elf_object.cc revision 4111:65fffcb4fae9
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_ident[EI_CLASS] == ELFCLASS64) { 93 arch = ObjectFile::Alpha; 94 } else { 95 warn("Unknown architecture: %d\n", ehdr.e_machine); 96 arch = ObjectFile::UnknownArch; 97 } 98 99 //Detect the operating system 100 switch (ehdr.e_ident[EI_OSABI]) 101 { 102 103 case ELFOSABI_LINUX: 104 opSys = ObjectFile::Linux; 105 break; 106 case ELFOSABI_SOLARIS: 107 opSys = ObjectFile::Solaris; 108 break; 109 case ELFOSABI_TRU64: 110 opSys = ObjectFile::Tru64; 111 break; 112 default: 113 opSys = ObjectFile::UnknownOpSys; 114 } 115 116 //take a look at the .note.ABI section 117 //It can let us know what's what. 118 if (opSys == ObjectFile::UnknownOpSys) { 119 Elf_Scn *section; 120 GElf_Shdr shdr; 121 Elf_Data *data; 122 uint32_t osAbi;; 123 int secIdx = 1; 124 125 // Get the first section 126 section = elf_getscn(elf, secIdx); 127 128 // While there are no more sections 129 while (section != NULL && opSys == ObjectFile::UnknownOpSys) { 130 gelf_getshdr(section, &shdr); 131 if (shdr.sh_type == SHT_NOTE && !strcmp(".note.ABI-tag", 132 elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) { 133 // we have found a ABI note section 134 // Check the 5th 32bit word for OS 0 == linux, 1 == hurd, 135 // 2 == solaris, 3 == freebsd 136 data = elf_rawdata(section, NULL); 137 assert(data->d_buf); 138 if(ehdr.e_ident[EI_DATA] == ELFDATA2LSB) 139 osAbi = htole(((uint32_t*)data->d_buf)[4]); 140 else 141 osAbi = htobe(((uint32_t*)data->d_buf)[4]); 142 143 switch(osAbi) { 144 case 0: 145 opSys = ObjectFile::Linux; 146 break; 147 case 2: 148 opSys = ObjectFile::Solaris; 149 break; 150 } 151 } // if section found 152 if (!strcmp(".SUNW_version", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) 153 opSys = ObjectFile::Solaris; 154 if (!strcmp(".stab.index", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) 155 opSys = ObjectFile::Solaris; 156 157 section = elf_getscn(elf, ++secIdx); 158 } // while sections 159 } 160 161 ElfObject * result = new ElfObject(fname, fd, len, data, arch, opSys); 162 163 //The number of headers in the file 164 result->_programHeaderCount = ehdr.e_phnum; 165 //Record the size of each entry 166 result->_programHeaderSize = ehdr.e_phentsize; 167 if(result->_programHeaderCount) //If there is a program header table 168 { 169 //Figure out the virtual address of the header table in the 170 //final memory image. We use the program headers themselves 171 //to translate from a file offset to the address in the image. 172 GElf_Phdr phdr; 173 uint64_t e_phoff = ehdr.e_phoff; 174 result->_programHeaderTable = 0; 175 for(int hdrnum = 0; hdrnum < result->_programHeaderCount; hdrnum++) 176 { 177 gelf_getphdr(elf, hdrnum, &phdr); 178 //Check if we've found the segment with the headers in it 179 if(phdr.p_offset <= e_phoff && 180 phdr.p_offset + phdr.p_filesz > e_phoff) 181 { 182 result->_programHeaderTable = phdr.p_vaddr + e_phoff; 183 break; 184 } 185 } 186 } 187 else 188 result->_programHeaderTable = 0; 189 190 191 elf_end(elf); 192 return result; 193 } 194} 195 196 197ElfObject::ElfObject(const string &_filename, int _fd, 198 size_t _len, uint8_t *_data, 199 Arch _arch, OpSys _opSys) 200 : ObjectFile(_filename, _fd, _len, _data, _arch, _opSys) 201 202{ 203 Elf *elf; 204 GElf_Ehdr ehdr; 205 206 // check that header matches library version 207 if (elf_version(EV_CURRENT) == EV_NONE) 208 panic("wrong elf version number!"); 209 210 // get a pointer to elf structure 211 elf = elf_memory((char*)fileData,len); 212 // will only fail if fd is invalid 213 assert(elf != NULL); 214 215 // Check that we actually have a elf file 216 if (gelf_getehdr(elf, &ehdr) ==0) { 217 panic("Not ELF, shouldn't be here"); 218 } 219 220 entry = ehdr.e_entry; 221 222 223 // initialize segment sizes to 0 in case they're not present 224 text.size = data.size = bss.size = 0; 225 226 for (int i = 0; i < ehdr.e_phnum; ++i) { 227 GElf_Phdr phdr; 228 if (gelf_getphdr(elf, i, &phdr) == 0) { 229 panic("gelf_getphdr failed for section %d", i); 230 } 231 232 // for now we don't care about non-loadable segments 233 if (!(phdr.p_type & PT_LOAD)) 234 continue; 235 236 // the headers don't explicitly distinguish text from data, 237 // but empirically the text segment comes first. 238 if (text.size == 0) { // haven't seen text segment yet 239 text.baseAddr = phdr.p_vaddr; 240 text.size = phdr.p_filesz; 241 text.fileImage = fileData + phdr.p_offset; 242 // if there's any padding at the end that's not in the 243 // file, call it the bss. This happens in the "text" 244 // segment if there's only one loadable segment (as for 245 // kernel images). 246 bss.size = phdr.p_memsz - phdr.p_filesz; 247 bss.baseAddr = phdr.p_vaddr + phdr.p_filesz; 248 bss.fileImage = NULL; 249 } else if (data.size == 0) { // have text, this must be data 250 data.baseAddr = phdr.p_vaddr; 251 data.size = phdr.p_filesz; 252 data.fileImage = fileData + phdr.p_offset; 253 // if there's any padding at the end that's not in the 254 // file, call it the bss. Warn if this happens for both 255 // the text & data segments (should only have one bss). 256 if (phdr.p_memsz - phdr.p_filesz > 0 && bss.size != 0) { 257 warn("Two implied bss segments in file!\n"); 258 } 259 bss.size = phdr.p_memsz - phdr.p_filesz; 260 bss.baseAddr = phdr.p_vaddr + phdr.p_filesz; 261 bss.fileImage = NULL; 262 } else { 263 warn("More than two loadable segments in ELF object."); 264 warn("Ignoring segment @ 0x%x length 0x%x.", 265 phdr.p_vaddr, phdr.p_filesz); 266 } 267 } 268 269 // should have found at least one loadable segment 270 assert(text.size != 0); 271 272 DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n", 273 text.baseAddr, text.size, data.baseAddr, data.size, 274 bss.baseAddr, bss.size); 275 276 elf_end(elf); 277 278 // We will actually read the sections when we need to load them 279} 280 281 282bool 283ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding) 284{ 285 Elf *elf; 286 int sec_idx = 1; // there is a 0 but it is nothing, go figure 287 Elf_Scn *section; 288 GElf_Shdr shdr; 289 Elf_Data *data; 290 int count, ii; 291 bool found = false; 292 GElf_Sym sym; 293 294 if (!symtab) 295 return false; 296 297 // check that header matches library version 298 if (elf_version(EV_CURRENT) == EV_NONE) 299 panic("wrong elf version number!"); 300 301 // get a pointer to elf structure 302 elf = elf_memory((char*)fileData,len); 303 304 assert(elf != NULL); 305 306 // Get the first section 307 section = elf_getscn(elf, sec_idx); 308 309 // While there are no more sections 310 while (section != NULL) { 311 gelf_getshdr(section, &shdr); 312 313 if (shdr.sh_type == SHT_SYMTAB) { 314 found = true; 315 data = elf_getdata(section, NULL); 316 count = shdr.sh_size / shdr.sh_entsize; 317 DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count); 318 319 // loop through all the symbols, only loading global ones 320 for (ii = 0; ii < count; ++ii) { 321 gelf_getsym(data, ii, &sym); 322 if (GELF_ST_BIND(sym.st_info) == binding) { 323 symtab->insert(sym.st_value, 324 elf_strptr(elf, shdr.sh_link, sym.st_name)); 325 } 326 } 327 } 328 ++sec_idx; 329 section = elf_getscn(elf, sec_idx); 330 } 331 332 elf_end(elf); 333 334 return found; 335} 336 337bool 338ElfObject::loadGlobalSymbols(SymbolTable *symtab, Addr addrMask) 339{ 340 return loadSomeSymbols(symtab, STB_GLOBAL); 341} 342 343bool 344ElfObject::loadLocalSymbols(SymbolTable *symtab, Addr addrMask) 345{ 346 return loadSomeSymbols(symtab, STB_LOCAL); 347} 348 349bool 350ElfObject::isDynamic() 351{ 352 Elf *elf; 353 int sec_idx = 1; // there is a 0 but it is nothing, go figure 354 Elf_Scn *section; 355 GElf_Shdr shdr; 356 357 GElf_Ehdr ehdr; 358 359 // check that header matches library version 360 if (elf_version(EV_CURRENT) == EV_NONE) 361 panic("wrong elf version number!"); 362 363 // get a pointer to elf structure 364 elf = elf_memory((char*)fileData,len); 365 assert(elf != NULL); 366 367 // Check that we actually have a elf file 368 if (gelf_getehdr(elf, &ehdr) ==0) { 369 panic("Not ELF, shouldn't be here"); 370 } 371 372 // Get the first section 373 section = elf_getscn(elf, sec_idx); 374 375 // While there are no more sections 376 while (section != NULL) { 377 gelf_getshdr(section, &shdr); 378 if (!strcmp(".interp", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) 379 return true; 380 section = elf_getscn(elf, ++sec_idx); 381 } // while sections 382 return false; 383} 384 385 386