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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. /** Find the definition of a symbol.
  107.  *
  108.  * By definition in System V ABI, if module origin has the flag DT_SYMBOLIC,
  109.  * origin is searched first. Otherwise, or if the symbol hasn't been found,
  110.  * the module dependency graph is searched breadth-first, beginning
  111.  * from the executable program.
  112.  *
  113.  * @param name      Name of the symbol to search for.
  114.  * @param origin    Module in which the dependency originates.
  115.  * @param mod       (output) Will be filled with a pointer to the module
  116.  *          that contains the symbol.
  117.  */
  118. elf_symbol_t *symbol_def_find(char *name, module_t *origin, module_t **mod)
  119. {
  120.     module_t *m;
  121.     elf_symbol_t *sym;
  122.  
  123.     /* FIXME: support DT_SYMBOLIC */
  124.     //m = origin;
  125.  
  126.     /* Start in the executable program */
  127.     m = runtime_env.program;
  128.  
  129.     while (true) {
  130.         sym = def_find_in_module(name, m);
  131.         if (sym != NULL) {
  132.             *mod = m;
  133.             return sym;
  134.         }
  135.  
  136.         if (m->n_deps < 1) break;
  137.  
  138.         /* FIXME: support branching */
  139.         if (m->n_deps > 1) {
  140.             printf("error: BFS unimplemented\n");
  141.             exit(1);
  142.         }
  143.  
  144.         m = m->deps[0];
  145.     }
  146.  
  147.     printf("Error, symbol '%s' not found anywhere\n", name);
  148.     exit(1);
  149.     return NULL; /* Not found */
  150. }
  151.  
  152. uintptr_t symbol_get_addr(elf_symbol_t *sym, module_t *m)
  153. {
  154.     if (sym->st_shndx == SHN_ABS) {
  155.         /* Do not add bias to absolute symbols */
  156.         return sym->st_value;
  157.     } else {
  158.         return sym->st_value + m->bias;
  159.     }
  160. }
  161.  
  162. /** @}
  163.  */
  164.