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Diffstat (limited to 'toolkit/crashreporter/google-breakpad/src/common/dwarf/elf_reader.cc')
| -rw-r--r-- | toolkit/crashreporter/google-breakpad/src/common/dwarf/elf_reader.cc | 1273 |
1 files changed, 0 insertions, 1273 deletions
diff --git a/toolkit/crashreporter/google-breakpad/src/common/dwarf/elf_reader.cc b/toolkit/crashreporter/google-breakpad/src/common/dwarf/elf_reader.cc deleted file mode 100644 index 4135a51a9..000000000 --- a/toolkit/crashreporter/google-breakpad/src/common/dwarf/elf_reader.cc +++ /dev/null @@ -1,1273 +0,0 @@ -// Copyright 2005 Google Inc. All Rights Reserved. -// Author: chatham@google.com (Andrew Chatham) -// Author: satorux@google.com (Satoru Takabayashi) -// -// Code for reading in ELF files. -// -// For information on the ELF format, see -// http://www.x86.org/ftp/manuals/tools/elf.pdf -// -// I also liked: -// http://www.caldera.com/developers/gabi/1998-04-29/contents.html -// -// A note about types: When dealing with the file format, we use types -// like Elf32_Word, but in the public interfaces we treat all -// addresses as uint64. As a result, we should be able to symbolize -// 64-bit binaries from a 32-bit process (which we don't do, -// anyway). size_t should therefore be avoided, except where required -// by things like mmap(). -// -// Although most of this code can deal with arbitrary ELF files of -// either word size, the public ElfReader interface only examines -// files loaded into the current address space, which must all match -// __WORDSIZE. This code cannot handle ELF files with a non-native -// byte ordering. -// -// TODO(chatham): It would be nice if we could accomplish this task -// without using malloc(), so we could use it as the process is dying. - -#ifndef _GNU_SOURCE -#define _GNU_SOURCE // needed for pread() -#endif - -#include <sys/types.h> -#include <sys/stat.h> -#include <sys/mman.h> -#include <unistd.h> -#include <fcntl.h> -#include <string.h> - -#include <algorithm> -#include <map> -#include <string> -#include <vector> -// TODO(saugustine): Add support for compressed debug. -// Also need to add configure tests for zlib. -//#include "zlib.h" - -#include "third_party/musl/include/elf.h" -#include "elf_reader.h" -#include "common/using_std_string.h" - -// EM_AARCH64 is not defined by elf.h of GRTE v3 on x86. -// TODO(dougkwan): Remove this when v17 is retired. -#if !defined(EM_AARCH64) -#define EM_AARCH64 183 /* ARM AARCH64 */ -#endif - -// Map Linux macros to their Apple equivalents. -#if __APPLE__ -#ifndef __LITTLE_ENDIAN -#define __LITTLE_ENDIAN __ORDER_LITTLE_ENDIAN__ -#endif // __LITTLE_ENDIAN -#ifndef __BIG_ENDIAN -#define __BIG_ENDIAN __ORDER_BIG_ENDIAN__ -#endif // __BIG_ENDIAN -#ifndef __BYTE_ORDER -#define __BYTE_ORDER __BYTE_ORDER__ -#endif // __BYTE_ORDER -#endif // __APPLE__ - -// TODO(dthomson): Can be removed once all Java code is using the Google3 -// launcher. We need to avoid processing PLT functions as it causes memory -// fragmentation in malloc, which is fixed in tcmalloc - and if the Google3 -// launcher is used the JVM will then use tcmalloc. b/13735638 -//DEFINE_bool(elfreader_process_dynsyms, true, -// "Activate PLT function processing"); - -using std::vector; - -namespace { - -// The lowest bit of an ARM symbol value is used to indicate a Thumb address. -const int kARMThumbBitOffset = 0; - -// Converts an ARM Thumb symbol value to a true aligned address value. -template <typename T> -T AdjustARMThumbSymbolValue(const T& symbol_table_value) { - return symbol_table_value & ~(1 << kARMThumbBitOffset); -} - -// Names of PLT-related sections. -const char kElfPLTRelSectionName[] = ".rel.plt"; // Use Rel struct. -const char kElfPLTRelaSectionName[] = ".rela.plt"; // Use Rela struct. -const char kElfPLTSectionName[] = ".plt"; -const char kElfDynSymSectionName[] = ".dynsym"; - -const int kX86PLTCodeSize = 0x10; // Size of one x86 PLT function in bytes. -const int kARMPLTCodeSize = 0xc; -const int kAARCH64PLTCodeSize = 0x10; - -const int kX86PLT0Size = 0x10; // Size of the special PLT0 entry. -const int kARMPLT0Size = 0x14; -const int kAARCH64PLT0Size = 0x20; - -// Suffix for PLT functions when it needs to be explicitly identified as such. -const char kPLTFunctionSuffix[] = "@plt"; - -} // namespace - -namespace dwarf2reader { - -template <class ElfArch> class ElfReaderImpl; - -// 32-bit and 64-bit ELF files are processed exactly the same, except -// for various field sizes. Elf32 and Elf64 encompass all of the -// differences between the two formats, and all format-specific code -// in this file is templated on one of them. -class Elf32 { - public: - typedef Elf32_Ehdr Ehdr; - typedef Elf32_Shdr Shdr; - typedef Elf32_Phdr Phdr; - typedef Elf32_Word Word; - typedef Elf32_Sym Sym; - typedef Elf32_Rel Rel; - typedef Elf32_Rela Rela; - - // What should be in the EI_CLASS header. - static const int kElfClass = ELFCLASS32; - - // Given a symbol pointer, return the binding type (eg STB_WEAK). - static char Bind(const Elf32_Sym *sym) { - return ELF32_ST_BIND(sym->st_info); - } - // Given a symbol pointer, return the symbol type (eg STT_FUNC). - static char Type(const Elf32_Sym *sym) { - return ELF32_ST_TYPE(sym->st_info); - } - - // Extract the symbol index from the r_info field of a relocation. - static int r_sym(const Elf32_Word r_info) { - return ELF32_R_SYM(r_info); - } -}; - - -class Elf64 { - public: - typedef Elf64_Ehdr Ehdr; - typedef Elf64_Shdr Shdr; - typedef Elf64_Phdr Phdr; - typedef Elf64_Word Word; - typedef Elf64_Sym Sym; - typedef Elf64_Rel Rel; - typedef Elf64_Rela Rela; - - // What should be in the EI_CLASS header. - static const int kElfClass = ELFCLASS64; - - static char Bind(const Elf64_Sym *sym) { - return ELF64_ST_BIND(sym->st_info); - } - static char Type(const Elf64_Sym *sym) { - return ELF64_ST_TYPE(sym->st_info); - } - static int r_sym(const Elf64_Xword r_info) { - return ELF64_R_SYM(r_info); - } -}; - - -// ElfSectionReader mmaps a section of an ELF file ("section" is ELF -// terminology). The ElfReaderImpl object providing the section header -// must exist for the lifetime of this object. -// -// The motivation for mmaping individual sections of the file is that -// many Google executables are large enough when unstripped that we -// have to worry about running out of virtual address space. -// -// For compressed sections we have no choice but to allocate memory. -template<class ElfArch> -class ElfSectionReader { - public: - ElfSectionReader(const char *name, const string &path, int fd, - const typename ElfArch::Shdr §ion_header) - : contents_aligned_(NULL), - contents_(NULL), - header_(section_header) { - // Back up to the beginning of the page we're interested in. - const size_t additional = header_.sh_offset % getpagesize(); - const size_t offset_aligned = header_.sh_offset - additional; - section_size_ = header_.sh_size; - size_aligned_ = section_size_ + additional; - // If the section has been stripped or is empty, do not attempt - // to process its contents. - if (header_.sh_type == SHT_NOBITS || header_.sh_size == 0) - return; - contents_aligned_ = mmap(NULL, size_aligned_, PROT_READ, MAP_SHARED, - fd, offset_aligned); - // Set where the offset really should begin. - contents_ = reinterpret_cast<char *>(contents_aligned_) + - (header_.sh_offset - offset_aligned); - - // Check for and handle any compressed contents. - //if (strncmp(name, ".zdebug_", strlen(".zdebug_")) == 0) - // DecompressZlibContents(); - // TODO(saugustine): Add support for proposed elf-section flag - // "SHF_COMPRESS". - } - - ~ElfSectionReader() { - if (contents_aligned_ != NULL) - munmap(contents_aligned_, size_aligned_); - else - delete[] contents_; - } - - // Return the section header for this section. - typename ElfArch::Shdr const &header() const { return header_; } - - // Return memory at the given offset within this section. - const char *GetOffset(typename ElfArch::Word bytes) const { - return contents_ + bytes; - } - - const char *contents() const { return contents_; } - size_t section_size() const { return section_size_; } - - private: - // page-aligned file contents - void *contents_aligned_; - // contents as usable by the client. For non-compressed sections, - // pointer within contents_aligned_ to where the section data - // begins; for compressed sections, pointer to the decompressed - // data. - char *contents_; - // size of contents_aligned_ - size_t size_aligned_; - // size of contents. - size_t section_size_; - const typename ElfArch::Shdr header_; -}; - -// An iterator over symbols in a given section. It handles walking -// through the entries in the specified section and mapping symbol -// entries to their names in the appropriate string table (in -// another section). -template<class ElfArch> -class SymbolIterator { - public: - SymbolIterator(ElfReaderImpl<ElfArch> *reader, - typename ElfArch::Word section_type) - : symbol_section_(reader->GetSectionByType(section_type)), - string_section_(NULL), - num_symbols_in_section_(0), - symbol_within_section_(0) { - - // If this section type doesn't exist, leave - // num_symbols_in_section_ as zero, so this iterator is already - // done(). - if (symbol_section_ != NULL) { - num_symbols_in_section_ = symbol_section_->header().sh_size / - symbol_section_->header().sh_entsize; - - // Symbol sections have sh_link set to the section number of - // the string section containing the symbol names. - string_section_ = reader->GetSection(symbol_section_->header().sh_link); - } - } - - // Return true iff we have passed all symbols in this section. - bool done() const { - return symbol_within_section_ >= num_symbols_in_section_; - } - - // Advance to the next symbol in this section. - // REQUIRES: !done() - void Next() { ++symbol_within_section_; } - - // Return a pointer to the current symbol. - // REQUIRES: !done() - const typename ElfArch::Sym *GetSymbol() const { - return reinterpret_cast<const typename ElfArch::Sym*>( - symbol_section_->GetOffset(symbol_within_section_ * - symbol_section_->header().sh_entsize)); - } - - // Return the name of the current symbol, NULL if it has none. - // REQUIRES: !done() - const char *GetSymbolName() const { - int name_offset = GetSymbol()->st_name; - if (name_offset == 0) - return NULL; - return string_section_->GetOffset(name_offset); - } - - int GetCurrentSymbolIndex() const { - return symbol_within_section_; - } - - private: - const ElfSectionReader<ElfArch> *const symbol_section_; - const ElfSectionReader<ElfArch> *string_section_; - int num_symbols_in_section_; - int symbol_within_section_; -}; - - -// Copied from strings/strutil.h. Per chatham, -// this library should not depend on strings. - -static inline bool MyHasSuffixString(const string& str, const string& suffix) { - int len = str.length(); - int suflen = suffix.length(); - return (suflen <= len) && (str.compare(len-suflen, suflen, suffix) == 0); -} - - -// ElfReader loads an ELF binary and can provide information about its -// contents. It is most useful for matching addresses to function -// names. It does not understand debugging formats (eg dwarf2), so it -// can't print line numbers. It takes a path to an elf file and a -// readable file descriptor for that file, which it does not assume -// ownership of. -template<class ElfArch> -class ElfReaderImpl { - public: - explicit ElfReaderImpl(const string &path, int fd) - : path_(path), - fd_(fd), - section_headers_(NULL), - program_headers_(NULL), - opd_section_(NULL), - base_for_text_(0), - plts_supported_(false), - plt_code_size_(0), - plt0_size_(0), - visited_relocation_entries_(false) { - string error; - is_dwp_ = MyHasSuffixString(path, ".dwp"); - ParseHeaders(fd, path); - // Currently we need some extra information for PowerPC64 binaries - // including a way to read the .opd section for function descriptors and a - // way to find the linked base for function symbols. - if (header_.e_machine == EM_PPC64) { - // "opd_section_" must always be checked for NULL before use. - opd_section_ = GetSectionInfoByName(".opd", &opd_info_); - for (unsigned int k = 0u; k < GetNumSections(); ++k) { - const char *name = GetSectionName(section_headers_[k].sh_name); - if (strncmp(name, ".text", strlen(".text")) == 0) { - base_for_text_ = - section_headers_[k].sh_addr - section_headers_[k].sh_offset; - break; - } - } - } - // Turn on PLTs. - if (header_.e_machine == EM_386 || header_.e_machine == EM_X86_64) { - plt_code_size_ = kX86PLTCodeSize; - plt0_size_ = kX86PLT0Size; - plts_supported_ = true; - } else if (header_.e_machine == EM_ARM) { - plt_code_size_ = kARMPLTCodeSize; - plt0_size_ = kARMPLT0Size; - plts_supported_ = true; - } else if (header_.e_machine == EM_AARCH64) { - plt_code_size_ = kAARCH64PLTCodeSize; - plt0_size_ = kAARCH64PLT0Size; - plts_supported_ = true; - } - } - - ~ElfReaderImpl() { - for (unsigned int i = 0u; i < sections_.size(); ++i) - delete sections_[i]; - delete [] section_headers_; - delete [] program_headers_; - } - - // Examine the headers of the file and return whether the file looks - // like an ELF file for this architecture. Takes an already-open - // file descriptor for the candidate file, reading in the prologue - // to see if the ELF file appears to match the current - // architecture. If error is non-NULL, it will be set with a reason - // in case of failure. - static bool IsArchElfFile(int fd, string *error) { - unsigned char header[EI_NIDENT]; - if (pread(fd, header, sizeof(header), 0) != sizeof(header)) { - if (error != NULL) *error = "Could not read header"; - return false; - } - - if (memcmp(header, ELFMAG, SELFMAG) != 0) { - if (error != NULL) *error = "Missing ELF magic"; - return false; - } - - if (header[EI_CLASS] != ElfArch::kElfClass) { - if (error != NULL) *error = "Different word size"; - return false; - } - - int endian = 0; - if (header[EI_DATA] == ELFDATA2LSB) - endian = __LITTLE_ENDIAN; - else if (header[EI_DATA] == ELFDATA2MSB) - endian = __BIG_ENDIAN; - if (endian != __BYTE_ORDER) { - if (error != NULL) *error = "Different byte order"; - return false; - } - - return true; - } - - // Return true if we can use this symbol in Address-to-Symbol map. - bool CanUseSymbol(const char *name, const typename ElfArch::Sym *sym) { - // For now we only save FUNC and NOTYPE symbols. For now we just - // care about functions, but some functions written in assembler - // don't have a proper ELF type attached to them, so we store - // NOTYPE symbols as well. The remaining significant type is - // OBJECT (eg global variables), which represent about 25% of - // the symbols in a typical google3 binary. - if (ElfArch::Type(sym) != STT_FUNC && - ElfArch::Type(sym) != STT_NOTYPE) { - return false; - } - - // Target specific filtering. - switch (header_.e_machine) { - case EM_AARCH64: - case EM_ARM: - // Filter out '$x' special local symbols used by tools - return name[0] != '$' || ElfArch::Bind(sym) != STB_LOCAL; - case EM_X86_64: - // Filter out read-only constants like .LC123. - return name[0] != '.' || ElfArch::Bind(sym) != STB_LOCAL; - default: - return true; - } - } - - // Iterate over the symbols in a section, either SHT_DYNSYM or - // SHT_SYMTAB. Add all symbols to the given SymbolMap. - /* - void GetSymbolPositions(SymbolMap *symbols, - typename ElfArch::Word section_type, - uint64 mem_offset, - uint64 file_offset) { - // This map is used to filter out "nested" functions. - // See comment below. - AddrToSymMap addr_to_sym_map; - for (SymbolIterator<ElfArch> it(this, section_type); - !it.done(); it.Next()) { - const char *name = it.GetSymbolName(); - if (name == NULL) - continue; - const typename ElfArch::Sym *sym = it.GetSymbol(); - if (CanUseSymbol(name, sym)) { - const int sec = sym->st_shndx; - - // We don't support special section indices. The most common - // is SHN_ABS, for absolute symbols used deep in the bowels of - // glibc. Also ignore any undefined symbols. - if (sec == SHN_UNDEF || - (sec >= SHN_LORESERVE && sec <= SHN_HIRESERVE)) { - continue; - } - - const typename ElfArch::Shdr& hdr = section_headers_[sec]; - - // Adjust for difference between where we expected to mmap - // this section, and where it was actually mmapped. - const int64 expected_base = hdr.sh_addr - hdr.sh_offset; - const int64 real_base = mem_offset - file_offset; - const int64 adjust = real_base - expected_base; - - uint64 start = sym->st_value + adjust; - - // Adjust function symbols for PowerPC64 by dereferencing and adjusting - // the function descriptor to get the function address. - if (header_.e_machine == EM_PPC64 && ElfArch::Type(sym) == STT_FUNC) { - const uint64 opd_addr = - AdjustPPC64FunctionDescriptorSymbolValue(sym->st_value); - // Only adjust the returned value if the function address was found. - if (opd_addr != sym->st_value) { - const int64 adjust_function_symbols = - real_base - base_for_text_; - start = opd_addr + adjust_function_symbols; - } - } - - addr_to_sym_map.push_back(std::make_pair(start, sym)); - } - } - std::sort(addr_to_sym_map.begin(), addr_to_sym_map.end(), &AddrToSymSorter); - addr_to_sym_map.erase(std::unique(addr_to_sym_map.begin(), - addr_to_sym_map.end(), &AddrToSymEquals), - addr_to_sym_map.end()); - - // Squeeze out any "nested functions". - // Nested functions are not allowed in C, but libc plays tricks. - // - // For example, here is disassembly of /lib64/tls/libc-2.3.5.so: - // 0x00000000000aa380 <read+0>: cmpl $0x0,0x2781b9(%rip) - // 0x00000000000aa387 <read+7>: jne 0xaa39b <read+27> - // 0x00000000000aa389 <__read_nocancel+0>: mov $0x0,%rax - // 0x00000000000aa390 <__read_nocancel+7>: syscall - // 0x00000000000aa392 <__read_nocancel+9>: cmp $0xfffffffffffff001,%rax - // 0x00000000000aa398 <__read_nocancel+15>: jae 0xaa3ef <read+111> - // 0x00000000000aa39a <__read_nocancel+17>: retq - // 0x00000000000aa39b <read+27>: sub $0x28,%rsp - // 0x00000000000aa39f <read+31>: mov %rdi,0x8(%rsp) - // ... - // Without removing __read_nocancel, symbolizer will return NULL - // given e.g. 0xaa39f (because the lower bound is __read_nocancel, - // but 0xaa39f is beyond its end. - if (addr_to_sym_map.empty()) { - return; - } - const ElfSectionReader<ElfArch> *const symbol_section = - this->GetSectionByType(section_type); - const ElfSectionReader<ElfArch> *const string_section = - this->GetSection(symbol_section->header().sh_link); - - typename AddrToSymMap::iterator curr = addr_to_sym_map.begin(); - // Always insert the first symbol. - symbols->AddSymbol(string_section->GetOffset(curr->second->st_name), - curr->first, curr->second->st_size); - typename AddrToSymMap::iterator prev = curr++; - for (; curr != addr_to_sym_map.end(); ++curr) { - const uint64 prev_addr = prev->first; - const uint64 curr_addr = curr->first; - const typename ElfArch::Sym *const prev_sym = prev->second; - const typename ElfArch::Sym *const curr_sym = curr->second; - if (prev_addr + prev_sym->st_size <= curr_addr || - // The next condition is true if two symbols overlap like this: - // - // Previous symbol |----------------------------| - // Current symbol |-------------------------------| - // - // These symbols are not found in google3 codebase, but in - // jdk1.6.0_01_gg1/jre/lib/i386/server/libjvm.so. - // - // 0619e040 00000046 t CardTableModRefBS::write_region_work() - // 0619e070 00000046 t CardTableModRefBS::write_ref_array_work() - // - // We allow overlapped symbols rather than ignore these. - // Due to the way SymbolMap::GetSymbolAtPosition() works, - // lookup for any address in [curr_addr, curr_addr + its size) - // (e.g. 0619e071) will produce the current symbol, - // which is the desired outcome. - prev_addr + prev_sym->st_size < curr_addr + curr_sym->st_size) { - const char *name = string_section->GetOffset(curr_sym->st_name); - symbols->AddSymbol(name, curr_addr, curr_sym->st_size); - prev = curr; - } else { - // Current symbol is "nested" inside previous one like this: - // - // Previous symbol |----------------------------| - // Current symbol |---------------------| - // - // This happens within glibc, e.g. __read_nocancel is nested - // "inside" __read. Ignore "inner" symbol. - //DCHECK_LE(curr_addr + curr_sym->st_size, - // prev_addr + prev_sym->st_size); - ; - } - } - } -*/ - - void VisitSymbols(typename ElfArch::Word section_type, - ElfReader::SymbolSink *sink) { - VisitSymbols(section_type, sink, -1, -1, false); - } - - void VisitSymbols(typename ElfArch::Word section_type, - ElfReader::SymbolSink *sink, - int symbol_binding, - int symbol_type, - bool get_raw_symbol_values) { - for (SymbolIterator<ElfArch> it(this, section_type); - !it.done(); it.Next()) { - const char *name = it.GetSymbolName(); - if (!name) continue; - const typename ElfArch::Sym *sym = it.GetSymbol(); - if ((symbol_binding < 0 || ElfArch::Bind(sym) == symbol_binding) && - (symbol_type < 0 || ElfArch::Type(sym) == symbol_type)) { - typename ElfArch::Sym symbol = *sym; - // Add a PLT symbol in addition to the main undefined symbol. - // Only do this for SHT_DYNSYM, because PLT symbols are dynamic. - int symbol_index = it.GetCurrentSymbolIndex(); - // TODO(dthomson): Can be removed once all Java code is using the - // Google3 launcher. - if (section_type == SHT_DYNSYM && - static_cast<unsigned int>(symbol_index) < symbols_plt_offsets_.size() && - symbols_plt_offsets_[symbol_index] != 0) { - string plt_name = string(name) + kPLTFunctionSuffix; - if (plt_function_names_[symbol_index].empty()) { - plt_function_names_[symbol_index] = plt_name; - } else if (plt_function_names_[symbol_index] != plt_name) { - ; - } - sink->AddSymbol(plt_function_names_[symbol_index].c_str(), - symbols_plt_offsets_[it.GetCurrentSymbolIndex()], - plt_code_size_); - } - if (!get_raw_symbol_values) - AdjustSymbolValue(&symbol); - sink->AddSymbol(name, symbol.st_value, symbol.st_size); - } - } - } - - void VisitRelocationEntries() { - if (visited_relocation_entries_) { - return; - } - visited_relocation_entries_ = true; - - if (!plts_supported_) { - return; - } - // First determine if PLTs exist. If not, then there is nothing to do. - ElfReader::SectionInfo plt_section_info; - const char* plt_section = - GetSectionInfoByName(kElfPLTSectionName, &plt_section_info); - if (!plt_section) { - return; - } - if (plt_section_info.size == 0) { - return; - } - - // The PLTs could be referenced by either a Rel or Rela (Rel with Addend) - // section. - ElfReader::SectionInfo rel_section_info; - ElfReader::SectionInfo rela_section_info; - const char* rel_section = - GetSectionInfoByName(kElfPLTRelSectionName, &rel_section_info); - const char* rela_section = - GetSectionInfoByName(kElfPLTRelaSectionName, &rela_section_info); - - const typename ElfArch::Rel* rel = - reinterpret_cast<const typename ElfArch::Rel*>(rel_section); - const typename ElfArch::Rela* rela = - reinterpret_cast<const typename ElfArch::Rela*>(rela_section); - - if (!rel_section && !rela_section) { - return; - } - - // Use either Rel or Rela section, depending on which one exists. - size_t section_size = rel_section ? rel_section_info.size - : rela_section_info.size; - size_t entry_size = rel_section ? sizeof(typename ElfArch::Rel) - : sizeof(typename ElfArch::Rela); - - // Determine the number of entries in the dynamic symbol table. - ElfReader::SectionInfo dynsym_section_info; - const char* dynsym_section = - GetSectionInfoByName(kElfDynSymSectionName, &dynsym_section_info); - // The dynsym section might not exist, or it might be empty. In either case - // there is nothing to be done so return. - if (!dynsym_section || dynsym_section_info.size == 0) { - return; - } - size_t num_dynamic_symbols = - dynsym_section_info.size / dynsym_section_info.entsize; - symbols_plt_offsets_.resize(num_dynamic_symbols, 0); - - // TODO(dthomson): Can be removed once all Java code is using the - // Google3 launcher. - // Make storage room for PLT function name strings. - plt_function_names_.resize(num_dynamic_symbols); - - for (size_t i = 0; i < section_size / entry_size; ++i) { - // Determine symbol index from the |r_info| field. - int sym_index = ElfArch::r_sym(rel_section ? rel[i].r_info - : rela[i].r_info); - if (static_cast<unsigned int>(sym_index) >= symbols_plt_offsets_.size()) { - continue; - } - symbols_plt_offsets_[sym_index] = - plt_section_info.addr + plt0_size_ + i * plt_code_size_; - } - } - - // Return an ElfSectionReader for the first section of the given - // type by iterating through all section headers. Returns NULL if - // the section type is not found. - const ElfSectionReader<ElfArch> *GetSectionByType( - typename ElfArch::Word section_type) { - for (unsigned int k = 0u; k < GetNumSections(); ++k) { - if (section_headers_[k].sh_type == section_type) { - return GetSection(k); - } - } - return NULL; - } - - // Return the name of section "shndx". Returns NULL if the section - // is not found. - const char *GetSectionNameByIndex(int shndx) { - return GetSectionName(section_headers_[shndx].sh_name); - } - - // Return a pointer to section "shndx", and store the size in - // "size". Returns NULL if the section is not found. - const char *GetSectionContentsByIndex(int shndx, size_t *size) { - const ElfSectionReader<ElfArch> *section = GetSection(shndx); - if (section != NULL) { - *size = section->section_size(); - return section->contents(); - } - return NULL; - } - - // Return a pointer to the first section of the given name by - // iterating through all section headers, and store the size in - // "size". Returns NULL if the section name is not found. - const char *GetSectionContentsByName(const string §ion_name, - size_t *size) { - for (unsigned int k = 0u; k < GetNumSections(); ++k) { - // When searching for sections in a .dwp file, the sections - // we're looking for will always be at the end of the section - // table, so reverse the direction of iteration. - int shndx = is_dwp_ ? GetNumSections() - k - 1 : k; - const char *name = GetSectionName(section_headers_[shndx].sh_name); - if (name != NULL && ElfReader::SectionNamesMatch(section_name, name)) { - const ElfSectionReader<ElfArch> *section = GetSection(shndx); - if (section == NULL) { - return NULL; - } else { - *size = section->section_size(); - return section->contents(); - } - } - } - return NULL; - } - - // This is like GetSectionContentsByName() but it returns a lot of extra - // information about the section. - const char *GetSectionInfoByName(const string §ion_name, - ElfReader::SectionInfo *info) { - for (unsigned int k = 0u; k < GetNumSections(); ++k) { - // When searching for sections in a .dwp file, the sections - // we're looking for will always be at the end of the section - // table, so reverse the direction of iteration. - int shndx = is_dwp_ ? GetNumSections() - k - 1 : k; - const char *name = GetSectionName(section_headers_[shndx].sh_name); - if (name != NULL && ElfReader::SectionNamesMatch(section_name, name)) { - const ElfSectionReader<ElfArch> *section = GetSection(shndx); - if (section == NULL) { - return NULL; - } else { - info->type = section->header().sh_type; - info->flags = section->header().sh_flags; - info->addr = section->header().sh_addr; - info->offset = section->header().sh_offset; - info->size = section->header().sh_size; - info->link = section->header().sh_link; - info->info = section->header().sh_info; - info->addralign = section->header().sh_addralign; - info->entsize = section->header().sh_entsize; - return section->contents(); - } - } - } - return NULL; - } - - // p_vaddr of the first PT_LOAD segment (if any), or 0 if no PT_LOAD - // segments are present. This is the address an ELF image was linked - // (by static linker) to be loaded at. Usually (but not always) 0 for - // shared libraries and position-independent executables. - uint64 VaddrOfFirstLoadSegment() const { - // Relocatable objects (of type ET_REL) do not have LOAD segments. - if (header_.e_type == ET_REL) { - return 0; - } - for (int i = 0; i < GetNumProgramHeaders(); ++i) { - if (program_headers_[i].p_type == PT_LOAD) { - return program_headers_[i].p_vaddr; - } - } - return 0; - } - - // According to the LSB ("ELF special sections"), sections with debug - // info are prefixed by ".debug". The names are not specified, but they - // look like ".debug_line", ".debug_info", etc. - bool HasDebugSections() { - // Debug sections are likely to be near the end, so reverse the - // direction of iteration. - for (int k = GetNumSections() - 1; k >= 0; --k) { - const char *name = GetSectionName(section_headers_[k].sh_name); - if (strncmp(name, ".debug", strlen(".debug")) == 0) return true; - if (strncmp(name, ".zdebug", strlen(".zdebug")) == 0) return true; - } - return false; - } - - bool IsDynamicSharedObject() const { - return header_.e_type == ET_DYN; - } - - // Return the number of sections. - uint64_t GetNumSections() const { - if (HasManySections()) - return first_section_header_.sh_size; - return header_.e_shnum; - } - - private: - typedef vector<pair<uint64, const typename ElfArch::Sym *> > AddrToSymMap; - - static bool AddrToSymSorter(const typename AddrToSymMap::value_type& lhs, - const typename AddrToSymMap::value_type& rhs) { - return lhs.first < rhs.first; - } - - static bool AddrToSymEquals(const typename AddrToSymMap::value_type& lhs, - const typename AddrToSymMap::value_type& rhs) { - return lhs.first == rhs.first; - } - - // Does this ELF file have too many sections to fit in the program header? - bool HasManySections() const { - return header_.e_shnum == SHN_UNDEF; - } - - // Return the number of program headers. - int GetNumProgramHeaders() const { - if (HasManySections() && header_.e_phnum == 0xffff && - first_section_header_.sh_info != 0) - return first_section_header_.sh_info; - return header_.e_phnum; - } - - // Return the index of the string table. - int GetStringTableIndex() const { - if (HasManySections()) { - if (header_.e_shstrndx == 0xffff) - return first_section_header_.sh_link; - else if (header_.e_shstrndx >= GetNumSections()) - return 0; - } - return header_.e_shstrndx; - } - - // Given an offset into the section header string table, return the - // section name. - const char *GetSectionName(typename ElfArch::Word sh_name) { - const ElfSectionReader<ElfArch> *shstrtab = - GetSection(GetStringTableIndex()); - if (shstrtab != NULL) { - return shstrtab->GetOffset(sh_name); - } - return NULL; - } - - // Return an ElfSectionReader for the given section. The reader will - // be freed when this object is destroyed. - const ElfSectionReader<ElfArch> *GetSection(int num) { - const char *name; - // Hard-coding the name for the section-name string table prevents - // infinite recursion. - if (num == GetStringTableIndex()) - name = ".shstrtab"; - else - name = GetSectionNameByIndex(num); - ElfSectionReader<ElfArch> *& reader = sections_[num]; - if (reader == NULL) - reader = new ElfSectionReader<ElfArch>(name, path_, fd_, - section_headers_[num]); - return reader; - } - - // Parse out the overall header information from the file and assert - // that it looks sane. This contains information like the magic - // number and target architecture. - bool ParseHeaders(int fd, const string &path) { - // Read in the global ELF header. - if (pread(fd, &header_, sizeof(header_), 0) != sizeof(header_)) { - return false; - } - - // Must be an executable, dynamic shared object or relocatable object - if (header_.e_type != ET_EXEC && - header_.e_type != ET_DYN && - header_.e_type != ET_REL) { - return false; - } - // Need a section header. - if (header_.e_shoff == 0) { - return false; - } - - if (header_.e_shnum == SHN_UNDEF) { - // The number of sections in the program header is only a 16-bit value. In - // the event of overflow (greater than SHN_LORESERVE sections), e_shnum - // will read SHN_UNDEF and the true number of section header table entries - // is found in the sh_size field of the first section header. - // See: http://www.sco.com/developers/gabi/2003-12-17/ch4.sheader.html - if (pread(fd, &first_section_header_, sizeof(first_section_header_), - header_.e_shoff) != sizeof(first_section_header_)) { - return false; - } - } - - // Dynamically allocate enough space to store the section headers - // and read them out of the file. - const int section_headers_size = - GetNumSections() * sizeof(*section_headers_); - section_headers_ = new typename ElfArch::Shdr[section_headers_size]; - if (pread(fd, section_headers_, section_headers_size, header_.e_shoff) != - section_headers_size) { - return false; - } - - // Dynamically allocate enough space to store the program headers - // and read them out of the file. - //const int program_headers_size = - // GetNumProgramHeaders() * sizeof(*program_headers_); - program_headers_ = new typename ElfArch::Phdr[GetNumProgramHeaders()]; - - // Presize the sections array for efficiency. - sections_.resize(GetNumSections(), NULL); - return true; - } - - // Given the "value" of a function descriptor return the address of the - // function (i.e. the dereferenced value). Otherwise return "value". - uint64 AdjustPPC64FunctionDescriptorSymbolValue(uint64 value) { - if (opd_section_ != NULL && - opd_info_.addr <= value && - value < opd_info_.addr + opd_info_.size) { - uint64 offset = value - opd_info_.addr; - return (*reinterpret_cast<const uint64*>(opd_section_ + offset)); - } - return value; - } - - void AdjustSymbolValue(typename ElfArch::Sym* sym) { - switch (header_.e_machine) { - case EM_ARM: - // For ARM architecture, if the LSB of the function symbol offset is set, - // it indicates a Thumb function. This bit should not be taken literally. - // Clear it. - if (ElfArch::Type(sym) == STT_FUNC) - sym->st_value = AdjustARMThumbSymbolValue(sym->st_value); - break; - case EM_386: - // No adjustment needed for Intel x86 architecture. However, explicitly - // define this case as we use it quite often. - break; - case EM_PPC64: - // PowerPC64 currently has function descriptors as part of the ABI. - // Function symbols need to be adjusted accordingly. - if (ElfArch::Type(sym) == STT_FUNC) - sym->st_value = AdjustPPC64FunctionDescriptorSymbolValue(sym->st_value); - break; - default: - break; - } - } - - friend class SymbolIterator<ElfArch>; - - // The file we're reading. - const string path_; - // Open file descriptor for path_. Not owned by this object. - const int fd_; - - // The global header of the ELF file. - typename ElfArch::Ehdr header_; - - // The header of the first section. This may be used to supplement the ELF - // file header. - typename ElfArch::Shdr first_section_header_; - - // Array of GetNumSections() section headers, allocated when we read - // in the global header. - typename ElfArch::Shdr *section_headers_; - - // Array of GetNumProgramHeaders() program headers, allocated when we read - // in the global header. - typename ElfArch::Phdr *program_headers_; - - // An array of pointers to ElfSectionReaders. Sections are - // mmaped as they're needed and not released until this object is - // destroyed. - vector<ElfSectionReader<ElfArch>*> sections_; - - // For PowerPC64 we need to keep track of function descriptors when looking up - // values for funtion symbols values. Function descriptors are kept in the - // .opd section and are dereferenced to find the function address. - ElfReader::SectionInfo opd_info_; - const char *opd_section_; // Must be checked for NULL before use. - int64 base_for_text_; - - // Read PLT-related sections for the current architecture. - bool plts_supported_; - // Code size of each PLT function for the current architecture. - size_t plt_code_size_; - // Size of the special first entry in the .plt section that calls the runtime - // loader resolution routine, and that all other entries jump to when doing - // lazy symbol binding. - size_t plt0_size_; - - // Maps a dynamic symbol index to a PLT offset. - // The vector entry index is the dynamic symbol index. - std::vector<uint64> symbols_plt_offsets_; - - // Container for PLT function name strings. These strings are passed by - // reference to SymbolSink::AddSymbol() so they need to be stored somewhere. - std::vector<string> plt_function_names_; - - bool visited_relocation_entries_; - - // True if this is a .dwp file. - bool is_dwp_; -}; - -ElfReader::ElfReader(const string &path) - : path_(path), fd_(-1), impl32_(NULL), impl64_(NULL) { - // linux 2.6.XX kernel can show deleted files like this: - // /var/run/nscd/dbYLJYaE (deleted) - // and the kernel-supplied vdso and vsyscall mappings like this: - // [vdso] - // [vsyscall] - if (MyHasSuffixString(path, " (deleted)")) - return; - if (path == "[vdso]") - return; - if (path == "[vsyscall]") - return; - - fd_ = open(path.c_str(), O_RDONLY); -} - -ElfReader::~ElfReader() { - if (fd_ != -1) - close(fd_); - if (impl32_ != NULL) - delete impl32_; - if (impl64_ != NULL) - delete impl64_; -} - - -// The only word-size specific part of this file is IsNativeElfFile(). -#if __WORDSIZE == 32 -#define NATIVE_ELF_ARCH Elf32 -#elif __WORDSIZE == 64 -#define NATIVE_ELF_ARCH Elf64 -#else -#error "Invalid word size" -#endif - -template <typename ElfArch> -static bool IsElfFile(const int fd, const string &path) { - if (fd < 0) - return false; - if (!ElfReaderImpl<ElfArch>::IsArchElfFile(fd, NULL)) { - // No error message here. IsElfFile gets called many times. - return false; - } - return true; -} - -bool ElfReader::IsNativeElfFile() const { - return IsElfFile<NATIVE_ELF_ARCH>(fd_, path_); -} - -bool ElfReader::IsElf32File() const { - return IsElfFile<Elf32>(fd_, path_); -} - -bool ElfReader::IsElf64File() const { - return IsElfFile<Elf64>(fd_, path_); -} - -/* -void ElfReader::AddSymbols(SymbolMap *symbols, - uint64 mem_offset, uint64 file_offset, - uint64 length) { - if (fd_ < 0) - return; - // TODO(chatham): Actually use the information about file offset and - // the length of the mapped section. On some machines the data - // section gets mapped as executable, and we'll end up reading the - // file twice and getting some of the offsets wrong. - if (IsElf32File()) { - GetImpl32()->GetSymbolPositions(symbols, SHT_SYMTAB, - mem_offset, file_offset); - GetImpl32()->GetSymbolPositions(symbols, SHT_DYNSYM, - mem_offset, file_offset); - } else if (IsElf64File()) { - GetImpl64()->GetSymbolPositions(symbols, SHT_SYMTAB, - mem_offset, file_offset); - GetImpl64()->GetSymbolPositions(symbols, SHT_DYNSYM, - mem_offset, file_offset); - } -} -*/ - -void ElfReader::VisitSymbols(ElfReader::SymbolSink *sink) { - VisitSymbols(sink, -1, -1); -} - -void ElfReader::VisitSymbols(ElfReader::SymbolSink *sink, - int symbol_binding, - int symbol_type) { - VisitSymbols(sink, symbol_binding, symbol_type, false); -} - -void ElfReader::VisitSymbols(ElfReader::SymbolSink *sink, - int symbol_binding, - int symbol_type, - bool get_raw_symbol_values) { - if (IsElf32File()) { - GetImpl32()->VisitRelocationEntries(); - GetImpl32()->VisitSymbols(SHT_SYMTAB, sink, symbol_binding, symbol_type, - get_raw_symbol_values); - GetImpl32()->VisitSymbols(SHT_DYNSYM, sink, symbol_binding, symbol_type, - get_raw_symbol_values); - } else if (IsElf64File()) { - GetImpl64()->VisitRelocationEntries(); - GetImpl64()->VisitSymbols(SHT_SYMTAB, sink, symbol_binding, symbol_type, - get_raw_symbol_values); - GetImpl64()->VisitSymbols(SHT_DYNSYM, sink, symbol_binding, symbol_type, - get_raw_symbol_values); - } -} - -uint64 ElfReader::VaddrOfFirstLoadSegment() { - if (IsElf32File()) { - return GetImpl32()->VaddrOfFirstLoadSegment(); - } else if (IsElf64File()) { - return GetImpl64()->VaddrOfFirstLoadSegment(); - } else { - return 0; - } -} - -const char *ElfReader::GetSectionName(int shndx) { - if (shndx < 0 || static_cast<unsigned int>(shndx) >= GetNumSections()) return NULL; - if (IsElf32File()) { - return GetImpl32()->GetSectionNameByIndex(shndx); - } else if (IsElf64File()) { - return GetImpl64()->GetSectionNameByIndex(shndx); - } else { - return NULL; - } -} - -uint64 ElfReader::GetNumSections() { - if (IsElf32File()) { - return GetImpl32()->GetNumSections(); - } else if (IsElf64File()) { - return GetImpl64()->GetNumSections(); - } else { - return 0; - } -} - -const char *ElfReader::GetSectionByIndex(int shndx, size_t *size) { - if (IsElf32File()) { - return GetImpl32()->GetSectionContentsByIndex(shndx, size); - } else if (IsElf64File()) { - return GetImpl64()->GetSectionContentsByIndex(shndx, size); - } else { - return NULL; - } -} - -const char *ElfReader::GetSectionByName(const string §ion_name, - size_t *size) { - if (IsElf32File()) { - return GetImpl32()->GetSectionContentsByName(section_name, size); - } else if (IsElf64File()) { - return GetImpl64()->GetSectionContentsByName(section_name, size); - } else { - return NULL; - } -} - -const char *ElfReader::GetSectionInfoByName(const string §ion_name, - SectionInfo *info) { - if (IsElf32File()) { - return GetImpl32()->GetSectionInfoByName(section_name, info); - } else if (IsElf64File()) { - return GetImpl64()->GetSectionInfoByName(section_name, info); - } else { - return NULL; - } -} - -bool ElfReader::SectionNamesMatch(const string &name, const string &sh_name) { - if ((name.find(".debug_", 0) == 0) && (sh_name.find(".zdebug_", 0) == 0)) { - const string name_suffix(name, strlen(".debug_")); - const string sh_name_suffix(sh_name, strlen(".zdebug_")); - return name_suffix == sh_name_suffix; - } - return name == sh_name; -} - -bool ElfReader::IsDynamicSharedObject() { - if (IsElf32File()) { - return GetImpl32()->IsDynamicSharedObject(); - } else if (IsElf64File()) { - return GetImpl64()->IsDynamicSharedObject(); - } else { - return false; - } -} - -ElfReaderImpl<Elf32> *ElfReader::GetImpl32() { - if (impl32_ == NULL) { - impl32_ = new ElfReaderImpl<Elf32>(path_, fd_); - } - return impl32_; -} - -ElfReaderImpl<Elf64> *ElfReader::GetImpl64() { - if (impl64_ == NULL) { - impl64_ = new ElfReaderImpl<Elf64>(path_, fd_); - } - return impl64_; -} - -// Return true if file is an ELF binary of ElfArch, with unstripped -// debug info (debug_only=true) or symbol table (debug_only=false). -// Otherwise, return false. -template <typename ElfArch> -static bool IsNonStrippedELFBinaryImpl(const string &path, const int fd, - bool debug_only) { - if (!ElfReaderImpl<ElfArch>::IsArchElfFile(fd, NULL)) return false; - ElfReaderImpl<ElfArch> elf_reader(path, fd); - return debug_only ? - elf_reader.HasDebugSections() - : (elf_reader.GetSectionByType(SHT_SYMTAB) != NULL); -} - -// Helper for the IsNon[Debug]StrippedELFBinary functions. -static bool IsNonStrippedELFBinaryHelper(const string &path, - bool debug_only) { - const int fd = open(path.c_str(), O_RDONLY); - if (fd == -1) { - return false; - } - - if (IsNonStrippedELFBinaryImpl<Elf32>(path, fd, debug_only) || - IsNonStrippedELFBinaryImpl<Elf64>(path, fd, debug_only)) { - close(fd); - return true; - } - close(fd); - return false; -} - -bool ElfReader::IsNonStrippedELFBinary(const string &path) { - return IsNonStrippedELFBinaryHelper(path, false); -} - -bool ElfReader::IsNonDebugStrippedELFBinary(const string &path) { - return IsNonStrippedELFBinaryHelper(path, true); -} -} // namespace dwarf2reader |