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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 <smc.h>
  54. #include <loader/pcb.h>
  55.  
  56. #include "elf.h"
  57. #include "elf_load.h"
  58. #include "arch.h"
  59.  
  60. static char *error_codes[] = {
  61.     "no error",
  62.     "invalid image",
  63.     "address space error",
  64.     "incompatible image",
  65.     "unsupported image type",
  66.     "irrecoverable error"
  67. };
  68.  
  69. static unsigned int elf_load(elf_ld_t *elf, size_t so_bias);
  70. static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry);
  71. static int section_header(elf_ld_t *elf, elf_section_header_t *entry);
  72. static int load_segment(elf_ld_t *elf, elf_segment_header_t *entry);
  73.  
  74. /** Read until the buffer is read in its entirety. */
  75. static int my_read(int fd, char *buf, size_t len)
  76. {
  77.     int cnt = 0;
  78.     do {
  79.         buf += cnt;
  80.         len -= cnt;
  81.         cnt = read(fd, buf, len);
  82.     } while ((cnt > 0) && ((len - cnt) > 0));
  83.  
  84.     return cnt;
  85. }
  86.  
  87. /** Load ELF binary from a file.
  88.  *
  89.  * Load an ELF binary from the specified file. If the file is
  90.  * an executable program, it is loaded unbiased. If it is a shared
  91.  * object, it is loaded with the bias @a so_bias. Some information
  92.  * extracted from the binary is stored in a elf_info_t structure
  93.  * pointed to by @a info.
  94.  *
  95.  * @param file_name Path to the ELF file.
  96.  * @param so_bias   Bias to use if the file is a shared object.
  97.  * @param info      Pointer to a structure for storing information
  98.  *          extracted from the binary.
  99.  *
  100.  * @return EOK on success or negative error code.
  101.  */
  102. int elf_load_file(char *file_name, size_t so_bias, eld_flags_t flags,
  103.     elf_info_t *info)
  104. {
  105.     elf_ld_t elf;
  106.  
  107.     int fd;
  108.     int rc;
  109.  
  110. //  printf("open and read '%s'...\n", file_name);
  111.  
  112.     fd = open(file_name, O_RDONLY);
  113.     if (fd < 0) {
  114.         printf("failed opening file (error %d)\n", fd);
  115.         return -1;
  116.     }
  117.  
  118.     elf.fd = fd;
  119.     elf.info = info;
  120.     elf.flags = flags;
  121.  
  122.     rc = elf_load(&elf, so_bias);
  123.  
  124.     close(fd);
  125.  
  126.     return rc;
  127. }
  128.  
  129. /** Run an ELF executable.
  130.  *
  131.  * Transfers control to the entry point of an ELF executable loaded
  132.  * earlier with elf_load_file(). This function does not return.
  133.  *
  134.  * @param info  Info structure filled earlier by elf_load_file()
  135.  */
  136. void elf_run(elf_info_t *info, pcb_t *pcb)
  137. {
  138.     program_run(info->entry, pcb);
  139.  
  140.     /* not reached */
  141. }
  142.  
  143. /** Create the program control block (PCB).
  144.  *
  145.  * Fills the program control block @a pcb with information from
  146.  * @a info.
  147.  *
  148.  * @param info  Program info structure
  149.  * @return EOK on success or negative error code
  150.  */
  151. void elf_create_pcb(elf_info_t *info, pcb_t *pcb)
  152. {
  153.     pcb->entry = info->entry;
  154.     pcb->dynamic = info->dynamic;
  155. }
  156.  
  157.  
  158. /** Load an ELF binary.
  159.  *
  160.  * The @a elf structure contains the loader state, including
  161.  * an open file, from which the binary will be loaded,
  162.  * a pointer to the @c info structure etc.
  163.  *
  164.  * @param elf       Pointer to loader state buffer.
  165.  * @param so_bias   Bias to use if the file is a shared object.
  166.  * @return EE_OK on success or EE_xx error code.
  167.  */
  168. static unsigned int elf_load(elf_ld_t *elf, size_t so_bias)
  169. {
  170.     elf_header_t header_buf;
  171.     elf_header_t *header = &header_buf;
  172.     int i, rc;
  173.  
  174.     rc = my_read(elf->fd, header, sizeof(elf_header_t));
  175.     if (rc < 0) {
  176.         printf("read error\n");
  177.         return EE_INVALID;
  178.     }
  179.  
  180.     elf->header = header;
  181.  
  182. //  printf("ELF-load:");
  183.     /* Identify ELF */
  184.     if (header->e_ident[EI_MAG0] != ELFMAG0 ||
  185.         header->e_ident[EI_MAG1] != ELFMAG1 ||
  186.         header->e_ident[EI_MAG2] != ELFMAG2 ||
  187.         header->e_ident[EI_MAG3] != ELFMAG3) {
  188.         printf("invalid header\n");
  189.         return EE_INVALID;
  190.     }
  191.    
  192.     /* Identify ELF compatibility */
  193.     if (header->e_ident[EI_DATA] != ELF_DATA_ENCODING ||
  194.         header->e_machine != ELF_MACHINE ||
  195.         header->e_ident[EI_VERSION] != EV_CURRENT ||
  196.         header->e_version != EV_CURRENT ||
  197.         header->e_ident[EI_CLASS] != ELF_CLASS) {
  198.         printf("incompatible data/version/class\n");
  199.         return EE_INCOMPATIBLE;
  200.     }
  201.  
  202.     if (header->e_phentsize != sizeof(elf_segment_header_t)) {
  203.         printf("e_phentsize:%d != %d\n", header->e_phentsize,
  204.             sizeof(elf_segment_header_t));
  205.         return EE_INCOMPATIBLE;
  206.     }
  207.  
  208.     if (header->e_shentsize != sizeof(elf_section_header_t)) {
  209.         printf("e_shentsize:%d != %d\n", header->e_shentsize,
  210.             sizeof(elf_section_header_t));
  211.         return EE_INCOMPATIBLE;
  212.     }
  213.  
  214.     /* Check if the object type is supported. */
  215.     if (header->e_type != ET_EXEC && header->e_type != ET_DYN) {
  216.         printf("Object type %d is not supported\n", header->e_type);
  217.         return EE_UNSUPPORTED;
  218.     }
  219.  
  220.     /* Shared objects can be loaded with a bias */
  221. //  printf("Object type: %d\n", header->e_type);
  222.     if (header->e_type == ET_DYN)
  223.         elf->bias = so_bias;
  224.     else
  225.         elf->bias = 0;
  226.  
  227. //  printf("Bias set to 0x%x\n", elf->bias);
  228.     elf->info->interp = NULL;
  229.     elf->info->dynamic = NULL;
  230.  
  231. //  printf("parse segments\n");
  232.  
  233.     /* Walk through all segment headers and process them. */
  234.     for (i = 0; i < header->e_phnum; i++) {
  235.         elf_segment_header_t segment_hdr;
  236.  
  237.         /* Seek to start of segment header */
  238.         lseek(elf->fd, header->e_phoff
  239.                 + i * sizeof(elf_segment_header_t), SEEK_SET);
  240.  
  241.         rc = my_read(elf->fd, &segment_hdr,
  242.             sizeof(elf_segment_header_t));
  243.         if (rc < 0) {
  244.             printf("read error\n");
  245.             return EE_INVALID;
  246.         }
  247.  
  248.         rc = segment_header(elf, &segment_hdr);
  249.         if (rc != EE_OK)
  250.             return rc;
  251.     }
  252.  
  253. //  printf("parse sections\n");
  254.  
  255.     /* Inspect all section headers and proccess them. */
  256.     for (i = 0; i < header->e_shnum; i++) {
  257.         elf_section_header_t section_hdr;
  258.  
  259.         /* Seek to start of section header */
  260.         lseek(elf->fd, header->e_shoff
  261.             + i * sizeof(elf_section_header_t), SEEK_SET);
  262.  
  263.         rc = my_read(elf->fd, &section_hdr,
  264.             sizeof(elf_section_header_t));
  265.         if (rc < 0) {
  266.             printf("read error\n");
  267.             return EE_INVALID;
  268.         }
  269.  
  270.         rc = section_header(elf, &section_hdr);
  271.         if (rc != EE_OK)
  272.             return rc;
  273.     }
  274.  
  275.     elf->info->entry =
  276.         (entry_point_t)((uint8_t *)header->e_entry + elf->bias);
  277.  
  278. //  printf("done\n");
  279.  
  280.     return EE_OK;
  281. }
  282.  
  283. /** Print error message according to error code.
  284.  *
  285.  * @param rc Return code returned by elf_load().
  286.  *
  287.  * @return NULL terminated description of error.
  288.  */
  289. char *elf_error(unsigned int rc)
  290. {
  291.     assert(rc < sizeof(error_codes) / sizeof(char *));
  292.  
  293.     return error_codes[rc];
  294. }
  295.  
  296. /** Process segment header.
  297.  *
  298.  * @param entry Segment header.
  299.  *
  300.  * @return EE_OK on success, error code otherwise.
  301.  */
  302. static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry)
  303. {
  304.     switch (entry->p_type) {
  305.     case PT_NULL:
  306.     case PT_PHDR:
  307.         break;
  308.     case PT_LOAD:
  309.         return load_segment(elf, entry);
  310.         break;
  311.     case PT_INTERP:
  312.         /* Assume silently interp == "/lib/rtld" */
  313.         elf->info->interp = "/lib/rtld";
  314.         break;
  315.     case PT_DYNAMIC:
  316.     case PT_SHLIB:
  317.     case PT_NOTE:
  318.     case PT_LOPROC:
  319.     case PT_HIPROC:
  320.     default:
  321.         printf("segment p_type %d unknown\n", entry->p_type);
  322.         return EE_UNSUPPORTED;
  323.         break;
  324.     }
  325.     return EE_OK;
  326. }
  327.  
  328. /** Load segment described by program header entry.
  329.  *
  330.  * @param elf   Loader state.
  331.  * @param entry Program header entry describing segment to be loaded.
  332.  *
  333.  * @return EE_OK on success, error code otherwise.
  334.  */
  335. int load_segment(elf_ld_t *elf, elf_segment_header_t *entry)
  336. {
  337.     void *a;
  338.     int flags = 0;
  339.     uintptr_t bias;
  340.     uintptr_t base;
  341.     size_t mem_sz;
  342.     int rc;
  343.  
  344. //  printf("load segment at addr 0x%x, size 0x%x\n", entry->p_vaddr,
  345. //      entry->p_memsz);
  346.    
  347.     bias = elf->bias;
  348.  
  349.     if (entry->p_align > 1) {
  350.         if ((entry->p_offset % entry->p_align) !=
  351.             (entry->p_vaddr % entry->p_align)) {
  352.             printf("align check 1 failed offset%%align=%d, "
  353.                 "vaddr%%align=%d\n",
  354.                 entry->p_offset % entry->p_align,
  355.                 entry->p_vaddr % entry->p_align
  356.             );
  357.             return EE_INVALID;
  358.         }
  359.     }
  360.  
  361.     /* Final flags that will be set for the memory area */
  362.  
  363.     if (entry->p_flags & PF_X)
  364.         flags |= AS_AREA_EXEC;
  365.     if (entry->p_flags & PF_W)
  366.         flags |= AS_AREA_WRITE;
  367.     if (entry->p_flags & PF_R)
  368.         flags |= AS_AREA_READ;
  369.     flags |= AS_AREA_CACHEABLE;
  370.    
  371.     base = ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE);
  372.     mem_sz = entry->p_memsz + (entry->p_vaddr - base);
  373.  
  374. //  printf("map to p_vaddr=0x%x-0x%x...\n", entry->p_vaddr + bias,
  375. //  entry->p_vaddr + bias + ALIGN_UP(entry->p_memsz, PAGE_SIZE));
  376.  
  377.     /*
  378.      * For the course of loading, the area needs to be readable
  379.      * and writeable.
  380.      */
  381.     a = as_area_create((uint8_t *)base + bias, mem_sz,
  382.         AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE);
  383.     if (a == (void *)(-1)) {
  384.         printf("memory mapping failed\n");
  385.         return EE_MEMORY;
  386.     }
  387.  
  388. //  printf("as_area_create(0x%lx, 0x%x, %d) -> 0x%lx\n",
  389. //      entry->p_vaddr+bias, entry->p_memsz, flags, (uintptr_t)a);
  390.  
  391.     /*
  392.      * Load segment data
  393.      */
  394. //  printf("seek to %d\n", entry->p_offset);
  395.     rc = lseek(elf->fd, entry->p_offset, SEEK_SET);
  396.     if (rc < 0) {
  397.         printf("seek error\n");
  398.         return EE_INVALID;
  399.     }
  400.  
  401. //  printf("read 0x%x bytes to address 0x%x\n", entry->p_filesz, entry->p_vaddr+bias);
  402. /*  rc = read(fd, (void *)(entry->p_vaddr + bias), entry->p_filesz);
  403.     if (rc < 0) { printf("read error\n"); return EE_INVALID; }*/
  404.  
  405.     /* Long reads are not possible yet. Load segment picewise */
  406.  
  407.     unsigned left, now;
  408.     uint8_t *dp;
  409.  
  410.     left = entry->p_filesz;
  411.     dp = (uint8_t *)(entry->p_vaddr + bias);
  412.  
  413.     while (left > 0) {
  414.         now = 16384;
  415.         if (now > left) now = left;
  416.  
  417. //      printf("read %d...", now);
  418.         rc = my_read(elf->fd, dp, now);
  419. //      printf("->%d\n", rc);
  420.  
  421.         if (rc < 0) {
  422.             printf("read error\n");
  423.             return EE_INVALID;
  424.         }
  425.  
  426.         left -= now;
  427.         dp += now;
  428.     }
  429.  
  430.     /*
  431.      * The caller wants to modify the segments first. He will then
  432.      * need to set the right access mode and ensure SMC coherence.
  433.      */
  434.     if ((elf->flags & ELDF_RW) != 0) return EE_OK;
  435.  
  436. //  printf("set area flags to %d\n", flags);
  437.     rc = as_area_change_flags((uint8_t *)entry->p_vaddr + bias, flags);
  438.     if (rc != 0) {
  439.         printf("failed to set memory area flags\n");
  440.         return EE_MEMORY;
  441.     }
  442.  
  443.     if (flags & AS_AREA_EXEC) {
  444.         /* Enforce SMC coherence for the segment */
  445.         if (smc_coherence(entry->p_vaddr + bias, entry->p_filesz))
  446.             return EE_MEMORY;
  447.     }
  448.  
  449.     return EE_OK;
  450. }
  451.  
  452. /** Process section header.
  453.  *
  454.  * @param elf   Loader state.
  455.  * @param entry Segment header.
  456.  *
  457.  * @return EE_OK on success, error code otherwise.
  458.  */
  459. static int section_header(elf_ld_t *elf, elf_section_header_t *entry)
  460. {
  461.     switch (entry->sh_type) {
  462.     case SHT_PROGBITS:
  463.         if (entry->sh_flags & SHF_TLS) {
  464.             /* .tdata */
  465.         }
  466.         break;
  467.     case SHT_NOBITS:
  468.         if (entry->sh_flags & SHF_TLS) {
  469.             /* .tbss */
  470.         }
  471.         break;
  472.     case SHT_DYNAMIC:
  473.         /* Record pointer to dynamic section into info structure */
  474.         elf->info->dynamic =
  475.             (void *)((uint8_t *)entry->sh_addr + elf->bias);
  476.         printf("dynamic section found at 0x%x\n",
  477.             (uintptr_t)elf->info->dynamic);
  478.         break;
  479.     default:
  480.         break;
  481.     }
  482.    
  483.     return EE_OK;
  484. }
  485.  
  486. /** @}
  487.  */
  488.