1// ehframe.cc -- handle exception frame sections for gold 2 3// Copyright 2006, 2007, 2008 Free Software Foundation, Inc. 4// Written by Ian Lance Taylor <iant@google.com>. 5 6// This file is part of gold. 7 8// This program is free software; you can redistribute it and/or modify 9// it under the terms of the GNU General Public License as published by 10// the Free Software Foundation; either version 3 of the License, or 11// (at your option) any later version. 12 13// This program is distributed in the hope that it will be useful, 14// but WITHOUT ANY WARRANTY; without even the implied warranty of 15// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16// GNU General Public License for more details. 17 18// You should have received a copy of the GNU General Public License 19// along with this program; if not, write to the Free Software 20// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, 21// MA 02110-1301, USA. 22 23#include "gold.h" 24 25#include <cstring> 26#include <algorithm> 27 28#include "elfcpp.h" 29#include "dwarf.h" 30#include "symtab.h" 31#include "reloc.h" 32#include "ehframe.h" 33 34namespace gold 35{ 36 37// This file handles generation of the exception frame header that 38// gcc's runtime support libraries use to find unwind information at 39// runtime. This file also handles discarding duplicate exception 40// frame information. 41 42// The exception frame header starts with four bytes: 43 44// 0: The version number, currently 1. 45 46// 1: The encoding of the pointer to the exception frames. This can 47// be any DWARF unwind encoding (DW_EH_PE_*). It is normally a 4 48// byte PC relative offset (DW_EH_PE_pcrel | DW_EH_PE_sdata4). 49 50// 2: The encoding of the count of the number of FDE pointers in the 51// lookup table. This can be any DWARF unwind encoding, and in 52// particular can be DW_EH_PE_omit if the count is omitted. It is 53// normally a 4 byte unsigned count (DW_EH_PE_udata4). 54 55// 3: The encoding of the lookup table entries. Currently gcc's 56// libraries will only support DW_EH_PE_datarel | DW_EH_PE_sdata4, 57// which means that the values are 4 byte offsets from the start of 58// the table. 59 60// The exception frame header is followed by a pointer to the contents 61// of the exception frame section (.eh_frame). This pointer is 62// encoded as specified in the byte at offset 1 of the header (i.e., 63// it is normally a 4 byte PC relative offset). 64 65// If there is a lookup table, this is followed by the count of the 66// number of FDE pointers, encoded as specified in the byte at offset 67// 2 of the header (i.e., normally a 4 byte unsigned integer). 68 69// This is followed by the table, which should start at an 4-byte 70// aligned address in memory. Each entry in the table is 8 bytes. 71// Each entry represents an FDE. The first four bytes of each entry 72// are an offset to the starting PC for the FDE. The last four bytes 73// of each entry are an offset to the FDE data. The offsets are from 74// the start of the exception frame header information. The entries 75// are in sorted order by starting PC. 76 77const int eh_frame_hdr_size = 4; 78 79// Construct the exception frame header. 80 81Eh_frame_hdr::Eh_frame_hdr(Output_section* eh_frame_section, 82 const Eh_frame* eh_frame_data) 83 : Output_section_data(4), 84 eh_frame_section_(eh_frame_section), 85 eh_frame_data_(eh_frame_data), 86 fde_offsets_(), 87 any_unrecognized_eh_frame_sections_(false) 88{ 89} 90 91// Set the size of the exception frame header. 92 93void 94Eh_frame_hdr::set_final_data_size() 95{ 96 unsigned int data_size = eh_frame_hdr_size + 4; 97 if (!this->any_unrecognized_eh_frame_sections_) 98 { 99 unsigned int fde_count = this->eh_frame_data_->fde_count(); 100 if (fde_count != 0) 101 data_size += 4 + 8 * fde_count; 102 this->fde_offsets_.reserve(fde_count); 103 } 104 this->set_data_size(data_size); 105} 106 107// Write the data to the flie. 108 109void 110Eh_frame_hdr::do_write(Output_file* of) 111{ 112 switch (parameters->size_and_endianness()) 113 { 114#ifdef HAVE_TARGET_32_LITTLE 115 case Parameters::TARGET_32_LITTLE: 116 this->do_sized_write<32, false>(of); 117 break; 118#endif 119#ifdef HAVE_TARGET_32_BIG 120 case Parameters::TARGET_32_BIG: 121 this->do_sized_write<32, true>(of); 122 break; 123#endif 124#ifdef HAVE_TARGET_64_LITTLE 125 case Parameters::TARGET_64_LITTLE: 126 this->do_sized_write<64, false>(of); 127 break; 128#endif 129#ifdef HAVE_TARGET_64_BIG 130 case Parameters::TARGET_64_BIG: 131 this->do_sized_write<64, true>(of); 132 break; 133#endif 134 default: 135 gold_unreachable(); 136 } 137} 138 139// Write the data to the file with the right endianness. 140 141template<int size, bool big_endian> 142void 143Eh_frame_hdr::do_sized_write(Output_file* of) 144{ 145 const off_t off = this->offset(); 146 const off_t oview_size = this->data_size(); 147 unsigned char* const oview = of->get_output_view(off, oview_size); 148 149 // Version number. 150 oview[0] = 1; 151 152 // Write out a 4 byte PC relative offset to the address of the 153 // .eh_frame section. 154 oview[1] = elfcpp::DW_EH_PE_pcrel | elfcpp::DW_EH_PE_sdata4; 155 uint64_t eh_frame_address = this->eh_frame_section_->address(); 156 uint64_t eh_frame_hdr_address = this->address(); 157 uint64_t eh_frame_offset = (eh_frame_address - 158 (eh_frame_hdr_address + 4)); 159 elfcpp::Swap<32, big_endian>::writeval(oview + 4, eh_frame_offset); 160 161 if (this->any_unrecognized_eh_frame_sections_ 162 || this->fde_offsets_.empty()) 163 { 164 // There are no FDEs, or we didn't recognize the format of the 165 // some of the .eh_frame sections, so we can't write out the 166 // sorted table. 167 oview[2] = elfcpp::DW_EH_PE_omit; 168 oview[3] = elfcpp::DW_EH_PE_omit; 169 170 gold_assert(oview_size == 8); 171 } 172 else 173 { 174 oview[2] = elfcpp::DW_EH_PE_udata4; 175 oview[3] = elfcpp::DW_EH_PE_datarel | elfcpp::DW_EH_PE_sdata4; 176 177 elfcpp::Swap<32, big_endian>::writeval(oview + 8, 178 this->fde_offsets_.size()); 179 180 // We have the offsets of the FDEs in the .eh_frame section. We 181 // couldn't easily get the PC values before, as they depend on 182 // relocations which are, of course, target specific. This code 183 // is run after all those relocations have been applied to the 184 // output file. Here we read the output file again to find the 185 // PC values. Then we sort the list and write it out. 186 187 Fde_addresses<size> fde_addresses(this->fde_offsets_.size()); 188 this->get_fde_addresses<size, big_endian>(of, &this->fde_offsets_, 189 &fde_addresses); 190 191 std::sort(fde_addresses.begin(), fde_addresses.end(), 192 Fde_address_compare<size>()); 193 194 typename elfcpp::Elf_types<size>::Elf_Addr output_address; 195 output_address = this->address(); 196 197 unsigned char* pfde = oview + 12; 198 for (typename Fde_addresses<size>::iterator p = fde_addresses.begin(); 199 p != fde_addresses.end(); 200 ++p) 201 { 202 elfcpp::Swap<32, big_endian>::writeval(pfde, 203 p->first - output_address); 204 elfcpp::Swap<32, big_endian>::writeval(pfde + 4, 205 p->second - output_address); 206 pfde += 8; 207 } 208 209 gold_assert(pfde - oview == oview_size); 210 } 211 212 of->write_output_view(off, oview_size, oview); 213} 214 215// Given the offset FDE_OFFSET of an FDE in the .eh_frame section, and 216// the contents of the .eh_frame section EH_FRAME_CONTENTS, where the 217// FDE's encoding is FDE_ENCODING, return the output address of the 218// FDE's PC. 219 220template<int size, bool big_endian> 221typename elfcpp::Elf_types<size>::Elf_Addr 222Eh_frame_hdr::get_fde_pc( 223 typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address, 224 const unsigned char* eh_frame_contents, 225 section_offset_type fde_offset, 226 unsigned char fde_encoding) 227{ 228 // The FDE starts with a 4 byte length and a 4 byte offset to the 229 // CIE. The PC follows. 230 const unsigned char* p = eh_frame_contents + fde_offset + 8; 231 232 typename elfcpp::Elf_types<size>::Elf_Addr pc; 233 bool is_signed = (fde_encoding & elfcpp::DW_EH_PE_signed) != 0; 234 int pc_size = fde_encoding & 7; 235 if (pc_size == elfcpp::DW_EH_PE_absptr) 236 { 237 if (size == 32) 238 pc_size = elfcpp::DW_EH_PE_udata4; 239 else if (size == 64) 240 pc_size = elfcpp::DW_EH_PE_udata8; 241 else 242 gold_unreachable(); 243 } 244 245 switch (pc_size) 246 { 247 case elfcpp::DW_EH_PE_udata2: 248 pc = elfcpp::Swap<16, big_endian>::readval(p); 249 if (is_signed) 250 pc = (pc ^ 0x8000) - 0x8000; 251 break; 252 253 case elfcpp::DW_EH_PE_udata4: 254 pc = elfcpp::Swap<32, big_endian>::readval(p); 255 if (size > 32 && is_signed) 256 pc = (pc ^ 0x80000000) - 0x80000000; 257 break; 258 259 case elfcpp::DW_EH_PE_udata8: 260 gold_assert(size == 64); 261 pc = elfcpp::Swap_unaligned<64, big_endian>::readval(p); 262 break; 263 264 default: 265 // All other cases were rejected in Eh_frame::read_cie. 266 gold_unreachable(); 267 } 268 269 switch (fde_encoding & 0xf0) 270 { 271 case 0: 272 break; 273 274 case elfcpp::DW_EH_PE_pcrel: 275 pc += eh_frame_address + fde_offset + 8; 276 break; 277 278 default: 279 // If other cases arise, then we have to handle them, or we have 280 // to reject them by returning false in Eh_frame::read_cie. 281 gold_unreachable(); 282 } 283 284 return pc; 285} 286 287// Given an array of FDE offsets in the .eh_frame section, return an 288// array of offsets from the exception frame header to the FDE's 289// output PC and to the output address of the FDE itself. We get the 290// FDE's PC by actually looking in the .eh_frame section we just wrote 291// to the output file. 292 293template<int size, bool big_endian> 294void 295Eh_frame_hdr::get_fde_addresses(Output_file* of, 296 const Fde_offsets* fde_offsets, 297 Fde_addresses<size>* fde_addresses) 298{ 299 typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address; 300 eh_frame_address = this->eh_frame_section_->address(); 301 off_t eh_frame_offset = this->eh_frame_section_->offset(); 302 off_t eh_frame_size = this->eh_frame_section_->data_size(); 303 const unsigned char* eh_frame_contents = of->get_input_view(eh_frame_offset, 304 eh_frame_size); 305 306 for (Fde_offsets::const_iterator p = fde_offsets->begin(); 307 p != fde_offsets->end(); 308 ++p) 309 { 310 typename elfcpp::Elf_types<size>::Elf_Addr fde_pc; 311 fde_pc = this->get_fde_pc<size, big_endian>(eh_frame_address, 312 eh_frame_contents, 313 p->first, p->second); 314 fde_addresses->push_back(fde_pc, eh_frame_address + p->first); 315 } 316 317 of->free_input_view(eh_frame_offset, eh_frame_size, eh_frame_contents); 318} 319 320// Class Fde. 321 322// Write the FDE to OVIEW starting at OFFSET. CIE_OFFSET is the 323// offset of the CIE in OVIEW. FDE_ENCODING is the encoding, from the 324// CIE. ADDRALIGN is the required alignment. Record the FDE pc for 325// EH_FRAME_HDR. Return the new offset. 326 327template<int size, bool big_endian> 328section_offset_type 329Fde::write(unsigned char* oview, section_offset_type offset, 330 unsigned int addralign, section_offset_type cie_offset, 331 unsigned char fde_encoding, Eh_frame_hdr* eh_frame_hdr) 332{ 333 gold_assert((offset & (addralign - 1)) == 0); 334 335 size_t length = this->contents_.length(); 336 337 // We add 8 when getting the aligned length to account for the 338 // length word and the CIE offset. 339 size_t aligned_full_length = align_address(length + 8, addralign); 340 341 // Write the length of the FDE as a 32-bit word. The length word 342 // does not include the four bytes of the length word itself, but it 343 // does include the offset to the CIE. 344 elfcpp::Swap<32, big_endian>::writeval(oview + offset, 345 aligned_full_length - 4); 346 347 // Write the offset to the CIE as a 32-bit word. This is the 348 // difference between the address of the offset word itself and the 349 // CIE address. 350 elfcpp::Swap<32, big_endian>::writeval(oview + offset + 4, 351 offset + 4 - cie_offset); 352 353 // Copy the rest of the FDE. Note that this is run before 354 // relocation processing is done on this section, so the relocations 355 // will later be applied to the FDE data. 356 memcpy(oview + offset + 8, this->contents_.data(), length); 357 358 if (aligned_full_length > length + 8) 359 memset(oview + offset + length + 8, 0, aligned_full_length - (length + 8)); 360 361 // Tell the exception frame header about this FDE. 362 if (eh_frame_hdr != NULL) 363 eh_frame_hdr->record_fde(offset, fde_encoding); 364 365 return offset + aligned_full_length; 366} 367 368// Class Cie. 369 370// Destructor. 371 372Cie::~Cie() 373{ 374 for (std::vector<Fde*>::iterator p = this->fdes_.begin(); 375 p != this->fdes_.end(); 376 ++p) 377 delete *p; 378} 379 380// Set the output offset of a CIE. Return the new output offset. 381 382section_offset_type 383Cie::set_output_offset(section_offset_type output_offset, 384 unsigned int addralign, 385 Merge_map* merge_map) 386{ 387 size_t length = this->contents_.length(); 388 389 // Add 4 for length and 4 for zero CIE identifier tag. 390 length += 8; 391 392 merge_map->add_mapping(this->object_, this->shndx_, this->input_offset_, 393 length, output_offset); 394 395 length = align_address(length, addralign); 396 397 for (std::vector<Fde*>::const_iterator p = this->fdes_.begin(); 398 p != this->fdes_.end(); 399 ++p) 400 { 401 (*p)->add_mapping(output_offset + length, merge_map); 402 403 size_t fde_length = (*p)->length(); 404 fde_length = align_address(fde_length, addralign); 405 length += fde_length; 406 } 407 408 return output_offset + length; 409} 410 411// Write the CIE to OVIEW starting at OFFSET. EH_FRAME_HDR is for FDE 412// recording. Round up the bytes to ADDRALIGN. Return the new 413// offset. 414 415template<int size, bool big_endian> 416section_offset_type 417Cie::write(unsigned char* oview, section_offset_type offset, 418 unsigned int addralign, Eh_frame_hdr* eh_frame_hdr) 419{ 420 gold_assert((offset & (addralign - 1)) == 0); 421 422 section_offset_type cie_offset = offset; 423 424 size_t length = this->contents_.length(); 425 426 // We add 8 when getting the aligned length to account for the 427 // length word and the CIE tag. 428 size_t aligned_full_length = align_address(length + 8, addralign); 429 430 // Write the length of the CIE as a 32-bit word. The length word 431 // does not include the four bytes of the length word itself. 432 elfcpp::Swap<32, big_endian>::writeval(oview + offset, 433 aligned_full_length - 4); 434 435 // Write the tag which marks this as a CIE: a 32-bit zero. 436 elfcpp::Swap<32, big_endian>::writeval(oview + offset + 4, 0); 437 438 // Write out the CIE data. 439 memcpy(oview + offset + 8, this->contents_.data(), length); 440 441 if (aligned_full_length > length + 8) 442 memset(oview + offset + length + 8, 0, aligned_full_length - (length + 8)); 443 444 offset += aligned_full_length; 445 446 // Write out the associated FDEs. 447 unsigned char fde_encoding = this->fde_encoding_; 448 for (std::vector<Fde*>::const_iterator p = this->fdes_.begin(); 449 p != this->fdes_.end(); 450 ++p) 451 offset = (*p)->write<size, big_endian>(oview, offset, addralign, 452 cie_offset, fde_encoding, 453 eh_frame_hdr); 454 455 return offset; 456} 457 458// We track all the CIEs we see, and merge them when possible. This 459// works because each FDE holds an offset to the relevant CIE: we 460// rewrite the FDEs to point to the merged CIE. This is worthwhile 461// because in a typical C++ program many FDEs in many different object 462// files will use the same CIE. 463 464// An equality operator for Cie. 465 466bool 467operator==(const Cie& cie1, const Cie& cie2) 468{ 469 return (cie1.personality_name_ == cie2.personality_name_ 470 && cie1.contents_ == cie2.contents_); 471} 472 473// A less-than operator for Cie. 474 475bool 476operator<(const Cie& cie1, const Cie& cie2) 477{ 478 if (cie1.personality_name_ != cie2.personality_name_) 479 return cie1.personality_name_ < cie2.personality_name_; 480 return cie1.contents_ < cie2.contents_; 481} 482 483// Class Eh_frame. 484 485Eh_frame::Eh_frame() 486 : Output_section_data(Output_data::default_alignment()), 487 eh_frame_hdr_(NULL), 488 cie_offsets_(), 489 unmergeable_cie_offsets_(), 490 merge_map_(), 491 mappings_are_done_(false), 492 final_data_size_(0) 493{ 494} 495 496// Skip an LEB128, updating *PP to point to the next character. 497// Return false if we ran off the end of the string. 498 499bool 500Eh_frame::skip_leb128(const unsigned char** pp, const unsigned char* pend) 501{ 502 const unsigned char* p; 503 for (p = *pp; p < pend; ++p) 504 { 505 if ((*p & 0x80) == 0) 506 { 507 *pp = p + 1; 508 return true; 509 } 510 } 511 return false; 512} 513 514// Add input section SHNDX in OBJECT to an exception frame section. 515// SYMBOLS is the contents of the symbol table section (size 516// SYMBOLS_SIZE), SYMBOL_NAMES is the symbol names section (size 517// SYMBOL_NAMES_SIZE). RELOC_SHNDX is the index of a relocation 518// section applying to SHNDX, or 0 if none, or -1U if more than one. 519// RELOC_TYPE is the type of the reloc section if there is one, either 520// SHT_REL or SHT_RELA. We try to parse the input exception frame 521// data into our data structures. If we can't do it, we return false 522// to mean that the section should be handled as a normal input 523// section. 524 525template<int size, bool big_endian> 526bool 527Eh_frame::add_ehframe_input_section( 528 Sized_relobj<size, big_endian>* object, 529 const unsigned char* symbols, 530 section_size_type symbols_size, 531 const unsigned char* symbol_names, 532 section_size_type symbol_names_size, 533 unsigned int shndx, 534 unsigned int reloc_shndx, 535 unsigned int reloc_type) 536{ 537 // Get the section contents. 538 section_size_type contents_len; 539 const unsigned char* pcontents = object->section_contents(shndx, 540 &contents_len, 541 false); 542 if (contents_len == 0) 543 return false; 544 545 // If this is the marker section for the end of the data, then 546 // return false to force it to be handled as an ordinary input 547 // section. If we don't do this, we won't correctly handle the case 548 // of unrecognized .eh_frame sections. 549 if (contents_len == 4 550 && elfcpp::Swap<32, big_endian>::readval(pcontents) == 0) 551 return false; 552 553 New_cies new_cies; 554 if (!this->do_add_ehframe_input_section(object, symbols, symbols_size, 555 symbol_names, symbol_names_size, 556 shndx, reloc_shndx, 557 reloc_type, pcontents, 558 contents_len, &new_cies)) 559 { 560 if (this->eh_frame_hdr_ != NULL) 561 this->eh_frame_hdr_->found_unrecognized_eh_frame_section(); 562 563 for (New_cies::iterator p = new_cies.begin(); 564 p != new_cies.end(); 565 ++p) 566 delete p->first; 567 568 return false; 569 } 570 571 // Now that we know we are using this section, record any new CIEs 572 // that we found. 573 for (New_cies::const_iterator p = new_cies.begin(); 574 p != new_cies.end(); 575 ++p) 576 { 577 if (p->second) 578 this->cie_offsets_.insert(p->first); 579 else 580 this->unmergeable_cie_offsets_.push_back(p->first); 581 } 582 583 return true; 584} 585 586// The bulk of the implementation of add_ehframe_input_section. 587 588template<int size, bool big_endian> 589bool 590Eh_frame::do_add_ehframe_input_section( 591 Sized_relobj<size, big_endian>* object, 592 const unsigned char* symbols, 593 section_size_type symbols_size, 594 const unsigned char* symbol_names, 595 section_size_type symbol_names_size, 596 unsigned int shndx, 597 unsigned int reloc_shndx, 598 unsigned int reloc_type, 599 const unsigned char* pcontents, 600 section_size_type contents_len, 601 New_cies* new_cies) 602{ 603 typedef typename elfcpp::Elf_types<size>::Elf_Addr Address; 604 Track_relocs<size, big_endian> relocs; 605 606 const unsigned char* p = pcontents; 607 const unsigned char* pend = p + contents_len; 608 609 // Get the contents of the reloc section if any. 610 if (!relocs.initialize(object, reloc_shndx, reloc_type)) 611 return false; 612 613 // Keep track of which CIEs are at which offsets. 614 Offsets_to_cie cies; 615 616 while (p < pend) 617 { 618 if (pend - p < 4) 619 return false; 620 621 // There shouldn't be any relocations here. 622 if (relocs.advance(p + 4 - pcontents) > 0) 623 return false; 624 625 unsigned int len = elfcpp::Swap<32, big_endian>::readval(p); 626 p += 4; 627 if (len == 0) 628 { 629 // We should only find a zero-length entry at the end of the 630 // section. 631 if (p < pend) 632 return false; 633 break; 634 } 635 // We don't support a 64-bit .eh_frame. 636 if (len == 0xffffffff) 637 return false; 638 if (static_cast<unsigned int>(pend - p) < len) 639 return false; 640 641 const unsigned char* const pentend = p + len; 642 643 if (pend - p < 4) 644 return false; 645 if (relocs.advance(p + 4 - pcontents) > 0) 646 return false; 647 648 unsigned int id = elfcpp::Swap<32, big_endian>::readval(p); 649 p += 4; 650 651 if (id == 0) 652 { 653 // CIE. 654 if (!this->read_cie(object, shndx, symbols, symbols_size, 655 symbol_names, symbol_names_size, 656 pcontents, p, pentend, &relocs, &cies, 657 new_cies)) 658 return false; 659 } 660 else 661 { 662 // FDE. 663 if (!this->read_fde(object, shndx, symbols, symbols_size, 664 pcontents, id, p, pentend, &relocs, &cies)) 665 return false; 666 } 667 668 p = pentend; 669 } 670 671 return true; 672} 673 674// Read a CIE. Return false if we can't parse the information. 675 676template<int size, bool big_endian> 677bool 678Eh_frame::read_cie(Sized_relobj<size, big_endian>* object, 679 unsigned int shndx, 680 const unsigned char* symbols, 681 section_size_type symbols_size, 682 const unsigned char* symbol_names, 683 section_size_type symbol_names_size, 684 const unsigned char* pcontents, 685 const unsigned char* pcie, 686 const unsigned char* pcieend, 687 Track_relocs<size, big_endian>* relocs, 688 Offsets_to_cie* cies, 689 New_cies* new_cies) 690{ 691 bool mergeable = true; 692 693 // We need to find the personality routine if there is one, since we 694 // can only merge CIEs which use the same routine. We also need to 695 // find the FDE encoding if there is one, so that we can read the PC 696 // from the FDE. 697 698 const unsigned char* p = pcie; 699 700 if (pcieend - p < 1) 701 return false; 702 unsigned char version = *p++; 703 if (version != 1 && version != 3) 704 return false; 705 706 const unsigned char* paug = p; 707 const void* paugendv = memchr(p, '\0', pcieend - p); 708 const unsigned char* paugend = static_cast<const unsigned char*>(paugendv); 709 if (paugend == NULL) 710 return false; 711 p = paugend + 1; 712 713 if (paug[0] == 'e' && paug[1] == 'h') 714 { 715 // This is a CIE from gcc before version 3.0. We can't merge 716 // these. We can still read the FDEs. 717 mergeable = false; 718 paug += 2; 719 if (*paug != '\0') 720 return false; 721 if (pcieend - p < size / 8) 722 return false; 723 p += size / 8; 724 } 725 726 // Skip the code alignment. 727 if (!skip_leb128(&p, pcieend)) 728 return false; 729 730 // Skip the data alignment. 731 if (!skip_leb128(&p, pcieend)) 732 return false; 733 734 // Skip the return column. 735 if (version == 1) 736 { 737 if (pcieend - p < 1) 738 return false; 739 ++p; 740 } 741 else 742 { 743 if (!skip_leb128(&p, pcieend)) 744 return false; 745 } 746 747 if (*paug == 'z') 748 { 749 ++paug; 750 // Skip the augmentation size. 751 if (!skip_leb128(&p, pcieend)) 752 return false; 753 } 754 755 unsigned char fde_encoding = elfcpp::DW_EH_PE_absptr; 756 int per_offset = -1; 757 while (*paug != '\0') 758 { 759 switch (*paug) 760 { 761 case 'L': // LSDA encoding. 762 if (pcieend - p < 1) 763 return false; 764 ++p; 765 break; 766 767 case 'R': // FDE encoding. 768 if (pcieend - p < 1) 769 return false; 770 fde_encoding = *p; 771 switch (fde_encoding & 7) 772 { 773 case elfcpp::DW_EH_PE_absptr: 774 case elfcpp::DW_EH_PE_udata2: 775 case elfcpp::DW_EH_PE_udata4: 776 case elfcpp::DW_EH_PE_udata8: 777 break; 778 default: 779 // We don't expect to see any other cases here, and 780 // we're not prepared to handle them. 781 return false; 782 } 783 ++p; 784 break; 785 786 case 'S': 787 break; 788 789 case 'P': 790 // Personality encoding. 791 { 792 if (pcieend - p < 1) 793 return false; 794 unsigned char per_encoding = *p; 795 ++p; 796 797 if ((per_encoding & 0x60) == 0x60) 798 return false; 799 unsigned int per_width; 800 switch (per_encoding & 7) 801 { 802 case elfcpp::DW_EH_PE_udata2: 803 per_width = 2; 804 break; 805 case elfcpp::DW_EH_PE_udata4: 806 per_width = 4; 807 break; 808 case elfcpp::DW_EH_PE_udata8: 809 per_width = 8; 810 break; 811 case elfcpp::DW_EH_PE_absptr: 812 per_width = size / 8; 813 break; 814 default: 815 return false; 816 } 817 818 if ((per_encoding & 0xf0) == elfcpp::DW_EH_PE_aligned) 819 { 820 unsigned int len = p - pcie; 821 len += per_width - 1; 822 len &= ~ (per_width - 1); 823 if (static_cast<unsigned int>(pcieend - p) < len) 824 return false; 825 p += len; 826 } 827 828 per_offset = p - pcontents; 829 830 if (static_cast<unsigned int>(pcieend - p) < per_width) 831 return false; 832 p += per_width; 833 } 834 break; 835 836 default: 837 return false; 838 } 839 840 ++paug; 841 } 842 843 const char* personality_name = ""; 844 if (per_offset != -1) 845 { 846 if (relocs->advance(per_offset) > 0) 847 return false; 848 if (relocs->next_offset() != per_offset) 849 return false; 850 851 unsigned int personality_symndx = relocs->next_symndx(); 852 if (personality_symndx == -1U) 853 return false; 854 855 if (personality_symndx < object->local_symbol_count()) 856 { 857 // We can only merge this CIE if the personality routine is 858 // a global symbol. We can still read the FDEs. 859 mergeable = false; 860 } 861 else 862 { 863 const int sym_size = elfcpp::Elf_sizes<size>::sym_size; 864 if (personality_symndx >= symbols_size / sym_size) 865 return false; 866 elfcpp::Sym<size, big_endian> sym(symbols 867 + (personality_symndx * sym_size)); 868 unsigned int name_offset = sym.get_st_name(); 869 if (name_offset >= symbol_names_size) 870 return false; 871 personality_name = (reinterpret_cast<const char*>(symbol_names) 872 + name_offset); 873 } 874 875 int r = relocs->advance(per_offset + 1); 876 gold_assert(r == 1); 877 } 878 879 if (relocs->advance(pcieend - pcontents) > 0) 880 return false; 881 882 Cie cie(object, shndx, (pcie - 8) - pcontents, fde_encoding, 883 personality_name, pcie, pcieend - pcie); 884 Cie* cie_pointer = NULL; 885 if (mergeable) 886 { 887 Cie_offsets::iterator find_cie = this->cie_offsets_.find(&cie); 888 if (find_cie != this->cie_offsets_.end()) 889 cie_pointer = *find_cie; 890 else 891 { 892 // See if we already saw this CIE in this object file. 893 for (New_cies::const_iterator pc = new_cies->begin(); 894 pc != new_cies->end(); 895 ++pc) 896 { 897 if (*(pc->first) == cie) 898 { 899 cie_pointer = pc->first; 900 break; 901 } 902 } 903 } 904 } 905 906 if (cie_pointer == NULL) 907 { 908 cie_pointer = new Cie(cie); 909 new_cies->push_back(std::make_pair(cie_pointer, mergeable)); 910 } 911 else 912 { 913 // We are deleting this CIE. Record that in our mapping from 914 // input sections to the output section. At this point we don't 915 // know for sure that we are doing a special mapping for this 916 // input section, but that's OK--if we don't do a special 917 // mapping, nobody will ever ask for the mapping we add here. 918 this->merge_map_.add_mapping(object, shndx, (pcie - 8) - pcontents, 919 pcieend - (pcie - 8), -1); 920 } 921 922 // Record this CIE plus the offset in the input section. 923 cies->insert(std::make_pair(pcie - pcontents, cie_pointer)); 924 925 return true; 926} 927 928// Read an FDE. Return false if we can't parse the information. 929 930template<int size, bool big_endian> 931bool 932Eh_frame::read_fde(Sized_relobj<size, big_endian>* object, 933 unsigned int shndx, 934 const unsigned char* symbols, 935 section_size_type symbols_size, 936 const unsigned char* pcontents, 937 unsigned int offset, 938 const unsigned char* pfde, 939 const unsigned char* pfdeend, 940 Track_relocs<size, big_endian>* relocs, 941 Offsets_to_cie* cies) 942{ 943 // OFFSET is the distance between the 4 bytes before PFDE to the 944 // start of the CIE. The offset we recorded for the CIE is 8 bytes 945 // after the start of the CIE--after the length and the zero tag. 946 unsigned int cie_offset = (pfde - 4 - pcontents) - offset + 8; 947 Offsets_to_cie::const_iterator pcie = cies->find(cie_offset); 948 if (pcie == cies->end()) 949 return false; 950 Cie* cie = pcie->second; 951 952 // The FDE should start with a reloc to the start of the code which 953 // it describes. 954 if (relocs->advance(pfde - pcontents) > 0) 955 return false; 956 957 if (relocs->next_offset() != pfde - pcontents) 958 return false; 959 960 unsigned int symndx = relocs->next_symndx(); 961 if (symndx == -1U) 962 return false; 963 964 // There can be another reloc in the FDE, if the CIE specifies an 965 // LSDA (language specific data area). We currently don't care. We 966 // will care later if we want to optimize the LSDA from an absolute 967 // pointer to a PC relative offset when generating a shared library. 968 relocs->advance(pfdeend - pcontents); 969 970 unsigned int fde_shndx; 971 const int sym_size = elfcpp::Elf_sizes<size>::sym_size; 972 if (symndx >= symbols_size / sym_size) 973 return false; 974 elfcpp::Sym<size, big_endian> sym(symbols + symndx * sym_size); 975 bool is_ordinary; 976 fde_shndx = object->adjust_sym_shndx(symndx, sym.get_st_shndx(), 977 &is_ordinary); 978 979 if (is_ordinary 980 && fde_shndx != elfcpp::SHN_UNDEF 981 && fde_shndx < object->shnum() 982 && !object->is_section_included(fde_shndx)) 983 { 984 // This FDE applies to a section which we are discarding. We 985 // can discard this FDE. 986 this->merge_map_.add_mapping(object, shndx, (pfde - 8) - pcontents, 987 pfdeend - (pfde - 8), -1); 988 return true; 989 } 990 991 cie->add_fde(new Fde(object, shndx, (pfde - 8) - pcontents, 992 pfde, pfdeend - pfde)); 993 994 return true; 995} 996 997// Return the number of FDEs. 998 999unsigned int 1000Eh_frame::fde_count() const 1001{ 1002 unsigned int ret = 0; 1003 for (Unmergeable_cie_offsets::const_iterator p = 1004 this->unmergeable_cie_offsets_.begin(); 1005 p != this->unmergeable_cie_offsets_.end(); 1006 ++p) 1007 ret += (*p)->fde_count(); 1008 for (Cie_offsets::const_iterator p = this->cie_offsets_.begin(); 1009 p != this->cie_offsets_.end(); 1010 ++p) 1011 ret += (*p)->fde_count(); 1012 return ret; 1013} 1014 1015// Set the final data size. 1016 1017void 1018Eh_frame::set_final_data_size() 1019{ 1020 // We can be called more than once if Layout::set_segment_offsets 1021 // finds a better mapping. We don't want to add all the mappings 1022 // again. 1023 if (this->mappings_are_done_) 1024 { 1025 this->set_data_size(this->final_data_size_); 1026 return; 1027 } 1028 1029 section_offset_type output_offset = 0; 1030 1031 for (Unmergeable_cie_offsets::iterator p = 1032 this->unmergeable_cie_offsets_.begin(); 1033 p != this->unmergeable_cie_offsets_.end(); 1034 ++p) 1035 output_offset = (*p)->set_output_offset(output_offset, 1036 this->addralign(), 1037 &this->merge_map_); 1038 1039 for (Cie_offsets::iterator p = this->cie_offsets_.begin(); 1040 p != this->cie_offsets_.end(); 1041 ++p) 1042 output_offset = (*p)->set_output_offset(output_offset, 1043 this->addralign(), 1044 &this->merge_map_); 1045 1046 this->mappings_are_done_ = true; 1047 this->final_data_size_ = output_offset; 1048 1049 gold_assert((output_offset & (this->addralign() - 1)) == 0); 1050 this->set_data_size(output_offset); 1051} 1052 1053// Return an output offset for an input offset. 1054 1055bool 1056Eh_frame::do_output_offset(const Relobj* object, unsigned int shndx, 1057 section_offset_type offset, 1058 section_offset_type* poutput) const 1059{ 1060 return this->merge_map_.get_output_offset(object, shndx, offset, poutput); 1061} 1062 1063// Return whether this is the merge section for an input section. 1064 1065bool 1066Eh_frame::do_is_merge_section_for(const Relobj* object, 1067 unsigned int shndx) const 1068{ 1069 return this->merge_map_.is_merge_section_for(object, shndx); 1070} 1071 1072// Write the data to the output file. 1073 1074void 1075Eh_frame::do_write(Output_file* of) 1076{ 1077 const off_t offset = this->offset(); 1078 const off_t oview_size = this->data_size(); 1079 unsigned char* const oview = of->get_output_view(offset, oview_size); 1080 1081 switch (parameters->size_and_endianness()) 1082 { 1083#ifdef HAVE_TARGET_32_LITTLE 1084 case Parameters::TARGET_32_LITTLE: 1085 this->do_sized_write<32, false>(oview); 1086 break; 1087#endif 1088#ifdef HAVE_TARGET_32_BIG 1089 case Parameters::TARGET_32_BIG: 1090 this->do_sized_write<32, true>(oview); 1091 break; 1092#endif 1093#ifdef HAVE_TARGET_64_LITTLE 1094 case Parameters::TARGET_64_LITTLE: 1095 this->do_sized_write<64, false>(oview); 1096 break; 1097#endif 1098#ifdef HAVE_TARGET_64_BIG 1099 case Parameters::TARGET_64_BIG: 1100 this->do_sized_write<64, true>(oview); 1101 break; 1102#endif 1103 default: 1104 gold_unreachable(); 1105 } 1106 1107 of->write_output_view(offset, oview_size, oview); 1108} 1109 1110// Write the data to the output file--template version. 1111 1112template<int size, bool big_endian> 1113void 1114Eh_frame::do_sized_write(unsigned char* oview) 1115{ 1116 unsigned int addralign = this->addralign(); 1117 section_offset_type o = 0; 1118 for (Unmergeable_cie_offsets::iterator p = 1119 this->unmergeable_cie_offsets_.begin(); 1120 p != this->unmergeable_cie_offsets_.end(); 1121 ++p) 1122 o = (*p)->write<size, big_endian>(oview, o, addralign, 1123 this->eh_frame_hdr_); 1124 for (Cie_offsets::iterator p = this->cie_offsets_.begin(); 1125 p != this->cie_offsets_.end(); 1126 ++p) 1127 o = (*p)->write<size, big_endian>(oview, o, addralign, 1128 this->eh_frame_hdr_); 1129} 1130 1131#ifdef HAVE_TARGET_32_LITTLE 1132template 1133bool 1134Eh_frame::add_ehframe_input_section<32, false>( 1135 Sized_relobj<32, false>* object, 1136 const unsigned char* symbols, 1137 section_size_type symbols_size, 1138 const unsigned char* symbol_names, 1139 section_size_type symbol_names_size, 1140 unsigned int shndx, 1141 unsigned int reloc_shndx, 1142 unsigned int reloc_type); 1143#endif 1144 1145#ifdef HAVE_TARGET_32_BIG 1146template 1147bool 1148Eh_frame::add_ehframe_input_section<32, true>( 1149 Sized_relobj<32, true>* object, 1150 const unsigned char* symbols, 1151 section_size_type symbols_size, 1152 const unsigned char* symbol_names, 1153 section_size_type symbol_names_size, 1154 unsigned int shndx, 1155 unsigned int reloc_shndx, 1156 unsigned int reloc_type); 1157#endif 1158 1159#ifdef HAVE_TARGET_64_LITTLE 1160template 1161bool 1162Eh_frame::add_ehframe_input_section<64, false>( 1163 Sized_relobj<64, false>* object, 1164 const unsigned char* symbols, 1165 section_size_type symbols_size, 1166 const unsigned char* symbol_names, 1167 section_size_type symbol_names_size, 1168 unsigned int shndx, 1169 unsigned int reloc_shndx, 1170 unsigned int reloc_type); 1171#endif 1172 1173#ifdef HAVE_TARGET_64_BIG 1174template 1175bool 1176Eh_frame::add_ehframe_input_section<64, true>( 1177 Sized_relobj<64, true>* object, 1178 const unsigned char* symbols, 1179 section_size_type symbols_size, 1180 const unsigned char* symbol_names, 1181 section_size_type symbol_names_size, 1182 unsigned int shndx, 1183 unsigned int reloc_shndx, 1184 unsigned int reloc_type); 1185#endif 1186 1187} // End namespace gold. 1188