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