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  1. /*
  2.  * Copyright (c) 2006 Sergey Bondari
  3.  * Copyright (c) 2006 Jakub Jermar
  4.  * Copyright (c) 2008 Jiri Svoboda
  5.  * All rights reserved.
  6.  *
  7.  * Redistribution and use in source and binary forms, with or without
  8.  * modification, are permitted provided that the following conditions
  9.  * are met:
  10.  *
  11.  * - Redistributions of source code must retain the above copyright
  12.  *   notice, this list of conditions and the following disclaimer.
  13.  * - Redistributions in binary form must reproduce the above copyright
  14.  *   notice, this list of conditions and the following disclaimer in the
  15.  *   documentation and/or other materials provided with the distribution.
  16.  * - The name of the author may not be used to endorse or promote products
  17.  *   derived from this software without specific prior written permission.
  18.  *
  19.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  20.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  22.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  23.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  24.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  28.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29.  */
  30.  
  31. /** @addtogroup generic
  32.  * @{
  33.  */
  34.  
  35. /**
  36.  * @file
  37.  * @brief   Userspace ELF loader.
  38.  *
  39.  * This module allows loading ELF binaries (both executables and
  40.  * shared objects) from VFS. The current implementation allocates
  41.  * anonymous memory, fills it with segment data and then adjusts
  42.  * the memory areas' flags to the final value. In the future,
  43.  * the segments will be mapped directly from the file.
  44.  */
  45.  
  46. #include <stdio.h>
  47. #include <sys/types.h>
  48. #include <align.h>
  49. #include <assert.h>
  50. #include <as.h>
  51. #include <unistd.h>
  52. #include <fcntl.h>
  53. #include <loader/pcb.h>
  54.  
  55. #include "elf.h"
  56. #include "elf_load.h"
  57. #include "arch.h"
  58.  
  59. static char *error_codes[] = {
  60.     "no error",
  61.     "invalid image",
  62.     "address space error",
  63.     "incompatible image",
  64.     "unsupported image type",
  65.     "irrecoverable error"
  66. };
  67.  
  68. static unsigned int elf_load(elf_ld_t *elf, size_t so_bias);
  69. static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry);
  70. static int section_header(elf_ld_t *elf, elf_section_header_t *entry);
  71. static int load_segment(elf_ld_t *elf, elf_segment_header_t *entry);
  72.  
  73. /** Load ELF binary from a file.
  74.  *
  75.  * Load an ELF binary from the specified file. If the file is
  76.  * an executable program, it is loaded unbiased. If it is a shared
  77.  * object, it is loaded with the bias @a so_bias. Some information
  78.  * extracted from the binary is stored in a elf_info_t structure
  79.  * pointed to by @a info.
  80.  *
  81.  * @param file_name Path to the ELF file.
  82.  * @param so_bias   Bias to use if the file is a shared object.
  83.  * @param info      Pointer to a structure for storing information
  84.  *          extracted from the binary.
  85.  *
  86.  * @return EOK on success or negative error code.
  87.  */
  88. int elf_load_file(char *file_name, size_t so_bias, elf_info_t *info)
  89. {
  90.     elf_ld_t elf;
  91.  
  92.     int fd;
  93.     int rc;
  94.  
  95. //  printf("open and read '%s'...\n", file_name);
  96.  
  97.     fd = open(file_name, O_RDONLY);
  98.     if (fd < 0) {
  99.         printf("failed opening file\n");
  100.         return -1;
  101.     }
  102.  
  103.     elf.fd = fd;
  104.     elf.info = info;
  105.  
  106.     rc = elf_load(&elf, so_bias);
  107.  
  108.     close(fd);
  109.  
  110.     return rc;
  111. }
  112.  
  113. /** Run an ELF executable.
  114.  *
  115.  * Transfers control to the entry point of an ELF executable loaded
  116.  * earlier with elf_load_file(). This function does not return.
  117.  *
  118.  * @param info  Info structure filled earlier by elf_load_file()
  119.  */
  120. void elf_run(elf_info_t *info, pcb_t *pcb)
  121. {
  122.     program_run(info->entry, pcb);
  123.  
  124.     /* not reached */
  125. }
  126.  
  127. /** Create the program control block (PCB).
  128.  *
  129.  * Fills the program control block @a pcb with information from
  130.  * @a info.
  131.  *
  132.  * @param info  Program info structure
  133.  * @return EOK on success or negative error code
  134.  */
  135. void elf_create_pcb(elf_info_t *info, pcb_t *pcb)
  136. {
  137.     pcb->entry = info->entry;
  138.     pcb->dynamic = info->dynamic;
  139. }
  140.  
  141.  
  142. /** Load an ELF binary.
  143.  *
  144.  * The @a elf structure contains the loader state, including
  145.  * an open file, from which the binary will be loaded,
  146.  * a pointer to the @c info structure etc.
  147.  *
  148.  * @param elf       Pointer to loader state buffer.
  149.  * @param so_bias   Bias to use if the file is a shared object.
  150.  * @return EE_OK on success or EE_xx error code.
  151.  */
  152. static unsigned int elf_load(elf_ld_t *elf, size_t so_bias)
  153. {
  154.     elf_header_t header_buf;
  155.     elf_header_t *header = &header_buf;
  156.     int i, rc;
  157.  
  158.     rc = read(elf->fd, header, sizeof(elf_header_t));
  159.     if (rc < 0) {
  160.         printf("read error\n");
  161.         return EE_INVALID;
  162.     }
  163.  
  164.     elf->header = header;
  165.  
  166. //  printf("ELF-load:");
  167.     /* Identify ELF */
  168.     if (header->e_ident[EI_MAG0] != ELFMAG0 ||
  169.         header->e_ident[EI_MAG1] != ELFMAG1 ||
  170.         header->e_ident[EI_MAG2] != ELFMAG2 ||
  171.         header->e_ident[EI_MAG3] != ELFMAG3) {
  172.         printf("invalid header\n");
  173.         return EE_INVALID;
  174.     }
  175.    
  176.     /* Identify ELF compatibility */
  177.     if (header->e_ident[EI_DATA] != ELF_DATA_ENCODING ||
  178.         header->e_machine != ELF_MACHINE ||
  179.         header->e_ident[EI_VERSION] != EV_CURRENT ||
  180.         header->e_version != EV_CURRENT ||
  181.         header->e_ident[EI_CLASS] != ELF_CLASS) {
  182.         printf("incompatible data/version/class\n");
  183.         return EE_INCOMPATIBLE;
  184.     }
  185.  
  186.     if (header->e_phentsize != sizeof(elf_segment_header_t)) {
  187.         printf("e_phentsize:%d != %d\n", header->e_phentsize,
  188.             sizeof(elf_segment_header_t));
  189.         return EE_INCOMPATIBLE;
  190.     }
  191.  
  192.     if (header->e_shentsize != sizeof(elf_section_header_t)) {
  193.         printf("e_shentsize:%d != %d\n", header->e_shentsize,
  194.             sizeof(elf_section_header_t));
  195.         return EE_INCOMPATIBLE;
  196.     }
  197.  
  198.     /* Check if the object type is supported. */
  199.     if (header->e_type != ET_EXEC && header->e_type != ET_DYN) {
  200.         printf("Object type %d is not supported\n", header->e_type);
  201.         return EE_UNSUPPORTED;
  202.     }
  203.  
  204.     /* Shared objects can be loaded with a bias */
  205. //  printf("Object type: %d\n", header->e_type);
  206.     if (header->e_type == ET_DYN)
  207.         elf->bias = so_bias;
  208.     else
  209.         elf->bias = 0;
  210.  
  211. //  printf("Bias set to 0x%x\n", elf->bias);
  212.     elf->info->interp = NULL;
  213.     elf->info->dynamic = NULL;
  214.  
  215. //  printf("parse segments\n");
  216.  
  217.     /* Walk through all segment headers and process them. */
  218.     for (i = 0; i < header->e_phnum; i++) {
  219.         elf_segment_header_t segment_hdr;
  220.  
  221.         /* Seek to start of segment header */
  222.         lseek(elf->fd, header->e_phoff
  223.                 + i * sizeof(elf_segment_header_t), SEEK_SET);
  224.  
  225.         rc = read(elf->fd, &segment_hdr, sizeof(elf_segment_header_t));
  226.         if (rc < 0) { printf("read error\n"); return EE_INVALID; }
  227.  
  228.         rc = segment_header(elf, &segment_hdr);
  229.         if (rc != EE_OK)
  230.             return rc;
  231.     }
  232.  
  233. //  printf("parse sections\n");
  234.  
  235.     /* Inspect all section headers and proccess them. */
  236.     for (i = 0; i < header->e_shnum; i++) {
  237.         elf_section_header_t section_hdr;
  238.  
  239.         /* Seek to start of section header */
  240.         lseek(elf->fd, header->e_shoff
  241.             + i * sizeof(elf_section_header_t), SEEK_SET);
  242.  
  243.         rc = read(elf->fd, &section_hdr, sizeof(elf_section_header_t));
  244.         if (rc < 0) { printf("read error\n"); return EE_INVALID; }
  245.  
  246.         rc = section_header(elf, &section_hdr);
  247.         if (rc != EE_OK)
  248.             return rc;
  249.     }
  250.  
  251.     elf->info->entry =
  252.         (entry_point_t)((uint8_t *)header->e_entry + elf->bias);
  253.  
  254. //  printf("done\n");
  255.  
  256.     return EE_OK;
  257. }
  258.  
  259. /** Print error message according to error code.
  260.  *
  261.  * @param rc Return code returned by elf_load().
  262.  *
  263.  * @return NULL terminated description of error.
  264.  */
  265. char *elf_error(unsigned int rc)
  266. {
  267.     assert(rc < sizeof(error_codes) / sizeof(char *));
  268.  
  269.     return error_codes[rc];
  270. }
  271.  
  272. /** Process segment header.
  273.  *
  274.  * @param entry Segment header.
  275.  *
  276.  * @return EE_OK on success, error code otherwise.
  277.  */
  278. static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry)
  279. {
  280.     switch (entry->p_type) {
  281.     case PT_NULL:
  282.     case PT_PHDR:
  283.         break;
  284.     case PT_LOAD:
  285.         return load_segment(elf, entry);
  286.         break;
  287.     case PT_INTERP:
  288.         /* Assume silently interp == "/rtld.so" */
  289.         elf->info->interp = "/rtld.so";
  290.         break;
  291.     case PT_DYNAMIC:
  292.     case PT_SHLIB:
  293.     case PT_NOTE:
  294.     case PT_LOPROC:
  295.     case PT_HIPROC:
  296.     default:
  297.         printf("segment p_type %d unknown\n", entry->p_type);
  298.         return EE_UNSUPPORTED;
  299.         break;
  300.     }
  301.     return EE_OK;
  302. }
  303.  
  304. /** Load segment described by program header entry.
  305.  *
  306.  * @param elf   Loader state.
  307.  * @param entry Program header entry describing segment to be loaded.
  308.  *
  309.  * @return EE_OK on success, error code otherwise.
  310.  */
  311. int load_segment(elf_ld_t *elf, elf_segment_header_t *entry)
  312. {
  313.     void *a;
  314.     int flags = 0;
  315.     uintptr_t bias;
  316.     uintptr_t base;
  317.     size_t mem_sz;
  318.     int rc;
  319.  
  320. //  printf("load segment at addr 0x%x, size 0x%x\n", entry->p_vaddr,
  321. //      entry->p_memsz);
  322.    
  323.     bias = elf->bias;
  324.  
  325.     if (entry->p_align > 1) {
  326.         if ((entry->p_offset % entry->p_align) !=
  327.             (entry->p_vaddr % entry->p_align)) {
  328.             printf("align check 1 failed offset%%align=%d, vaddr%%align=%d\n",
  329.             entry->p_offset % entry->p_align,
  330.             entry->p_vaddr % entry->p_align
  331.             );
  332.             return EE_INVALID;
  333.         }
  334.     }
  335.  
  336.     /* Final flags that will be set for the memory area */
  337.  
  338.     if (entry->p_flags & PF_X)
  339.         flags |= AS_AREA_EXEC;
  340.     if (entry->p_flags & PF_W)
  341.         flags |= AS_AREA_WRITE;
  342.     if (entry->p_flags & PF_R)
  343.         flags |= AS_AREA_READ;
  344.     flags |= AS_AREA_CACHEABLE;
  345.    
  346.     base = ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE);
  347.     mem_sz = entry->p_memsz + (entry->p_vaddr - base);
  348.  
  349. //  printf("map to p_vaddr=0x%x-0x%x...\n", entry->p_vaddr + bias,
  350. //  entry->p_vaddr + bias + ALIGN_UP(entry->p_memsz, PAGE_SIZE));
  351.  
  352.     /*
  353.      * For the course of loading, the area needs to be readable
  354.      * and writeable.
  355.      */
  356.     a = as_area_create((uint8_t *)base + bias,
  357.         mem_sz, AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE);
  358.     if (a == (void *)(-1)) {
  359.         printf("memory mapping failed\n");
  360.         return EE_MEMORY;
  361.     }
  362.  
  363. //  printf("as_area_create(0x%lx, 0x%x, %d) -> 0x%lx\n",
  364. //      entry->p_vaddr+bias, entry->p_memsz, flags, (uintptr_t)a);
  365.  
  366.     /*
  367.      * Load segment data
  368.      */
  369. //  printf("seek to %d\n", entry->p_offset);
  370.     rc = lseek(elf->fd, entry->p_offset, SEEK_SET);
  371.     if (rc < 0) { printf("seek error\n"); return EE_INVALID; }
  372.  
  373. //  printf("read 0x%x bytes to address 0x%x\n", entry->p_filesz, entry->p_vaddr+bias);
  374. /*  rc = read(fd, (void *)(entry->p_vaddr + bias), entry->p_filesz);
  375.     if (rc < 0) { printf("read error\n"); return EE_INVALID; }*/
  376.  
  377.     /* Long reads are not possible yet. Load segment picewise */
  378.  
  379.     unsigned left, now;
  380.     uint8_t *dp;
  381.  
  382.     left = entry->p_filesz;
  383.     dp = (uint8_t *)(entry->p_vaddr + bias);
  384.  
  385.     while (left > 0) {
  386.         now = 16384;
  387.         if (now > left) now = left;
  388.  
  389. //      printf("read %d...", now);
  390.         rc = read(elf->fd, dp, now);
  391. //      printf("->%d\n", rc);
  392.  
  393.         if (rc < 0) { printf("read error\n"); return EE_INVALID; }
  394.  
  395.         left -= now;
  396.         dp += now;
  397.     }
  398.  
  399. //  printf("set area flags to %d\n", flags);
  400.     rc = as_area_change_flags((uint8_t *)entry->p_vaddr + bias, flags);
  401.     if (rc != 0) {
  402.         printf("failed to set memory area flags\n");
  403.         return EE_MEMORY;
  404.     }
  405.  
  406.     return EE_OK;
  407. }
  408.  
  409. /** Process section header.
  410.  *
  411.  * @param elf   Loader state.
  412.  * @param entry Segment header.
  413.  *
  414.  * @return EE_OK on success, error code otherwise.
  415.  */
  416. static int section_header(elf_ld_t *elf, elf_section_header_t *entry)
  417. {
  418.     switch (entry->sh_type) {
  419.     case SHT_PROGBITS:
  420.         if (entry->sh_flags & SHF_TLS) {
  421.             /* .tdata */
  422.         }
  423.         break;
  424.     case SHT_NOBITS:
  425.         if (entry->sh_flags & SHF_TLS) {
  426.             /* .tbss */
  427.         }
  428.         break;
  429.     case SHT_DYNAMIC:
  430.         /* Record pointer to dynamic section into info structure */
  431.         elf->info->dynamic =
  432.             (void *)((uint8_t *)entry->sh_addr + elf->bias);
  433.         printf("dynamic section found at 0x%x\n",
  434.             (uintptr_t)elf->info->dynamic);
  435.         break;
  436.     default:
  437.         break;
  438.     }
  439.    
  440.     return EE_OK;
  441. }
  442.  
  443. /** @}
  444.  */
  445.