elf_object.cc revision 4166
1/* 2 * Copyright (c) 2003-2005 The Regents of The University of Michigan 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are 7 * met: redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer; 9 * redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution; 12 * neither the name of the copyright holders nor the names of its 13 * contributors may be used to endorse or promote products derived from 14 * this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 * 28 * Authors: Steve Reinhardt 29 * Ali Saidi 30 */ 31 32#include <string> 33 34// Because of the -Wundef flag we have to do this 35#define __LIBELF_INTERNAL__ 0 36#define __LIBELF_NEED_LINK_H 0 37#define __LIBELF_SYMBOL_VERSIONS 0 38 39#include "gelf.h" 40 41#include "base/loader/elf_object.hh" 42#include "base/misc.hh" 43 44#include "base/loader/symtab.hh" 45 46#include "base/trace.hh" // for DPRINTF 47 48#include "sim/byteswap.hh" 49 50 51using namespace std; 52 53ObjectFile * 54ElfObject::tryFile(const string &fname, int fd, size_t len, uint8_t *data) 55{ 56 Elf *elf; 57 GElf_Ehdr ehdr; 58 Arch arch = UnknownArch; 59 OpSys opSys = UnknownOpSys; 60 61 // check that header matches library version 62 if (elf_version(EV_CURRENT) == EV_NONE) 63 panic("wrong elf version number!"); 64 65 // get a pointer to elf structure 66 elf = elf_memory((char*)data,len); 67 // will only fail if fd is invalid 68 assert(elf != NULL); 69 70 // Check that we actually have a elf file 71 if (gelf_getehdr(elf, &ehdr) ==0) { 72 DPRINTFR(Loader, "Not ELF\n"); 73 elf_end(elf); 74 return NULL; 75 } else { 76 //Detect the architecture 77 //Since we don't know how to check for alpha right now, we'll 78 //just assume if it wasn't something else and it's 64 bit, that's 79 //what it must be. 80 if (ehdr.e_machine == EM_SPARC64 || 81 (ehdr.e_machine == EM_SPARC && 82 ehdr.e_ident[EI_CLASS] == ELFCLASS64)|| 83 ehdr.e_machine == EM_SPARCV9) { 84 arch = ObjectFile::SPARC64; 85 } else if (ehdr.e_machine == EM_SPARC32PLUS || 86 (ehdr.e_machine == EM_SPARC && 87 ehdr.e_ident[EI_CLASS] == ELFCLASS32)) { 88 arch = ObjectFile::SPARC32; 89 } else if (ehdr.e_machine == EM_MIPS 90 && ehdr.e_ident[EI_CLASS] == ELFCLASS32) { 91 arch = ObjectFile::Mips; 92 } else if (ehdr.e_machine == EM_X86_64 && 93 ehdr.e_ident[EI_CLASS] == ELFCLASS64) { 94 //In the future, we might want to differentiate between 32 bit 95 //and 64 bit x86 processes in case there are differences in their 96 //initial stack frame. 97 arch = ObjectFile::X86; 98 } else if (ehdr.e_ident[EI_CLASS] == ELFCLASS64) { 99 arch = ObjectFile::Alpha; 100 } else { 101 warn("Unknown architecture: %d\n", ehdr.e_machine); 102 arch = ObjectFile::UnknownArch; 103 } 104 105 //Detect the operating system 106 switch (ehdr.e_ident[EI_OSABI]) 107 { 108 109 case ELFOSABI_LINUX: 110 opSys = ObjectFile::Linux; 111 break; 112 case ELFOSABI_SOLARIS: 113 opSys = ObjectFile::Solaris; 114 break; 115 case ELFOSABI_TRU64: 116 opSys = ObjectFile::Tru64; 117 break; 118 default: 119 opSys = ObjectFile::UnknownOpSys; 120 } 121 122 //take a look at the .note.ABI section 123 //It can let us know what's what. 124 if (opSys == ObjectFile::UnknownOpSys) { 125 Elf_Scn *section; 126 GElf_Shdr shdr; 127 Elf_Data *data; 128 uint32_t osAbi;; 129 int secIdx = 1; 130 131 // Get the first section 132 section = elf_getscn(elf, secIdx); 133 134 // While there are no more sections 135 while (section != NULL && opSys == ObjectFile::UnknownOpSys) { 136 gelf_getshdr(section, &shdr); 137 if (shdr.sh_type == SHT_NOTE && !strcmp(".note.ABI-tag", 138 elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) { 139 // we have found a ABI note section 140 // Check the 5th 32bit word for OS 0 == linux, 1 == hurd, 141 // 2 == solaris, 3 == freebsd 142 data = elf_rawdata(section, NULL); 143 assert(data->d_buf); 144 if(ehdr.e_ident[EI_DATA] == ELFDATA2LSB) 145 osAbi = htole(((uint32_t*)data->d_buf)[4]); 146 else 147 osAbi = htobe(((uint32_t*)data->d_buf)[4]); 148 149 switch(osAbi) { 150 case 0: 151 opSys = ObjectFile::Linux; 152 break; 153 case 2: 154 opSys = ObjectFile::Solaris; 155 break; 156 } 157 } // if section found 158 if (!strcmp(".SUNW_version", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) 159 opSys = ObjectFile::Solaris; 160 if (!strcmp(".stab.index", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) 161 opSys = ObjectFile::Solaris; 162 163 section = elf_getscn(elf, ++secIdx); 164 } // while sections 165 } 166 167 ElfObject * result = new ElfObject(fname, fd, len, data, arch, opSys); 168 169 //The number of headers in the file 170 result->_programHeaderCount = ehdr.e_phnum; 171 //Record the size of each entry 172 result->_programHeaderSize = ehdr.e_phentsize; 173 if(result->_programHeaderCount) //If there is a program header table 174 { 175 //Figure out the virtual address of the header table in the 176 //final memory image. We use the program headers themselves 177 //to translate from a file offset to the address in the image. 178 GElf_Phdr phdr; 179 uint64_t e_phoff = ehdr.e_phoff; 180 result->_programHeaderTable = 0; 181 for(int hdrnum = 0; hdrnum < result->_programHeaderCount; hdrnum++) 182 { 183 gelf_getphdr(elf, hdrnum, &phdr); 184 //Check if we've found the segment with the headers in it 185 if(phdr.p_offset <= e_phoff && 186 phdr.p_offset + phdr.p_filesz > e_phoff) 187 { 188 result->_programHeaderTable = phdr.p_vaddr + e_phoff; 189 break; 190 } 191 } 192 } 193 else 194 result->_programHeaderTable = 0; 195 196 197 elf_end(elf); 198 return result; 199 } 200} 201 202 203ElfObject::ElfObject(const string &_filename, int _fd, 204 size_t _len, uint8_t *_data, 205 Arch _arch, OpSys _opSys) 206 : ObjectFile(_filename, _fd, _len, _data, _arch, _opSys) 207 208{ 209 Elf *elf; 210 GElf_Ehdr ehdr; 211 212 // check that header matches library version 213 if (elf_version(EV_CURRENT) == EV_NONE) 214 panic("wrong elf version number!"); 215 216 // get a pointer to elf structure 217 elf = elf_memory((char*)fileData,len); 218 // will only fail if fd is invalid 219 assert(elf != NULL); 220 221 // Check that we actually have a elf file 222 if (gelf_getehdr(elf, &ehdr) ==0) { 223 panic("Not ELF, shouldn't be here"); 224 } 225 226 entry = ehdr.e_entry; 227 228 229 // initialize segment sizes to 0 in case they're not present 230 text.size = data.size = bss.size = 0; 231 232 for (int i = 0; i < ehdr.e_phnum; ++i) { 233 GElf_Phdr phdr; 234 if (gelf_getphdr(elf, i, &phdr) == 0) { 235 panic("gelf_getphdr failed for section %d", i); 236 } 237 238 // for now we don't care about non-loadable segments 239 if (!(phdr.p_type & PT_LOAD)) 240 continue; 241 242 // the headers don't explicitly distinguish text from data, 243 // but empirically the text segment comes first. 244 if (text.size == 0) { // haven't seen text segment yet 245 text.baseAddr = phdr.p_vaddr; 246 text.size = phdr.p_filesz; 247 text.fileImage = fileData + phdr.p_offset; 248 // if there's any padding at the end that's not in the 249 // file, call it the bss. This happens in the "text" 250 // segment if there's only one loadable segment (as for 251 // kernel images). 252 bss.size = phdr.p_memsz - phdr.p_filesz; 253 bss.baseAddr = phdr.p_vaddr + phdr.p_filesz; 254 bss.fileImage = NULL; 255 } else if (data.size == 0) { // have text, this must be data 256 data.baseAddr = phdr.p_vaddr; 257 data.size = phdr.p_filesz; 258 data.fileImage = fileData + phdr.p_offset; 259 // if there's any padding at the end that's not in the 260 // file, call it the bss. Warn if this happens for both 261 // the text & data segments (should only have one bss). 262 if (phdr.p_memsz - phdr.p_filesz > 0 && bss.size != 0) { 263 warn("Two implied bss segments in file!\n"); 264 } 265 bss.size = phdr.p_memsz - phdr.p_filesz; 266 bss.baseAddr = phdr.p_vaddr + phdr.p_filesz; 267 bss.fileImage = NULL; 268 } else { 269 warn("More than two loadable segments in ELF object."); 270 warn("Ignoring segment @ 0x%x length 0x%x.", 271 phdr.p_vaddr, phdr.p_filesz); 272 } 273 } 274 275 // should have found at least one loadable segment 276 assert(text.size != 0); 277 278 DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n", 279 text.baseAddr, text.size, data.baseAddr, data.size, 280 bss.baseAddr, bss.size); 281 282 elf_end(elf); 283 284 // We will actually read the sections when we need to load them 285} 286 287 288bool 289ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding) 290{ 291 Elf *elf; 292 int sec_idx = 1; // there is a 0 but it is nothing, go figure 293 Elf_Scn *section; 294 GElf_Shdr shdr; 295 Elf_Data *data; 296 int count, ii; 297 bool found = false; 298 GElf_Sym sym; 299 300 if (!symtab) 301 return false; 302 303 // check that header matches library version 304 if (elf_version(EV_CURRENT) == EV_NONE) 305 panic("wrong elf version number!"); 306 307 // get a pointer to elf structure 308 elf = elf_memory((char*)fileData,len); 309 310 assert(elf != NULL); 311 312 // Get the first section 313 section = elf_getscn(elf, sec_idx); 314 315 // While there are no more sections 316 while (section != NULL) { 317 gelf_getshdr(section, &shdr); 318 319 if (shdr.sh_type == SHT_SYMTAB) { 320 found = true; 321 data = elf_getdata(section, NULL); 322 count = shdr.sh_size / shdr.sh_entsize; 323 DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count); 324 325 // loop through all the symbols, only loading global ones 326 for (ii = 0; ii < count; ++ii) { 327 gelf_getsym(data, ii, &sym); 328 if (GELF_ST_BIND(sym.st_info) == binding) { 329 symtab->insert(sym.st_value, 330 elf_strptr(elf, shdr.sh_link, sym.st_name)); 331 } 332 } 333 } 334 ++sec_idx; 335 section = elf_getscn(elf, sec_idx); 336 } 337 338 elf_end(elf); 339 340 return found; 341} 342 343bool 344ElfObject::loadGlobalSymbols(SymbolTable *symtab, Addr addrMask) 345{ 346 return loadSomeSymbols(symtab, STB_GLOBAL); 347} 348 349bool 350ElfObject::loadLocalSymbols(SymbolTable *symtab, Addr addrMask) 351{ 352 return loadSomeSymbols(symtab, STB_LOCAL); 353} 354 355bool 356ElfObject::isDynamic() 357{ 358 Elf *elf; 359 int sec_idx = 1; // there is a 0 but it is nothing, go figure 360 Elf_Scn *section; 361 GElf_Shdr shdr; 362 363 GElf_Ehdr ehdr; 364 365 // check that header matches library version 366 if (elf_version(EV_CURRENT) == EV_NONE) 367 panic("wrong elf version number!"); 368 369 // get a pointer to elf structure 370 elf = elf_memory((char*)fileData,len); 371 assert(elf != NULL); 372 373 // Check that we actually have a elf file 374 if (gelf_getehdr(elf, &ehdr) ==0) { 375 panic("Not ELF, shouldn't be here"); 376 } 377 378 // Get the first section 379 section = elf_getscn(elf, sec_idx); 380 381 // While there are no more sections 382 while (section != NULL) { 383 gelf_getshdr(section, &shdr); 384 if (!strcmp(".interp", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) 385 return true; 386 section = elf_getscn(elf, ++sec_idx); 387 } // while sections 388 return false; 389} 390 391 392