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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   Kernel ELF loader.
  38.  */
  39.  
  40. #include <stdio.h>
  41. #include <sys/types.h>
  42. #include <align.h>
  43. #include <assert.h>
  44. #include <as.h>
  45. #include <unistd.h>
  46. #include <fcntl.h>
  47.  
  48. #include "elf.h"
  49. #include "pcb.h"
  50. #include "elf_load.h"
  51.  
  52. static char *error_codes[] = {
  53.     "no error",
  54.     "invalid image",
  55.     "address space error",
  56.     "incompatible image",
  57.     "unsupported image type",
  58.     "irrecoverable error"
  59. };
  60.  
  61. static unsigned int elf_load(elf_ld_t *elf, size_t so_bias);
  62. static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry);
  63. static int section_header(elf_ld_t *elf, elf_section_header_t *entry);
  64. static int load_segment(elf_ld_t *elf, elf_segment_header_t *entry);
  65.  
  66. int elf_load_file(char *file_name, size_t so_bias, elf_info_t *info)
  67. {
  68.     elf_ld_t elf;
  69.  
  70.     int fd;
  71.     int rc;
  72.  
  73.     printf("open and read '%s'...\n", file_name);
  74.  
  75.     fd = open(file_name, 0);
  76.     if (fd < 0) {
  77.         printf("failed opening file\n");
  78.         return -1;
  79.     }
  80.  
  81.     elf.fd = fd;
  82.     elf.info = info;
  83.  
  84.     rc = elf_load(&elf, so_bias);
  85.     printf("elf_load() -> %d\n", rc);
  86.  
  87.     close(fd);
  88.  
  89.     return rc;
  90. }
  91.  
  92. void elf_run(elf_info_t *info)
  93. {
  94.     (*info->entry)();
  95.  
  96.     /* not reached */
  97. }
  98.  
  99. int elf_create_pcb(elf_info_t *info)
  100. {
  101.     pcb_t *pcb;
  102.     void *a;
  103.  
  104.     pcb = (pcb_t *)PCB_ADDRESS;
  105.  
  106.     a = as_area_create(pcb, sizeof(pcb_t), AS_AREA_READ | AS_AREA_WRITE);
  107.     if (a == (void *)(-1)) {
  108.         printf("elf_create_pcb: memory mapping failed\n");
  109.         return EE_MEMORY;
  110.     }
  111.  
  112.     pcb->entry = info->entry;
  113.     pcb->dynamic = info->dynamic;
  114.  
  115.     return 0;
  116. }
  117.  
  118.  
  119. /** ELF loader
  120.  *
  121.  * @param header Pointer to ELF header in memory
  122.  * @return EE_OK on success
  123.  */
  124. static unsigned int elf_load(elf_ld_t *elf, size_t so_bias)
  125. {
  126.     elf_header_t header_buf;
  127.     elf_header_t *header = &header_buf;
  128.     int i, rc;
  129.  
  130.     rc = read(elf->fd, header, sizeof(elf_header_t));
  131.     if (rc < 0) {
  132.         printf("read error\n");
  133.         return EE_INVALID;
  134.     }
  135.  
  136.     elf->header = header;
  137.  
  138.     printf("ELF-load:");
  139.     /* Identify ELF */
  140.     if (header->e_ident[EI_MAG0] != ELFMAG0 ||
  141.         header->e_ident[EI_MAG1] != ELFMAG1 ||
  142.         header->e_ident[EI_MAG2] != ELFMAG2 ||
  143.         header->e_ident[EI_MAG3] != ELFMAG3) {
  144.         printf("invalid header\n");
  145.         return EE_INVALID;
  146.     }
  147.    
  148.     /* Identify ELF compatibility */
  149.     if (header->e_ident[EI_DATA] != ELF_DATA_ENCODING ||
  150.         header->e_machine != ELF_MACHINE ||
  151.         header->e_ident[EI_VERSION] != EV_CURRENT ||
  152.         header->e_version != EV_CURRENT ||
  153.         header->e_ident[EI_CLASS] != ELF_CLASS) {
  154.         printf("incompatible data/version/class\n");
  155.         return EE_INCOMPATIBLE;
  156.     }
  157.  
  158.     if (header->e_phentsize != sizeof(elf_segment_header_t))
  159.         return EE_INCOMPATIBLE;
  160.  
  161.     if (header->e_shentsize != sizeof(elf_section_header_t))
  162.         return EE_INCOMPATIBLE;
  163.  
  164.     /* Check if the object type is supported. */
  165.     if (header->e_type != ET_EXEC && header->e_type != ET_DYN) {
  166.         printf("Object type %d is not supported\n", header->e_type);
  167.         return EE_UNSUPPORTED;
  168.     }
  169.  
  170.     /* Shared objects can be loaded with a bias */
  171.     printf("Object type: %d\n", header->e_type);
  172.     if (header->e_type == ET_DYN)
  173.         elf->bias = so_bias;
  174.     else
  175.         elf->bias = 0;
  176.  
  177.     printf("Bias set to 0x%x\n", elf->bias);
  178.  
  179.     printf("parse segments\n");
  180.  
  181.     /* Walk through all segment headers and process them. */
  182.     for (i = 0; i < header->e_phnum; i++) {
  183.         elf_segment_header_t segment_hdr;
  184.  
  185.         /* Seek to start of segment header */
  186.         lseek(elf->fd, header->e_phoff
  187.                 + i * sizeof(elf_segment_header_t), SEEK_SET);
  188.  
  189.         rc = read(elf->fd, &segment_hdr, sizeof(elf_segment_header_t));
  190.         if (rc < 0) { printf("read error\n"); return EE_INVALID; }
  191.  
  192.         rc = segment_header(elf, &segment_hdr);
  193.         if (rc != EE_OK)
  194.             return rc;
  195.     }
  196.  
  197.     printf("parse sections\n");
  198.  
  199.     /* Inspect all section headers and proccess them. */
  200.     for (i = 0; i < header->e_shnum; i++) {
  201.         elf_section_header_t section_hdr;
  202.  
  203.         /* Seek to start of section header */
  204.         lseek(elf->fd, header->e_shoff
  205.             + i * sizeof(elf_section_header_t), SEEK_SET);
  206.  
  207.         rc = read(elf->fd, &section_hdr, sizeof(elf_section_header_t));
  208.         if (rc < 0) { printf("read error\n"); return EE_INVALID; }
  209.  
  210.         rc = section_header(elf, &section_hdr);
  211.         if (rc != EE_OK)
  212.             return rc;
  213.     }
  214.  
  215.     elf->info->entry =
  216.         (entry_point_t)((uint8_t *)header->e_entry + elf->bias);
  217.  
  218.     printf("done\n");
  219.  
  220.     return EE_OK;
  221. }
  222.  
  223. /** Print error message according to error code.
  224.  *
  225.  * @param rc Return code returned by elf_load().
  226.  *
  227.  * @return NULL terminated description of error.
  228.  */
  229. char *elf_error(unsigned int rc)
  230. {
  231.     assert(rc < sizeof(error_codes) / sizeof(char *));
  232.  
  233.     return error_codes[rc];
  234. }
  235.  
  236. /** Process segment header.
  237.  *
  238.  * @param entry Segment header.
  239.  * @param elf ELF header.
  240.  *
  241.  * @return EE_OK on success, error code otherwise.
  242.  */
  243. static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry)
  244. {
  245.     switch (entry->p_type) {
  246.     case PT_NULL:
  247.     case PT_PHDR:
  248.         break;
  249.     case PT_LOAD:
  250.         return load_segment(elf, entry);
  251.         break;
  252.     case PT_DYNAMIC:
  253.     case PT_INTERP:
  254.     case PT_SHLIB:
  255.     case PT_NOTE:
  256.     case PT_LOPROC:
  257.     case PT_HIPROC:
  258.     default:
  259.         printf("segment p_type %d unknown\n", entry->p_type);
  260.         return EE_UNSUPPORTED;
  261.         break;
  262.     }
  263.     return EE_OK;
  264. }
  265.  
  266. /** Load segment described by program header entry.
  267.  *
  268.  * @param entry Program header entry describing segment to be loaded.
  269.  * @param elf ELF header.
  270.  *
  271.  * @return EE_OK on success, error code otherwise.
  272.  */
  273. int load_segment(elf_ld_t *elf, elf_segment_header_t *entry)
  274. {
  275.     void *a;
  276.     int flags = 0;
  277.     uintptr_t bias;
  278.     int rc;
  279.  
  280.     printf("load segment at addr 0x%x, size 0x%x\n", entry->p_vaddr,
  281.         entry->p_memsz);
  282.    
  283.     bias = elf->bias;
  284.  
  285.     if (entry->p_align > 1) {
  286.         if ((entry->p_offset % entry->p_align) !=
  287.             (entry->p_vaddr % entry->p_align)) {
  288.             printf("align check 1 failed offset%%align=%d, vaddr%%align=%d\n",
  289.             entry->p_offset % entry->p_align,
  290.             entry->p_vaddr % entry->p_align
  291.             );
  292.             return EE_INVALID;
  293.         }
  294.     }
  295.  
  296. /*  if (entry->p_flags & PF_X)
  297.         flags |= AS_AREA_EXEC;
  298.     if (entry->p_flags & PF_W)
  299.         flags |= AS_AREA_WRITE;
  300.     if (entry->p_flags & PF_R)
  301.         flags |= AS_AREA_READ;
  302.     flags |= AS_AREA_CACHEABLE;
  303. */
  304.     /* FIXME: Kernel won't normally allow this, unless you "patch" it */
  305. //  flags = AS_AREA_READ | AS_AREA_WRITE | AS_AREA_EXEC | AS_AREA_CACHEABLE;
  306.     flags = AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE;
  307.  
  308.     /*
  309.      * Check if the virtual address starts on page boundary.
  310.      */
  311.     if (ALIGN_UP(entry->p_vaddr, PAGE_SIZE) != entry->p_vaddr) {
  312.         printf("align check 2 failed - not page-aligned\n");
  313.         printf("vaddr = 0x%x, should be 0x%x\n",
  314.             entry->p_vaddr, ALIGN_UP(entry->p_vaddr, PAGE_SIZE));
  315.         return EE_UNSUPPORTED;
  316.     }
  317.    
  318.     printf("map to p_vaddr=0x%x-0x%x...\n", entry->p_vaddr + bias,
  319.     entry->p_vaddr + bias + ALIGN_UP(entry->p_memsz, PAGE_SIZE));
  320.  
  321.     a = as_area_create((uint8_t *)entry->p_vaddr + bias,
  322.         entry->p_memsz, flags);
  323.     if (a == (void *)(-1)) {
  324.         printf("memory mapping failed\n");
  325.         return EE_MEMORY;
  326.     }
  327.  
  328.     printf("as_area_create(0x%x, 0x%x, %d) -> 0x%x\n",
  329.         entry->p_vaddr+bias, entry->p_memsz, flags, (unsigned)a);
  330.  
  331.     /*
  332.      * Load segment data
  333.      */
  334.     printf("seek to %d\n", entry->p_offset);
  335.     rc = lseek(elf->fd, entry->p_offset, SEEK_SET);
  336.     if (rc < 0) { printf("seek error\n"); return EE_INVALID; }
  337.  
  338.     printf("read 0x%x bytes to address 0x%x\n", entry->p_filesz, entry->p_vaddr+bias);
  339. /*  rc = read(fd, (void *)(entry->p_vaddr + bias), entry->p_filesz);
  340.     if (rc < 0) { printf("read error\n"); return EE_INVALID; }*/
  341.     unsigned left, now;
  342.     uint8_t *dp;
  343.  
  344.     left = entry->p_filesz;
  345.     dp = (uint8_t *)(entry->p_vaddr + bias);
  346.  
  347.     while (left > 0) {
  348.         now = 4096;
  349.         if (now > left) now=left;
  350.         printf("read %d...", now);
  351.         rc = read(elf->fd, dp, now);
  352.         if (rc < 0) { printf("read error\n"); return EE_INVALID; }
  353.         printf("->%d\n", rc);
  354.         left -= now;
  355.         dp += now;
  356.     }
  357.  
  358.     return EE_OK;
  359. }
  360.  
  361. /** Process section header.
  362.  *
  363.  * @param entry Segment header.
  364.  * @param elf ELF header.
  365.  *
  366.  * @return EE_OK on success, error code otherwise.
  367.  */
  368. static int section_header(elf_ld_t *elf, elf_section_header_t *entry)
  369. {
  370.     switch (entry->sh_type) {
  371.     case SHT_PROGBITS:
  372.         if (entry->sh_flags & SHF_TLS) {
  373.             /* .tdata */
  374.         }
  375.         break;
  376.     case SHT_NOBITS:
  377.         if (entry->sh_flags & SHF_TLS) {
  378.             /* .tbss */
  379.         }
  380.         break;
  381.     case SHT_DYNAMIC:
  382.         elf->info->dynamic =
  383.             (void *)((uint8_t *)entry->sh_addr + elf->bias);
  384.         printf("dynamic section found at 0x%x\n",
  385.             (uintptr_t)elf->info->dynamic);
  386.         break;
  387.     default:
  388.         break;
  389.     }
  390.    
  391.     return EE_OK;
  392. }
  393.  
  394. /** @}
  395.  */
  396.