2 * AcessOS 1 - Dynamic Loader
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11 # define DEBUGS(v...) SysDebug(v)
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18 //static const char *csaDT_NAMES[] = {"DT_NULL", "DT_NEEDED", "DT_PLTRELSZ", "DT_PLTGOT", "DT_HASH", "DT_STRTAB", "DT_SYMTAB", "DT_RELA", "DT_RELASZ", "DT_RELAENT", "DT_STRSZ", "DT_SYMENT", "DT_INIT", "DT_FINI", "DT_SONAME", "DT_RPATH", "DT_SYMBOLIC", "DT_REL", "DT_RELSZ", "DT_RELENT", "DT_PLTREL", "DT_DEBUG", "DT_TEXTREL", "DT_JMPREL"};
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19 static const char *csaR_NAMES[] = {"R_386_NONE", "R_386_32", "R_386_PC32", "R_386_GOT32", "R_386_PLT32", "R_386_COPY", "R_386_GLOB_DAT", "R_386_JMP_SLOT", "R_386_RELATIVE", "R_386_GOTOFF", "R_386_GOTPC", "R_386_LAST"};
22 // === PROTOTYPES ===
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23 void elf_doRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base);
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24 Uint ElfHashString(char *name);
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28 \fn int ElfRelocate(void *Base, char **envp, char *Filename)
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29 \brief Relocates a loaded ELF Executable
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31 int ElfRelocate(void *Base, char **envp, char *Filename)
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33 Elf32_Ehdr *hdr = Base;
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35 int i, j; // Counters
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37 Uint iRealBase = -1;
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41 Elf32_Rel *rel = NULL;
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42 Elf32_Rela *rela = NULL;
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43 Uint32 *pltgot = NULL;
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45 int relSz=0, relEntSz=8;
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46 int relaSz=0, relaEntSz=8;
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47 int pltSz=0, pltType=0;
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48 Elf32_Dyn *dynamicTab = NULL; // Dynamic Table Pointer
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49 char *dynstrtab = NULL; // .dynamic String Table
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50 Elf32_Sym *dynsymtab;
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52 DEBUGS("ElfRelocate: (Base=0x%x)\n", Base);
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54 // Check magic header
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57 // Parse Program Header to get Dynamic Table
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58 phtab = Base + hdr->phoff;
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59 iSegmentCount = hdr->phentcount;
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60 for(i=0;i<iSegmentCount;i++)
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62 // Determine linked base address
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63 if(phtab[i].Type == PT_LOAD && iRealBase > phtab[i].VAddr)
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64 iRealBase = phtab[i].VAddr;
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66 // Find Dynamic Section
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67 if(phtab[i].Type == PT_DYNAMIC) {
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69 DEBUGS(" WARNING - elf_relocate: Multiple PT_DYNAMIC segments\n");
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72 dynamicTab = (void *) phtab[i].VAddr;
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73 j = i; // Save Dynamic Table ID
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77 // Page Align real base
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78 iRealBase &= ~0xFFF;
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79 DEBUGS(" elf_relocate: True Base = 0x%x, Compiled Base = 0x%x\n", Base, iRealBase);
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81 // Adjust "Real" Base
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82 iBaseDiff = (Uint)Base - iRealBase;
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84 hdr->entrypoint += iBaseDiff; // Adjust Entrypoint
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86 // Check if a PT_DYNAMIC segement was found
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88 SysDebug(" elf_relocate: No PT_DYNAMIC segment in image, returning\n");
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89 return hdr->entrypoint;
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92 // Adjust Dynamic Table
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93 dynamicTab = (void *) ((Uint)dynamicTab + iBaseDiff);
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95 // === Get Symbol table and String Table ===
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96 for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
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98 switch(dynamicTab[j].d_tag)
100 // --- Symbol Table ---
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102 DEBUGS(" elf_relocate: DYNAMIC Symbol Table 0x%x (0x%x)\n",
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103 dynamicTab[j].d_val, dynamicTab[j].d_val + iBaseDiff);
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104 dynamicTab[j].d_val += iBaseDiff;
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105 dynsymtab = (void*)(dynamicTab[j].d_val);
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106 hdr->misc.SymTable = dynamicTab[j].d_val; // Saved in unused bytes of ident
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108 // --- String Table ---
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110 DEBUGS(" elf_relocate: DYNAMIC String Table 0x%x (0x%x)\n",
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111 dynamicTab[j].d_val, dynamicTab[j].d_val + iBaseDiff);
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112 dynamicTab[j].d_val += iBaseDiff;
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113 dynstrtab = (void*)(dynamicTab[j].d_val);
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115 // --- Hash Table --
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117 dynamicTab[j].d_val += iBaseDiff;
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118 iSymCount = ((Uint*)(dynamicTab[j].d_val))[1];
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119 hdr->misc.HashTable = dynamicTab[j].d_val; // Saved in unused bytes of ident
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124 if(dynsymtab == NULL) {
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125 SysDebug("ld-acess.so - WARNING: No Dynamic Symbol table, returning\n");
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126 return hdr->entrypoint;
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129 // Alter Symbols to true base
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130 for(i=0;i<iSymCount;i++)
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132 dynsymtab[i].value += iBaseDiff;
133 dynsymtab[i].nameOfs += (Uint)dynstrtab;
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134 //DEBUGS("elf_relocate: Sym '%s' = 0x%x (relocated)\n", dynsymtab[i].name, dynsymtab[i].value);
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137 // === Add to loaded list (can be imported now) ===
138 AddLoaded( Filename, (Uint)Base );
140 // === Parse Relocation Data ===
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141 DEBUGS(" elf_relocate: dynamicTab = 0x%x\n", dynamicTab);
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142 for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
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144 switch(dynamicTab[j].d_tag)
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146 // --- Shared Library Name ---
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148 DEBUGS(" elf_relocate: .so Name '%s'\n", dynstrtab+dynamicTab[j].d_val);
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150 // --- Needed Library ---
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152 libPath = dynstrtab + dynamicTab[j].d_val;
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153 DEBUGS(" Required Library '%s'\n", libPath);
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154 if(LoadLibrary(libPath, NULL, envp) == 0) {
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156 DEBUGS(" elf_relocate: Unable to load '%s'\n", libPath);
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158 SysDebug("Unable to load required library '%s'\n", libPath);
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164 case DT_PLTGOT: pltgot = (void*)iBaseDiff+(dynamicTab[j].d_val); break;
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165 case DT_JMPREL: plt = (void*)(iBaseDiff+dynamicTab[j].d_val); break;
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166 case DT_PLTREL: pltType = dynamicTab[j].d_val; break;
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167 case DT_PLTRELSZ: pltSz = dynamicTab[j].d_val; break;
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169 // --- Relocation ---
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170 case DT_REL: rel = (void*)(iBaseDiff + dynamicTab[j].d_val); break;
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171 case DT_RELSZ: relSz = dynamicTab[j].d_val; break;
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172 case DT_RELENT: relEntSz = dynamicTab[j].d_val; break;
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173 case DT_RELA: rela = (void*)(iBaseDiff + dynamicTab[j].d_val); break;
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174 case DT_RELASZ: relaSz = dynamicTab[j].d_val; break;
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175 case DT_RELAENT: relaEntSz = dynamicTab[j].d_val; break;
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177 // --- Symbol Table ---
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179 // --- Hash Table ---
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181 // --- String Table ---
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187 if(dynamicTab[j].d_tag > DT_JMPREL) continue;
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188 //DEBUGS(" elf_relocate: %i-%i = %s,0x%x\n",
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189 // i,j, csaDT_NAMES[dynamicTab[j].d_tag],dynamicTab[j].d_val);
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194 DEBUGS(" elf_relocate: Beginning Relocation\n");
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196 // Parse Relocation Entries
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200 DEBUGS(" elf_relocate: rel=0x%x, relSz=0x%x, relEntSz=0x%x\n", rel, relSz, relEntSz);
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201 j = relSz / relEntSz;
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202 for( i = 0; i < j; i++ )
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204 //DEBUGS(" Rel %i: 0x%x+0x%x\n", i, iBaseDiff, rel[i].r_offset);
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205 ptr = (void*)(iBaseDiff + rel[i].r_offset);
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206 elf_doRelocate(rel[i].r_info, ptr, *ptr, dynsymtab, iBaseDiff);
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209 // Parse Relocation Entries
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213 DEBUGS(" elf_relocate: rela=0x%x, relaSz=0x%x, relaEntSz=0x%x\n", rela, relaSz, relaEntSz);
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214 j = relaSz / relaEntSz;
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215 for( i = 0; i < j; i++ )
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217 ptr = (void*)(iBaseDiff + rela[i].r_offset);
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218 elf_doRelocate(rel[i].r_info, ptr, rela[i].r_addend, dynsymtab, iBaseDiff);
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222 // === Process PLT (Procedure Linkage Table) ===
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226 DEBUGS(" elf_relocate: Relocate PLT, plt=0x%x\n", plt);
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227 if(pltType == DT_REL)
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229 Elf32_Rel *pltRel = plt;
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230 j = pltSz / sizeof(Elf32_Rel);
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231 DEBUGS(" elf_relocate: PLT Reloc Type = Rel, %i entries\n", j);
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234 ptr = (void*)(iBaseDiff + pltRel[i].r_offset);
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235 elf_doRelocate(pltRel[i].r_info, ptr, *ptr, dynsymtab, iRealBase);
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240 Elf32_Rela *pltRela = plt;
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241 j = pltSz / sizeof(Elf32_Rela);
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242 DEBUGS(" elf_relocate: PLT Reloc Type = Rela, %i entries\n", j);
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245 ptr = (void*)(iRealBase + pltRela[i].r_offset);
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246 elf_doRelocate(pltRela[i].r_info, ptr, pltRela[i].r_addend, dynsymtab, iRealBase);
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251 DEBUGS("ElfRelocate: RETURN 0x%x", hdr->entrypoint);
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252 return hdr->entrypoint;
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255 void elf_doRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base)
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257 int type = ELF32_R_TYPE(r_info);
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258 int sym = ELF32_R_SYM(r_info);
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262 // Standard 32 Bit Relocation (S+A)
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264 val = GetSymbol( symtab[sym].name );
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265 DEBUGS(" elf_doRelocate: R_386_32 *0x%x += 0x%x('%s')\n",
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266 ptr, val, symtab[sym].name);
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267 *ptr = val + addend;
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270 // 32 Bit Relocation wrt. Offset (S+A-P)
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272 DEBUGS(" elf_doRelocate: #%i: '%s'\n", sym, symtab[sym].name);
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273 val = GetSymbol( symtab[sym].name );
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274 DEBUGS(" elf_doRelocate: R_386_PC32 *0x%x = 0x%x + 0x%x - 0x%x\n",
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275 ptr, *ptr, val, (Uint)ptr );
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276 *ptr = val + addend - (Uint)ptr;
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277 //*ptr = val + addend - ((Uint)ptr - base);
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280 // Absolute Value of a symbol (S)
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281 case R_386_GLOB_DAT:
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283 DEBUGS(" elf_doRelocate: #%i: '%s'\n", sym, symtab[sym].name);
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284 val = GetSymbol( symtab[sym].name );
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285 DEBUGS(" elf_doRelocate: %s *0x%x = 0x%x\n", csaR_NAMES[type], ptr, val);
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289 // Base Address (B+A)
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290 case R_386_RELATIVE:
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291 DEBUGS(" elf_doRelocate: R_386_RELATIVE *0x%x = 0x%x + 0x%x\n", ptr, base, addend);
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292 *ptr = base + addend;
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296 DEBUGS(" elf_doRelocate: Rel 0x%x: 0x%x,%s\n", ptr, sym, csaR_NAMES[type]);
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303 * \fn int ElfGetSymbol(Uint Base, char *name, Uint *ret)
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305 int ElfGetSymbol(Uint Base, char *Name, Uint *ret)
307 Elf32_Ehdr *hdr = (void*)Base;
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316 //DEBUGS("ElfGetSymbol: (Base=0x%x, Name='%s')\n", Base, Name);
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318 // Catch the current executable
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320 if( !hdr->misc.HashTable )
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323 Elf32_Dyn *dynTab = NULL;
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326 // Locate the tables
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327 phtab = (void*)( Base + hdr->phoff );
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328 for( i = 0; i < hdr->phentcount; i ++ )
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330 if( phtab[i].Type == PT_DYNAMIC ) {
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331 dynTab = (void*)phtab[i].VAddr;
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336 SysDebug("ERROR - Unable to find DYNAMIC segment in %p", (void*)Base);
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340 for( j = 0; dynTab[j].d_tag != DT_NULL; j++)
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342 switch(dynTab[j].d_tag)
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344 // --- Symbol Table ---
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346 hdr->misc.SymTable = dynTab[j].d_val;
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348 // --- Hash Table --
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350 hdr->misc.HashTable = dynTab[j].d_val;
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357 if( !hdr->misc.SymTable || !hdr->misc.HashTable ) {
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361 pBuckets = (void *) hdr->misc.HashTable;
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362 symtab = (void *) hdr->misc.SymTable;
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364 nbuckets = pBuckets[0];
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365 iSymCount = pBuckets[1];
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366 pBuckets = &pBuckets[2];
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367 pChains = &pBuckets[ nbuckets ];
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370 iNameHash = ElfHashString(Name);
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371 iNameHash %= nbuckets;
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372 //DEBUGS(" ElfGetSymbol: iNameHash = 0x%x\n", iNameHash);
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375 i = pBuckets[ iNameHash ];
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376 //DEBUGS(" ElfGetSymbol: strcmp(Name, \"%s\")\n", symtab[i].name);
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377 if(symtab[i].shndx != SHN_UNDEF && strcmp(symtab[i].name, Name) == 0) {
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378 *ret = symtab[ i ].value;
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382 //DEBUGS(" ElfGetSymbol: Hash of first = 0x%x\n", ElfHashString( symtab[i].name ) % nbuckets);
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383 while(pChains[i] != STN_UNDEF)
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385 //DEBUGS(" pChains[%i] = %i\n", i, pChains[i]);
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387 //DEBUGS(" ElfGetSymbol: strcmp(Name, \"%s\")\n", symtab[ i ].name);
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388 if(symtab[i].shndx != SHN_UNDEF && strcmp(symtab[ i ].name, Name) == 0) {
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389 //DEBUGS("ElfGetSymbol: RETURN 1, '%s' = 0x%x\n", symtab[ i ].name, symtab[ i ].value);
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390 *ret = symtab[ i ].value;
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395 //DEBUGS("ElfGetSymbol: RETURN 0, Symbol '%s' not found\n", Name);
399 Uint ElfHashString(char *name)
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404 h = (h << 4) + *name++;
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405 if( (g = h & 0xf0000000) )
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413 unsigned long elf_hash(const unsigned char *name)
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415 unsigned long h = 0, g;
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418 h = (h << 4) + *name++;
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419 if (g = h & 0xf0000000)
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