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  1. /*
  2.  * Copyright (C) 2006 Sergey Bondari
  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    elf.c
  31.  * @brief   Kernel ELF loader.
  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 char *error_codes[] = {
  47.     "no error",
  48.     "invalid image",
  49.     "address space error",
  50.     "incompatible image",
  51.     "unsupported image type",
  52.     "irrecoverable error"
  53. };
  54.  
  55. static int segment_header(elf_segment_header_t *entry, elf_header_t *elf, as_t *as);
  56. static int section_header(elf_section_header_t *entry, elf_header_t *elf, as_t *as);
  57. static int load_segment(elf_segment_header_t *entry, elf_header_t *elf, as_t *as);
  58.  
  59. static int elf_page_fault(as_area_t *area, __address addr, pf_access_t access);
  60. static void elf_frame_free(as_area_t *area, __address page, __address frame);
  61.  
  62. mem_backend_t elf_backend = {
  63.     .backend_page_fault = elf_page_fault,
  64.     .backend_frame_free = elf_frame_free
  65. };
  66.  
  67. /** ELF loader
  68.  *
  69.  * @param header Pointer to ELF header in memory
  70.  * @param as Created and properly mapped address space
  71.  * @return EE_OK on success
  72.  */
  73. int elf_load(elf_header_t *header, as_t * as)
  74. {
  75.     int i, rc;
  76.  
  77.     /* Identify ELF */
  78.     if (header->e_ident[EI_MAG0] != ELFMAG0 || header->e_ident[EI_MAG1] != ELFMAG1 ||
  79.         header->e_ident[EI_MAG2] != ELFMAG2 || header->e_ident[EI_MAG3] != ELFMAG3) {
  80.         return EE_INVALID;
  81.     }
  82.    
  83.     /* Identify ELF compatibility */
  84.     if (header->e_ident[EI_DATA] != ELF_DATA_ENCODING || header->e_machine != ELF_MACHINE ||
  85.         header->e_ident[EI_VERSION] != EV_CURRENT || header->e_version != EV_CURRENT ||
  86.         header->e_ident[EI_CLASS] != ELF_CLASS) {
  87.         return EE_INCOMPATIBLE;
  88.     }
  89.  
  90.     if (header->e_phentsize != sizeof(elf_segment_header_t))
  91.         return EE_INCOMPATIBLE;
  92.  
  93.     if (header->e_shentsize != sizeof(elf_section_header_t))
  94.         return EE_INCOMPATIBLE;
  95.  
  96.     /* Check if the object type is supported. */
  97.     if (header->e_type != ET_EXEC)
  98.         return EE_UNSUPPORTED;
  99.  
  100.     /* Walk through all segment headers and process them. */
  101.     for (i = 0; i < header->e_phnum; i++) {
  102.         rc = segment_header(&((elf_segment_header_t *)(((__u8 *) header) + header->e_phoff))[i], header, as);
  103.         if (rc != EE_OK)
  104.             return rc;
  105.     }
  106.  
  107.     /* Inspect all section headers and proccess them. */
  108.     for (i = 0; i < header->e_shnum; i++) {
  109.         rc = section_header(&((elf_section_header_t *)(((__u8 *) header) + header->e_shoff))[i], header, as);
  110.         if (rc != EE_OK)
  111.             return rc;
  112.     }
  113.  
  114.     return EE_OK;
  115. }
  116.  
  117. /** Print error message according to error code.
  118.  *
  119.  * @param rc Return code returned by elf_load().
  120.  *
  121.  * @return NULL terminated description of error.
  122.  */
  123. char *elf_error(int rc)
  124. {
  125.     ASSERT(rc < sizeof(error_codes)/sizeof(char *));
  126.  
  127.     return error_codes[rc];
  128. }
  129.  
  130. /** Process segment header.
  131.  *
  132.  * @param entry Segment header.
  133.  * @param elf ELF header.
  134.  * @param as Address space into wich the ELF is being loaded.
  135.  *
  136.  * @return EE_OK on success, error code otherwise.
  137.  */
  138. static int segment_header(elf_segment_header_t *entry, elf_header_t *elf, as_t *as)
  139. {
  140.     switch (entry->p_type) {
  141.         case PT_NULL:
  142.         case PT_PHDR:
  143.         break;
  144.         case PT_LOAD:
  145.         return load_segment(entry, elf, as);
  146.         break;
  147.         case PT_DYNAMIC:
  148.         case PT_INTERP:
  149.         case PT_SHLIB:
  150.         case PT_NOTE:
  151.         case PT_LOPROC:
  152.         case PT_HIPROC:
  153.         default:
  154.         return EE_UNSUPPORTED;
  155.         break;
  156.     }
  157.     return EE_OK;
  158. }
  159.  
  160. /** Load segment described by program header entry.
  161.  *
  162.  * @param entry Program header entry describing segment to be loaded.
  163.  * @param elf ELF header.
  164.  * @param as Address space into wich the ELF is being loaded.
  165.  *
  166.  * @return EE_OK on success, error code otherwise.
  167.  */
  168. int load_segment(elf_segment_header_t *entry, elf_header_t *elf, as_t *as)
  169. {
  170.     as_area_t *a;
  171.     int flags = 0;
  172.     void *backend_data[2] = { elf, entry };
  173.  
  174.     if (entry->p_align > 1) {
  175.         if ((entry->p_offset % entry->p_align) != (entry->p_vaddr % entry->p_align)) {
  176.             return EE_INVALID;
  177.         }
  178.     }
  179.  
  180.     if (entry->p_flags & PF_X)
  181.         flags |= AS_AREA_EXEC;
  182.     if (entry->p_flags & PF_W)
  183.         flags |= AS_AREA_WRITE;
  184.     if (entry->p_flags & PF_R)
  185.         flags |= AS_AREA_READ;
  186.  
  187.     /*
  188.      * Check if the virtual address starts on page boundary.
  189.      */
  190.     if (ALIGN_UP(entry->p_vaddr, PAGE_SIZE) != entry->p_vaddr)
  191.         return EE_UNSUPPORTED;
  192.  
  193.     a = as_area_create(as, flags, entry->p_memsz, entry->p_vaddr, AS_AREA_ATTR_NONE, &elf_backend, backend_data);
  194.     if (!a)
  195.         return EE_MEMORY;
  196.    
  197.     /*
  198.      * The segment will be mapped on demand by elf_page_fault().
  199.      */
  200.  
  201.     return EE_OK;
  202. }
  203.  
  204. /** Process section header.
  205.  *
  206.  * @param entry Segment header.
  207.  * @param elf ELF header.
  208.  * @param as Address space into wich the ELF is being loaded.
  209.  *
  210.  * @return EE_OK on success, error code otherwise.
  211.  */
  212. static int section_header(elf_section_header_t *entry, elf_header_t *elf, as_t *as)
  213. {
  214.     switch (entry->sh_type) {
  215.         default:
  216.         break;
  217.     }
  218.    
  219.     return EE_OK;
  220. }
  221.  
  222. /** Service a page fault in the ELF backend address space area.
  223.  *
  224.  * The address space area and page tables must be already locked.
  225.  *
  226.  * @param area Pointer to the address space area.
  227.  * @param addr Faulting virtual address.
  228.  * @param access Access mode that caused the fault (i.e. read/write/exec).
  229.  *
  230.  * @return AS_PF_FAULT on failure (i.e. page fault) or AS_PF_OK on success (i.e. serviced).
  231.  */
  232. int elf_page_fault(as_area_t *area, __address addr, pf_access_t access)
  233. {
  234.     elf_header_t *elf = (elf_header_t *) area->backend_data[0];
  235.     elf_segment_header_t *entry = (elf_segment_header_t *) area->backend_data[1];
  236.     __address base, frame;
  237.     index_t i;
  238.  
  239.     if (!as_area_check_access(area, access))
  240.         return AS_PF_FAULT;
  241.  
  242.     ASSERT((addr >= entry->p_vaddr) && (addr < entry->p_vaddr + entry->p_memsz));
  243.     i = (addr - entry->p_vaddr) >> PAGE_WIDTH;
  244.     base = (__address) (((void *) elf) + entry->p_offset);
  245.     ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
  246.    
  247.     if (ALIGN_DOWN(addr, PAGE_SIZE) + PAGE_SIZE < entry->p_vaddr + entry->p_filesz) {
  248.         /*
  249.          * Initialized portion of the segment. The memory is backed
  250.          * directly by the content of the ELF image. Pages are
  251.          * only copied if the segment is writable so that there
  252.          * can be more instantions of the same memory ELF image
  253.          * used at a time. Note that this could be later done
  254.          * as COW.
  255.          */
  256.         if (entry->p_flags & PF_W) {
  257.             frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  258.             memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), FRAME_SIZE);
  259.         } else {
  260.             frame = KA2PA(base + i*FRAME_SIZE);
  261.         }  
  262.     } else if (ALIGN_DOWN(addr, PAGE_SIZE) >= ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
  263.         /*
  264.          * This is the uninitialized portion of the segment.
  265.          * It is not physically present in the ELF image.
  266.          * To resolve the situation, a frame must be allocated
  267.          * and cleared.
  268.          */
  269.         frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  270.         memsetb(PA2KA(frame), FRAME_SIZE, 0);
  271.     } else {
  272.         size_t size;
  273.         /*
  274.          * The mixed case.
  275.          * The lower part is backed by the ELF image and
  276.          * the upper part is anonymous memory.
  277.          */
  278.         size = entry->p_filesz - (i<<PAGE_WIDTH);
  279.         frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
  280.         memsetb(PA2KA(frame) + size, FRAME_SIZE - size, 0);
  281.         memcpy((void *) PA2KA(frame), (void *) (base + i*FRAME_SIZE), size);
  282.     }
  283.    
  284.     page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
  285.         if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
  286.                 panic("Could not insert used space.\n");
  287.  
  288.     return AS_PF_OK;
  289. }
  290.  
  291. /** Free a frame that is backed by the ELF backend.
  292.  *
  293.  * The address space area and page tables must be already locked.
  294.  *
  295.  * @param area Pointer to the address space area.
  296.  * @param page Page that is mapped to frame. Must be aligned to PAGE_SIZE.
  297.  * @param frame Frame to be released.
  298.  *
  299.  */
  300. void elf_frame_free(as_area_t *area, __address page, __address frame)
  301. {
  302.     elf_header_t *elf = (elf_header_t *) area->backend_data[0];
  303.     elf_segment_header_t *entry = (elf_segment_header_t *) area->backend_data[1];
  304.     __address base;
  305.     index_t i;
  306.    
  307.     ASSERT((page >= entry->p_vaddr) && (page < entry->p_vaddr + entry->p_memsz));
  308.     i = (page - entry->p_vaddr) >> PAGE_WIDTH;
  309.     base = (__address) (((void *) elf) + entry->p_offset);
  310.     ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
  311.    
  312.     if (page + PAGE_SIZE < ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
  313.         if (entry->p_flags & PF_W) {
  314.             /*
  315.              * Free the frame with the copy of writable segment data.
  316.              */
  317.             frame_free(ADDR2PFN(frame));
  318.         }
  319.     } else {
  320.         /*
  321.          * The frame is either anonymous memory or the mixed case (i.e. lower
  322.          * part is backed by the ELF image and the upper is anonymous).
  323.          * In any case, a frame needs to be freed.
  324.          */
  325.         frame_free(ADDR2PFN(frame));
  326.     }
  327. }
  328.