Add Elf_file interface which can be used by both Sized_relobj and

Sized_dynobj.

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)