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