3 * ELF Executable Loader Code
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10 #define DEBUG_WARN 1
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13 // === PROTOTYPES ===
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14 tBinary *Elf_Load(int fp);
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15 int Elf_Relocate(void *Base);
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16 int Elf_GetSymbol(void *Base, char *Name, Uint *ret);
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17 int Elf_Int_DoRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base);
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18 Uint Elf_Int_HashString(char *str);
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21 tBinaryType gELF_Info = {
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23 0x464C457F, 0xFFFFFFFF, // '\x7FELF'
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25 Elf_Load, Elf_Relocate, Elf_GetSymbol
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29 tBinary *Elf_Load(int fp)
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41 VFS_Read(fp, sizeof(hdr), &hdr);
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43 // Check the file type
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44 if(hdr.ident[0] != 0x7F || hdr.ident[1] != 'E' || hdr.ident[2] != 'L' || hdr.ident[3] != 'F') {
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45 Warning("Non-ELF File was passed to the ELF loader\n");
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50 // Check for a program header
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51 if(hdr.phoff == 0) {
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53 Warning("ELF File does not contain a program header\n");
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59 // Read Program Header Table
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60 phtab = malloc(sizeof(Elf32_Phdr)*hdr.phentcount);
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61 VFS_Seek(fp, hdr.phoff, SEEK_SET);
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62 VFS_Read(fp, sizeof(Elf32_Phdr)*hdr.phentcount, phtab);
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66 LOG("hdr.phentcount = %i", hdr.phentcount);
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67 for( i = 0; i < hdr.phentcount; i++ )
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69 // Ignore Non-LOAD types
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70 if(phtab[i].Type != PT_LOAD)
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72 iPageCount += ((phtab[i].VAddr&0xFFF) + phtab[i].MemSize + 0xFFF) >> 12;
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73 LOG("phtab[%i] = {VAddr:0x%x, MemSize:0x%x}", i, phtab[i].VAddr, phtab[i].MemSize);
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76 LOG("iPageCount = %i", iPageCount);
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78 // Allocate Information Structure
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79 ret = malloc( sizeof(tBinary) + sizeof(tBinaryPage)*iPageCount );
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81 ret->Entry = hdr.entrypoint;
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82 ret->Base = -1; // Set Base to maximum value
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83 ret->NumPages = iPageCount;
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84 ret->Interpreter = NULL;
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88 for( i = 0; i < hdr.phentcount; i++ )
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91 LOG("phtab[%i].Type = 0x%x", i, phtab[i].Type);
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92 // Get Interpreter Name
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93 if( phtab[i].Type == PT_INTERP )
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96 if(ret->Interpreter) continue;
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97 tmp = malloc(phtab[i].FileSize);
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98 VFS_Seek(fp, phtab[i].Offset, 1);
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99 VFS_Read(fp, phtab[i].FileSize, tmp);
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100 ret->Interpreter = Binary_RegInterp(tmp);
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101 LOG("Interpreter '%s'", tmp);
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105 // Ignore non-LOAD types
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106 if(phtab[i].Type != PT_LOAD) continue;
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109 if(phtab[i].VAddr < ret->Base) ret->Base = phtab[i].VAddr;
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111 LOG("phtab[%i] = {VAddr:0x%x,Offset:0x%x,FileSize:0x%x}",
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112 i, phtab[i].VAddr, phtab[i].Offset, phtab[i].FileSize);
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114 if( (phtab[i].FileSize & 0xFFF) < 0x1000 - (phtab[i].VAddr & 0xFFF) )
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115 lastSize = phtab[i].FileSize;
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117 lastSize = (phtab[i].FileSize & 0xFFF) + (phtab[i].VAddr & 0xFFF);
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120 LOG("lastSize = 0x%x", lastSize);
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123 count = ( (phtab[i].VAddr&0xFFF) + phtab[i].FileSize + 0xFFF) >> 12;
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124 for( k = 0; k < count; k ++ )
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126 ret->Pages[j+k].Virtual = phtab[i].VAddr + (k<<12);
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127 ret->Pages[j+k].Physical = phtab[i].Offset + (k<<12); // Store the offset in the physical address
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129 ret->Pages[j+k].Physical -= ret->Pages[j+k].Virtual&0xFFF;
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130 ret->Pages[j+k].Virtual &= ~0xFFF;
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133 ret->Pages[j+k].Size = lastSize; // Byte count in page
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135 ret->Pages[j+k].Size = 4096 - (phtab[i].VAddr&0xFFF);
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137 ret->Pages[j+k].Size = 4096;
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138 LOG("ret->Pages[%i].Size = 0x%x", j+k, ret->Pages[j+k].Size);
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139 ret->Pages[j+k].Flags = 0;
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141 count = (phtab[i].MemSize + 0xFFF) >> 12;
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144 ret->Pages[j+k].Virtual = phtab[i].VAddr + (k<<12);
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145 ret->Pages[j+k].Physical = -1; // -1 = Fill with zeros
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146 if(k != 0) ret->Pages[j+k].Virtual &= ~0xFFF;
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147 if(k == count-1 && (phtab[i].MemSize & 0xFFF))
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148 ret->Pages[j+k].Size = phtab[i].MemSize & 0xFFF; // Byte count in page
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150 ret->Pages[j+k].Size = 4096;
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151 ret->Pages[j+k].Flags = 0;
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152 LOG("%i - 0x%x => 0x%x - 0x%x", j+k,
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153 ret->Pages[j+k].Physical, ret->Pages[j+k].Virtual, ret->Pages[j+k].Size);
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159 LOG("Cleaning up overlaps");
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160 // Clear up Overlaps
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169 tmpRgns = malloc(sizeof(*tmpRgns)*count);
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171 for(i=0;i<count;i++) {
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172 tmpRgns[i].V = ret->Pages[i].Virtual;
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173 tmpRgns[i].P = ret->Pages[i].Physical;
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174 tmpRgns[i].S = ret->Pages[i].Size;
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175 tmpRgns[i].F = ret->Pages[i].Flags;
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178 for(i=1,j=0; i < count; i++)
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180 if( tmpRgns[j].F == tmpRgns[i].F
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181 && tmpRgns[j].V + tmpRgns[j].S == tmpRgns[i].V
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182 && ((tmpRgns[j].P == -1 && tmpRgns[i].P == -1)
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183 || (tmpRgns[j].P + tmpRgns[j].S == tmpRgns[i].P)) )
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185 tmpRgns[j].S += tmpRgns[i].S;
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188 tmpRgns[j].V = tmpRgns[i].V;
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189 tmpRgns[j].P = tmpRgns[i].P;
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190 tmpRgns[j].F = tmpRgns[i].F;
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191 tmpRgns[j].S = tmpRgns[i].S;
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197 for(i=0;i<count;i++) {
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198 //LogF(" Elf_Load: %i - 0x%x => 0x%x - 0x%x\n", i, tmpRgns[i].P, tmpRgns[i].V, tmpRgns[i].S);
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199 tmpRgns[i].S += tmpRgns[i].V & 0xFFF;
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200 if(tmpRgns[i].P != -1) tmpRgns[i].P -= tmpRgns[i].V & 0xFFF;
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201 tmpRgns[i].V &= ~0xFFF;
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202 j += (tmpRgns[i].S + 0xFFF) >> 12;
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203 //LogF(" Elf_Load: %i - 0x%x => 0x%x - 0x%x\n", i, tmpRgns[i].P, tmpRgns[i].V, tmpRgns[i].S);
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206 ret = realloc( ret, sizeof(tBinary) + 3*sizeof(Uint)*j );
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208 Warning("BIN", "ElfLoad: Unable to reallocate return structure");
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214 for(i=0;i<count;i++) {
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215 for( j = 0; j < (tmpRgns[i].S + 0xFFF) >> 12; j++,k++ ) {
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216 ret->Pages[k].Flags = tmpRgns[i].F;
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217 ret->Pages[k].Virtual = tmpRgns[i].V + (j<<12);
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218 if(tmpRgns[i].P != -1) {
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219 ret->Pages[k].Physical = tmpRgns[i].P + (j<<12);
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221 ret->Pages[k].Physical = -1;
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222 ret->Pages[k].Size = tmpRgns[i].S - (j << 12);
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223 // Clamp to page size
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224 if(ret->Pages[k].Size > 0x1000) ret->Pages[k].Size = 0x1000;
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239 // --- ELF RELOCATION ---
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240 // Taken from 'ld-acess.so'
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242 \fn int Elf_Relocate(void *Base)
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243 \brief Relocates a loaded ELF Executable
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245 int Elf_Relocate(void *Base)
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247 Elf32_Ehdr *hdr = Base;
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249 int i, j; // Counters
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251 Uint iRealBase = -1;
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255 Elf32_Rel *rel = NULL;
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256 Elf32_Rela *rela = NULL;
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257 Uint32 *pltgot = NULL;
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260 int relSz=0, relEntSz=8;
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261 int relaSz=0, relaEntSz=8;
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262 int pltSz=0, pltType=0;
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263 Elf32_Dyn *dynamicTab = NULL; // Dynamic Table Pointer
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264 char *dynstrtab = NULL; // .dynamic String Table
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265 Elf32_Sym *dynsymtab = NULL;
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268 ENTER("pBase", Base);
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270 // Parse Program Header to get Dynamic Table
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271 phtab = Base + hdr->phoff;
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272 iSegmentCount = hdr->phentcount;
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273 for(i=0;i<iSegmentCount;i++)
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275 // Determine linked base address
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276 if(phtab[i].Type == PT_LOAD && iRealBase > phtab[i].VAddr)
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277 iRealBase = phtab[i].VAddr;
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279 // Find Dynamic Section
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280 if(phtab[i].Type == PT_DYNAMIC) {
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282 Warning("ELF", "Elf_Relocate - Multiple PT_DYNAMIC segments\n");
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285 dynamicTab = (void *) phtab[i].VAddr;
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286 j = i; // Save Dynamic Table ID
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291 // Check if a PT_DYNAMIC segement was found
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293 Warning("ELF", "Elf_Relocate: No PT_DYNAMIC segment in image, returning\n");
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294 LEAVE('x', hdr->entrypoint);
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295 return hdr->entrypoint;
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298 // Page Align real base
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299 iRealBase &= ~0xFFF;
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301 // Adjust "Real" Base
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302 iBaseDiff = (Uint)Base - iRealBase;
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303 // Adjust Dynamic Table
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304 dynamicTab = (void *) ((Uint)dynamicTab + iBaseDiff);
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306 // === Get Symbol table and String Table ===
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307 for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
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309 switch(dynamicTab[j].d_tag)
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311 // --- Symbol Table ---
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313 dynamicTab[j].d_val += iBaseDiff;
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314 dynsymtab = (void*)(dynamicTab[j].d_val);
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315 hdr->misc.SymTable = dynamicTab[j].d_val; // Saved in unused bytes of ident
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318 // --- String Table ---
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320 dynamicTab[j].d_val += iBaseDiff;
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321 dynstrtab = (void*)(dynamicTab[j].d_val);
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324 // --- Hash Table --
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326 dynamicTab[j].d_val += iBaseDiff;
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327 iSymCount = ((Uint*)(dynamicTab[j].d_val))[1];
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328 hdr->misc.HashTable = dynamicTab[j].d_val; // Saved in unused bytes of ident
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334 // Alter Symbols to true base
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335 for(i=0;i<iSymCount;i++)
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337 dynsymtab[i].value += iBaseDiff;
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338 dynsymtab[i].nameOfs += (Uint)dynstrtab;
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339 //LOG("Sym '%s' = 0x%x (relocated)\n", dynsymtab[i].name, dynsymtab[i].value);
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342 // === Add to loaded list (can be imported now) ===
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343 //Binary_AddLoaded( (Uint)Base );
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345 // === Parse Relocation Data ===
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346 for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
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348 switch(dynamicTab[j].d_tag)
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350 // --- Shared Library Name ---
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352 LOG(".so Name '%s'\n", dynstrtab+dynamicTab[j].d_val);
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354 // --- Needed Library ---
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356 libPath = dynstrtab + dynamicTab[j].d_val;
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357 LOG("Required Library '%s' (IGNORED in kernel mode)\n", libPath);
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360 case DT_PLTGOT: pltgot = (void*)iBaseDiff+(dynamicTab[j].d_val); break;
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361 case DT_JMPREL: plt = (void*)(iBaseDiff+dynamicTab[j].d_val); break;
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362 case DT_PLTREL: pltType = dynamicTab[j].d_val; break;
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363 case DT_PLTRELSZ: pltSz = dynamicTab[j].d_val; break;
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365 // --- Relocation ---
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366 case DT_REL: rel = (void*)(iBaseDiff + dynamicTab[j].d_val); break;
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367 case DT_RELSZ: relSz = dynamicTab[j].d_val; break;
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368 case DT_RELENT: relEntSz = dynamicTab[j].d_val; break;
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369 case DT_RELA: rela = (void*)(iBaseDiff + dynamicTab[j].d_val); break;
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370 case DT_RELASZ: relaSz = dynamicTab[j].d_val; break;
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371 case DT_RELAENT: relaEntSz = dynamicTab[j].d_val; break;
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375 // Parse Relocation Entries
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378 j = relSz / relEntSz;
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379 for( i = 0; i < j; i++ )
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381 ptr = (void*)(iBaseDiff + rel[i].r_offset);
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382 if( !Elf_Int_DoRelocate(rel[i].r_info, ptr, *ptr, dynsymtab, (Uint)Base) ) {
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387 // Parse Relocation Entries
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390 j = relaSz / relaEntSz;
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391 for( i = 0; i < j; i++ )
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393 ptr = (void*)(iBaseDiff + rela[i].r_offset);
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394 if( !Elf_Int_DoRelocate(rel[i].r_info, ptr, rela[i].r_addend, dynsymtab, (Uint)Base) ) {
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400 // === Process PLT (Procedure Linkage Table) ===
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403 if(pltType == DT_REL)
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405 Elf32_Rel *pltRel = plt;
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406 j = pltSz / sizeof(Elf32_Rel);
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407 for(i = 0; i < j; i++)
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409 ptr = (void*)(iBaseDiff + pltRel[i].r_offset);
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410 if( !Elf_Int_DoRelocate(pltRel[i].r_info, ptr, *ptr, dynsymtab, (Uint)Base) ) {
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417 Elf32_Rela *pltRela = plt;
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418 j = pltSz / sizeof(Elf32_Rela);
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421 ptr = (void*)((Uint)Base + pltRela[i].r_offset);
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422 if( !Elf_Int_DoRelocate(pltRela[i].r_info, ptr, pltRela[i].r_addend, dynsymtab, (Uint)Base) ) {
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434 LEAVE('x', hdr->entrypoint);
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435 return hdr->entrypoint;
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439 * \fn void Elf_Int_DoRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base)
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440 * \brief Performs a relocation
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441 * \param r_info Field from relocation entry
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442 * \param ptr Pointer to location of relocation
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443 * \param addend Value to add to symbol
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444 * \param symtab Symbol Table
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445 * \param base Base of loaded binary
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447 int Elf_Int_DoRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base)
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450 int type = ELF32_R_TYPE(r_info);
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451 int sym = ELF32_R_SYM(r_info);
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452 char *sSymName = symtab[sym].name;
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454 //LogF("Elf_Int_DoRelocate: (r_info=0x%x, ptr=0x%x, addend=0x%x, .., base=0x%x)\n",
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455 // r_info, ptr, addend, base);
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459 // Standard 32 Bit Relocation (S+A)
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461 if( !Elf_GetSymbol((void*)base, sSymName, &val) ) // Search this binary first
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462 if( !Binary_GetSymbol( sSymName, &val ) )
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464 LOG("R_386_32 *0x%x += 0x%x('%s')", ptr, val, sSymName);
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465 *ptr = val + addend;
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468 // 32 Bit Relocation wrt. Offset (S+A-P)
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470 if( !Elf_GetSymbol( (void*)base, sSymName, &val ) )
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471 if( !Binary_GetSymbol( sSymName, &val ) )
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473 LOG("R_386_PC32 *0x%x = 0x%x + 0x%x('%s') - 0x%x", ptr, *ptr, val, sSymName, (Uint)ptr );
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474 // TODO: Check if it needs the true value of ptr or the compiled value
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475 // NOTE: Testing using true value
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476 *ptr = val + addend - (Uint)ptr;
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479 // Absolute Value of a symbol (S)
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480 case R_386_GLOB_DAT:
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481 if( !Elf_GetSymbol( (void*)base, sSymName, &val ) )
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482 if( !Binary_GetSymbol( sSymName, &val ) )
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484 LOG("R_386_GLOB_DAT *0x%x = 0x%x (%s)", ptr, val, sSymName);
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488 // Absolute Value of a symbol (S)
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489 case R_386_JMP_SLOT:
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490 if( !Elf_GetSymbol( (void*)base, sSymName, &val ) )
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491 if( !Binary_GetSymbol( sSymName, &val ) )
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493 LOG("R_386_JMP_SLOT *0x%x = 0x%x (%s)", ptr, val, sSymName);
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497 // Base Address (B+A)
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498 case R_386_RELATIVE:
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499 LOG("R_386_RELATIVE *0x%x = 0x%x + 0x%x", ptr, base, addend);
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500 *ptr = base + addend;
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504 LOG("Rel 0x%x: 0x%x,%i", ptr, sym, type);
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511 * \fn int Elf_GetSymbol(void *Base, char *name, Uint *ret)
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512 * \brief Get a symbol from the loaded binary
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514 int Elf_GetSymbol(void *Base, char *Name, Uint *ret)
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516 Elf32_Ehdr *hdr = (void*)Base;
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525 if(!Base) return 0;
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527 pBuckets = (void *) hdr->misc.HashTable;
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528 symtab = (void *) hdr->misc.SymTable;
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530 nbuckets = pBuckets[0];
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531 iSymCount = pBuckets[1];
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532 pBuckets = &pBuckets[2];
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533 pChains = &pBuckets[ nbuckets ];
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536 iNameHash = Elf_Int_HashString(Name);
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537 iNameHash %= nbuckets;
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540 i = pBuckets[ iNameHash ];
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541 if(symtab[i].shndx != SHN_UNDEF && strcmp(symtab[i].name, Name) == 0) {
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542 if(ret) *ret = symtab[ i ].value;
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547 while(pChains[i] != STN_UNDEF)
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550 if(symtab[i].shndx != SHN_UNDEF && strcmp(symtab[ i ].name, Name) == 0) {
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551 if(ret) *ret = symtab[ i ].value;
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559 * \fn Uint Elf_Int_HashString(char *str)
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560 * \brief Hash a string in the ELF format
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561 * \param str String to hash
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562 * \return Hash value
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564 Uint Elf_Int_HashString(char *str)
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569 h = (h << 4) + *str++;
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570 if( (g = h & 0xf0000000) )
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