inc/memlayout.h

   1 #ifndef JOS_INC_MEMLAYOUT_H
   2 #define JOS_INC_MEMLAYOUT_H
   3
   4 #ifndef __ASSEMBLER__
   5 #include <inc/types.h>
   6 #include <inc/queue.h>
   7 #include <inc/mmu.h>
   8 #endif /* not __ASSEMBLER__ */
   9
  10 /*
  11  * This file contains definitions for memory management in our OS,
  12  * which are relevant to both the kernel and user-mode software.
  13  */
  14
  15 // Global descriptor numbers
  16 #define GD_KT     0x08     // kernel text
  17 #define GD_KD     0x10     // kernel data
  18 #define GD_UT     0x18     // user text
  19 #define GD_UD     0x20     // user data
  20 #define GD_TSS    0x28     // Task segment selector
  21
  22 /*
  23  * Virtual memory map:                                Permissions
  24  *                                                    kernel/user
  25  *
  26  *    4 Gig -------->  +------------------------------+
  27  *                     |                              | RW/--
  28  *                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  29  *                     :              .               :
  30  *                     :              .               :
  31  *                     :              .               :
  32  *                     |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| RW/--
  33  *                     |                              | RW/--
  34  *                     |   Remapped Physical Memory   | RW/--
  35  *                     |                              | RW/--
  36  *    KERNBASE ----->  +------------------------------+ 0xf0000000
  37  *                     |  Cur. Page Table (Kern. RW)  | RW/--  PTSIZE
  38  *    VPT,KSTACKTOP--> +------------------------------+ 0xefc00000      --+
  39  *                     |         Kernel Stack         | RW/--  KSTKSIZE   |
  40  *                     | - - - - - - - - - - - - - - -|                 PTSIZE
  41  *                     |      Invalid Memory (*)      | --/--             |
  42  *    ULIM     ------> +------------------------------+ 0xef800000      --+
  43  *                     |  Cur. Page Table (User R-)   | R-/R-  PTSIZE
  44  *    UVPT      ---->  +------------------------------+ 0xef400000
  45  *                     |          RO PAGES            | R-/R-  PTSIZE
  46  *    UPAGES    ---->  +------------------------------+ 0xef000000
  47  *                     |           RO ENVS            | R-/R-  PTSIZE
  48  * UTOP,UENVS ------>  +------------------------------+ 0xeec00000
  49  * UXSTACKTOP -/       |     User Exception Stack     | RW/RW  PGSIZE
  50  *                     +------------------------------+ 0xeebff000
  51  *                     |       Empty Memory (*)       | --/--  PGSIZE
  52  *    USTACKTOP  --->  +------------------------------+ 0xeebfe000
  53  *                     |      Normal User Stack       | RW/RW  PGSIZE
  54  *                     +------------------------------+ 0xeebfd000
  55  *                     |                              |
  56  *                     |                              |
  57  *                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  58  *                     .                              .
  59  *                     .                              .
  60  *                     .                              .
  61  *                     |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
  62  *                     |     Program Data & Heap      |
  63  *    UTEXT -------->  +------------------------------+ 0x00800000
  64  *    PFTEMP ------->  |       Empty Memory (*)       |        PTSIZE
  65  *                     |                              |
  66  *    UTEMP -------->  +------------------------------+ 0x00400000      --+
  67  *                     |       Empty Memory (*)       |                   |
  68  *                     | - - - - - - - - - - - - - - -|                   |
  69  *                     |  User STAB Data (optional)   |                 PTSIZE
  70  *    USTABDATA ---->  +------------------------------+ 0x00200000        |
  71  *                     |       Empty Memory (*)       |                   |
  72  *    0 ------------>  +------------------------------+                 --+
  73  *
  74  * (*) Note: The kernel ensures that "Invalid Memory" (ULIM) is *never*
  75  *     mapped.  "Empty Memory" is normally unmapped, but user programs may
  76  *     map pages there if desired.  JOS user programs map pages temporarily
  77  *     at UTEMP.
  78  */
  79
  80
  81 // All physical memory mapped at this address
  82 #define KERNBASE        0xF0000000
  83
  84 // At IOPHYSMEM (640K) there is a 384K hole for I/O.  From the kernel,
  85 // IOPHYSMEM can be addressed at KERNBASE + IOPHYSMEM.  The hole ends
  86 // at physical address EXTPHYSMEM.
  87 #define IOPHYSMEM       0x0A0000
  88 #define EXTPHYSMEM      0x100000
  89
  90 // Virtual page table.  Entry PDX[VPT] in the PD contains a pointer to
  91 // the page directory itself, thereby turning the PD into a page table,
  92 // which maps all the PTEs containing the page mappings for the entire
  93 // virtual address space into that 4 Meg region starting at VPT.
  94 #define VPT             (KERNBASE - PTSIZE)
  95 #define KSTACKTOP       VPT
  96 #define KSTKSIZE        (8*PGSIZE)              // size of a kernel stack
  97 #define ULIM            (KSTACKTOP - PTSIZE)
  98
  99 /*
 100  * User read-only mappings! Anything below here til UTOP are readonly to user.
 101  * They are global pages mapped in at env allocation time.
 102  */
 103
 104 // Same as VPT but read-only for users
 105 #define UVPT            (ULIM - PTSIZE)
 106 // Read-only copies of the Page structures
 107 #define UPAGES          (UVPT - PTSIZE)
 108 // Read-only copies of the global env structures
 109 #define UENVS           (UPAGES - PTSIZE)
 110
 111 /*
 112  * Top of user VM. User can manipulate VA from UTOP-1 and down!
 113  */
 114
 115 // Top of user-accessible VM
 116 #define UTOP            UENVS
 117 // Top of one-page user exception stack
 118 #define UXSTACKTOP      UTOP
 119 // Next page left invalid to guard against exception stack overflow; then:
 120 // Top of normal user stack
 121 #define USTACKTOP       (UTOP - 2*PGSIZE)
 122
 123 // Where user programs generally begin
 124 #define UTEXT           (2*PTSIZE)
 125
 126 // Used for temporary page mappings.  Typed 'void*' for convenience
 127 #define UTEMP           ((void*) PTSIZE)
 128 // Used for temporary page mappings for the user page-fault handler
 129 // (should not conflict with other temporary page mappings)
 130 #define PFTEMP          (UTEMP + PTSIZE - PGSIZE)
 131 // The location of the user-level STABS data structure
 132 #define USTABDATA       (PTSIZE / 2)
 133
 134
 135 #ifndef __ASSEMBLER__
 136
 137 /*
 138  * The page directory entry corresponding to the virtual address range
 139  * [VPT, VPT + PTSIZE) points to the page directory itself.  Thus, the page
 140  * directory is treated as a page table as well as a page directory.
 141  *
 142  * One result of treating the page directory as a page table is that all PTEs
 143  * can be accessed through a "virtual page table" at virtual address VPT (to
 144  * which vpt is set in entry.S).  The PTE for page number N is stored in
 145  * vpt[N].  (It's worth drawing a diagram of this!)
 146  *
 147  * A second consequence is that the contents of the current page directory
 148  * will always be available at virtual address (VPT + (VPT >> PGSHIFT)), to
 149  * which vpd is set in entry.S.
 150  */
 151 typedef uint32_t pte_t;
 152 typedef uint32_t pde_t;
 153
 154 extern volatile pte_t vpt[];     // VA of "virtual page table"
 155 extern volatile pde_t vpd[];     // VA of current page directory
 156
 157
 158 /*
 159  * Page descriptor structures, mapped at UPAGES.
 160  * Read/write to the kernel, read-only to user programs.
 161  *
 162  * Each Page describes one physical page.
 163  * You can map a Page * to the corresponding physical address
 164  * with page2pa() in kern/pmap.h.
 165  */
 166 LIST_HEAD(Page_list, Page);
 167 typedef LIST_ENTRY(Page) Page_LIST_entry_t;
 168
 169 struct Page {
 170         Page_LIST_entry_t pp_link;      /* free list link */
 171
 172         // pp_ref is the count of pointers (usually in page table entries)
 173         // to this page, for pages allocated using page_alloc.
 174         // Pages allocated at boot time using pmap.c's
 175         // boot_alloc do not have valid reference count fields.
 176
 177         uint16_t pp_ref;
 178 };
 179
 180 #endif /* !__ASSEMBLER__ */
 181 #endif /* !JOS_INC_MEMLAYOUT_H */