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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 <align.h>
  51. #include <arch.h>
  52.  
  53. #ifdef CONFIG_VIRT_IDX_DCACHE
  54. #include <arch/mm/cache.h>
  55. #endif
  56.  
  57. static int anon_page_fault(as_area_t *area, uintptr_t addr, pf_access_t access);
  58. static void anon_frame_free(as_area_t *area, uintptr_t page, uintptr_t frame);
  59. static void anon_share(as_area_t *area);
  60.  
  61. mem_backend_t anon_backend = {
  62.     .page_fault = anon_page_fault,
  63.     .frame_free = anon_frame_free,
  64.     .share = anon_share
  65. };
  66.  
  67. /** Service a page fault in the anonymous memory address space area.
  68.  *
  69.  * The address space area and page tables must be already locked.
  70.  *
  71.  * @param area Pointer to the address space area.
  72.  * @param addr Faulting virtual address.
  73.  * @param access Access mode that caused the fault (i.e. read/write/exec).
  74.  *
  75.  * @return AS_PF_FAULT on failure (i.e. page fault) or AS_PF_OK on success (i.e.
  76.  *     serviced).
  77.  */
  78. int anon_page_fault(as_area_t *area, uintptr_t addr, pf_access_t access)
  79. {
  80.     uintptr_t frame;
  81.  
  82.     if (!as_area_check_access(area, access))
  83.         return AS_PF_FAULT;
  84.  
  85.     if (area->sh_info) {
  86.         btree_node_t *leaf;
  87.        
  88.         /*
  89.          * The area is shared, chances are that the mapping can be found
  90.          * in the pagemap of the address space area share info
  91.          * structure.
  92.          * In the case that the pagemap does not contain the respective
  93.          * mapping, a new frame is allocated and the mapping is created.
  94.          */
  95.         mutex_lock(&area->sh_info->lock);
  96.         frame = (uintptr_t) btree_search(&area->sh_info->pagemap,
  97.             ALIGN_DOWN(addr, PAGE_SIZE) - area->base, &leaf);
  98.         if (!frame) {
  99.             bool allocate = true;
  100.             unsigned int i;
  101.            
  102.             /*
  103.              * Zero can be returned as a valid frame address.
  104.              * Just a small workaround.
  105.              */
  106.             for (i = 0; i < leaf->keys; i++) {
  107.                 if (leaf->key[i] ==
  108.                     ALIGN_DOWN(addr, PAGE_SIZE) - area->base) {
  109.                     allocate = false;
  110.                     break;
  111.                 }
  112.             }
  113.             if (allocate) {
  114.                 frame = (uintptr_t) frame_alloc(ONE_FRAME, 0);
  115.                 memsetb((void *) PA2KA(frame), FRAME_SIZE, 0);
  116.                
  117.                 /*
  118.                  * Insert the address of the newly allocated
  119.                  * frame to the pagemap.
  120.                  */
  121.                 btree_insert(&area->sh_info->pagemap,
  122.                     ALIGN_DOWN(addr, PAGE_SIZE) - area->base,
  123.                     (void *) frame, leaf);
  124.             }
  125.         }
  126.         frame_reference_add(ADDR2PFN(frame));
  127.         mutex_unlock(&area->sh_info->lock);
  128.     } else {
  129.  
  130.         /*
  131.          * In general, there can be several reasons that
  132.          * can have caused this fault.
  133.          *
  134.          * - non-existent mapping: the area is an anonymous
  135.          *   area (e.g. heap or stack) and so far has not been
  136.          *   allocated a frame for the faulting page
  137.          *
  138.          * - non-present mapping: another possibility,
  139.          *   currently not implemented, would be frame
  140.          *   reuse; when this becomes a possibility,
  141.          *   do not forget to distinguish between
  142.          *   the different causes
  143.          */
  144.         frame = (uintptr_t) frame_alloc(ONE_FRAME, 0);
  145.         memsetb((void *) PA2KA(frame), FRAME_SIZE, 0);
  146.     }
  147.    
  148.     /*
  149.      * Map 'page' to 'frame'.
  150.      * Note that TLB shootdown is not attempted as only new information is
  151.      * being inserted into page tables.
  152.      */
  153.     page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
  154.     if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
  155.         panic("Cannot insert used space.");
  156.        
  157.     return AS_PF_OK;
  158. }
  159.  
  160. /** Free a frame that is backed by the anonymous memory backend.
  161.  *
  162.  * The address space area and page tables must be already locked.
  163.  *
  164.  * @param area Ignored.
  165.  * @param page Virtual address of the page corresponding to the frame.
  166.  * @param frame Frame to be released.
  167.  */
  168. void anon_frame_free(as_area_t *area, uintptr_t page, uintptr_t frame)
  169. {
  170.     frame_free(frame);
  171. }
  172.  
  173. /** Share the anonymous address space area.
  174.  *
  175.  * Sharing of anonymous area is done by duplicating its entire mapping
  176.  * to the pagemap. Page faults will primarily search for frames there.
  177.  *
  178.  * The address space and address space area must be already locked.
  179.  *
  180.  * @param area Address space area to be shared.
  181.  */
  182. void anon_share(as_area_t *area)
  183. {
  184.     link_t *cur;
  185.  
  186.     /*
  187.      * Copy used portions of the area to sh_info's page map.
  188.      */
  189.     mutex_lock(&area->sh_info->lock);
  190.     for (cur = area->used_space.leaf_head.next;
  191.         cur != &area->used_space.leaf_head; cur = cur->next) {
  192.         btree_node_t *node;
  193.         unsigned int i;
  194.        
  195.         node = list_get_instance(cur, btree_node_t, leaf_link);
  196.         for (i = 0; i < node->keys; i++) {
  197.             uintptr_t base = node->key[i];
  198.             size_t count = (size_t) node->value[i];
  199.             unsigned int j;
  200.            
  201.             for (j = 0; j < count; j++) {
  202.                 pte_t *pte;
  203.            
  204.                 page_table_lock(area->as, false);
  205.                 pte = page_mapping_find(area->as,
  206.                     base + j * PAGE_SIZE);
  207.                 ASSERT(pte && PTE_VALID(pte) &&
  208.                     PTE_PRESENT(pte));
  209.                 btree_insert(&area->sh_info->pagemap,
  210.                     (base + j * PAGE_SIZE) - area->base,
  211.                     (void *) PTE_GET_FRAME(pte), NULL);
  212.                 page_table_unlock(area->as, false);
  213.  
  214.                 pfn_t pfn = ADDR2PFN(PTE_GET_FRAME(pte));
  215.                 frame_reference_add(pfn);
  216.             }
  217.  
  218.         }
  219.     }
  220.     mutex_unlock(&area->sh_info->lock);
  221. }
  222.  
  223. /** @}
  224.  */
  225.