elf_object.cc revision 3925
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_machine == EM_SPARCV9) { 83 arch = ObjectFile::SPARC; 84 } else if (ehdr.e_machine == EM_MIPS 85 && ehdr.e_ident[EI_CLASS] == ELFCLASS32) { 86 arch = ObjectFile::Mips; 87 } else if (ehdr.e_ident[EI_CLASS] == ELFCLASS64) { 88 arch = ObjectFile::Alpha; 89 } else { 90 warn("Unknown architecture: %d\n", ehdr.e_machine); 91 arch = ObjectFile::UnknownArch; 92 } 93 94 //Detect the operating system 95 switch (ehdr.e_ident[EI_OSABI]) 96 { 97 98 case ELFOSABI_LINUX: 99 opSys = ObjectFile::Linux; 100 break; 101 case ELFOSABI_SOLARIS: 102 opSys = ObjectFile::Solaris; 103 break; 104 case ELFOSABI_TRU64: 105 opSys = ObjectFile::Tru64; 106 break; 107 default: 108 opSys = ObjectFile::UnknownOpSys; 109 } 110 111 //take a look at the .note.ABI section 112 //It can let us know what's what. 113 if (opSys == ObjectFile::UnknownOpSys) { 114 Elf_Scn *section; 115 GElf_Shdr shdr; 116 Elf_Data *data; 117 uint32_t osAbi;; 118 int secIdx = 1; 119 120 // Get the first section 121 section = elf_getscn(elf, secIdx); 122 123 // While there are no more sections 124 while (section != NULL && opSys == ObjectFile::UnknownOpSys) { 125 gelf_getshdr(section, &shdr); 126 if (shdr.sh_type == SHT_NOTE && !strcmp(".note.ABI-tag", 127 elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) { 128 // we have found a ABI note section 129 // Check the 5th 32bit word for OS 0 == linux, 1 == hurd, 130 // 2 == solaris, 3 == freebsd 131 data = elf_rawdata(section, NULL); 132 assert(data->d_buf); 133 if(ehdr.e_ident[EI_DATA] == ELFDATA2LSB) 134 osAbi = htole(((uint32_t*)data->d_buf)[4]); 135 else 136 osAbi = htobe(((uint32_t*)data->d_buf)[4]); 137 138 switch(osAbi) { 139 case 0: 140 opSys = ObjectFile::Linux; 141 break; 142 case 2: 143 opSys = ObjectFile::Solaris; 144 break; 145 } 146 } // if section found 147 if (!strcmp(".SUNW_version", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) 148 opSys = ObjectFile::Solaris; 149 if (!strcmp(".stab.index", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) 150 opSys = ObjectFile::Solaris; 151 152 section = elf_getscn(elf, ++secIdx); 153 } // while sections 154 } 155 156 ElfObject * result = new ElfObject(fname, fd, len, data, arch, opSys); 157 158 //The number of headers in the file 159 result->_programHeaderCount = ehdr.e_phnum; 160 //Record the size of each entry 161 result->_programHeaderSize = ehdr.e_phentsize; 162 if(result->_programHeaderCount) //If there is a program header table 163 { 164 //Figure out the virtual address of the header table in the 165 //final memory image. We use the program headers themselves 166 //to translate from a file offset to the address in the image. 167 GElf_Phdr phdr; 168 uint64_t e_phoff = ehdr.e_phoff; 169 result->_programHeaderTable = 0; 170 for(int hdrnum = 0; hdrnum < result->_programHeaderCount; hdrnum++) 171 { 172 gelf_getphdr(elf, hdrnum, &phdr); 173 //Check if we've found the segment with the headers in it 174 if(phdr.p_offset <= e_phoff && 175 phdr.p_offset + phdr.p_filesz > e_phoff) 176 { 177 result->_programHeaderTable = phdr.p_vaddr + e_phoff; 178 break; 179 } 180 } 181 } 182 else 183 result->_programHeaderTable = 0; 184 185 186 elf_end(elf); 187 return result; 188 } 189} 190 191 192ElfObject::ElfObject(const string &_filename, int _fd, 193 size_t _len, uint8_t *_data, 194 Arch _arch, OpSys _opSys) 195 : ObjectFile(_filename, _fd, _len, _data, _arch, _opSys) 196 197{ 198 Elf *elf; 199 GElf_Ehdr ehdr; 200 201 // check that header matches library version 202 if (elf_version(EV_CURRENT) == EV_NONE) 203 panic("wrong elf version number!"); 204 205 // get a pointer to elf structure 206 elf = elf_memory((char*)fileData,len); 207 // will only fail if fd is invalid 208 assert(elf != NULL); 209 210 // Check that we actually have a elf file 211 if (gelf_getehdr(elf, &ehdr) ==0) { 212 panic("Not ELF, shouldn't be here"); 213 } 214 215 entry = ehdr.e_entry; 216 217 218 // initialize segment sizes to 0 in case they're not present 219 text.size = data.size = bss.size = 0; 220 221 for (int i = 0; i < ehdr.e_phnum; ++i) { 222 GElf_Phdr phdr; 223 if (gelf_getphdr(elf, i, &phdr) == 0) { 224 panic("gelf_getphdr failed for section %d", i); 225 } 226 227 // for now we don't care about non-loadable segments 228 if (!(phdr.p_type & PT_LOAD)) 229 continue; 230 231 // the headers don't explicitly distinguish text from data, 232 // but empirically the text segment comes first. 233 if (text.size == 0) { // haven't seen text segment yet 234 text.baseAddr = phdr.p_vaddr; 235 text.size = phdr.p_filesz; 236 text.fileImage = fileData + phdr.p_offset; 237 // if there's any padding at the end that's not in the 238 // file, call it the bss. This happens in the "text" 239 // segment if there's only one loadable segment (as for 240 // kernel images). 241 bss.size = phdr.p_memsz - phdr.p_filesz; 242 bss.baseAddr = phdr.p_vaddr + phdr.p_filesz; 243 bss.fileImage = NULL; 244 } else if (data.size == 0) { // have text, this must be data 245 data.baseAddr = phdr.p_vaddr; 246 data.size = phdr.p_filesz; 247 data.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. Warn if this happens for both 250 // the text & data segments (should only have one bss). 251 if (phdr.p_memsz - phdr.p_filesz > 0 && bss.size != 0) { 252 warn("Two implied bss segments in file!\n"); 253 } 254 bss.size = phdr.p_memsz - phdr.p_filesz; 255 bss.baseAddr = phdr.p_vaddr + phdr.p_filesz; 256 bss.fileImage = NULL; 257 } else { 258 warn("More than two loadable segments in ELF object."); 259 warn("Ignoring segment @ 0x%x length 0x%x.", 260 phdr.p_vaddr, phdr.p_filesz); 261 } 262 } 263 264 // should have found at least one loadable segment 265 assert(text.size != 0); 266 267 DPRINTFR(Loader, "text: 0x%x %d\ndata: 0x%x %d\nbss: 0x%x %d\n", 268 text.baseAddr, text.size, data.baseAddr, data.size, 269 bss.baseAddr, bss.size); 270 271 elf_end(elf); 272 273 // We will actually read the sections when we need to load them 274} 275 276 277bool 278ElfObject::loadSomeSymbols(SymbolTable *symtab, int binding) 279{ 280 Elf *elf; 281 int sec_idx = 1; // there is a 0 but it is nothing, go figure 282 Elf_Scn *section; 283 GElf_Shdr shdr; 284 Elf_Data *data; 285 int count, ii; 286 bool found = false; 287 GElf_Sym sym; 288 289 if (!symtab) 290 return false; 291 292 // check that header matches library version 293 if (elf_version(EV_CURRENT) == EV_NONE) 294 panic("wrong elf version number!"); 295 296 // get a pointer to elf structure 297 elf = elf_memory((char*)fileData,len); 298 299 assert(elf != NULL); 300 301 // Get the first section 302 section = elf_getscn(elf, sec_idx); 303 304 // While there are no more sections 305 while (section != NULL) { 306 gelf_getshdr(section, &shdr); 307 308 if (shdr.sh_type == SHT_SYMTAB) { 309 found = true; 310 data = elf_getdata(section, NULL); 311 count = shdr.sh_size / shdr.sh_entsize; 312 DPRINTF(Loader, "Found Symbol Table, %d symbols present\n", count); 313 314 // loop through all the symbols, only loading global ones 315 for (ii = 0; ii < count; ++ii) { 316 gelf_getsym(data, ii, &sym); 317 if (GELF_ST_BIND(sym.st_info) == binding) { 318 symtab->insert(sym.st_value, 319 elf_strptr(elf, shdr.sh_link, sym.st_name)); 320 } 321 } 322 } 323 ++sec_idx; 324 section = elf_getscn(elf, sec_idx); 325 } 326 327 elf_end(elf); 328 329 return found; 330} 331 332bool 333ElfObject::loadGlobalSymbols(SymbolTable *symtab, Addr addrMask) 334{ 335 return loadSomeSymbols(symtab, STB_GLOBAL); 336} 337 338bool 339ElfObject::loadLocalSymbols(SymbolTable *symtab, Addr addrMask) 340{ 341 return loadSomeSymbols(symtab, STB_LOCAL); 342} 343 344bool 345ElfObject::isDynamic() 346{ 347 Elf *elf; 348 int sec_idx = 1; // there is a 0 but it is nothing, go figure 349 Elf_Scn *section; 350 GElf_Shdr shdr; 351 352 GElf_Ehdr ehdr; 353 354 // check that header matches library version 355 if (elf_version(EV_CURRENT) == EV_NONE) 356 panic("wrong elf version number!"); 357 358 // get a pointer to elf structure 359 elf = elf_memory((char*)fileData,len); 360 assert(elf != NULL); 361 362 // Check that we actually have a elf file 363 if (gelf_getehdr(elf, &ehdr) ==0) { 364 panic("Not ELF, shouldn't be here"); 365 } 366 367 // Get the first section 368 section = elf_getscn(elf, sec_idx); 369 370 // While there are no more sections 371 while (section != NULL) { 372 gelf_getshdr(section, &shdr); 373 if (!strcmp(".interp", elf_strptr(elf, ehdr.e_shstrndx, shdr.sh_name))) 374 return true; 375 section = elf_getscn(elf, ++sec_idx); 376 } // while sections 377 return false; 378} 379 380 381