summaryrefslogtreecommitdiffstats
path: root/arch/arm/include/asm/pgtable-2level.h
blob: 2317a71c8f8ec4c2cbc5404d96d1c3953877eda8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
/*
 *  arch/arm/include/asm/pgtable-2level.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 _ASM_PGTABLE_2LEVEL_H
#define _ASM_PGTABLE_2LEVEL_H

/*
 * 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, preceded 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
 * +- - - - +       | Linux pt 0 |
 * |        |       +------------+ +1024
 * +--------+ +0    | Linux pt 1 |
 * |        |-----> +------------+ +2048
 * +- - - - + +4    |  h/w pt 0  |
 * |        |-----> +------------+ +3072
 * +--------+ +8    |  h/w 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

#define PTE_HWTABLE_PTRS	(PTRS_PER_PTE)
#define PTE_HWTABLE_OFF		(PTE_HWTABLE_PTRS * sizeof(pte_t))
#define PTE_HWTABLE_SIZE	(PTRS_PER_PTE * sizeof(u32))

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

/*
 * 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))

#define USER_PTRS_PER_PGD	(TASK_SIZE / PGDIR_SIZE)

/*
 * "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		(_AT(pteval_t, 1) << 0)
#define L_PTE_YOUNG		(_AT(pteval_t, 1) << 1)
#define L_PTE_FILE		(_AT(pteval_t, 1) << 2)	/* only when !PRESENT */
#define L_PTE_DIRTY		(_AT(pteval_t, 1) << 6)
#define L_PTE_RDONLY		(_AT(pteval_t, 1) << 7)
#define L_PTE_USER		(_AT(pteval_t, 1) << 8)
#define L_PTE_XN		(_AT(pteval_t, 1) << 9)
#define L_PTE_SHARED		(_AT(pteval_t, 1) << 10)	/* shared(v6), coherent(xsc3) */

/*
 * These are the memory types, defined to be compatible with
 * pre-ARMv6 CPUs cacheable and bufferable bits:   XXCB
 */
#define L_PTE_MT_UNCACHED	(_AT(pteval_t, 0x00) << 2)	/* 0000 */
#define L_PTE_MT_BUFFERABLE	(_AT(pteval_t, 0x01) << 2)	/* 0001 */
#define L_PTE_MT_WRITETHROUGH	(_AT(pteval_t, 0x02) << 2)	/* 0010 */
#define L_PTE_MT_WRITEBACK	(_AT(pteval_t, 0x03) << 2)	/* 0011 */
#define L_PTE_MT_MINICACHE	(_AT(pteval_t, 0x06) << 2)	/* 0110 (sa1100, xscale) */
#define L_PTE_MT_WRITEALLOC	(_AT(pteval_t, 0x07) << 2)	/* 0111 */
#define L_PTE_MT_DEV_SHARED	(_AT(pteval_t, 0x04) << 2)	/* 0100 */
#define L_PTE_MT_DEV_NONSHARED	(_AT(pteval_t, 0x0c) << 2)	/* 1100 */
#define L_PTE_MT_DEV_WC		(_AT(pteval_t, 0x09) << 2)	/* 1001 */
#define L_PTE_MT_DEV_CACHED	(_AT(pteval_t, 0x0b) << 2)	/* 1011 */
#define L_PTE_MT_MASK		(_AT(pteval_t, 0x0f) << 2)

#ifndef __ASSEMBLY__

/*
 * The "pud_xxx()" functions here are trivial when the pmd is folded into
 * the pud: the pud entry is never bad, always exists, and can't be set or
 * cleared.
 */
#define pud_none(pud)		(0)
#define pud_bad(pud)		(0)
#define pud_present(pud)	(1)
#define pud_clear(pudp)		do { } while (0)
#define set_pud(pud,pudp)	do { } while (0)

static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
{
	return (pmd_t *)pud;
}

#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)

/* we don't need complex calculations here as the pmd is folded into the pgd */
#define pmd_addr_end(addr,end) (end)

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

#endif /* __ASSEMBLY__ */

#endif /* _ASM_PGTABLE_2LEVEL_H */