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17f57211 CM |
1 | /* |
2 | * arch/arm/include/asm/pgtable-2level.h | |
3 | * | |
4 | * Copyright (C) 1995-2002 Russell King | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2 as | |
8 | * published by the Free Software Foundation. | |
9 | */ | |
10 | #ifndef _ASM_PGTABLE_2LEVEL_H | |
11 | #define _ASM_PGTABLE_2LEVEL_H | |
12 | ||
13 | /* | |
14 | * Hardware-wise, we have a two level page table structure, where the first | |
15 | * level has 4096 entries, and the second level has 256 entries. Each entry | |
16 | * is one 32-bit word. Most of the bits in the second level entry are used | |
17 | * by hardware, and there aren't any "accessed" and "dirty" bits. | |
18 | * | |
19 | * Linux on the other hand has a three level page table structure, which can | |
20 | * be wrapped to fit a two level page table structure easily - using the PGD | |
21 | * and PTE only. However, Linux also expects one "PTE" table per page, and | |
22 | * at least a "dirty" bit. | |
23 | * | |
24 | * Therefore, we tweak the implementation slightly - we tell Linux that we | |
25 | * have 2048 entries in the first level, each of which is 8 bytes (iow, two | |
26 | * hardware pointers to the second level.) The second level contains two | |
27 | * hardware PTE tables arranged contiguously, preceded by Linux versions | |
28 | * which contain the state information Linux needs. We, therefore, end up | |
29 | * with 512 entries in the "PTE" level. | |
30 | * | |
31 | * This leads to the page tables having the following layout: | |
32 | * | |
33 | * pgd pte | |
34 | * | | | |
35 | * +--------+ | |
36 | * | | +------------+ +0 | |
37 | * +- - - - + | Linux pt 0 | | |
38 | * | | +------------+ +1024 | |
39 | * +--------+ +0 | Linux pt 1 | | |
40 | * | |-----> +------------+ +2048 | |
41 | * +- - - - + +4 | h/w pt 0 | | |
42 | * | |-----> +------------+ +3072 | |
43 | * +--------+ +8 | h/w pt 1 | | |
44 | * | | +------------+ +4096 | |
45 | * | |
46 | * See L_PTE_xxx below for definitions of bits in the "Linux pt", and | |
47 | * PTE_xxx for definitions of bits appearing in the "h/w pt". | |
48 | * | |
49 | * PMD_xxx definitions refer to bits in the first level page table. | |
50 | * | |
51 | * The "dirty" bit is emulated by only granting hardware write permission | |
52 | * iff the page is marked "writable" and "dirty" in the Linux PTE. This | |
53 | * means that a write to a clean page will cause a permission fault, and | |
54 | * the Linux MM layer will mark the page dirty via handle_pte_fault(). | |
55 | * For the hardware to notice the permission change, the TLB entry must | |
56 | * be flushed, and ptep_set_access_flags() does that for us. | |
57 | * | |
58 | * The "accessed" or "young" bit is emulated by a similar method; we only | |
59 | * allow accesses to the page if the "young" bit is set. Accesses to the | |
60 | * page will cause a fault, and handle_pte_fault() will set the young bit | |
61 | * for us as long as the page is marked present in the corresponding Linux | |
62 | * PTE entry. Again, ptep_set_access_flags() will ensure that the TLB is | |
63 | * up to date. | |
64 | * | |
65 | * However, when the "young" bit is cleared, we deny access to the page | |
66 | * by clearing the hardware PTE. Currently Linux does not flush the TLB | |
67 | * for us in this case, which means the TLB will retain the transation | |
68 | * until either the TLB entry is evicted under pressure, or a context | |
69 | * switch which changes the user space mapping occurs. | |
70 | */ | |
71 | #define PTRS_PER_PTE 512 | |
72 | #define PTRS_PER_PMD 1 | |
73 | #define PTRS_PER_PGD 2048 | |
74 | ||
75 | #define PTE_HWTABLE_PTRS (PTRS_PER_PTE) | |
76 | #define PTE_HWTABLE_OFF (PTE_HWTABLE_PTRS * sizeof(pte_t)) | |
77 | #define PTE_HWTABLE_SIZE (PTRS_PER_PTE * sizeof(u32)) | |
78 | ||
79 | /* | |
80 | * PMD_SHIFT determines the size of the area a second-level page table can map | |
81 | * PGDIR_SHIFT determines what a third-level page table entry can map | |
82 | */ | |
83 | #define PMD_SHIFT 21 | |
84 | #define PGDIR_SHIFT 21 | |
85 | ||
86 | #define PMD_SIZE (1UL << PMD_SHIFT) | |
87 | #define PMD_MASK (~(PMD_SIZE-1)) | |
88 | #define PGDIR_SIZE (1UL << PGDIR_SHIFT) | |
89 | #define PGDIR_MASK (~(PGDIR_SIZE-1)) | |
90 | ||
91 | /* | |
92 | * section address mask and size definitions. | |
93 | */ | |
94 | #define SECTION_SHIFT 20 | |
95 | #define SECTION_SIZE (1UL << SECTION_SHIFT) | |
96 | #define SECTION_MASK (~(SECTION_SIZE-1)) | |
97 | ||
98 | /* | |
99 | * ARMv6 supersection address mask and size definitions. | |
100 | */ | |
101 | #define SUPERSECTION_SHIFT 24 | |
102 | #define SUPERSECTION_SIZE (1UL << SUPERSECTION_SHIFT) | |
103 | #define SUPERSECTION_MASK (~(SUPERSECTION_SIZE-1)) | |
104 | ||
105 | #define USER_PTRS_PER_PGD (TASK_SIZE / PGDIR_SIZE) | |
106 | ||
107 | /* | |
108 | * "Linux" PTE definitions. | |
109 | * | |
110 | * We keep two sets of PTEs - the hardware and the linux version. | |
111 | * This allows greater flexibility in the way we map the Linux bits | |
112 | * onto the hardware tables, and allows us to have YOUNG and DIRTY | |
113 | * bits. | |
114 | * | |
115 | * The PTE table pointer refers to the hardware entries; the "Linux" | |
116 | * entries are stored 1024 bytes below. | |
117 | */ | |
dbf62d50 | 118 | #define L_PTE_VALID (_AT(pteval_t, 1) << 0) /* Valid */ |
17f57211 CM |
119 | #define L_PTE_PRESENT (_AT(pteval_t, 1) << 0) |
120 | #define L_PTE_YOUNG (_AT(pteval_t, 1) << 1) | |
121 | #define L_PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !PRESENT */ | |
122 | #define L_PTE_DIRTY (_AT(pteval_t, 1) << 6) | |
123 | #define L_PTE_RDONLY (_AT(pteval_t, 1) << 7) | |
124 | #define L_PTE_USER (_AT(pteval_t, 1) << 8) | |
125 | #define L_PTE_XN (_AT(pteval_t, 1) << 9) | |
126 | #define L_PTE_SHARED (_AT(pteval_t, 1) << 10) /* shared(v6), coherent(xsc3) */ | |
127 | ||
128 | /* | |
129 | * These are the memory types, defined to be compatible with | |
130 | * pre-ARMv6 CPUs cacheable and bufferable bits: XXCB | |
131 | */ | |
132 | #define L_PTE_MT_UNCACHED (_AT(pteval_t, 0x00) << 2) /* 0000 */ | |
133 | #define L_PTE_MT_BUFFERABLE (_AT(pteval_t, 0x01) << 2) /* 0001 */ | |
134 | #define L_PTE_MT_WRITETHROUGH (_AT(pteval_t, 0x02) << 2) /* 0010 */ | |
135 | #define L_PTE_MT_WRITEBACK (_AT(pteval_t, 0x03) << 2) /* 0011 */ | |
136 | #define L_PTE_MT_MINICACHE (_AT(pteval_t, 0x06) << 2) /* 0110 (sa1100, xscale) */ | |
137 | #define L_PTE_MT_WRITEALLOC (_AT(pteval_t, 0x07) << 2) /* 0111 */ | |
138 | #define L_PTE_MT_DEV_SHARED (_AT(pteval_t, 0x04) << 2) /* 0100 */ | |
139 | #define L_PTE_MT_DEV_NONSHARED (_AT(pteval_t, 0x0c) << 2) /* 1100 */ | |
140 | #define L_PTE_MT_DEV_WC (_AT(pteval_t, 0x09) << 2) /* 1001 */ | |
141 | #define L_PTE_MT_DEV_CACHED (_AT(pteval_t, 0x0b) << 2) /* 1011 */ | |
142 | #define L_PTE_MT_MASK (_AT(pteval_t, 0x0f) << 2) | |
143 | ||
e0c0313b CM |
144 | #ifndef __ASSEMBLY__ |
145 | ||
146 | /* | |
147 | * The "pud_xxx()" functions here are trivial when the pmd is folded into | |
148 | * the pud: the pud entry is never bad, always exists, and can't be set or | |
149 | * cleared. | |
150 | */ | |
151 | #define pud_none(pud) (0) | |
152 | #define pud_bad(pud) (0) | |
153 | #define pud_present(pud) (1) | |
154 | #define pud_clear(pudp) do { } while (0) | |
155 | #define set_pud(pud,pudp) do { } while (0) | |
156 | ||
157 | static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr) | |
158 | { | |
159 | return (pmd_t *)pud; | |
160 | } | |
161 | ||
162 | #define pmd_bad(pmd) (pmd_val(pmd) & 2) | |
163 | ||
164 | #define copy_pmd(pmdpd,pmdps) \ | |
165 | do { \ | |
166 | pmdpd[0] = pmdps[0]; \ | |
167 | pmdpd[1] = pmdps[1]; \ | |
168 | flush_pmd_entry(pmdpd); \ | |
169 | } while (0) | |
170 | ||
171 | #define pmd_clear(pmdp) \ | |
172 | do { \ | |
173 | pmdp[0] = __pmd(0); \ | |
174 | pmdp[1] = __pmd(0); \ | |
175 | clean_pmd_entry(pmdp); \ | |
176 | } while (0) | |
177 | ||
178 | /* we don't need complex calculations here as the pmd is folded into the pgd */ | |
179 | #define pmd_addr_end(addr,end) (end) | |
180 | ||
181 | #define set_pte_ext(ptep,pte,ext) cpu_set_pte_ext(ptep,pte,ext) | |
182 | ||
183 | #endif /* __ASSEMBLY__ */ | |
184 | ||
17f57211 | 185 | #endif /* _ASM_PGTABLE_2LEVEL_H */ |