pgtable.h

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/*
 *  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/memory.h>
#include <asm/proc-fns.h>
#include <asm/arch/vmalloc.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_establish() 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_establish() 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)

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

/*
 * Hardware page table definitions.
 *
 * + Level 1 descriptor (PMD)
 *   - common
 */
#define PMD_TYPE_MASK		(3 << 0)
#define PMD_TYPE_FAULT		(0 << 0)
#define PMD_TYPE_TABLE		(1 << 0)
#define PMD_TYPE_SECT		(2 << 0)
#define PMD_BIT4		(1 << 4)
#define PMD_DOMAIN(x)		((x) << 5)
#define PMD_PROTECTION		(1 << 9)	/* v5 */
/*
 *   - section
 */
#define PMD_SECT_BUFFERABLE	(1 << 2)
#define PMD_SECT_CACHEABLE	(1 << 3)
#define PMD_SECT_AP_WRITE	(1 << 10)
#define PMD_SECT_AP_READ	(1 << 11)
#define PMD_SECT_TEX(x)		((x) << 12)	/* v5 */
#define PMD_SECT_APX		(1 << 15)	/* v6 */
#define PMD_SECT_S		(1 << 16)	/* v6 */
#define PMD_SECT_nG		(1 << 17)	/* v6 */
#define PMD_SECT_SUPER		(1 << 18)	/* v6 */

#define PMD_SECT_UNCACHED	(0)
#define PMD_SECT_BUFFERED	(PMD_SECT_BUFFERABLE)
#define PMD_SECT_WT		(PMD_SECT_CACHEABLE)
#define PMD_SECT_WB		(PMD_SECT_CACHEABLE | PMD_SECT_BUFFERABLE)
#define PMD_SECT_MINICACHE	(PMD_SECT_TEX(1) | PMD_SECT_CACHEABLE)
#define PMD_SECT_WBWA		(PMD_SECT_TEX(1) | PMD_SECT_CACHEABLE | PMD_SECT_BUFFERABLE)

/*
 *   - coarse table (not used)
 */

/*
 * + Level 2 descriptor (PTE)
 *   - common
 */
#define PTE_TYPE_MASK		(3 << 0)
#define PTE_TYPE_FAULT		(0 << 0)
#define PTE_TYPE_LARGE		(1 << 0)
#define PTE_TYPE_SMALL		(2 << 0)
#define PTE_TYPE_EXT		(3 << 0)	/* v5 */
#define PTE_BUFFERABLE		(1 << 2)
#define PTE_CACHEABLE		(1 << 3)

/*
 *   - extended small page/tiny page
 */
#define PTE_EXT_XN		(1 << 0)	/* v6 */
#define PTE_EXT_AP_MASK		(3 << 4)
#define PTE_EXT_AP0		(1 << 4)
#define PTE_EXT_AP1		(2 << 4)
#define PTE_EXT_AP_UNO_SRO	(0 << 4)
#define PTE_EXT_AP_UNO_SRW	(PTE_EXT_AP0)
#define PTE_EXT_AP_URO_SRW	(PTE_EXT_AP1)
#define PTE_EXT_AP_URW_SRW	(PTE_EXT_AP1|PTE_EXT_AP0)
#define PTE_EXT_TEX(x)		((x) << 6)	/* v5 */
#define PTE_EXT_APX		(1 << 9)	/* v6 */
#define PTE_EXT_SHARED		(1 << 10)	/* v6 */
#define PTE_EXT_NG		(1 << 11)	/* v6 */

/*
 *   - small page
 */
#define PTE_SMALL_AP_MASK	(0xff << 4)
#define PTE_SMALL_AP_UNO_SRO	(0x00 << 4)
#define PTE_SMALL_AP_UNO_SRW	(0x55 << 4)
#define PTE_SMALL_AP_URO_SRW	(0xaa << 4)
#define PTE_SMALL_AP_URW_SRW	(0xff << 4)

/*
 * "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)