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  1. /*
  2.  * Copyright (C) 2001-2004 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. #include <arch/types.h>
  30. #include <config.h>
  31. #include <func.h>
  32. #include <mm/frame.h>
  33. #include <mm/page.h>
  34. #include <arch/mm/page.h>
  35. #include <arch/interrupt.h>
  36. #include <arch/asm.h>
  37. #include <synch/spinlock.h>
  38.  
  39. /*
  40.  * Note.
  41.  * This is the preliminary code for controlling paging mechanism on i386. It is
  42.  * needed by other parts of the kernel for its ability to map virtual addresses
  43.  * to physical. SMP code relies on this feature. Other than that, this code is
  44.  * by no means meant to implement virtual memory in terms of swapping pages in
  45.  * and out.
  46.  */
  47.  
  48. __address bootstrap_dba;
  49.  
  50. void page_arch_init(void)
  51. {
  52.     __address dba;
  53.     __u32 i;
  54.  
  55.     if (config.cpu_active == 1) {
  56.         dba = frame_alloc(FRAME_KA | FRAME_PANIC);
  57.         memsetb(dba, PAGE_SIZE, 0);
  58.         cpu_write_dba(dba);
  59.        
  60.         bootstrap_dba = dba;
  61.  
  62.         /*
  63.          * Identity mapping for all but 0th page.
  64.          */
  65.         for (i = 1; i < frames; i++)
  66.             map_page_to_frame(i * PAGE_SIZE, i * PAGE_SIZE, PAGE_CACHEABLE, 0);
  67.  
  68.         trap_register(14, page_fault);
  69.     }
  70.     else {
  71.  
  72.         /*
  73.          * Application processors need to create their own view of the
  74.          * virtual address space. Because of that, each AP copies
  75.          * already-initialized paging information from the bootstrap
  76.          * processor and adjusts it to fulfill its needs.
  77.          */
  78.  
  79.         dba = frame_alloc(FRAME_KA | FRAME_PANIC);
  80.         memcopy(bootstrap_dba, dba, PAGE_SIZE);
  81.         cpu_write_dba(dba);
  82.     }
  83.  
  84.     paging_on();
  85. }
  86.  
  87. /*
  88.  * Besides mapping pages to frames, this function also sets the present bit of
  89.  * the page's specifier in both page directory and respective page table. If
  90.  * the page table for this page has not been allocated so far, it will take
  91.  * care of it and allocate the necessary frame.
  92.  *
  93.  * When the copy parameter is positive, map_page_to_frame will not overwrite
  94.  * the current mapping. It will allocate a new frame and do the mapping on it
  95.  * instead.
  96.  *
  97.  * PAGE_CACHEABLE flag: when set, it turns caches for that page on
  98.  * PAGE_NOT_PRESENT flag: when set, it marks the page not present
  99.  * PAGE_USER flag: when set, the page is accessible from userspace
  100.  */
  101. void map_page_to_frame(__address page, __address frame, int flags, int copy)
  102. {
  103.     struct page_specifier *pd, *pt;
  104.     __address dba, newpt;
  105.     int pde, pte;
  106.  
  107.     dba = cpu_read_dba();
  108.  
  109.     pde = page >> 22;       /* page directory entry */
  110.     pte = (page >> 12) & 0x3ff; /* page table entry */
  111.    
  112.     pd = (struct page_specifier *) dba;
  113.    
  114.     if (!pd[pde].present) {
  115.         /*
  116.          * There is currently no page table for this address. Allocate
  117.          * frame for the page table and clean it.
  118.          */
  119.         newpt = frame_alloc(FRAME_KA);
  120.         pd[pde].frame_address = newpt >> 12;
  121.         memsetb(newpt, PAGE_SIZE, 0);
  122.         pd[pde].present = 1;
  123.         pd[pde].uaccessible = 1;
  124.     }
  125.     if (copy) {
  126.         newpt = frame_alloc(FRAME_KA);
  127.         memcopy(pd[pde].frame_address << 12, newpt, PAGE_SIZE);
  128.         pd[pde].frame_address = newpt >> 12;
  129.     }
  130.     pt = (struct page_specifier *) (pd[pde].frame_address << 12);
  131.  
  132.     pt[pte].frame_address = frame >> 12;
  133.     pt[pte].present = !(flags & PAGE_NOT_PRESENT);
  134.     pt[pte].page_cache_disable = !(flags & PAGE_CACHEABLE);
  135.     pt[pte].uaccessible = (flags & PAGE_USER) != 0;
  136.     pt[pte].writeable = (flags & PAGE_WRITE) != 0; 
  137. }
  138.