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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_elf.c
  31.  * @brief   Backend for address space areas backed by an ELF image.
  32.  */
  33.  
  34. #include <elf.h>
  35. #include <debug.h>
  36. #include <arch/types.h>
  37. #include <typedefs.h>
  38. #include <mm/as.h>
  39. #include <mm/frame.h>
  40. #include <mm/slab.h>
  41. #include <mm/page.h>
  42. #include <genarch/mm/page_pt.h>
  43. #include <genarch/mm/page_ht.h>
  44. #include <align.h>
  45. #include <memstr.h>
  46. #include <macros.h>
  47. #include <arch.h>
  48.  
  49. static int elf_page_fault(as_area_t *area, __address addr, pf_access_t access);
  50. static void elf_frame_free(as_area_t *area, __address page, __address frame);
  51. static void elf_share(as_area_t *area);
  52.  
  53. mem_backend_t elf_backend = {
  54.     .page_fault = elf_page_fault,
  55.     .frame_free = elf_frame_free,
  56.     .share = elf_share
  57. };
  58.  
  59. /** Service a page fault in the ELF backend address space area.
  60.  *
  61.  * The address space area and page tables must be already locked.
  62.  *
  63.  * @param area Pointer to the address space area.
  64.  * @param addr Faulting virtual address.
  65.  * @param access Access mode that caused the fault (i.e. read/write/exec).
  66.  *
  67.  * @return AS_PF_FAULT on failure (i.e. page fault) or AS_PF_OK on success (i.e. serviced).
  68.  */
  69. int elf_page_fault(as_area_t *area, __address addr, pf_access_t access)
  70. {
  71.     elf_header_t *elf = area->backend_data.elf;
  72.     elf_segment_header_t *entry = area->backend_data.segment;
  73.     btree_node_t *leaf;
  74.     __address base, frame;
  75.     index_t i;
  76.  
  77.     if (!as_area_check_access(area, access))
  78.         return AS_PF_FAULT;
  79.  
  80.     ASSERT((addr >= entry->p_vaddr) && (addr < entry->p_vaddr + entry->p_memsz));
  81.     i = (addr - entry->p_vaddr) >> PAGE_WIDTH;
  82.     base = (__address) (((void *) elf) + entry->p_offset);
  83.     ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
  84.  
  85.     if (area->sh_info) {
  86.         bool found = false;
  87.  
  88.         /*
  89.          * The address space area is shared.
  90.          */
  91.          
  92.         mutex_lock(&area->sh_info->lock);
  93.         frame = (__address) btree_search(&area->sh_info->pagemap,
  94.             ALIGN_DOWN(addr, PAGE_SIZE) - area->base, &leaf);
  95.         if (!frame) {
  96.             int i;
  97.  
  98.             /*
  99.              * Workaround for valid NULL address.
  100.              */
  101.  
  102.             for (i = 0; i < leaf->keys; i++) {
  103.                 if (leaf->key[i] == ALIGN_DOWN(addr, PAGE_SIZE)) {
  104.                     found = true;
  105.                     break;
  106.                 }
  107.             }
  108.         }
  109.         if (frame || found) {
  110.             page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
  111.             if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
  112.                 panic("Could not insert used space.\n");
  113.             mutex_unlock(&area->sh_info->lock);
  114.             return AS_PF_OK;
  115.         }
  116.     }
  117.    
  118.     /*
  119.      * The area is either not shared or the pagemap does not contain the mapping.
  120.      */
  121.    
  122.     if (ALIGN_DOWN(addr, PAGE_SIZE) + PAGE_SIZE < entry->p_vaddr + entry->p_filesz) {
  123.         /*
  124.          * Initialized portion of the segment. The memory is backed
  125.          * directly by the content of the ELF image. Pages are
  126.          * only copied if the segment is writable so that there
  127.          * can be more instantions of the same memory ELF image
  128.          * used at a time. Note that this could be later done
  129.          * as COW.
  130.          */
  131.         if (entry->p_flags & PF_W) {
  132.             frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  133.             memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), FRAME_SIZE);
  134.            
  135.             if (area->sh_info) {
  136.                 btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base,
  137.                     (void *) frame, leaf);
  138.             }
  139.  
  140.         } else {
  141.             frame = KA2PA(base + i*FRAME_SIZE);
  142.         }  
  143.     } else if (ALIGN_DOWN(addr, PAGE_SIZE) >= ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
  144.         /*
  145.          * This is the uninitialized portion of the segment.
  146.          * It is not physically present in the ELF image.
  147.          * To resolve the situation, a frame must be allocated
  148.          * and cleared.
  149.          */
  150.         frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  151.         memsetb(PA2KA(frame), FRAME_SIZE, 0);
  152.  
  153.         if (area->sh_info) {
  154.             btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base,
  155.                 (void *) frame, leaf);
  156.         }
  157.  
  158.     } else {
  159.         size_t size;
  160.         /*
  161.          * The mixed case.
  162.          * The lower part is backed by the ELF image and
  163.          * the upper part is anonymous memory.
  164.          */
  165.         size = entry->p_filesz - (i<<PAGE_WIDTH);
  166.         frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  167.         memsetb(PA2KA(frame) + size, FRAME_SIZE - size, 0);
  168.         memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), size);
  169.  
  170.         if (area->sh_info) {
  171.             btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base,
  172.                 (void *) frame, leaf);
  173.         }
  174.  
  175.     }
  176.    
  177.     if (area->sh_info)
  178.         mutex_unlock(&area->sh_info->lock);
  179.    
  180.     page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
  181.     if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
  182.         panic("Could not insert used space.\n");
  183.  
  184.     return AS_PF_OK;
  185. }
  186.  
  187. /** Free a frame that is backed by the ELF backend.
  188.  *
  189.  * The address space area and page tables must be already locked.
  190.  *
  191.  * @param area Pointer to the address space area.
  192.  * @param page Page that is mapped to frame. Must be aligned to PAGE_SIZE.
  193.  * @param frame Frame to be released.
  194.  *
  195.  */
  196. void elf_frame_free(as_area_t *area, __address page, __address frame)
  197. {
  198.     elf_header_t *elf = area->backend_data.elf;
  199.     elf_segment_header_t *entry = area->backend_data.segment;
  200.     __address base;
  201.     index_t i;
  202.    
  203.     ASSERT((page >= entry->p_vaddr) && (page < entry->p_vaddr + entry->p_memsz));
  204.     i = (page - entry->p_vaddr) >> PAGE_WIDTH;
  205.     base = (__address) (((void *) elf) + entry->p_offset);
  206.     ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
  207.    
  208.     if (page + PAGE_SIZE < ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
  209.         if (entry->p_flags & PF_W) {
  210.             /*
  211.              * Free the frame with the copy of writable segment data.
  212.              */
  213.             frame_free(ADDR2PFN(frame));
  214.         }
  215.     } else {
  216.         /*
  217.          * The frame is either anonymous memory or the mixed case (i.e. lower
  218.          * part is backed by the ELF image and the upper is anonymous).
  219.          * In any case, a frame needs to be freed.
  220.          */
  221.         frame_free(ADDR2PFN(frame));
  222.     }
  223. }
  224.  
  225. /** Share ELF image backed address space area.
  226.  *
  227.  * If the area is writable, then all mapped pages are duplicated in the pagemap.
  228.  * Otherwise only portions of the area that are not backed by the ELF image
  229.  * are put into the pagemap.
  230.  *
  231.  * The address space and address space area must be locked prior to the call.
  232.  *
  233.  * @param area Address space area.
  234.  */
  235. void elf_share(as_area_t *area)
  236. {
  237.     elf_segment_header_t *entry = area->backend_data.segment;
  238.     link_t *cur;
  239.     btree_node_t *leaf, *node;
  240.     __address start_anon = entry->p_vaddr + entry->p_filesz;
  241.  
  242.     /*
  243.      * Find the node in which to start linear search.
  244.      */
  245.     if (area->flags & AS_AREA_WRITE) {
  246.         node = list_get_instance(area->used_space.leaf_head.next, btree_node_t, leaf_link);
  247.     } else {
  248.         (void) btree_search(&area->sh_info->pagemap, start_anon, &leaf);
  249.         node = btree_leaf_node_left_neighbour(&area->sh_info->pagemap, leaf);
  250.         if (!node)
  251.             node = leaf;
  252.     }
  253.  
  254.     /*
  255.      * Copy used anonymous portions of the area to sh_info's page map.
  256.      */
  257.     mutex_lock(&area->sh_info->lock);
  258.     for (cur = &node->leaf_link; cur != &area->used_space.leaf_head; cur = cur->next) {
  259.         int i;
  260.        
  261.         node = list_get_instance(cur, btree_node_t, leaf_link);
  262.        
  263.         for (i = 0; i < node->keys; i++) {
  264.             __address base = node->key[i];
  265.             count_t count = (count_t) node->value[i];
  266.             int j;
  267.            
  268.             /*
  269.              * Skip read-only areas of used space that are backed
  270.              * by the ELF image.
  271.              */
  272.             if (!(area->flags & AS_AREA_WRITE))
  273.                 if (base + count*PAGE_SIZE <= start_anon)
  274.                     continue;
  275.            
  276.             for (j = 0; j < count; j++) {
  277.                 pte_t *pte;
  278.            
  279.                 /*
  280.                  * Skip read-only pages that are backed by the ELF image.
  281.                  */
  282.                 if (!(area->flags & AS_AREA_WRITE))
  283.                     if (base + (j + 1)*PAGE_SIZE <= start_anon)
  284.                         continue;
  285.                
  286.                 page_table_lock(area->as, false);
  287.                 pte = page_mapping_find(area->as, base + j*PAGE_SIZE);
  288.                 ASSERT(pte && PTE_VALID(pte) && PTE_PRESENT(pte));
  289.                 btree_insert(&area->sh_info->pagemap, (base + j*PAGE_SIZE) - area->base,
  290.                     (void *) PTE_GET_FRAME(pte), NULL);
  291.                 page_table_unlock(area->as, false);
  292.             }
  293.                
  294.         }
  295.     }
  296.     mutex_unlock(&area->sh_info->lock);
  297. }
  298.