Usermode/Libraries/ld-acess.so_src/elf.c

   1 /*
   2  * AcessOS 1 - Dynamic Loader
   3  * By thePowersGang
   4  */
   5 #include "common.h"
   6 #include <stdint.h>
   7 #include "elf32.h"
   8
   9 #define DEBUG   0
  10
  11 #if DEBUG
  12 # define        DEBUGS(v...)    SysDebug(v)
  13 #else
  14 # define        DEBUGS(...)
  15 #endif
  16
  17 // === CONSTANTS ===
  18 #if DEBUG
  19 //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"};
  20 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"};
  21 #endif
  22
  23 // === PROTOTYPES ===
  24 void elf_doRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base);
  25 Uint ElfHashString(char *name);
  26
  27 // === CODE ===
  28 /**
  29  \fn int ElfRelocate(void *Base, char **envp, char *Filename)
  30  \brief Relocates a loaded ELF Executable
  31 */
  32 void *ElfRelocate(void *Base, char **envp, char *Filename)
  33 {
  34         Elf32_Ehdr      *hdr = Base;
  35         Elf32_Phdr      *phtab;
  36          int    i, j;   // Counters
  37         char    *libPath;
  38         Uint    iRealBase = -1;
  39         Uint    iBaseDiff;
  40          int    iSegmentCount;
  41          int    iSymCount;
  42         Elf32_Rel       *rel = NULL;
  43         Elf32_Rela      *rela = NULL;
  44         Uint32  *pltgot = NULL;
  45         void    *plt = NULL;
  46          int    relSz=0, relEntSz=8;
  47          int    relaSz=0, relaEntSz=8;
  48          int    pltSz=0, pltType=0;
  49         Elf32_Dyn       *dynamicTab = NULL;     // Dynamic Table Pointer
  50         char    *dynstrtab = NULL;      // .dynamic String Table
  51         Elf32_Sym       *dynsymtab;
  52
  53         DEBUGS("ElfRelocate: (Base=0x%x)\n", Base);
  54
  55         // Check magic header
  56
  57
  58         // Parse Program Header to get Dynamic Table
  59         phtab = Base + hdr->phoff;
  60         iSegmentCount = hdr->phentcount;
  61         for(i=0;i<iSegmentCount;i++)
  62         {
  63                 // Determine linked base address
  64                 if(phtab[i].Type == PT_LOAD && iRealBase > phtab[i].VAddr)
  65                         iRealBase = phtab[i].VAddr;
  66
  67                 // Find Dynamic Section
  68                 if(phtab[i].Type == PT_DYNAMIC) {
  69                         if(dynamicTab) {
  70                                 DEBUGS(" WARNING - elf_relocate: Multiple PT_DYNAMIC segments\n");
  71                                 continue;
  72                         }
  73                         dynamicTab = (void *) (intptr_t) phtab[i].VAddr;
  74                         j = i;  // Save Dynamic Table ID
  75                 }
  76         }
  77
  78         // Page Align real base
  79         iRealBase &= ~0xFFF;
  80         DEBUGS(" elf_relocate: True Base = 0x%x, Compiled Base = 0x%x\n", Base, iRealBase);
  81
  82         // Adjust "Real" Base
  83         iBaseDiff = (intptr_t)Base - iRealBase;
  84
  85         hdr->entrypoint += iBaseDiff;   // Adjust Entrypoint
  86
  87         // Check if a PT_DYNAMIC segement was found
  88         if(!dynamicTab) {
  89                 SysDebug(" elf_relocate: No PT_DYNAMIC segment in image, returning\n");
  90                 return (void *)hdr->entrypoint;
  91         }
  92
  93         // Adjust Dynamic Table
  94         dynamicTab = (void *)( (intptr_t)dynamicTab + iBaseDiff );
  95
  96         // === Get Symbol table and String Table ===
  97         for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
  98         {
  99                 switch(dynamicTab[j].d_tag)
 100                 {
 101                 // --- Symbol Table ---
 102                 case DT_SYMTAB:
 103                         DEBUGS(" elf_relocate: DYNAMIC Symbol Table 0x%x (0x%x)\n",
 104                                 dynamicTab[j].d_val, dynamicTab[j].d_val + iBaseDiff);
 105                         dynamicTab[j].d_val += iBaseDiff;
 106                         dynsymtab = (void*)(dynamicTab[j].d_val);
 107                         hdr->misc.SymTable = dynamicTab[j].d_val;       // Saved in unused bytes of ident
 108                         break;
 109                 // --- String Table ---
 110                 case DT_STRTAB:
 111                         DEBUGS(" elf_relocate: DYNAMIC String Table 0x%x (0x%x)\n",
 112                                 dynamicTab[j].d_val, dynamicTab[j].d_val + iBaseDiff);
 113                         dynamicTab[j].d_val += iBaseDiff;
 114                         dynstrtab = (void*)(dynamicTab[j].d_val);
 115                         break;
 116                 // --- Hash Table --
 117                 case DT_HASH:
 118                         dynamicTab[j].d_val += iBaseDiff;
 119                         iSymCount = ((Uint*)(dynamicTab[j].d_val))[1];
 120                         hdr->misc.HashTable = dynamicTab[j].d_val;      // Saved in unused bytes of ident
 121                         break;
 122                 }
 123         }
 124
 125         if(dynsymtab == NULL) {
 126                 SysDebug("ld-acess.so - WARNING: No Dynamic Symbol table, returning\n");
 127                 return (void *) hdr->entrypoint;
 128         }
 129
 130         // Alter Symbols to true base
 131         for(i=0;i<iSymCount;i++)
 132         {
 133                 dynsymtab[i].value += iBaseDiff;
 134                 dynsymtab[i].nameOfs += (intptr_t)dynstrtab;
 135                 //DEBUGS("elf_relocate: Sym '%s' = 0x%x (relocated)\n", dynsymtab[i].name, dynsymtab[i].value);
 136         }
 137
 138         // === Add to loaded list (can be imported now) ===
 139         AddLoaded( Filename, Base );
 140
 141         // === Parse Relocation Data ===
 142         DEBUGS(" elf_relocate: dynamicTab = 0x%x\n", dynamicTab);
 143         for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
 144         {
 145                 switch(dynamicTab[j].d_tag)
 146                 {
 147                 // --- Shared Library Name ---
 148                 case DT_SONAME:
 149                         DEBUGS(" elf_relocate: .so Name '%s'\n", dynstrtab+dynamicTab[j].d_val);
 150                         break;
 151                 // --- Needed Library ---
 152                 case DT_NEEDED:
 153                         libPath = dynstrtab + dynamicTab[j].d_val;
 154                         DEBUGS(" Required Library '%s'\n", libPath);
 155                         if(LoadLibrary(libPath, NULL, envp) == 0) {
 156                                 #if DEBUG
 157                                         DEBUGS(" elf_relocate: Unable to load '%s'\n", libPath);
 158                                 #else
 159                                 SysDebug("Unable to load required library '%s'\n", libPath);
 160                                 #endif
 161                                 return 0;
 162                         }
 163                         break;
 164                 // --- PLT/GOT ---
 165                 case DT_PLTGOT: pltgot = (void*)(iBaseDiff + dynamicTab[j].d_val);      break;
 166                 case DT_JMPREL: plt = (void*)(iBaseDiff + dynamicTab[j].d_val); break;
 167                 case DT_PLTREL: pltType = dynamicTab[j].d_val;  break;
 168                 case DT_PLTRELSZ:       pltSz = dynamicTab[j].d_val;    break;
 169
 170                 // --- Relocation ---
 171                 case DT_REL:    rel = (void*)(iBaseDiff + dynamicTab[j].d_val); break;
 172                 case DT_RELSZ:  relSz = dynamicTab[j].d_val;    break;
 173                 case DT_RELENT: relEntSz = dynamicTab[j].d_val; break;
 174                 case DT_RELA:   rela = (void*)(iBaseDiff + dynamicTab[j].d_val);        break;
 175                 case DT_RELASZ: relaSz = dynamicTab[j].d_val;   break;
 176                 case DT_RELAENT:        relaEntSz = dynamicTab[j].d_val;        break;
 177
 178                 // --- Symbol Table ---
 179                 case DT_SYMTAB:
 180                 // --- Hash Table ---
 181                 case DT_HASH:
 182                 // --- String Table ---
 183                 case DT_STRTAB:
 184                         break;
 185
 186                 // --- Unknown ---
 187                 default:
 188                         if(dynamicTab[j].d_tag > DT_JMPREL)     continue;
 189                         //DEBUGS(" elf_relocate: %i-%i = %s,0x%x\n",
 190                         //      i,j, csaDT_NAMES[dynamicTab[j].d_tag],dynamicTab[j].d_val);
 191                         break;
 192                 }
 193         }
 194
 195         DEBUGS(" elf_relocate: Beginning Relocation\n");
 196
 197         // Parse Relocation Entries
 198         if(rel && relSz)
 199         {
 200                 Uint32  *ptr;
 201                 DEBUGS(" elf_relocate: rel=0x%x, relSz=0x%x, relEntSz=0x%x\n", rel, relSz, relEntSz);
 202                 j = relSz / relEntSz;
 203                 for( i = 0; i < j; i++ )
 204                 {
 205                         //DEBUGS("  Rel %i: 0x%x+0x%x\n", i, iBaseDiff, rel[i].r_offset);
 206                         ptr = (void*)(iBaseDiff + rel[i].r_offset);
 207                         elf_doRelocate(rel[i].r_info, ptr, *ptr, dynsymtab, iBaseDiff);
 208                 }
 209         }
 210         // Parse Relocation Entries
 211         if(rela && relaSz)
 212         {
 213                 Uint32  *ptr;
 214                 DEBUGS(" elf_relocate: rela=0x%x, relaSz=0x%x, relaEntSz=0x%x\n", rela, relaSz, relaEntSz);
 215                 j = relaSz / relaEntSz;
 216                 for( i = 0; i < j; i++ )
 217                 {
 218                         ptr = (void*)(iBaseDiff + rela[i].r_offset);
 219                         elf_doRelocate(rel[i].r_info, ptr, rela[i].r_addend, dynsymtab, iBaseDiff);
 220                 }
 221         }
 222
 223         // === Process PLT (Procedure Linkage Table) ===
 224         if(plt && pltSz)
 225         {
 226                 Uint32  *ptr;
 227                 DEBUGS(" elf_relocate: Relocate PLT, plt=0x%x\n", plt);
 228                 if(pltType == DT_REL)
 229                 {
 230                         Elf32_Rel       *pltRel = plt;
 231                         j = pltSz / sizeof(Elf32_Rel);
 232                         DEBUGS(" elf_relocate: PLT Reloc Type = Rel, %i entries\n", j);
 233                         for(i=0;i<j;i++)
 234                         {
 235                                 ptr = (void*)(iBaseDiff + pltRel[i].r_offset);
 236                                 elf_doRelocate(pltRel[i].r_info, ptr, *ptr, dynsymtab, iRealBase);
 237                         }
 238                 }
 239                 else
 240                 {
 241                         Elf32_Rela      *pltRela = plt;
 242                         j = pltSz / sizeof(Elf32_Rela);
 243                         DEBUGS(" elf_relocate: PLT Reloc Type = Rela, %i entries\n", j);
 244                         for(i=0;i<j;i++)
 245                         {
 246                                 ptr = (void*)(iRealBase + pltRela[i].r_offset);
 247                                 elf_doRelocate(pltRela[i].r_info, ptr, pltRela[i].r_addend, dynsymtab, iRealBase);
 248                         }
 249                 }
 250         }
 251
 252         DEBUGS("ElfRelocate: RETURN 0x%x", hdr->entrypoint);
 253         return (void*)hdr->entrypoint;
 254 }
 255
 256 void elf_doRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base)
 257 {
 258          int    type = ELF32_R_TYPE(r_info);
 259          int    sym = ELF32_R_SYM(r_info);
 260         Uint32  val;
 261         switch( type )
 262         {
 263         // Standard 32 Bit Relocation (S+A)
 264         case R_386_32:
 265                 val = (intptr_t) GetSymbol( symtab[sym].name );
 266                 DEBUGS(" elf_doRelocate: R_386_32 *0x%x += 0x%x('%s')\n",
 267                         ptr, val, symtab[sym].name);
 268                 *ptr = val + addend;
 269                 break;
 270
 271         // 32 Bit Relocation wrt. Offset (S+A-P)
 272         case R_386_PC32:
 273                 DEBUGS(" elf_doRelocate: #%i: '%s'\n", sym, symtab[sym].name);
 274                 val = (intptr_t) GetSymbol( symtab[sym].name );
 275                 DEBUGS(" elf_doRelocate: R_386_PC32 *0x%x = 0x%x + 0x%x - 0x%x\n",
 276                         ptr, *ptr, val, (Uint)ptr );
 277                 *ptr = val + addend - (intptr_t)ptr;
 278                 //*ptr = val + addend - ((Uint)ptr - base);
 279                 break;
 280
 281         // Absolute Value of a symbol (S)
 282         case R_386_GLOB_DAT:
 283         case R_386_JMP_SLOT:
 284                 DEBUGS(" elf_doRelocate: #%i: '%s'\n", sym, symtab[sym].name);
 285                 val = (intptr_t) GetSymbol( symtab[sym].name );
 286                 DEBUGS(" elf_doRelocate: %s *0x%x = 0x%x\n", csaR_NAMES[type], ptr, val);
 287                 *ptr = val;
 288                 break;
 289
 290         // Base Address (B+A)
 291         case R_386_RELATIVE:
 292                 DEBUGS(" elf_doRelocate: R_386_RELATIVE *0x%x = 0x%x + 0x%x\n", ptr, base, addend);
 293                 *ptr = base + addend;
 294                 break;
 295
 296         default:
 297                 DEBUGS(" elf_doRelocate: Rel 0x%x: 0x%x,%s\n", ptr, sym, csaR_NAMES[type]);
 298                 break;
 299         }
 300
 301 }
 302
 303 /**
 304  * \fn int ElfGetSymbol(Uint Base, char *name, void **ret)
 305  */
 306 int ElfGetSymbol(void *Base, char *Name, void **ret)
 307 {
 308         Elf32_Ehdr      *hdr = Base;
 309         Elf32_Sym       *symtab;
 310          int    nbuckets = 0;
 311          int    iSymCount = 0;
 312          int    i;
 313         Uint    *pBuckets;
 314         Uint    *pChains;
 315         Uint    iNameHash;
 316
 317         //DEBUGS("ElfGetSymbol: (Base=0x%x, Name='%s')\n", Base, Name);
 318
 319         // Catch the current executable
 320         #if 0
 321         if( !hdr->misc.HashTable )
 322         {
 323                 Elf32_Phdr      *phtab;
 324                 Elf32_Dyn       *dynTab = NULL;
 325                  int    j;
 326
 327                 // Locate the tables
 328                 phtab = (void*)( Base + hdr->phoff );
 329                 for( i = 0; i < hdr->phentcount; i ++ )
 330                 {
 331                         if( phtab[i].Type == PT_DYNAMIC ) {
 332                                 dynTab = (void*)phtab[i].VAddr;
 333                                 break ;
 334                         }
 335                 }
 336                 if( !dynTab ) {
 337                         SysDebug("ERROR - Unable to find DYNAMIC segment in %p", (void*)Base);
 338                         return 0;
 339                 }
 340
 341                 for( j = 0; dynTab[j].d_tag != DT_NULL; j++)
 342                 {
 343                         switch(dynTab[j].d_tag)
 344                         {
 345                         // --- Symbol Table ---
 346                         case DT_SYMTAB:
 347                                 hdr->misc.SymTable = dynTab[j].d_val;
 348                                 break;
 349                         // --- Hash Table --
 350                         case DT_HASH:
 351                                 hdr->misc.HashTable = dynTab[j].d_val;
 352                                 break;
 353                         }
 354                 }
 355         }
 356         #endif
 357
 358         if( !hdr->misc.SymTable || !hdr->misc.HashTable ) {
 359                 return 0;
 360         }
 361
 362         pBuckets = (void *) (intptr_t) hdr->misc.HashTable;
 363         symtab = (void *) (intptr_t) hdr->misc.SymTable;
 364
 365         nbuckets = pBuckets[0];
 366         iSymCount = pBuckets[1];
 367         pBuckets = &pBuckets[2];
 368         pChains = &pBuckets[ nbuckets ];
 369
 370         // Get hash
 371         iNameHash = ElfHashString(Name);
 372         iNameHash %= nbuckets;
 373         //DEBUGS(" ElfGetSymbol: iNameHash = 0x%x\n", iNameHash);
 374
 375         // Walk Chain
 376         i = pBuckets[ iNameHash ];
 377         //DEBUGS(" ElfGetSymbol: strcmp(Name, \"%s\")\n", symtab[i].name);
 378         if(symtab[i].shndx != SHN_UNDEF && strcmp(symtab[i].name, Name) == 0) {
 379                 *ret = (void*) (intptr_t) symtab[ i ].value;
 380                 return 1;
 381         }
 382
 383         //DEBUGS(" ElfGetSymbol: Hash of first = 0x%x\n", ElfHashString( symtab[i].name ) % nbuckets);
 384         while(pChains[i] != STN_UNDEF)
 385         {
 386                 //DEBUGS(" pChains[%i] = %i\n", i, pChains[i]);
 387                 i = pChains[i];
 388                 //DEBUGS(" ElfGetSymbol: strcmp(Name, \"%s\")\n", symtab[ i ].name);
 389                 if(symtab[i].shndx != SHN_UNDEF && strcmp(symtab[ i ].name, Name) == 0) {
 390                         //DEBUGS("ElfGetSymbol: RETURN 1, '%s' = 0x%x\n", symtab[ i ].name, symtab[ i ].value);
 391                         *ret = (void*)(intptr_t)symtab[ i ].value;
 392                         return 1;
 393                 }
 394         }
 395
 396         //DEBUGS("ElfGetSymbol: RETURN 0, Symbol '%s' not found\n", Name);
 397         return 0;
 398 }
 399
 400 Uint ElfHashString(char *name)
 401 {
 402         Uint    h = 0, g;
 403         while(*name)
 404         {
 405                 h = (h << 4) + *name++;
 406                 if( (g = h & 0xf0000000) )
 407                         h ^= g >> 24;
 408                 h &= ~g;
 409         }
 410         return h;
 411 }
 412
 413 #if 0
 414 unsigned long elf_hash(const unsigned char *name)
 415 {
 416         unsigned long   h = 0, g;
 417         while (*name)
 418         {
 419                 h = (h << 4) + *name++;
 420                 if (g = h & 0xf0000000)
 421                         h ^= g >> 24;
 422                 h &= ~g;
 423         }
 424         return h;
 425 }
 426 #endif