elf.c

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