108 lines
4 KiB
C
108 lines
4 KiB
C
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#ifndef THREADS_PTE_H
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#define THREADS_PTE_H
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#include "threads/vaddr.h"
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/* Functions and macros for working with x86 hardware page
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tables.
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See vaddr.h for more generic functions and macros for virtual
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addresses.
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Virtual addresses are structured as follows:
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31 22 21 12 11 0
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+----------------------+----------------------+----------------------+
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| Page Directory Index | Page Table Index | Page Offset |
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+----------------------+----------------------+----------------------+
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*/
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/* Page table index (bits 12:21). */
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#define PTSHIFT PGBITS /* First page table bit. */
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#define PTBITS 10 /* Number of page table bits. */
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#define PTSPAN (1 << PTBITS << PGBITS) /* Bytes covered by a page table. */
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#define PTMASK BITMASK(PTSHIFT, PTBITS) /* Page table bits (12:21). */
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/* Page directory index (bits 22:31). */
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#define PDSHIFT (PTSHIFT + PTBITS) /* First page directory bit. */
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#define PDBITS 10 /* Number of page dir bits. */
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#define PDMASK BITMASK(PDSHIFT, PDBITS) /* Page directory bits (22:31). */
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/* Obtains page table index from a virtual address. */
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static inline unsigned pt_no (const void *va) {
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return ((uintptr_t) va & PTMASK) >> PTSHIFT;
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}
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/* Obtains page directory index from a virtual address. */
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static inline uintptr_t pd_no (const void *va) {
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return (uintptr_t) va >> PDSHIFT;
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}
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/* Page directory and page table entries.
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For more information see the section on page tables in the
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Pintos reference guide chapter, or [IA32-v3a] 3.7.6
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"Page-Directory and Page-Table Entries".
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PDEs and PTEs share a common format:
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31 12 11 0
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+------------------------------------+------------------------+
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| Physical Address | Flags |
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+------------------------------------+------------------------+
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In a PDE, the physical address points to a page table.
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In a PTE, the physical address points to a data or code page.
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The important flags are listed below.
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When a PDE or PTE is not "present", the other flags are
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ignored.
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A PDE or PTE that is initialized to 0 will be interpreted as
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"not present", which is just fine. */
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#define PTE_FLAGS 0x00000fff /* Flag bits. */
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#define PTE_ADDR 0xfffff000 /* Address bits. */
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#define PTE_AVL 0x00000e00 /* Bits available for OS use. */
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#define PTE_P 0x1 /* 1=present, 0=not present. */
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#define PTE_W 0x2 /* 1=read/write, 0=read-only. */
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#define PTE_U 0x4 /* 1=user/kernel, 0=kernel only. */
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#define PTE_A 0x20 /* 1=accessed, 0=not acccessed. */
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#define PTE_D 0x40 /* 1=dirty, 0=not dirty (PTEs only). */
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/* Returns a PDE that points to page table PT. */
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static inline uint32_t pde_create (uint32_t *pt) {
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ASSERT (pg_ofs (pt) == 0);
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return vtop (pt) | PTE_U | PTE_P | PTE_W;
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}
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/* Returns a pointer to the page table that page directory entry
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PDE, which must "present", points to. */
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static inline uint32_t *pde_get_pt (uint32_t pde) {
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ASSERT (pde & PTE_P);
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return ptov (pde & PTE_ADDR);
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}
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/* Returns a PTE that points to PAGE.
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The PTE's page is readable.
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If WRITABLE is true then it will be writable as well.
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The page will be usable only by ring 0 code (the kernel). */
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static inline uint32_t pte_create_kernel (void *page, bool writable) {
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ASSERT (pg_ofs (page) == 0);
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return vtop (page) | PTE_P | (writable ? PTE_W : 0);
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}
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/* Returns a PTE that points to PAGE.
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The PTE's page is readable.
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If WRITABLE is true then it will be writable as well.
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The page will be usable by both user and kernel code. */
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static inline uint32_t pte_create_user (void *page, bool writable) {
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return pte_create_kernel (page, writable) | PTE_U;
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}
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/* Returns a pointer to the page that page table entry PTE points
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to. */
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static inline void *pte_get_page (uint32_t pte) {
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return ptov (pte & PTE_ADDR);
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}
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#endif /* threads/pte.h */
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