arch/arm/include/asm/pgtable-2level.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  *  arch/arm/include/asm/pgtable-2level.h
   4  *
   5  *  Copyright (C) 1995-2002 Russell King
   6  */
   7 #ifndef _ASM_PGTABLE_2LEVEL_H
   8 #define _ASM_PGTABLE_2LEVEL_H
   9
  10 #define __PAGETABLE_PMD_FOLDED 1
  11
  12 /*
  13  * Hardware-wise, we have a two level page table structure, where the first
  14  * level has 4096 entries, and the second level has 256 entries.  Each entry
  15  * is one 32-bit word.  Most of the bits in the second level entry are used
  16  * by hardware, and there aren't any "accessed" and "dirty" bits.
  17  *
  18  * Linux on the other hand has a three level page table structure, which can
  19  * be wrapped to fit a two level page table structure easily - using the PGD
  20  * and PTE only.  However, Linux also expects one "PTE" table per page, and
  21  * at least a "dirty" bit.
  22  *
  23  * Therefore, we tweak the implementation slightly - we tell Linux that we
  24  * have 2048 entries in the first level, each of which is 8 bytes (iow, two
  25  * hardware pointers to the second level.)  The second level contains two
  26  * hardware PTE tables arranged contiguously, preceded by Linux versions
  27  * which contain the state information Linux needs.  We, therefore, end up
  28  * with 512 entries in the "PTE" level.
  29  *
  30  * This leads to the page tables having the following layout:
  31  *
  32  *    pgd             pte
  33  * |        |
  34  * +--------+
  35  * |        |       +------------+ +0
  36  * +- - - - +       | Linux pt 0 |
  37  * |        |       +------------+ +1024
  38  * +--------+ +0    | Linux pt 1 |
  39  * |        |-----> +------------+ +2048
  40  * +- - - - + +4    |  h/w pt 0  |
  41  * |        |-----> +------------+ +3072
  42  * +--------+ +8    |  h/w pt 1  |
  43  * |        |       +------------+ +4096
  44  *
  45  * See L_PTE_xxx below for definitions of bits in the "Linux pt", and
  46  * PTE_xxx for definitions of bits appearing in the "h/w pt".
  47  *
  48  * PMD_xxx definitions refer to bits in the first level page table.
  49  *
  50  * The "dirty" bit is emulated by only granting hardware write permission
  51  * iff the page is marked "writable" and "dirty" in the Linux PTE.  This
  52  * means that a write to a clean page will cause a permission fault, and
  53  * the Linux MM layer will mark the page dirty via handle_pte_fault().
  54  * For the hardware to notice the permission change, the TLB entry must
  55  * be flushed, and ptep_set_access_flags() does that for us.
  56  *
  57  * The "accessed" or "young" bit is emulated by a similar method; we only
  58  * allow accesses to the page if the "young" bit is set.  Accesses to the
  59  * page will cause a fault, and handle_pte_fault() will set the young bit
  60  * for us as long as the page is marked present in the corresponding Linux
  61  * PTE entry.  Again, ptep_set_access_flags() will ensure that the TLB is
  62  * up to date.
  63  *
  64  * However, when the "young" bit is cleared, we deny access to the page
  65  * by clearing the hardware PTE.  Currently Linux does not flush the TLB
  66  * for us in this case, which means the TLB will retain the transation
  67  * until either the TLB entry is evicted under pressure, or a context
  68  * switch which changes the user space mapping occurs.
  69  */
  70 #define PTRS_PER_PTE            512
  71 #define PTRS_PER_PMD            1
  72 #define PTRS_PER_PGD            2048
  73
  74 #define PTE_HWTABLE_PTRS        (PTRS_PER_PTE)
  75 #define PTE_HWTABLE_OFF         (PTE_HWTABLE_PTRS * sizeof(pte_t))
  76 #define PTE_HWTABLE_SIZE        (PTRS_PER_PTE * sizeof(u32))
  77
  78 /*
  79  * PMD_SHIFT determines the size of the area a second-level page table can map
  80  * PGDIR_SHIFT determines what a third-level page table entry can map
  81  */
  82 #define PMD_SHIFT               21
  83 #define PGDIR_SHIFT             21
  84
  85 #define PMD_SIZE                (1UL << PMD_SHIFT)
  86 #define PMD_MASK                (~(PMD_SIZE-1))
  87 #define PGDIR_SIZE              (1UL << PGDIR_SHIFT)
  88 #define PGDIR_MASK              (~(PGDIR_SIZE-1))
  89
  90 /*
  91  * section address mask and size definitions.
  92  */
  93 #define SECTION_SHIFT           20
  94 #define SECTION_SIZE            (1UL << SECTION_SHIFT)
  95 #define SECTION_MASK            (~(SECTION_SIZE-1))
  96
  97 /*
  98  * ARMv6 supersection address mask and size definitions.
  99  */
 100 #define SUPERSECTION_SHIFT      24
 101 #define SUPERSECTION_SIZE       (1UL << SUPERSECTION_SHIFT)
 102 #define SUPERSECTION_MASK       (~(SUPERSECTION_SIZE-1))
 103
 104 #define USER_PTRS_PER_PGD       (TASK_SIZE / PGDIR_SIZE)
 105
 106 /*
 107  * "Linux" PTE definitions.
 108  *
 109  * We keep two sets of PTEs - the hardware and the linux version.
 110  * This allows greater flexibility in the way we map the Linux bits
 111  * onto the hardware tables, and allows us to have YOUNG and DIRTY
 112  * bits.
 113  *
 114  * The PTE table pointer refers to the hardware entries; the "Linux"
 115  * entries are stored 1024 bytes below.
 116  */
 117 #define L_PTE_VALID             (_AT(pteval_t, 1) << 0)         /* Valid */
 118 #define L_PTE_PRESENT           (_AT(pteval_t, 1) << 0)
 119 #define L_PTE_YOUNG             (_AT(pteval_t, 1) << 1)
 120 #define L_PTE_DIRTY             (_AT(pteval_t, 1) << 6)
 121 #define L_PTE_RDONLY            (_AT(pteval_t, 1) << 7)
 122 #define L_PTE_USER              (_AT(pteval_t, 1) << 8)
 123 #define L_PTE_XN                (_AT(pteval_t, 1) << 9)
 124 #define L_PTE_SHARED            (_AT(pteval_t, 1) << 10)        /* shared(v6), coherent(xsc3) */
 125 #define L_PTE_NONE              (_AT(pteval_t, 1) << 11)
 126
 127 /*
 128  * These are the memory types, defined to be compatible with
 129  * pre-ARMv6 CPUs cacheable and bufferable bits: n/a,n/a,C,B
 130  * ARMv6+ without TEX remapping, they are a table index.
 131  * ARMv6+ with TEX remapping, they correspond to n/a,TEX(0),C,B
 132  *
 133  * MT type              Pre-ARMv6       ARMv6+ type / cacheable status
 134  * UNCACHED             Uncached        Strongly ordered
 135  * BUFFERABLE           Bufferable      Normal memory / non-cacheable
 136  * WRITETHROUGH         Writethrough    Normal memory / write through
 137  * WRITEBACK            Writeback       Normal memory / write back, read alloc
 138  * MINICACHE            Minicache       N/A
 139  * WRITEALLOC           Writeback       Normal memory / write back, write alloc
 140  * DEV_SHARED           Uncached        Device memory (shared)
 141  * DEV_NONSHARED        Uncached        Device memory (non-shared)
 142  * DEV_WC               Bufferable      Normal memory / non-cacheable
 143  * DEV_CACHED           Writeback       Normal memory / write back, read alloc
 144  * VECTORS              Variable        Normal memory / variable
 145  *
 146  * All normal memory mappings have the following properties:
 147  * - reads can be repeated with no side effects
 148  * - repeated reads return the last value written
 149  * - reads can fetch additional locations without side effects
 150  * - writes can be repeated (in certain cases) with no side effects
 151  * - writes can be merged before accessing the target
 152  * - unaligned accesses can be supported
 153  *
 154  * All device mappings have the following properties:
 155  * - no access speculation
 156  * - no repetition (eg, on return from an exception)
 157  * - number, order and size of accesses are maintained
 158  * - unaligned accesses are "unpredictable"
 159  */
 160 #define L_PTE_MT_UNCACHED       (_AT(pteval_t, 0x00) << 2)      /* 0000 */
 161 #define L_PTE_MT_BUFFERABLE     (_AT(pteval_t, 0x01) << 2)      /* 0001 */
 162 #define L_PTE_MT_WRITETHROUGH   (_AT(pteval_t, 0x02) << 2)      /* 0010 */
 163 #define L_PTE_MT_WRITEBACK      (_AT(pteval_t, 0x03) << 2)      /* 0011 */
 164 #define L_PTE_MT_MINICACHE      (_AT(pteval_t, 0x06) << 2)      /* 0110 (sa1100, xscale) */
 165 #define L_PTE_MT_WRITEALLOC     (_AT(pteval_t, 0x07) << 2)      /* 0111 */
 166 #define L_PTE_MT_DEV_SHARED     (_AT(pteval_t, 0x04) << 2)      /* 0100 */
 167 #define L_PTE_MT_DEV_NONSHARED  (_AT(pteval_t, 0x0c) << 2)      /* 1100 */
 168 #define L_PTE_MT_DEV_WC         (_AT(pteval_t, 0x09) << 2)      /* 1001 */
 169 #define L_PTE_MT_DEV_CACHED     (_AT(pteval_t, 0x0b) << 2)      /* 1011 */
 170 #define L_PTE_MT_VECTORS        (_AT(pteval_t, 0x0f) << 2)      /* 1111 */
 171 #define L_PTE_MT_MASK           (_AT(pteval_t, 0x0f) << 2)
 172
 173 #ifndef __ASSEMBLY__
 174
 175 /*
 176  * The "pud_xxx()" functions here are trivial when the pmd is folded into
 177  * the pud: the pud entry is never bad, always exists, and can't be set or
 178  * cleared.
 179  */
 180 #define pud_none(pud)           (0)
 181 #define pud_bad(pud)            (0)
 182 #define pud_present(pud)        (1)
 183 #define pud_clear(pudp)         do { } while (0)
 184 #define set_pud(pud,pudp)       do { } while (0)
 185
 186 static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
 187 {
 188         return (pmd_t *)pud;
 189 }
 190
 191 #define pmd_large(pmd)          (pmd_val(pmd) & 2)
 192 #define pmd_leaf(pmd)           (pmd_val(pmd) & 2)
 193 #define pmd_bad(pmd)            (pmd_val(pmd) & 2)
 194 #define pmd_present(pmd)        (pmd_val(pmd))
 195
 196 #define copy_pmd(pmdpd,pmdps)           \
 197         do {                            \
 198                 pmdpd[0] = pmdps[0];    \
 199                 pmdpd[1] = pmdps[1];    \
 200                 flush_pmd_entry(pmdpd); \
 201         } while (0)
 202
 203 #define pmd_clear(pmdp)                 \
 204         do {                            \
 205                 pmdp[0] = __pmd(0);     \
 206                 pmdp[1] = __pmd(0);     \
 207                 clean_pmd_entry(pmdp);  \
 208         } while (0)
 209
 210 /* we don't need complex calculations here as the pmd is folded into the pgd */
 211 #define pmd_addr_end(addr,end) (end)
 212
 213 #define set_pte_ext(ptep,pte,ext) cpu_set_pte_ext(ptep,pte,ext)
 214 #define pte_special(pte)        (0)
 215 static inline pte_t pte_mkspecial(pte_t pte) { return pte; }
 216
 217 /*
 218  * We don't have huge page support for short descriptors, for the moment
 219  * define empty stubs for use by pin_page_for_write.
 220  */
 221 #define pmd_hugewillfault(pmd)  (0)
 222 #define pmd_thp_or_huge(pmd)    (0)
 223
 224 #endif /* __ASSEMBLY__ */
 225
 226 #endif /* _ASM_PGTABLE_2LEVEL_H */