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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 <align.h>
  42. #include <memstr.h>
  43. #include <macros.h>
  44. #include <arch.h>
  45.  
  46. static int elf_page_fault(as_area_t *area, __address addr, pf_access_t access);
  47. static void elf_frame_free(as_area_t *area, __address page, __address frame);
  48.  
  49. mem_backend_t elf_backend = {
  50.     .page_fault = elf_page_fault,
  51.     .frame_free = elf_frame_free,
  52.     .share = NULL
  53. };
  54.  
  55. /** Service a page fault in the ELF backend address space area.
  56.  *
  57.  * The address space area and page tables must be already locked.
  58.  *
  59.  * @param area Pointer to the address space area.
  60.  * @param addr Faulting virtual address.
  61.  * @param access Access mode that caused the fault (i.e. read/write/exec).
  62.  *
  63.  * @return AS_PF_FAULT on failure (i.e. page fault) or AS_PF_OK on success (i.e. serviced).
  64.  */
  65. int elf_page_fault(as_area_t *area, __address addr, pf_access_t access)
  66. {
  67.     elf_header_t *elf = area->backend_data.elf;
  68.     elf_segment_header_t *entry = area->backend_data.segment;
  69.     __address base, frame;
  70.     index_t i;
  71.  
  72.     if (!as_area_check_access(area, access))
  73.         return AS_PF_FAULT;
  74.  
  75.     ASSERT((addr >= entry->p_vaddr) && (addr < entry->p_vaddr + entry->p_memsz));
  76.     i = (addr - entry->p_vaddr) >> PAGE_WIDTH;
  77.     base = (__address) (((void *) elf) + entry->p_offset);
  78.     ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
  79.    
  80.     if (ALIGN_DOWN(addr, PAGE_SIZE) + PAGE_SIZE < entry->p_vaddr + entry->p_filesz) {
  81.         /*
  82.          * Initialized portion of the segment. The memory is backed
  83.          * directly by the content of the ELF image. Pages are
  84.          * only copied if the segment is writable so that there
  85.          * can be more instantions of the same memory ELF image
  86.          * used at a time. Note that this could be later done
  87.          * as COW.
  88.          */
  89.         if (entry->p_flags & PF_W) {
  90.             frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  91.             memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), FRAME_SIZE);
  92.         } else {
  93.             frame = KA2PA(base + i*FRAME_SIZE);
  94.         }  
  95.     } else if (ALIGN_DOWN(addr, PAGE_SIZE) >= ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
  96.         /*
  97.          * This is the uninitialized portion of the segment.
  98.          * It is not physically present in the ELF image.
  99.          * To resolve the situation, a frame must be allocated
  100.          * and cleared.
  101.          */
  102.         frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  103.         memsetb(PA2KA(frame), FRAME_SIZE, 0);
  104.     } else {
  105.         size_t size;
  106.         /*
  107.          * The mixed case.
  108.          * The lower part is backed by the ELF image and
  109.          * the upper part is anonymous memory.
  110.          */
  111.         size = entry->p_filesz - (i<<PAGE_WIDTH);
  112.         frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  113.         memsetb(PA2KA(frame) + size, FRAME_SIZE - size, 0);
  114.         memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), size);
  115.     }
  116.    
  117.     page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
  118.         if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
  119.                 panic("Could not insert used space.\n");
  120.  
  121.     return AS_PF_OK;
  122. }
  123.  
  124. /** Free a frame that is backed by the ELF backend.
  125.  *
  126.  * The address space area and page tables must be already locked.
  127.  *
  128.  * @param area Pointer to the address space area.
  129.  * @param page Page that is mapped to frame. Must be aligned to PAGE_SIZE.
  130.  * @param frame Frame to be released.
  131.  *
  132.  */
  133. void elf_frame_free(as_area_t *area, __address page, __address frame)
  134. {
  135.     elf_header_t *elf = area->backend_data.elf;
  136.     elf_segment_header_t *entry = area->backend_data.segment;
  137.     __address base;
  138.     index_t i;
  139.    
  140.     ASSERT((page >= entry->p_vaddr) && (page < entry->p_vaddr + entry->p_memsz));
  141.     i = (page - entry->p_vaddr) >> PAGE_WIDTH;
  142.     base = (__address) (((void *) elf) + entry->p_offset);
  143.     ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
  144.    
  145.     if (page + PAGE_SIZE < ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
  146.         if (entry->p_flags & PF_W) {
  147.             /*
  148.              * Free the frame with the copy of writable segment data.
  149.              */
  150.             frame_free(ADDR2PFN(frame));
  151.         }
  152.     } else {
  153.         /*
  154.          * The frame is either anonymous memory or the mixed case (i.e. lower
  155.          * part is backed by the ELF image and the upper is anonymous).
  156.          * In any case, a frame needs to be freed.
  157.          */
  158.         frame_free(ADDR2PFN(frame));
  159.     }
  160. }
  161.