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Edit File: pgtable-2level.h

/* SPDX-License-Identifier: GPL-2.0-only */ /* * arch/arm/include/asm/pgtable-2level.h * * Copyright (C) 1995-2002 Russell King */ #ifndef _ASM_PGTABLE_2LEVEL_H #define _ASM_PGTABLE_2LEVEL_H #define __PAGETABLE_PMD_FOLDED 1 /* * 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)) #define MAX_POSSIBLE_PHYSMEM_BITS 32 /* * 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_VALID (_AT(pteval_t, 1) << 0) /* Valid */ #define L_PTE_PRESENT (_AT(pteval_t, 1) << 0) #define L_PTE_YOUNG (_AT(pteval_t, 1) << 1) #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) */ #define L_PTE_NONE (_AT(pteval_t, 1) << 11) /* * These are the memory types, defined to be compatible with * pre-ARMv6 CPUs cacheable and bufferable bits: n/a,n/a,C,B * ARMv6+ without TEX remapping, they are a table index. * ARMv6+ with TEX remapping, they correspond to n/a,TEX(0),C,B * * MT type Pre-ARMv6 ARMv6+ type / cacheable status * UNCACHED Uncached Strongly ordered * BUFFERABLE Bufferable Normal memory / non-cacheable * WRITETHROUGH Writethrough Normal memory / write through * WRITEBACK Writeback Normal memory / write back, read alloc * MINICACHE Minicache N/A * WRITEALLOC Writeback Normal memory / write back, write alloc * DEV_SHARED Uncached Device memory (shared) * DEV_NONSHARED Uncached Device memory (non-shared) * DEV_WC Bufferable Normal memory / non-cacheable * DEV_CACHED Writeback Normal memory / write back, read alloc * VECTORS Variable Normal memory / variable * * All normal memory mappings have the following properties: * - reads can be repeated with no side effects * - repeated reads return the last value written * - reads can fetch additional locations without side effects * - writes can be repeated (in certain cases) with no side effects * - writes can be merged before accessing the target * - unaligned accesses can be supported * * All device mappings have the following properties: * - no access speculation * - no repetition (eg, on return from an exception) * - number, order and size of accesses are maintained * - unaligned accesses are "unpredictable" */ #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_VECTORS (_AT(pteval_t, 0x0f) << 2) /* 1111 */ #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_large(pmd) (pmd_val(pmd) & 2) #define pmd_bad(pmd) (pmd_val(pmd) & 2) #define pmd_present(pmd) (pmd_val(pmd)) #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) #define pte_special(pte) (0) static inline pte_t pte_mkspecial(pte_t pte) { return pte; } /* * We don't have huge page support for short descriptors, for the moment * define empty stubs for use by pin_page_for_write. */ #define pmd_hugewillfault(pmd) (0) #define pmd_thp_or_huge(pmd) (0) #endif /* __ASSEMBLY__ */ #endif /* _ASM_PGTABLE_2LEVEL_H */