2 * AcessOS 1 - Dynamic Loader
12 # define DEBUGS(v...) SysDebug(v)
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"};
24 void elf_doRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base);
25 Uint ElfHashString(char *name);
29 \fn int ElfRelocate(void *Base, char **envp, char *Filename)
30 \brief Relocates a loaded ELF Executable
32 void *ElfRelocate(void *Base, char **envp, char *Filename)
34 Elf32_Ehdr *hdr = Base;
42 Elf32_Rel *rel = NULL;
43 Elf32_Rela *rela = NULL;
44 Uint32 *pltgot = 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
53 DEBUGS("ElfRelocate: (Base=0x%x)\n", Base);
58 // Parse Program Header to get Dynamic Table
59 phtab = Base + hdr->phoff;
60 iSegmentCount = hdr->phentcount;
61 for(i=0;i<iSegmentCount;i++)
63 // Determine linked base address
64 if(phtab[i].Type == PT_LOAD && iRealBase > phtab[i].VAddr)
65 iRealBase = phtab[i].VAddr;
67 // Find Dynamic Section
68 if(phtab[i].Type == PT_DYNAMIC) {
70 DEBUGS(" WARNING - elf_relocate: Multiple PT_DYNAMIC segments\n");
73 dynamicTab = (void *) (intptr_t) phtab[i].VAddr;
74 j = i; // Save Dynamic Table ID
78 // Page Align real base
80 DEBUGS(" elf_relocate: True Base = 0x%x, Compiled Base = 0x%x\n", Base, iRealBase);
83 iBaseDiff = (intptr_t)Base - iRealBase;
85 hdr->entrypoint += iBaseDiff; // Adjust Entrypoint
87 // Check if a PT_DYNAMIC segement was found
89 SysDebug(" elf_relocate: No PT_DYNAMIC segment in image, returning\n");
90 return (void *)hdr->entrypoint;
93 // Adjust Dynamic Table
94 dynamicTab = (void *)( (intptr_t)dynamicTab + iBaseDiff );
96 // === Get Symbol table and String Table ===
97 for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
99 switch(dynamicTab[j].d_tag)
101 // --- Symbol Table ---
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
109 // --- String Table ---
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);
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
125 if(dynsymtab == NULL) {
126 SysDebug("ld-acess.so - WARNING: No Dynamic Symbol table, returning\n");
127 return (void *) hdr->entrypoint;
130 // Alter Symbols to true base
131 for(i=0;i<iSymCount;i++)
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);
138 // === Add to loaded list (can be imported now) ===
139 AddLoaded( Filename, Base );
141 // === Parse Relocation Data ===
142 DEBUGS(" elf_relocate: dynamicTab = 0x%x\n", dynamicTab);
143 for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
145 switch(dynamicTab[j].d_tag)
147 // --- Shared Library Name ---
149 DEBUGS(" elf_relocate: .so Name '%s'\n", dynstrtab+dynamicTab[j].d_val);
151 // --- Needed Library ---
153 libPath = dynstrtab + dynamicTab[j].d_val;
154 DEBUGS(" Required Library '%s'\n", libPath);
155 if(LoadLibrary(libPath, NULL, envp) == 0) {
157 DEBUGS(" elf_relocate: Unable to load '%s'\n", libPath);
159 SysDebug("Unable to load required library '%s'\n", libPath);
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;
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;
178 // --- Symbol Table ---
180 // --- Hash Table ---
182 // --- String Table ---
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);
195 DEBUGS(" elf_relocate: Beginning Relocation\n");
197 // Parse Relocation Entries
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++ )
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);
210 // Parse Relocation Entries
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++ )
218 ptr = (void*)(iBaseDiff + rela[i].r_offset);
219 elf_doRelocate(rel[i].r_info, ptr, rela[i].r_addend, dynsymtab, iBaseDiff);
223 // === Process PLT (Procedure Linkage Table) ===
227 DEBUGS(" elf_relocate: Relocate PLT, plt=0x%x\n", plt);
228 if(pltType == DT_REL)
230 Elf32_Rel *pltRel = plt;
231 j = pltSz / sizeof(Elf32_Rel);
232 DEBUGS(" elf_relocate: PLT Reloc Type = Rel, %i entries\n", j);
235 ptr = (void*)(iBaseDiff + pltRel[i].r_offset);
236 elf_doRelocate(pltRel[i].r_info, ptr, *ptr, dynsymtab, iRealBase);
241 Elf32_Rela *pltRela = plt;
242 j = pltSz / sizeof(Elf32_Rela);
243 DEBUGS(" elf_relocate: PLT Reloc Type = Rela, %i entries\n", j);
246 ptr = (void*)(iRealBase + pltRela[i].r_offset);
247 elf_doRelocate(pltRela[i].r_info, ptr, pltRela[i].r_addend, dynsymtab, iRealBase);
252 DEBUGS("ElfRelocate: RETURN 0x%x", hdr->entrypoint);
253 return (void*)hdr->entrypoint;
256 void elf_doRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base)
258 int type = ELF32_R_TYPE(r_info);
259 int sym = ELF32_R_SYM(r_info);
263 // Standard 32 Bit Relocation (S+A)
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);
271 // 32 Bit Relocation wrt. Offset (S+A-P)
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);
281 // Absolute Value of a symbol (S)
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);
290 // Base Address (B+A)
292 DEBUGS(" elf_doRelocate: R_386_RELATIVE *0x%x = 0x%x + 0x%x\n", ptr, base, addend);
293 *ptr = base + addend;
297 DEBUGS(" elf_doRelocate: Rel 0x%x: 0x%x,%s\n", ptr, sym, csaR_NAMES[type]);
304 * \fn int ElfGetSymbol(Uint Base, char *name, void **ret)
306 int ElfGetSymbol(void *Base, char *Name, void **ret)
308 Elf32_Ehdr *hdr = Base;
317 //DEBUGS("ElfGetSymbol: (Base=0x%x, Name='%s')\n", Base, Name);
319 // Catch the current executable
321 if( !hdr->misc.HashTable )
324 Elf32_Dyn *dynTab = NULL;
328 phtab = (void*)( Base + hdr->phoff );
329 for( i = 0; i < hdr->phentcount; i ++ )
331 if( phtab[i].Type == PT_DYNAMIC ) {
332 dynTab = (void*)phtab[i].VAddr;
337 SysDebug("ERROR - Unable to find DYNAMIC segment in %p", (void*)Base);
341 for( j = 0; dynTab[j].d_tag != DT_NULL; j++)
343 switch(dynTab[j].d_tag)
345 // --- Symbol Table ---
347 hdr->misc.SymTable = dynTab[j].d_val;
351 hdr->misc.HashTable = dynTab[j].d_val;
358 if( !hdr->misc.SymTable || !hdr->misc.HashTable ) {
362 pBuckets = (void *) (intptr_t) hdr->misc.HashTable;
363 symtab = (void *) (intptr_t) hdr->misc.SymTable;
365 nbuckets = pBuckets[0];
366 iSymCount = pBuckets[1];
367 pBuckets = &pBuckets[2];
368 pChains = &pBuckets[ nbuckets ];
371 iNameHash = ElfHashString(Name);
372 iNameHash %= nbuckets;
373 //DEBUGS(" ElfGetSymbol: iNameHash = 0x%x\n", iNameHash);
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;
383 //DEBUGS(" ElfGetSymbol: Hash of first = 0x%x\n", ElfHashString( symtab[i].name ) % nbuckets);
384 while(pChains[i] != STN_UNDEF)
386 //DEBUGS(" pChains[%i] = %i\n", 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;
396 //DEBUGS("ElfGetSymbol: RETURN 0, Symbol '%s' not found\n", Name);
400 Uint ElfHashString(char *name)
405 h = (h << 4) + *name++;
406 if( (g = h & 0xf0000000) )
414 unsigned long elf_hash(const unsigned char *name)
416 unsigned long h = 0, g;
419 h = (h << 4) + *name++;
420 if (g = h & 0xf0000000)