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Diffstat (limited to 'elfcpp/elfcpp_file.h')
| -rw-r--r-- | elfcpp/elfcpp_file.h | 255 |
1 files changed, 255 insertions, 0 deletions
diff --git a/elfcpp/elfcpp_file.h b/elfcpp/elfcpp_file.h new file mode 100644 index 0000000..043c269 --- /dev/null +++ b/elfcpp/elfcpp_file.h @@ -0,0 +1,255 @@ +// elfcpp_file.h -- file access for elfcpp -*- C++ -*- + +// This header file defines the class Elf_file which can be used to +// read useful data from an ELF file. The functions here are all +// templates which take a file interface object as a parameter. This +// type must have a subtype View. This type must support two methods: +// View view(off_t file_offset, off_t data_size) +// returns a View for the specified part of the file. +// void error(const char* printf_format, ...) +// prints an error message and does not return. The subtype View must +// support a method +// const unsigned char* data() +// which returns a pointer to a buffer containing the requested data. +// This general interface is used to read data from the file. Objects +// of type View will never survive longer than the elfcpp function. + +// Some of these functions must return a reference to part of the +// file. To use these, the file interface must support a subtype +// Location: +// Location(off_t file_offset, off_t data_size) +// To use this in conjunction with the accessors types Shdr, etc., the +// file interface should support an overload of view: +// View view(Location) +// This permits writing +// elfcpp::Shdr shdr(file, ef.section_header(n)); + +#ifndef ELFPCP_FILE_H +#define ELFCPP_FILE_H + +#include <string> +#include <cstring> + +namespace elfcpp +{ + +// This object is used to read an ELF file. +// SIZE: The size of file, 32 or 64. +// BIG_ENDIAN: Whether the file is in big-endian format. +// FILE: A file reading type as described above. + +template<int size, bool big_endian, typename File> +class Elf_file +{ + private: + typedef Elf_file<size, big_endian, File> This; + + public: + static const int ehdr_size = Elf_sizes<size>::ehdr_size; + static const int phdr_size = Elf_sizes<size>::phdr_size; + static const int shdr_size = Elf_sizes<size>::shdr_size; + static const int sym_size = Elf_sizes<size>::sym_size; + static const int rel_size = Elf_sizes<size>::rel_size; + static const int rela_size = Elf_sizes<size>::rela_size; + + typedef Ehdr<size, big_endian> Ef_ehdr; + typedef Phdr<size, big_endian> Ef_phdr; + typedef Shdr<size, big_endian> Ef_shdr; + typedef Sym<size, big_endian> Ef_sym; + + // Construct an Elf_file given an ELF file header. + Elf_file(File* file, const Ef_ehdr& ehdr) + { this->construct(file, ehdr); } + + // Construct an ELF file. + inline + Elf_file(File* file); + + // Return the file offset to the section headers. + off_t + shoff() const + { return this->shoff_; } + + // Return the number of sections. + unsigned int + shnum() + { + this->initialize_shnum(); + return this->shnum_; + } + + // Return the section index of the section name string table. + unsigned int + shstrndx() + { + this->initialize_shnum(); + return this->shstrndx_; + } + + // Return the location of the header of section SHNDX. + typename File::Location + section_header(unsigned int shndx) + { + return typename File::Location(this->section_header_offset(shndx), + shdr_size); + } + + // Return the name of section SHNDX. + std::string + section_name(unsigned int shndx); + + // Return the location of the contents of section SHNDX. + typename File::Location + section_contents(unsigned int shndx); + + private: + // Shared constructor code. + void + construct(File* file, const Ef_ehdr& ehdr); + + // Initialize shnum_ and shstrndx_. + void + initialize_shnum(); + + // Return the file offset of the header of section SHNDX. + off_t + section_header_offset(unsigned int shndx); + + // The file we are reading. + File* file_; + // The file offset to the section headers. + off_t shoff_; + // The number of sections. + unsigned int shnum_; + // The section index of the section name string table. + unsigned int shstrndx_; +}; + +// Template function definitions. + +// Construct an Elf_file given an ELF file header. + +template<int size, bool big_endian, typename File> +void +Elf_file<size, big_endian, File>::construct(File* file, const Ef_ehdr& ehdr) +{ + this->file_ = file; + this->shoff_ = ehdr.get_e_shoff(); + this->shnum_ = ehdr.get_e_shnum(); + this->shstrndx_ = ehdr.get_e_shstrndx(); + if (ehdr.get_e_ehsize() != This::ehdr_size) + file->error(_("bad e_ehsize (%d != %d)"), + ehdr.get_e_ehsize(), This::ehdr_size); + if (ehdr.get_e_shentsize() != This::shdr_size) + file->error(_("bad e_shentsize (%d != %d)"), + ehdr.get_e_shentsize(), This::shdr_size); +} + +// Construct an ELF file. + +template<int size, bool big_endian, typename File> +inline +Elf_file<size, big_endian, File>::Elf_file(File* file) +{ + typename File::View v(file->view(file_header_offset, This::ehdr_size)); + this->construct(file, Ef_ehdr(v.data())); +} + +// Initialize the shnum_ and shstrndx_ fields, handling overflow. + +template<int size, bool big_endian, typename File> +void +Elf_file<size, big_endian, File>::initialize_shnum() +{ + if ((this->shnum_ == 0 || this->shstrndx_ == SHN_XINDEX) + && this->shoff_ != 0) + { + typename File::View v(this->file_->view(this->shoff_, This::shdr_size)); + Ef_shdr shdr(v.data()); + if (this->shnum_ == 0) + this->shnum_ = shdr.get_sh_size(); + if (this->shstrndx_ == SHN_XINDEX) + this->shstrndx_ = shdr.get_sh_link(); + } +} + +// Return the file offset of the section header of section SHNDX. + +template<int size, bool big_endian, typename File> +off_t +Elf_file<size, big_endian, File>::section_header_offset(unsigned int shndx) +{ + if (shndx >= this->shnum()) + this->file_->error(_("section_header_offset: bad shndx %u >= %u"), + shndx, this->shnum()); + return this->shoff_ + This::shdr_size * shndx; +} + +// Return the name of section SHNDX. + +template<int size, bool big_endian, typename File> +std::string +Elf_file<size, big_endian, File>::section_name(unsigned int shndx) +{ + File* const file = this->file_; + + // Get the section name offset. + unsigned int sh_name; + { + typename File::View v(file->view(this->section_header_offset(shndx), + This::shdr_size)); + Ef_shdr shdr(v.data()); + sh_name = shdr.get_sh_name(); + } + + // Get the file offset for the section name string table data. + off_t shstr_off; + off_t shstr_size; + { + const unsigned int shstrndx = this->shstrndx_; + typename File::View v(file->view(this->section_header_offset(shstrndx), + This::shdr_size)); + Ef_shdr shstr_shdr(v.data()); + shstr_off = shstr_shdr.get_sh_offset(); + shstr_size = shstr_shdr.get_sh_size(); + } + + if (sh_name >= shstr_size) + file->error(_("bad section name offset for section %u: %u"), + shndx, sh_name); + + typename File::View v(file->view(shstr_off, shstr_size)); + + const unsigned char* datau = v.data(); + const char* data = reinterpret_cast<const char*>(datau); + const void* p = ::memchr(data + sh_name, '\0', shstr_size - sh_name); + if (p == NULL) + file->error(_("missing null terminator for name of section %u"), + shndx); + + size_t len = static_cast<const char*>(p) - (data + sh_name); + + return std::string(data + sh_name, len); +} + +// Return the contents of section SHNDX. + +template<int size, bool big_endian, typename File> +typename File::Location +Elf_file<size, big_endian, File>::section_contents(unsigned int shndx) +{ + File* const file = this->file_; + + if (shndx >= this->shnum()) + file->error(_("section_contents: bad shndx %u >= %u"), + shndx, this->shnum()); + + typename File::View v(file->view(this->section_header_offset(shndx), + This::shdr_size)); + Ef_shdr shdr(v.data()); + return typename File::Location(shdr.get_sh_offset(), shdr.get_sh_size()); +} + +} // End namespace elfcpp. + +#endif // !defined(ELFCPP_FILE_H) |