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