3 * ELF Executable Loader Code
\r
10 #define DEBUG_WARN 1
\r
12 // === PROTOTYPES ===
\r
13 tBinary *Elf_Load(int fp);
\r
14 int Elf_Relocate(void *Base);
\r
15 int Elf_GetSymbol(void *Base, const char *Name, Uint *ret);
\r
16 int Elf_Int_DoRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base);
\r
17 Uint Elf_Int_HashString(const char *str);
\r
20 tBinaryType gELF_Info = {
\r
22 0x464C457F, 0xFFFFFFFF, // '\x7FELF'
\r
24 Elf_Load, Elf_Relocate, Elf_GetSymbol
\r
28 tBinary *Elf_Load(int fp)
\r
39 VFS_Read(fp, sizeof(hdr), &hdr);
\r
41 // Check the file type
\r
42 if(hdr.ident[0] != 0x7F || hdr.ident[1] != 'E' || hdr.ident[2] != 'L' || hdr.ident[3] != 'F') {
\r
43 Log_Warning("ELF", "Non-ELF File was passed to the ELF loader");
\r
48 // Check for a program header
\r
49 if(hdr.phoff == 0) {
\r
51 Log_Warning("ELF", "File does not contain a program header (phoff == 0)");
\r
57 // Read Program Header Table
\r
58 phtab = malloc( sizeof(Elf32_Phdr) * hdr.phentcount );
\r
63 LOG("hdr.phoff = 0x%08x", hdr.phoff);
\r
64 VFS_Seek(fp, hdr.phoff, SEEK_SET);
\r
65 VFS_Read(fp, sizeof(Elf32_Phdr)*hdr.phentcount, phtab);
\r
69 LOG("hdr.phentcount = %i", hdr.phentcount);
\r
70 for( i = 0; i < hdr.phentcount; i++ )
\r
72 // Ignore Non-LOAD types
\r
73 if(phtab[i].Type != PT_LOAD)
\r
76 LOG("phtab[%i] = {VAddr:0x%x, MemSize:0x%x}", i, phtab[i].VAddr, phtab[i].MemSize);
\r
79 LOG("iLoadCount = %i", iLoadCount);
\r
81 // Allocate Information Structure
\r
82 ret = malloc( sizeof(tBinary) + sizeof(tBinarySection)*iLoadCount );
\r
84 ret->Entry = hdr.entrypoint;
\r
85 ret->Base = -1; // Set Base to maximum value
\r
86 ret->NumSections = iLoadCount;
\r
87 ret->Interpreter = NULL;
\r
91 for( i = 0; i < hdr.phentcount; i++ )
\r
93 //LOG("phtab[%i].Type = 0x%x", i, phtab[i].Type);
\r
94 LOG("phtab[%i] = {", i);
\r
95 LOG(" .Type = 0x%08x", phtab[i].Type);
\r
96 LOG(" .Offset = 0x%08x", phtab[i].Offset);
\r
97 LOG(" .VAddr = 0x%08x", phtab[i].VAddr);
\r
98 LOG(" .PAddr = 0x%08x", phtab[i].PAddr);
\r
99 LOG(" .FileSize = 0x%08x", phtab[i].FileSize);
\r
100 LOG(" .MemSize = 0x%08x", phtab[i].MemSize);
\r
101 LOG(" .Flags = 0x%08x", phtab[i].Flags);
\r
102 LOG(" .Align = 0x%08x", phtab[i].Align);
\r
104 // Get Interpreter Name
\r
105 if( phtab[i].Type == PT_INTERP )
\r
108 if(ret->Interpreter) continue;
\r
109 tmp = malloc(phtab[i].FileSize);
\r
110 VFS_Seek(fp, phtab[i].Offset, 1);
\r
111 VFS_Read(fp, phtab[i].FileSize, tmp);
\r
112 ret->Interpreter = Binary_RegInterp(tmp);
\r
113 LOG("Interpreter '%s'", tmp);
\r
117 // Ignore non-LOAD types
\r
118 if(phtab[i].Type != PT_LOAD) continue;
\r
121 if(phtab[i].VAddr < ret->Base) ret->Base = phtab[i].VAddr;
\r
123 LOG("phtab[%i] = {VAddr:0x%x,Offset:0x%x,FileSize:0x%x}",
\r
124 i, phtab[i].VAddr, phtab[i].Offset, phtab[i].FileSize);
\r
126 ret->LoadSections[j].Offset = phtab[i].Offset;
\r
127 ret->LoadSections[j].FileSize = phtab[i].FileSize;
\r
128 ret->LoadSections[j].Virtual = phtab[i].VAddr;
\r
129 ret->LoadSections[j].MemSize = phtab[i].MemSize;
\r
130 ret->LoadSections[j].Flags = 0;
\r
131 if( !(phtab[i].Flags & PF_W) )
\r
132 ret->LoadSections[j].Flags |= BIN_SECTFLAG_RO;
\r
133 if( phtab[i].Flags & PF_X )
\r
134 ret->LoadSections[j].Flags |= BIN_SECTFLAG_EXEC;
\r
145 // --- ELF RELOCATION ---
\r
146 // Taken from 'ld-acess.so'
\r
148 \fn int Elf_Relocate(void *Base)
\r
149 \brief Relocates a loaded ELF Executable
\r
151 int Elf_Relocate(void *Base)
\r
153 Elf32_Ehdr *hdr = Base;
\r
155 int i, j; // Counters
\r
157 Uint iRealBase = -1;
\r
161 Elf32_Rel *rel = NULL;
\r
162 Elf32_Rela *rela = NULL;
\r
163 Uint32 *pltgot = NULL;
\r
166 int relSz=0, relEntSz=8;
\r
167 int relaSz=0, relaEntSz=8;
\r
168 int pltSz=0, pltType=0;
\r
169 Elf32_Dyn *dynamicTab = NULL; // Dynamic Table Pointer
\r
170 char *dynstrtab = NULL; // .dynamic String Table
\r
171 Elf32_Sym *dynsymtab = NULL;
\r
174 ENTER("pBase", Base);
\r
176 // Parse Program Header to get Dynamic Table
\r
177 phtab = (void *)( (tVAddr)Base + hdr->phoff );
\r
178 iSegmentCount = hdr->phentcount;
\r
179 for(i = 0; i < iSegmentCount; i ++ )
\r
181 // Determine linked base address
\r
182 if(phtab[i].Type == PT_LOAD && iRealBase > phtab[i].VAddr)
\r
183 iRealBase = phtab[i].VAddr;
\r
185 // Find Dynamic Section
\r
186 if(phtab[i].Type == PT_DYNAMIC) {
\r
188 Log_Warning("ELF", "Elf_Relocate - Multiple PT_DYNAMIC segments\n");
\r
191 dynamicTab = (void *) (tVAddr) phtab[i].VAddr;
\r
192 j = i; // Save Dynamic Table ID
\r
197 // Check if a PT_DYNAMIC segement was found
\r
199 Log_Warning("ELF", "Elf_Relocate: No PT_DYNAMIC segment in image, returning\n");
\r
200 LEAVE('x', hdr->entrypoint);
\r
201 return hdr->entrypoint;
\r
204 // Page Align real base
\r
205 iRealBase &= ~0xFFF;
\r
207 // Adjust "Real" Base
\r
208 iBaseDiff = (Uint)Base - iRealBase;
\r
209 // Adjust Dynamic Table
\r
210 dynamicTab = (void *) ((Uint)dynamicTab + iBaseDiff);
\r
212 // === Get Symbol table and String Table ===
\r
213 for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
\r
215 switch(dynamicTab[j].d_tag)
\r
217 // --- Symbol Table ---
\r
219 dynamicTab[j].d_val += iBaseDiff;
\r
220 dynsymtab = (void*) (tVAddr) dynamicTab[j].d_val;
\r
221 hdr->misc.SymTable = dynamicTab[j].d_val; // Saved in unused bytes of ident
\r
224 // --- String Table ---
\r
226 dynamicTab[j].d_val += iBaseDiff;
\r
227 dynstrtab = (void*) (tVAddr) dynamicTab[j].d_val;
\r
230 // --- Hash Table --
\r
232 dynamicTab[j].d_val += iBaseDiff;
\r
233 iSymCount = ((Uint*)((tVAddr)dynamicTab[j].d_val))[1];
\r
234 hdr->misc.HashTable = dynamicTab[j].d_val; // Saved in unused bytes of ident
\r
239 if( !dynsymtab && iSymCount > 0 ) {
\r
240 Log_Warning("ELF", "Elf_Relocate: No Dynamic symbol table, but count >0");
\r
244 // Alter Symbols to true base
\r
245 for(i = 0; i < iSymCount; i ++)
\r
247 dynsymtab[i].value += iBaseDiff;
\r
248 dynsymtab[i].nameOfs += (Uint)dynstrtab;
\r
249 //LOG("Sym '%s' = 0x%x (relocated)\n", dynsymtab[i].name, dynsymtab[i].value);
\r
252 // === Add to loaded list (can be imported now) ===
\r
253 //Binary_AddLoaded( (Uint)Base );
\r
255 // === Parse Relocation Data ===
\r
256 for( j = 0; dynamicTab[j].d_tag != DT_NULL; j++)
\r
258 switch(dynamicTab[j].d_tag)
\r
260 // --- Shared Library Name ---
\r
262 LOG(".so Name '%s'\n", dynstrtab+dynamicTab[j].d_val);
\r
264 // --- Needed Library ---
\r
266 libPath = dynstrtab + dynamicTab[j].d_val;
\r
267 Log_Notice("ELF", "%p - Required Library '%s' (Ignored in kernel mode)\n", Base, libPath);
\r
270 case DT_PLTGOT: pltgot = (void*)(iBaseDiff+dynamicTab[j].d_val); break;
\r
271 case DT_JMPREL: plt = (void*)(iBaseDiff+dynamicTab[j].d_val); break;
\r
272 case DT_PLTREL: pltType = dynamicTab[j].d_val; break;
\r
273 case DT_PLTRELSZ: pltSz = dynamicTab[j].d_val; break;
\r
275 // --- Relocation ---
\r
276 case DT_REL: rel = (void*)(iBaseDiff + dynamicTab[j].d_val); break;
\r
277 case DT_RELSZ: relSz = dynamicTab[j].d_val; break;
\r
278 case DT_RELENT: relEntSz = dynamicTab[j].d_val; break;
\r
280 case DT_RELA: rela = (void*)(iBaseDiff + dynamicTab[j].d_val); break;
\r
281 case DT_RELASZ: relaSz = dynamicTab[j].d_val; break;
\r
282 case DT_RELAENT: relaEntSz = dynamicTab[j].d_val; break;
\r
286 // Parse Relocation Entries
\r
289 j = relSz / relEntSz;
\r
290 for( i = 0; i < j; i++ )
\r
292 ptr = (void*)(iBaseDiff + rel[i].r_offset);
\r
293 if( !Elf_Int_DoRelocate(rel[i].r_info, ptr, *ptr, dynsymtab, (Uint)Base) ) {
\r
298 // Parse Relocation Entries
\r
301 j = relaSz / relaEntSz;
\r
302 for( i = 0; i < j; i++ )
\r
304 ptr = (void*)(iBaseDiff + rela[i].r_offset);
\r
305 if( !Elf_Int_DoRelocate(rela[i].r_info, ptr, rela[i].r_addend, dynsymtab, (Uint)Base) ) {
\r
311 // === Process PLT (Procedure Linkage Table) ===
\r
314 if(pltType == DT_REL)
\r
316 Elf32_Rel *pltRel = plt;
\r
317 j = pltSz / sizeof(Elf32_Rel);
\r
318 LOG("PLT Rel - plt = %p, pltSz = %i (%i ents)", plt, pltSz, j);
\r
319 for(i = 0; i < j; i++)
\r
321 ptr = (void*)(iBaseDiff + pltRel[i].r_offset);
\r
322 if( !Elf_Int_DoRelocate(pltRel[i].r_info, ptr, *ptr, dynsymtab, (Uint)Base) ) {
\r
329 Elf32_Rela *pltRela = plt;
\r
330 j = pltSz / sizeof(Elf32_Rela);
\r
331 LOG("PLT RelA - plt = %p, pltSz = %i (%i ents)", plt, pltSz, j);
\r
334 ptr = (void*)(iBaseDiff + pltRela[i].r_offset);
\r
335 if( !Elf_Int_DoRelocate(pltRela[i].r_info, ptr, pltRela[i].r_addend, dynsymtab, (Uint)Base) ) {
\r
352 * \fn void Elf_Int_DoRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base)
\r
353 * \brief Performs a relocation
\r
354 * \param r_info Field from relocation entry
\r
355 * \param ptr Pointer to location of relocation
\r
356 * \param addend Value to add to symbol
\r
357 * \param symtab Symbol Table
\r
358 * \param base Base of loaded binary
\r
360 int Elf_Int_DoRelocate(Uint r_info, Uint32 *ptr, Uint32 addend, Elf32_Sym *symtab, Uint base)
\r
363 int type = ELF32_R_TYPE(r_info);
\r
364 int sym = ELF32_R_SYM(r_info);
\r
365 char *sSymName = symtab[sym].name;
\r
367 //LogF("Elf_Int_DoRelocate: (r_info=0x%x, ptr=0x%x, addend=0x%x, .., base=0x%x)\n",
\r
368 // r_info, ptr, addend, base);
\r
372 // Standard 32 Bit Relocation (S+A)
\r
374 if( !Elf_GetSymbol((void*)base, sSymName, &val) ) // Search this binary first
\r
375 if( !Binary_GetSymbol( sSymName, &val ) )
\r
377 LOG("%08x R_386_32 *0x%x += 0x%x('%s')", r_info, ptr, val, sSymName);
\r
378 *ptr = val + addend;
\r
381 // 32 Bit Relocation wrt. Offset (S+A-P)
\r
383 if( !Elf_GetSymbol( (void*)base, sSymName, &val ) )
\r
384 if( !Binary_GetSymbol( sSymName, &val ) )
\r
386 LOG("%08x R_386_PC32 *0x%x = 0x%x + 0x%x('%s') - 0x%x", r_info, ptr, *ptr, val, sSymName, (Uint)ptr );
\r
387 // TODO: Check if it needs the true value of ptr or the compiled value
\r
388 // NOTE: Testing using true value
\r
389 *ptr = val + addend - (Uint)ptr;
\r
392 // Absolute Value of a symbol (S)
\r
393 case R_386_GLOB_DAT:
\r
394 if( !Elf_GetSymbol( (void*)base, sSymName, &val ) )
\r
395 if( !Binary_GetSymbol( sSymName, &val ) )
\r
397 LOG("%08x R_386_GLOB_DAT *0x%x = 0x%x (%s)", r_info, ptr, val, sSymName);
\r
401 // Absolute Value of a symbol (S)
\r
402 case R_386_JMP_SLOT:
\r
403 if( !Elf_GetSymbol( (void*)base, sSymName, &val ) )
\r
404 if( !Binary_GetSymbol( sSymName, &val ) )
\r
406 LOG("%08x R_386_JMP_SLOT *0x%x = 0x%x (%s)", r_info, ptr, val, sSymName);
\r
410 // Base Address (B+A)
\r
411 case R_386_RELATIVE:
\r
412 LOG("%08x R_386_RELATIVE *0x%x = 0x%x + 0x%x", r_info, ptr, base, addend);
\r
413 *ptr = base + addend;
\r
417 LOG("Rel 0x%x: 0x%x,%i", ptr, sym, type);
\r
424 * \fn int Elf_GetSymbol(void *Base, const char *name, Uint *ret)
\r
425 * \brief Get a symbol from the loaded binary
\r
427 int Elf_GetSymbol(void *Base, const char *Name, Uint *ret)
\r
429 Elf32_Ehdr *hdr = (void*)Base;
\r
438 if(!Base) return 0;
\r
440 pBuckets = (void *) hdr->misc.HashTable;
\r
441 symtab = (void *) hdr->misc.SymTable;
\r
443 nbuckets = pBuckets[0];
\r
444 iSymCount = pBuckets[1];
\r
445 pBuckets = &pBuckets[2];
\r
446 pChains = &pBuckets[ nbuckets ];
\r
449 iNameHash = Elf_Int_HashString(Name);
\r
450 iNameHash %= nbuckets;
\r
453 i = pBuckets[ iNameHash ];
\r
454 if(symtab[i].shndx != SHN_UNDEF && strcmp(symtab[i].name, Name) == 0) {
\r
455 if(ret) *ret = symtab[ i ].value;
\r
460 while(pChains[i] != STN_UNDEF)
\r
463 if(symtab[i].shndx != SHN_UNDEF && strcmp(symtab[ i ].name, Name) == 0) {
\r
464 if(ret) *ret = symtab[ i ].value;
\r
472 * \fn Uint Elf_Int_HashString(char *str)
\r
473 * \brief Hash a string in the ELF format
\r
474 * \param str String to hash
\r
475 * \return Hash value
\r
477 Uint Elf_Int_HashString(const char *str)
\r
482 h = (h << 4) + *str++;
\r
483 if( (g = h & 0xf0000000) )
\r