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  1. /*
  2.  * Copyright (c) 2008 Jiri Svoboda
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup rtld rtld
  30.  * @brief
  31.  * @{
  32.  */
  33. /**
  34.  * @file
  35.  */
  36.  
  37. #include <stdio.h>
  38. #include <stdlib.h>
  39. #include <string.h>
  40.  
  41. #include <rtld.h>
  42. #include <symbol.h>
  43. #include <elf.h>
  44.  
  45. /*
  46.  * Hash tables are 32-bit (elf_word) even for 64-bit ELF files.
  47.  */
  48. static elf_word elf_hash(const unsigned char *name)
  49. {
  50.     elf_word h = 0, g;
  51.  
  52.     while (*name) {
  53.         h = (h << 4) + *name++;
  54.         g = h & 0xf0000000;
  55.         if (g != 0) h ^= g >> 24;
  56.         h &= ~g;
  57.     }
  58.  
  59.     return h;
  60. }
  61.  
  62. static elf_symbol_t *def_find_in_module(char *name, module_t *m)
  63. {
  64.     elf_symbol_t *sym_table;
  65.     elf_symbol_t *s, *sym;
  66.     elf_word nbucket;
  67.     elf_word nchain;
  68.     elf_word i;
  69.     char *s_name;
  70.     elf_word bucket;
  71.  
  72. //  module_name = m->dyn.soname;
  73. //  printf("def_find_in_module('%s', %s)\n", name, module_name);
  74.  
  75.     sym_table = m->dyn.sym_tab;
  76.     nbucket = m->dyn.hash[0];
  77.     nchain = m->dyn.hash[1];
  78.  
  79.     bucket = elf_hash((unsigned char *)name) % nbucket;
  80.     i = m->dyn.hash[2 + bucket];
  81.  
  82.     sym = NULL;
  83.     while (i != STN_UNDEF) {
  84.         s = &sym_table[i];
  85.         s_name = m->dyn.str_tab + s->st_name;
  86.  
  87.         if (strcmp(name, s_name) == 0) {
  88.             sym = s;
  89.             break;
  90.         }
  91.  
  92.         i = m->dyn.hash[2 + nbucket + i];
  93.     }
  94.  
  95.     if (!sym)
  96.         return NULL;    /* Not found */
  97.  
  98.     if (sym->st_shndx == SHN_UNDEF) {
  99.         /* Not a definition */
  100.         return NULL;
  101.     }
  102.  
  103.     return sym; /* Found */
  104. }
  105.  
  106.  
  107. elf_symbol_t *symbol_def_find(char *name, module_t **m)
  108. {
  109.     elf_symbol_t *sym;
  110.  
  111.     sym = def_find_in_module(name, runtime_env.program);
  112.     if (sym != NULL) { *m = runtime_env.program; return sym; } 
  113.  
  114.     sym = def_find_in_module(name, runtime_env.libc);
  115.     if (sym != NULL) { *m = runtime_env.libc; return sym; }
  116.  
  117.     sym = def_find_in_module(name, &runtime_env.rtld);
  118.     if (sym != NULL) { *m = &runtime_env.rtld; return sym; }
  119.  
  120.     printf("symbol found nowhere\n");
  121.     *m = NULL;
  122.     return NULL;
  123. }
  124.  
  125. uintptr_t symbol_get_addr(elf_symbol_t *sym, module_t *m)
  126. {
  127.     if (sym->st_shndx == SHN_ABS) {
  128.         /* Do not add bias to absolute symbols */
  129.         return sym->st_value;
  130.     } else {
  131.         return sym->st_value + m->bias;
  132.     }
  133. }
  134.  
  135. /** @}
  136.  */
  137.