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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.  
  54. #include "elf.h"
  55. #include "pcb.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)
  121. {
  122.     program_run(info->entry);
  123.  
  124.     /* not reached */
  125. }
  126.  
  127. /** Create the program control block (PCB).
  128.  *
  129.  * Create and install the program control block, initialising it
  130.  * with program information from @a info.
  131.  *
  132.  * @param info  Program info structure
  133.  * @return EOK on success or negative error code
  134.  */
  135. int elf_create_pcb(elf_info_t *info)
  136. {
  137.     pcb_t *pcb;
  138.     void *a;
  139.  
  140.     pcb = __pcb_get();
  141.  
  142.     a = as_area_create(pcb, sizeof(pcb_t), AS_AREA_READ | AS_AREA_WRITE);
  143.     if (a == (void *)(-1)) {
  144.         printf("elf_create_pcb: memory mapping failed\n");
  145.         return EE_MEMORY;
  146.     }
  147.  
  148.     pcb->entry = info->entry;
  149.     pcb->dynamic = info->dynamic;
  150.  
  151.     return 0;
  152. }
  153.  
  154.  
  155. /** Load an ELF binary.
  156.  *
  157.  * The @a elf structure contains the loader state, including
  158.  * an open file, from which the binary will be loaded,
  159.  * a pointer to the @c info structure etc.
  160.  *
  161.  * @param elf       Pointer to loader state buffer.
  162.  * @param so_bias   Bias to use if the file is a shared object.
  163.  * @return EE_OK on success or EE_xx error code.
  164.  */
  165. static unsigned int elf_load(elf_ld_t *elf, size_t so_bias)
  166. {
  167.     elf_header_t header_buf;
  168.     elf_header_t *header = &header_buf;
  169.     int i, rc;
  170.  
  171.     rc = read(elf->fd, header, sizeof(elf_header_t));
  172.     if (rc < 0) {
  173.         printf("read error\n");
  174.         return EE_INVALID;
  175.     }
  176.  
  177.     elf->header = header;
  178.  
  179. //  printf("ELF-load:");
  180.     /* Identify ELF */
  181.     if (header->e_ident[EI_MAG0] != ELFMAG0 ||
  182.         header->e_ident[EI_MAG1] != ELFMAG1 ||
  183.         header->e_ident[EI_MAG2] != ELFMAG2 ||
  184.         header->e_ident[EI_MAG3] != ELFMAG3) {
  185.         printf("invalid header\n");
  186.         return EE_INVALID;
  187.     }
  188.    
  189.     /* Identify ELF compatibility */
  190.     if (header->e_ident[EI_DATA] != ELF_DATA_ENCODING ||
  191.         header->e_machine != ELF_MACHINE ||
  192.         header->e_ident[EI_VERSION] != EV_CURRENT ||
  193.         header->e_version != EV_CURRENT ||
  194.         header->e_ident[EI_CLASS] != ELF_CLASS) {
  195.         printf("incompatible data/version/class\n");
  196.         return EE_INCOMPATIBLE;
  197.     }
  198.  
  199.     if (header->e_phentsize != sizeof(elf_segment_header_t)) {
  200.         printf("e_phentsize:%d != %d\n", header->e_phentsize,
  201.             sizeof(elf_segment_header_t));
  202.         return EE_INCOMPATIBLE;
  203.     }
  204.  
  205.     if (header->e_shentsize != sizeof(elf_section_header_t)) {
  206.         printf("e_shentsize:%d != %d\n", header->e_shentsize,
  207.             sizeof(elf_section_header_t));
  208.         return EE_INCOMPATIBLE;
  209.     }
  210.  
  211.     /* Check if the object type is supported. */
  212.     if (header->e_type != ET_EXEC && header->e_type != ET_DYN) {
  213.         printf("Object type %d is not supported\n", header->e_type);
  214.         return EE_UNSUPPORTED;
  215.     }
  216.  
  217.     /* Shared objects can be loaded with a bias */
  218. //  printf("Object type: %d\n", header->e_type);
  219.     if (header->e_type == ET_DYN)
  220.         elf->bias = so_bias;
  221.     else
  222.         elf->bias = 0;
  223.  
  224. //  printf("Bias set to 0x%x\n", elf->bias);
  225.     elf->info->interp = NULL;
  226.     elf->info->dynamic = NULL;
  227.  
  228. //  printf("parse segments\n");
  229.  
  230.     /* Walk through all segment headers and process them. */
  231.     for (i = 0; i < header->e_phnum; i++) {
  232.         elf_segment_header_t segment_hdr;
  233.  
  234.         /* Seek to start of segment header */
  235.         lseek(elf->fd, header->e_phoff
  236.                 + i * sizeof(elf_segment_header_t), SEEK_SET);
  237.  
  238.         rc = read(elf->fd, &segment_hdr, sizeof(elf_segment_header_t));
  239.         if (rc < 0) { printf("read error\n"); return EE_INVALID; }
  240.  
  241.         rc = segment_header(elf, &segment_hdr);
  242.         if (rc != EE_OK)
  243.             return rc;
  244.     }
  245.  
  246. //  printf("parse sections\n");
  247.  
  248.     /* Inspect all section headers and proccess them. */
  249.     for (i = 0; i < header->e_shnum; i++) {
  250.         elf_section_header_t section_hdr;
  251.  
  252.         /* Seek to start of section header */
  253.         lseek(elf->fd, header->e_shoff
  254.             + i * sizeof(elf_section_header_t), SEEK_SET);
  255.  
  256.         rc = read(elf->fd, &section_hdr, sizeof(elf_section_header_t));
  257.         if (rc < 0) { printf("read error\n"); return EE_INVALID; }
  258.  
  259.         rc = section_header(elf, &section_hdr);
  260.         if (rc != EE_OK)
  261.             return rc;
  262.     }
  263.  
  264.     elf->info->entry =
  265.         (entry_point_t)((uint8_t *)header->e_entry + elf->bias);
  266.  
  267. //  printf("done\n");
  268.  
  269.     return EE_OK;
  270. }
  271.  
  272. /** Print error message according to error code.
  273.  *
  274.  * @param rc Return code returned by elf_load().
  275.  *
  276.  * @return NULL terminated description of error.
  277.  */
  278. char *elf_error(unsigned int rc)
  279. {
  280.     assert(rc < sizeof(error_codes) / sizeof(char *));
  281.  
  282.     return error_codes[rc];
  283. }
  284.  
  285. /** Process segment header.
  286.  *
  287.  * @param entry Segment header.
  288.  *
  289.  * @return EE_OK on success, error code otherwise.
  290.  */
  291. static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry)
  292. {
  293.     switch (entry->p_type) {
  294.     case PT_NULL:
  295.     case PT_PHDR:
  296.         break;
  297.     case PT_LOAD:
  298.         return load_segment(elf, entry);
  299.         break;
  300.     case PT_INTERP:
  301.         /* Assume silently interp == "/rtld.so" */
  302.         elf->info->interp = "/rtld.so";
  303.         break;
  304.     case PT_DYNAMIC:
  305.     case PT_SHLIB:
  306.     case PT_NOTE:
  307.     case PT_LOPROC:
  308.     case PT_HIPROC:
  309.     default:
  310.         printf("segment p_type %d unknown\n", entry->p_type);
  311.         return EE_UNSUPPORTED;
  312.         break;
  313.     }
  314.     return EE_OK;
  315. }
  316.  
  317. /** Load segment described by program header entry.
  318.  *
  319.  * @param elf   Loader state.
  320.  * @param entry Program header entry describing segment to be loaded.
  321.  *
  322.  * @return EE_OK on success, error code otherwise.
  323.  */
  324. int load_segment(elf_ld_t *elf, elf_segment_header_t *entry)
  325. {
  326.     void *a;
  327.     int flags = 0;
  328.     uintptr_t bias;
  329.     uintptr_t base;
  330.     size_t mem_sz;
  331.     int rc;
  332.  
  333. //  printf("load segment at addr 0x%x, size 0x%x\n", entry->p_vaddr,
  334. //      entry->p_memsz);
  335.    
  336.     bias = elf->bias;
  337.  
  338.     if (entry->p_align > 1) {
  339.         if ((entry->p_offset % entry->p_align) !=
  340.             (entry->p_vaddr % entry->p_align)) {
  341.             printf("align check 1 failed offset%%align=%d, vaddr%%align=%d\n",
  342.             entry->p_offset % entry->p_align,
  343.             entry->p_vaddr % entry->p_align
  344.             );
  345.             return EE_INVALID;
  346.         }
  347.     }
  348.  
  349.     /* Final flags that will be set for the memory area */
  350.  
  351.     if (entry->p_flags & PF_X)
  352.         flags |= AS_AREA_EXEC;
  353.     if (entry->p_flags & PF_W)
  354.         flags |= AS_AREA_WRITE;
  355.     if (entry->p_flags & PF_R)
  356.         flags |= AS_AREA_READ;
  357.     flags |= AS_AREA_CACHEABLE;
  358.    
  359.     base = ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE);
  360.     mem_sz = entry->p_memsz + (entry->p_vaddr - base);
  361.  
  362. //  printf("map to p_vaddr=0x%x-0x%x...\n", entry->p_vaddr + bias,
  363. //  entry->p_vaddr + bias + ALIGN_UP(entry->p_memsz, PAGE_SIZE));
  364.  
  365.     /*
  366.      * For the course of loading, the area needs to be readable
  367.      * and writeable.
  368.      */
  369.     a = as_area_create((uint8_t *)base + bias,
  370.         mem_sz, AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE);
  371.     if (a == (void *)(-1)) {
  372.         printf("memory mapping failed\n");
  373.         return EE_MEMORY;
  374.     }
  375.  
  376. //  printf("as_area_create(0x%lx, 0x%x, %d) -> 0x%lx\n",
  377. //      entry->p_vaddr+bias, entry->p_memsz, flags, (uintptr_t)a);
  378.  
  379.     /*
  380.      * Load segment data
  381.      */
  382. //  printf("seek to %d\n", entry->p_offset);
  383.     rc = lseek(elf->fd, entry->p_offset, SEEK_SET);
  384.     if (rc < 0) { printf("seek error\n"); return EE_INVALID; }
  385.  
  386. //  printf("read 0x%x bytes to address 0x%x\n", entry->p_filesz, entry->p_vaddr+bias);
  387. /*  rc = read(fd, (void *)(entry->p_vaddr + bias), entry->p_filesz);
  388.     if (rc < 0) { printf("read error\n"); return EE_INVALID; }*/
  389.  
  390.     /* Long reads are not possible yet. Load segment picewise */
  391.  
  392.     unsigned left, now;
  393.     uint8_t *dp;
  394.  
  395.     left = entry->p_filesz;
  396.     dp = (uint8_t *)(entry->p_vaddr + bias);
  397.  
  398.     while (left > 0) {
  399.         now = 16384;
  400.         if (now > left) now = left;
  401.  
  402. //      printf("read %d...", now);
  403.         rc = read(elf->fd, dp, now);
  404. //      printf("->%d\n", rc);
  405.  
  406.         if (rc < 0) { printf("read error\n"); return EE_INVALID; }
  407.  
  408.         left -= now;
  409.         dp += now;
  410.     }
  411.  
  412. //  printf("set area flags to %d\n", flags);
  413.     rc = as_area_change_flags((uint8_t *)entry->p_vaddr + bias, flags);
  414.     if (rc != 0) {
  415.         printf("failed to set memory area flags\n");
  416.         return EE_MEMORY;
  417.     }
  418.  
  419.     return EE_OK;
  420. }
  421.  
  422. /** Process section header.
  423.  *
  424.  * @param elf   Loader state.
  425.  * @param entry Segment header.
  426.  *
  427.  * @return EE_OK on success, error code otherwise.
  428.  */
  429. static int section_header(elf_ld_t *elf, elf_section_header_t *entry)
  430. {
  431.     switch (entry->sh_type) {
  432.     case SHT_PROGBITS:
  433.         if (entry->sh_flags & SHF_TLS) {
  434.             /* .tdata */
  435.         }
  436.         break;
  437.     case SHT_NOBITS:
  438.         if (entry->sh_flags & SHF_TLS) {
  439.             /* .tbss */
  440.         }
  441.         break;
  442.     case SHT_DYNAMIC:
  443.         /* Record pointer to dynamic section into info structure */
  444.         elf->info->dynamic =
  445.             (void *)((uint8_t *)entry->sh_addr + elf->bias);
  446.         printf("dynamic section found at 0x%x\n",
  447.             (uintptr_t)elf->info->dynamic);
  448.         break;
  449.     default:
  450.         break;
  451.     }
  452.    
  453.     return EE_OK;
  454. }
  455.  
  456. /** @}
  457.  */
  458.