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  1. /*
  2.  * Copyright (C) 2006 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.  /** @addtogroup genericmm
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file
  35.  * @brief   Backend for anonymous memory address space areas.
  36.  *
  37.  */
  38.  
  39. #include <mm/as.h>
  40. #include <mm/page.h>
  41. #include <genarch/mm/page_pt.h>
  42. #include <genarch/mm/page_ht.h>
  43. #include <mm/frame.h>
  44. #include <mm/slab.h>
  45. #include <synch/mutex.h>
  46. #include <adt/list.h>
  47. #include <adt/btree.h>
  48. #include <errno.h>
  49. #include <arch/types.h>
  50. #include <typedefs.h>
  51. #include <align.h>
  52. #include <arch.h>
  53.  
  54. static int anon_page_fault(as_area_t *area, __address addr, pf_access_t access);
  55. static void anon_frame_free(as_area_t *area, __address page, __address frame);
  56. static void anon_share(as_area_t *area);
  57.  
  58. mem_backend_t anon_backend = {
  59.     .page_fault = anon_page_fault,
  60.     .frame_free = anon_frame_free,
  61.     .share = anon_share
  62. };
  63.  
  64. /** Service a page fault in the anonymous memory address space area.
  65.  *
  66.  * The address space area and page tables must be already locked.
  67.  *
  68.  * @param area Pointer to the address space area.
  69.  * @param addr Faulting virtual address.
  70.  * @param access Access mode that caused the fault (i.e. read/write/exec).
  71.  *
  72.  * @return AS_PF_FAULT on failure (i.e. page fault) or AS_PF_OK on success (i.e. serviced).
  73.  */
  74. int anon_page_fault(as_area_t *area, __address addr, pf_access_t access)
  75. {
  76.     __address frame;
  77.  
  78.     if (!as_area_check_access(area, access))
  79.         return AS_PF_FAULT;
  80.  
  81.     if (area->sh_info) {
  82.         btree_node_t *leaf;
  83.        
  84.         /*
  85.          * The area is shared, chances are that the mapping can be found
  86.          * in the pagemap of the address space area share info structure.
  87.          * In the case that the pagemap does not contain the respective
  88.          * mapping, a new frame is allocated and the mapping is created.
  89.          */
  90.         mutex_lock(&area->sh_info->lock);
  91.         frame = (__address) btree_search(&area->sh_info->pagemap,
  92.             ALIGN_DOWN(addr, PAGE_SIZE) - area->base, &leaf);
  93.         if (!frame) {
  94.             bool allocate = true;
  95.             int i;
  96.            
  97.             /*
  98.              * Zero can be returned as a valid frame address.
  99.              * Just a small workaround.
  100.              */
  101.             for (i = 0; i < leaf->keys; i++) {
  102.                 if (leaf->key[i] == ALIGN_DOWN(addr, PAGE_SIZE)) {
  103.                     allocate = false;
  104.                     break;
  105.                 }
  106.             }
  107.             if (allocate) {
  108.                 frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  109.                 memsetb(PA2KA(frame), FRAME_SIZE, 0);
  110.                
  111.                 /*
  112.                  * Insert the address of the newly allocated frame to the pagemap.
  113.                  */
  114.                 btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base, (void *) frame, leaf);
  115.             }
  116.         }
  117.         frame_reference_add(ADDR2PFN(frame));
  118.         mutex_unlock(&area->sh_info->lock);
  119.     } else {
  120.  
  121.         /*
  122.          * In general, there can be several reasons that
  123.          * can have caused this fault.
  124.          *
  125.          * - non-existent mapping: the area is an anonymous
  126.          *   area (e.g. heap or stack) and so far has not been
  127.          *   allocated a frame for the faulting page
  128.          *
  129.          * - non-present mapping: another possibility,
  130.          *   currently not implemented, would be frame
  131.          *   reuse; when this becomes a possibility,
  132.          *   do not forget to distinguish between
  133.          *   the different causes
  134.          */
  135.         frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  136.         memsetb(PA2KA(frame), FRAME_SIZE, 0);
  137.     }
  138.    
  139.     /*
  140.      * Map 'page' to 'frame'.
  141.      * Note that TLB shootdown is not attempted as only new information is being
  142.      * inserted into page tables.
  143.      */
  144.     page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
  145.     if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
  146.         panic("Could not insert used space.\n");
  147.        
  148.     return AS_PF_OK;
  149. }
  150.  
  151. /** Free a frame that is backed by the anonymous memory backend.
  152.  *
  153.  * The address space area and page tables must be already locked.
  154.  *
  155.  * @param area Ignored.
  156.  * @param page Ignored.
  157.  * @param frame Frame to be released.
  158.  */
  159. void anon_frame_free(as_area_t *area, __address page, __address frame)
  160. {
  161.     frame_free(ADDR2PFN(frame));
  162. }
  163.  
  164. /** Share the anonymous address space area.
  165.  *
  166.  * Sharing of anonymous area is done by duplicating its entire mapping
  167.  * to the pagemap. Page faults will primarily search for frames there.
  168.  *
  169.  * The address space and address space area must be already locked.
  170.  *
  171.  * @param area Address space area to be shared.
  172.  */
  173. void anon_share(as_area_t *area)
  174. {
  175.     link_t *cur;
  176.  
  177.     /*
  178.      * Copy used portions of the area to sh_info's page map.
  179.      */
  180.     mutex_lock(&area->sh_info->lock);
  181.     for (cur = area->used_space.leaf_head.next; cur != &area->used_space.leaf_head; cur = cur->next) {
  182.         btree_node_t *node;
  183.         int i;
  184.        
  185.         node = list_get_instance(cur, btree_node_t, leaf_link);
  186.         for (i = 0; i < node->keys; i++) {
  187.             __address base = node->key[i];
  188.             count_t count = (count_t) node->value[i];
  189.             int j;
  190.            
  191.             for (j = 0; j < count; j++) {
  192.                 pte_t *pte;
  193.            
  194.                 page_table_lock(area->as, false);
  195.                 pte = page_mapping_find(area->as, base + j*PAGE_SIZE);
  196.                 ASSERT(pte && PTE_VALID(pte) && PTE_PRESENT(pte));
  197.                 btree_insert(&area->sh_info->pagemap, (base + j*PAGE_SIZE) - area->base,
  198.                     (void *) PTE_GET_FRAME(pte), NULL);
  199.                 page_table_unlock(area->as, false);
  200.                 frame_reference_add(ADDR2PFN(PTE_GET_FRAME(pte)));
  201.             }
  202.                
  203.         }
  204.     }
  205.     mutex_unlock(&area->sh_info->lock);
  206. }
  207.  
  208.  /** @}
  209.  */
  210.  
  211.