *
 * See L_PTE_xxx below for definitions of bits in the "Linux pt", and
 * PTE_xxx for definitions of bits appearing in the "h/w pt".
 *
 * PMD_xxx definitions refer to bits in the first level page table.
 *
 * The "dirty" bit is emulated by only granting hardware write permission
 * iff the page is marked "writable" and "dirty" in the Linux PTE.  This
 * means that a write to a clean page will cause a permission fault, and
 * the Linux MM layer will mark the page dirty via handle_pte_fault().
 * For the hardware to notice the permission change, the TLB entry must
 * be flushed, and ptep_set_access_flags() does that for us.
 *
 * The "accessed" or "young" bit is emulated by a similar method; we only
 * allow accesses to the page if the "young" bit is set.  Accesses to the
 * page will cause a fault, and handle_pte_fault() will set the young bit
 * for us as long as the page is marked present in the corresponding Linux
 * PTE entry.  Again, ptep_set_access_flags() will ensure that the TLB is
 * up to date.
 *
 * However, when the "young" bit is cleared, we deny access to the page
 * by clearing the hardware PTE.  Currently Linux does not flush the TLB
 * for us in this case, which means the TLB will retain the transation
 * until either the TLB entry is evicted under pressure, or a context
 * switch which changes the user space mapping occurs.
 */
#define PTRS_PER_PTE		512
#define PTRS_PER_PMD		1
#define PTRS_PER_PGD		2048

/*
 * 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
 */
#define PMD_SHIFT		21
#define PGDIR_SHIFT		21

#define LIBRARY_TEXT_START	0x0c000000

#ifndef __ASSEMBLY__
extern void __pte_error(const char *file, int line, unsigned long val);
extern void __pmd_error(const char *file, int line, unsigned long val);
extern void __pgd_error(const char *file, int line, unsigned long val);

#define pte_ERROR(pte)		__pte_error(__FILE__, __LINE__, pte_val(pte))
#define pmd_ERROR(pmd)		__pmd_error(__FILE__, __LINE__, pmd_val(pmd))
#define pgd_ERROR(pgd)		__pgd_error(__FILE__, __LINE__, pgd_val(pgd))
#endif /* !__ASSEMBLY__ */

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

/*
 * This is the lowest virtual address we can permit any user space
 * mapping to be mapped at.  This is particularly important for
 * non-high vector CPUs.
 */
#define FIRST_USER_ADDRESS	PAGE_SIZE

#define FIRST_USER_PGD_NR	1
#define USER_PTRS_PER_PGD	((TASK_SIZE/PGDIR_SIZE) - FIRST_USER_PGD_NR)

/*
 * section address mask and size definitions.
 */
#define SECTION_SHIFT		20
#define SECTION_SIZE		(1UL << SECTION_SHIFT)
#define SECTION_MASK		(~(SECTION_SIZE-1))

/*
 * ARMv6 supersection address mask and size definitions.
 */
#define SUPERSECTION_SHIFT	24
#define SUPERSECTION_SIZE	(1UL << SUPERSECTION_SHIFT)
#define SUPERSECTION_MASK	(~(SUPERSECTION_SIZE-1))

/*
 * "Linux" PTE definitions.
 *
 * We keep two sets of PTEs - the hardware and the linux version.
 * This allows greater flexibility in the way we map the Linux bits
 * onto the hardware tables, and allows us to have YOUNG and DIRTY
 * bits.
 *
 * The PTE table pointer refers to the hardware entries; the "Linux"
 * entries are stored 1024 bytes below.
 */
#define L_PTE_PRESENT		(1 << 0)
#define L_PTE_FILE		(1 << 1)	/* only when !PRESENT */
#define L_PTE_YOUNG		(1 << 1)
#define L_PTE_BUFFERABLE	(1 << 2)	/* matches PTE */
#define L_PTE_CACHEABLE		(1 << 3)	/* matches PTE */
#define L_PTE_USER		(1 << 4)
#define L_PTE_WRITE		(1 << 5)
#define L_PTE_EXEC		(1 << 6)
#define L_PTE_DIRTY		(1 << 7)
#define L_PTE_SHARED		(1 << 10)	/* shared(v6), coherent(xsc3) */

#ifndef __ASSEMBLY__

/*
 * The pgprot_* and protection_map entries will be fixed up in runtime
 * to include the cachable and bufferable bits based on memory policy,
 * as well as any architecture dependent bits like global/ASID and SMP
 * shared mapping bits.
 */
#define _L_PTE_DEFAULT	L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_CACHEABLE | L_PTE_BUFFERABLE
#define _L_PTE_READ	L_PTE_USER | L_PTE_EXEC

extern pgprot_t		pgprot_user;
extern pgprot_t		pgprot_kernel;

#define PAGE_NONE	pgprot_user
#define PAGE_COPY	__pgprot(pgprot_val(pgprot_user) | _L_PTE_READ)
#define PAGE_SHARED	__pgprot(pgprot_val(pgprot_user) | _L_PTE_READ | \
				 L_PTE_WRITE)
#define PAGE_READONLY	__pgprot(pgprot_val(pgprot_user) | _L_PTE_READ)
#define PAGE_KERNEL	pgprot_kernel

#define __PAGE_NONE	__pgprot(_L_PTE_DEFAULT)
#define __PAGE_COPY	__pgprot(_L_PTE_DEFAULT | _L_PTE_READ)
#define __PAGE_SHARED	__pgprot(_L_PTE_DEFAULT | _L_PTE_READ | L_PTE_WRITE)
#define __PAGE_READONLY	__pgprot(_L_PTE_DEFAULT | _L_PTE_READ)

#endif /* __ASSEMBLY__ */

/*
 * The table below defines the page protection levels that we insert into our
 * Linux page table version.  These get translated into the best that the
 * architecture can perform.  Note that on most ARM hardware:
 *  1) We cannot do execute protection
 *  2) If we could do execute protection, then read is implied
 *  3) write implies read permissions
 */
#define __P000  __PAGE_NONE
#define __P001  __PAGE_READONLY
#define __P010  __PAGE_COPY
#define __P011  __PAGE_COPY
#define __P100  __PAGE_READONLY
#define __P101  __PAGE_READONLY
#define __P110  __PAGE_COPY
#define __P111  __PAGE_COPY

#define __S000  __PAGE_NONE
#define __S001  __PAGE_READONLY
#define __S010  __PAGE_SHARED
#define __S011  __PAGE_SHARED
#define __S100  __PAGE_READONLY
#define __S101  __PAGE_READONLY
#define __S110  __PAGE_SHARED
#define __S111  __PAGE_SHARED

#ifndef __ASSEMBLY__
/*
 * ZERO_PAGE is a global shared page that is always zero: used
 * for zero-mapped memory areas etc..
 */
extern struct page *empty_zero_page;
#define ZERO_PAGE(vaddr)	(empty_zero_page)

#define pte_pfn(pte)		(pte_val(pte) >> PAGE_SHIFT)
#define pfn_pte(pfn,prot)	(__pte(((pfn) << PAGE_SHIFT) | pgprot_val(prot)))

#define pte_none(pte)		(!pte_val(pte))
#define pte_clear(mm,addr,ptep)	set_pte_ext(ptep, __pte(0), 0)
#define pte_page(pte)		(pfn_to_page(pte_pfn(pte)))
#define pte_offset_kernel(dir,addr)	(pmd_page_vaddr(*(dir)) + __pte_index(addr))
#define pte_offset_map(dir,addr)	(pmd_page_vaddr(*(dir)) + __pte_index(addr))
#define pte_offset_map_nested(dir,addr)	(pmd_page_vaddr(*(dir)) + __pte_index(addr))
#define pte_unmap(pte)		do { } while (0)
#define pte_unmap_nested(pte)	do { } while (0)

#define set_pte_ext(ptep,pte,ext) cpu_set_pte_ext(ptep,pte,ext)

#define set_pte_at(mm,addr,ptep,pteval) do { \
	set_pte_ext(ptep, pteval, (addr) >= TASK_SIZE ? 0 : PTE_EXT_NG); \
 } while (0)

/*
 * The following only work if pte_present() is true.
 * Undefined behaviour if not..
 */
#define pte_present(pte)	(pte_val(pte) & L_PTE_PRESENT)
#define pte_write(pte)		(pte_val(pte) & L_PTE_WRITE)
#define pte_dirty(pte)		(pte_val(pte) & L_PTE_DIRTY)
#define pte_young(pte)		(pte_val(pte) & L_PTE_YOUNG)
#define pte_special(pte)	(0)

/*
 * The following only works if pte_present() is not true.
 */
#define pte_file(pte)		(pte_val(pte) & L_PTE_FILE)
#define pte_to_pgoff(x)		(pte_val(x) >> 2)
#define pgoff_to_pte(x)		__pte(((x) << 2) | L_PTE_FILE)

#define PTE_FILE_MAX_BITS	30

#define PTE_BIT_FUNC(fn,op) \
static inline pte_t pte_##fn(pte_t pte) { pte_val(pte) op; return pte; }

PTE_BIT_FUNC(wrprotect, &= ~L_PTE_WRITE);
PTE_BIT_FUNC(mkwrite,   |= L_PTE_WRITE);
PTE_BIT_FUNC(mkclean,   &= ~L_PTE_DIRTY);
PTE_BIT_FUNC(mkdirty,   |= L_PTE_DIRTY);
PTE_BIT_FUNC(mkold,     &= ~L_PTE_YOUNG);
PTE_BIT_FUNC(mkyoung,   |= L_PTE_YOUNG);

static inline pte_t pte_mkspecial(pte_t pte) { return pte; }

/*
 * Mark the prot value as uncacheable and unbufferable.
 */
#define pgprot_noncached(prot)	__pgprot(pgprot_val(prot) & ~(L_PTE_CACHEABLE | L_PTE_BUFFERABLE))
#define pgprot_writecombine(prot) __pgprot(pgprot_val(prot) & ~L_PTE_CACHEABLE)

#define pmd_none(pmd)		(!pmd_val(pmd))
#define pmd_present(pmd)	(pmd_val(pmd))
#define pmd_bad(pmd)		(pmd_val(pmd) & 2)

#define copy_pmd(pmdpd,pmdps)		\
	do {				\
		pmdpd[0] = pmdps[0];	\
		pmdpd[1] = pmdps[1];	\
		flush_pmd_entry(pmdpd);	\
	} while (0)

#define pmd_clear(pmdp)			\
	do {				\
		pmdp[0] = __pmd(0);	\
		pmdp[1] = __pmd(0);	\
		clean_pmd_entry(pmdp);	\
	} while (0)

static inline pte_t *pmd_page_vaddr(pmd_t pmd)
{
	unsigned long ptr;

	ptr = pmd_val(pmd) & ~(PTRS_PER_PTE * sizeof(void *) - 1);
	ptr += PTRS_PER_PTE * sizeof(void *);

	return __va(ptr);
}

#define pmd_page(pmd) virt_to_page(__va(pmd_val(pmd)))

/*
 * Permanent address of a page. We never have highmem, so this is trivial.
 */
#define pages_to_mb(x)		((x) >> (20 - PAGE_SHIFT))

/*
 * 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 mk_pte(page,prot)	pfn_pte(page_to_pfn(page),prot)

/*
 * The "pgd_xxx()" functions here 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)
 */
#define pgd_none(pgd)		(0)
#define pgd_bad(pgd)		(0)
#define pgd_present(pgd)	(1)
#define pgd_clear(pgdp)		do { } while (0)
#define set_pgd(pgd,pgdp)	do { } while (0)

/* to find an entry in a page-table-directory */
#define pgd_index(addr)		((addr) >> PGDIR_SHIFT)

#define pgd_offset(mm, addr)	((mm)->pgd+pgd_index(addr))

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

/* Find an entry in the second-level page table.. */
#define pmd_offset(dir, addr)	((pmd_t *)(dir))

/* Find an entry in the third-level page table.. */
#define __pte_index(addr)	(((addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))

static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
{
	const unsigned long mask = L_PTE_EXEC | L_PTE_WRITE | L_PTE_USER;
	pte_val(pte) = (pte_val(pte) & ~mask) | (pgprot_val(newprot) & mask);
	return pte;
}

extern pgd_t swapper_pg_dir[PTRS_PER_PGD];

/* Encode and decode a swap entry.
 *
 * We support up to 32GB of swap on 4k machines
 */
#define __swp_type(x)		(((x).val >> 2) & 0x7f)
#define __swp_offset(x)		((x).val >> 9)
#define __swp_entry(type,offset) ((swp_entry_t) { ((type) << 2) | ((offset) << 9) })
#define __pte_to_swp_entry(pte)	((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(swp)	((pte_t) { (swp).val })

/* Needs to be defined here and not in linux/mm.h, as it is arch dependent */
/* FIXME: this is not correct */
#define kern_addr_valid(addr)	(1)

#include <asm-generic/pgtable.h>

/*
 * We provide our own arch_get_unmapped_area to cope with VIPT caches.
 */
#define HAVE_ARCH_UNMAPPED_AREA

/*
 * remap a physical page `pfn' of size `size' with page protection `prot'
 * into virtual address `from'
 */
#define io_remap_pfn_range(vma,from,pfn,size,prot) \
		remap_pfn_range(vma, from, pfn, size, prot)

#define pgtable_cache_init() do { } while (0)

#endif /* !__ASSEMBLY__ */

#endif /* CONFIG_MMU */

#endif /* _ASMARM_PGTABLE_H */