gold/ehframe.h

   1 // ehframe.h -- handle exception frame sections for gold  -*- C++ -*-
   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 #ifndef GOLD_EHFRAME_H
  24 #define GOLD_EHFRAME_H
  25
  26 #include <map>
  27 #include <set>
  28 #include <vector>
  29
  30 #include "output.h"
  31 #include "merge.h"
  32
  33 namespace gold
  34 {
  35
  36 template<int size, bool big_endian>
  37 class Track_relocs;
  38
  39 class Eh_frame;
  40
  41 // This class manages the .eh_frame_hdr section, which holds the data
  42 // for the PT_GNU_EH_FRAME segment.  gcc's unwind support code uses
  43 // the PT_GNU_EH_FRAME segment to find the list of FDEs.  This saves
  44 // the time required to register the exception handlers at startup
  45 // time and when a shared object is loaded, and the time required to
  46 // deregister the exception handlers when a shared object is unloaded.
  47
  48 // FIXME: gcc supports using storing a sorted lookup table for the
  49 // FDEs in the PT_GNU_EH_FRAME segment, but we do not yet generate
  50 // that.
  51
  52 class Eh_frame_hdr : public Output_section_data
  53 {
  54  public:
  55   Eh_frame_hdr(Output_section* eh_frame_section, const Eh_frame*);
  56
  57   // Record that we found an unrecognized .eh_frame section.
  58   void
  59   found_unrecognized_eh_frame_section()
  60   { this->any_unrecognized_eh_frame_sections_ = true; }
  61
  62   // Record an FDE.
  63   void
  64   record_fde(section_offset_type fde_offset, unsigned char fde_encoding)
  65   {
  66     if (!this->any_unrecognized_eh_frame_sections_)
  67       this->fde_offsets_.push_back(std::make_pair(fde_offset, fde_encoding));
  68   }
  69
  70  protected:
  71   // Set the final data size.
  72   void
  73   set_final_data_size();
  74
  75   // Write the data to the file.
  76   void
  77   do_write(Output_file*);
  78
  79   // Write to a map file.
  80   void
  81   do_print_to_mapfile(Mapfile* mapfile) const
  82   { mapfile->print_output_data(this, _("** eh_frame_hdr")); }
  83
  84  private:
  85   // Write the data to the file with the right endianness.
  86   template<int size, bool big_endian>
  87   void
  88   do_sized_write(Output_file*);
  89
  90   // The data we record for one FDE: the offset of the FDE within the
  91   // .eh_frame section, and the FDE encoding.
  92   typedef std::pair<section_offset_type, unsigned char> Fde_offset;
  93
  94   // The list of information we record for an FDE.
  95   typedef std::vector<Fde_offset> Fde_offsets;
  96
  97   // When writing out the header, we convert the FDE offsets into FDE
  98   // addresses.  This is a list of pairs of the offset from the header
  99   // to the FDE PC and to the FDE itself.
 100   template<int size>
 101   class Fde_addresses
 102   {
 103    public:
 104     typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
 105     typedef typename std::pair<Address, Address> Fde_address;
 106     typedef typename std::vector<Fde_address> Fde_address_list;
 107     typedef typename Fde_address_list::iterator iterator;
 108
 109     Fde_addresses(unsigned int reserve)
 110       : fde_addresses_()
 111     { this->fde_addresses_.reserve(reserve); }
 112
 113     void
 114     push_back(Address pc_address, Address fde_address)
 115     {
 116       this->fde_addresses_.push_back(std::make_pair(pc_address, fde_address));
 117     }
 118
 119     iterator
 120     begin()
 121     { return this->fde_addresses_.begin(); }
 122
 123     iterator
 124     end()
 125     { return this->fde_addresses_.end(); }
 126
 127    private:
 128     Fde_address_list fde_addresses_;
 129   };
 130
 131   // Compare Fde_address objects.
 132   template<int size>
 133   struct Fde_address_compare
 134   {
 135     bool
 136     operator()(const typename Fde_addresses<size>::Fde_address& f1,
 137                const typename Fde_addresses<size>::Fde_address& f2) const
 138     { return f1.first < f2.first; }
 139   };
 140
 141   // Return the PC to which an FDE refers.
 142   template<int size, bool big_endian>
 143   typename elfcpp::Elf_types<size>::Elf_Addr
 144   get_fde_pc(typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address,
 145              const unsigned char* eh_frame_contents,
 146              section_offset_type fde_offset, unsigned char fde_encoding);
 147
 148   // Convert Fde_offsets to Fde_addresses.
 149   template<int size, bool big_endian>
 150   void
 151   get_fde_addresses(Output_file* of,
 152                     const Fde_offsets* fde_offsets,
 153                     Fde_addresses<size>* fde_addresses);
 154
 155   // The .eh_frame section.
 156   Output_section* eh_frame_section_;
 157   // The .eh_frame section data.
 158   const Eh_frame* eh_frame_data_;
 159   // Data from the FDEs in the .eh_frame sections.
 160   Fde_offsets fde_offsets_;
 161   // Whether we found any .eh_frame sections which we could not
 162   // process.
 163   bool any_unrecognized_eh_frame_sections_;
 164 };
 165
 166 // This class holds an FDE.
 167
 168 class Fde
 169 {
 170  public:
 171   Fde(Relobj* object, unsigned int shndx, section_offset_type input_offset,
 172       const unsigned char* contents, size_t length)
 173     : object_(object), shndx_(shndx), input_offset_(input_offset),
 174       contents_(reinterpret_cast<const char*>(contents), length)
 175   { }
 176
 177   // Return the length of this FDE.  Add 4 for the length and 4 for
 178   // the offset to the CIE.
 179   size_t
 180   length() const
 181   { return this->contents_.length() + 8; }
 182
 183   // Add a mapping for this FDE to MERGE_MAP.
 184   void
 185   add_mapping(section_offset_type output_offset, Merge_map* merge_map) const
 186   {
 187     merge_map->add_mapping(this->object_, this->shndx_,
 188                            this->input_offset_, this->length(),
 189                            output_offset);
 190   }
 191
 192   // Write the FDE to OVIEW starting at OFFSET.  FDE_ENCODING is the
 193   // encoding, from the CIE.  Round up the bytes to ADDRALIGN if
 194   // necessary.  Record the FDE in EH_FRAME_HDR.  Return the new
 195   // offset.
 196   template<int size, bool big_endian>
 197   section_offset_type
 198   write(unsigned char* oview, section_offset_type offset,
 199         unsigned int addralign, section_offset_type cie_offset,
 200         unsigned char fde_encoding, Eh_frame_hdr* eh_frame_hdr);
 201
 202  private:
 203   // The object in which this FDE was seen.
 204   Relobj* object_;
 205   // Input section index for this FDE.
 206   unsigned int shndx_;
 207   // Offset within the input section for this FDE.
 208   section_offset_type input_offset_;
 209   // FDE data.
 210   std::string contents_;
 211 };
 212
 213 // This class holds a CIE.
 214
 215 class Cie
 216 {
 217  public:
 218   Cie(Relobj* object, unsigned int shndx, section_offset_type input_offset,
 219       unsigned char fde_encoding, const char* personality_name,
 220       const unsigned char* contents, size_t length)
 221     : object_(object),
 222       shndx_(shndx),
 223       input_offset_(input_offset),
 224       fde_encoding_(fde_encoding),
 225       personality_name_(personality_name),
 226       fdes_(),
 227       contents_(reinterpret_cast<const char*>(contents), length)
 228   { }
 229
 230   ~Cie();
 231
 232   // We permit copying a CIE when there are no FDEs.  This is
 233   // convenient in the code which creates them.
 234   Cie(const Cie& cie)
 235     : object_(cie.object_),
 236       shndx_(cie.shndx_),
 237       input_offset_(cie.input_offset_),
 238       fde_encoding_(cie.fde_encoding_),
 239       personality_name_(cie.personality_name_),
 240       fdes_(),
 241       contents_(cie.contents_)
 242   { gold_assert(cie.fdes_.empty()); }
 243
 244   // Add an FDE associated with this CIE.
 245   void
 246   add_fde(Fde* fde)
 247   { this->fdes_.push_back(fde); }
 248
 249   // Return the number of FDEs.
 250   unsigned int
 251   fde_count() const
 252   { return this->fdes_.size(); }
 253
 254   // Set the output offset of this CIE to OUTPUT_OFFSET.  It will be
 255   // followed by all its FDEs.  ADDRALIGN is the required address
 256   // alignment, typically 4 or 8.  This updates MERGE_MAP with the
 257   // mapping.  It returns the new output offset.
 258   section_offset_type
 259   set_output_offset(section_offset_type output_offset, unsigned int addralign,
 260                     Merge_map*);
 261
 262   // Write the CIE to OVIEW starting at OFFSET.  EH_FRAME_HDR is the
 263   // exception frame header for FDE recording.  Round up the bytes to
 264   // ADDRALIGN.  Return the new offset.
 265   template<int size, bool big_endian>
 266   section_offset_type
 267   write(unsigned char* oview, section_offset_type offset,
 268         unsigned int addralign, Eh_frame_hdr* eh_frame_hdr);
 269
 270   friend bool operator<(const Cie&, const Cie&);
 271   friend bool operator==(const Cie&, const Cie&);
 272
 273  private:
 274   // The class is not assignable.
 275   Cie& operator=(const Cie&);
 276
 277   // The object in which this CIE was first seen.
 278   Relobj* object_;
 279   // Input section index for this CIE.
 280   unsigned int shndx_;
 281   // Offset within the input section for this CIE.
 282   section_offset_type input_offset_;
 283   // The encoding of the FDE.  This is a DW_EH_PE code.
 284   unsigned char fde_encoding_;
 285   // The name of the personality routine.  This will be the name of a
 286   // global symbol, or will be the empty string.
 287   std::string personality_name_;
 288   // List of FDEs.
 289   std::vector<Fde*> fdes_;
 290   // CIE data.
 291   std::string contents_;
 292 };
 293
 294 extern bool operator<(const Cie&, const Cie&);
 295 extern bool operator==(const Cie&, const Cie&);
 296
 297 // This class manages .eh_frame sections.  It discards duplicate
 298 // exception information.
 299
 300 class Eh_frame : public Output_section_data
 301 {
 302  public:
 303   Eh_frame();
 304
 305   // Record the associated Eh_frame_hdr, if any.
 306   void
 307   set_eh_frame_hdr(Eh_frame_hdr* hdr)
 308   { this->eh_frame_hdr_ = hdr; }
 309
 310   // Add the input section SHNDX in OBJECT.  SYMBOLS is the contents
 311   // of the symbol table section (size SYMBOLS_SIZE), SYMBOL_NAMES is
 312   // the symbol names section (size SYMBOL_NAMES_SIZE).  RELOC_SHNDX
 313   // is the relocation section if any (0 for none, -1U for multiple).
 314   // RELOC_TYPE is the type of the relocation section if any.  This
 315   // returns whether the section was incorporated into the .eh_frame
 316   // data.
 317   template<int size, bool big_endian>
 318   bool
 319   add_ehframe_input_section(Sized_relobj<size, big_endian>* object,
 320                             const unsigned char* symbols,
 321                             section_size_type symbols_size,
 322                             const unsigned char* symbol_names,
 323                             section_size_type symbol_names_size,
 324                             unsigned int shndx, unsigned int reloc_shndx,
 325                             unsigned int reloc_type);
 326
 327   // Return the number of FDEs.
 328   unsigned int
 329   fde_count() const;
 330
 331  protected:
 332   // Set the final data size.
 333   void
 334   set_final_data_size();
 335
 336   // Return the output address for an input address.
 337   bool
 338   do_output_offset(const Relobj*, unsigned int shndx,
 339                    section_offset_type offset,
 340                    section_offset_type* poutput) const;
 341
 342   // Return whether this is the merge section for an input section.
 343   bool
 344   do_is_merge_section_for(const Relobj*, unsigned int shndx) const;
 345
 346   // Write the data to the file.
 347   void
 348   do_write(Output_file*);
 349
 350   // Write to a map file.
 351   void
 352   do_print_to_mapfile(Mapfile* mapfile) const
 353   { mapfile->print_output_data(this, _("** eh_frame")); }
 354
 355  private:
 356   // The comparison routine for the CIE map.
 357   struct Cie_less
 358   {
 359     bool
 360     operator()(const Cie* cie1, const Cie* cie2) const
 361     { return *cie1 < *cie2; }
 362   };
 363
 364   // A set of unique CIEs.
 365   typedef std::set<Cie*, Cie_less> Cie_offsets;
 366
 367   // A list of unmergeable CIEs.
 368   typedef std::vector<Cie*> Unmergeable_cie_offsets;
 369
 370   // A mapping from offsets to CIEs.  This is used while reading an
 371   // input section.
 372   typedef std::map<uint64_t, Cie*> Offsets_to_cie;
 373
 374   // A list of CIEs, and a bool indicating whether the CIE is
 375   // mergeable.
 376   typedef std::vector<std::pair<Cie*, bool> > New_cies;
 377
 378   // Skip an LEB128.
 379   static bool
 380   skip_leb128(const unsigned char**, const unsigned char*);
 381
 382   // The implementation of add_ehframe_input_section.
 383   template<int size, bool big_endian>
 384   bool
 385   do_add_ehframe_input_section(Sized_relobj<size, big_endian>* object,
 386                                const unsigned char* symbols,
 387                                section_size_type symbols_size,
 388                                const unsigned char* symbol_names,
 389                                section_size_type symbol_names_size,
 390                                unsigned int shndx,
 391                                unsigned int reloc_shndx,
 392                                unsigned int reloc_type,
 393                                const unsigned char* pcontents,
 394                                section_size_type contents_len,
 395                                New_cies*);
 396
 397   // Read a CIE.
 398   template<int size, bool big_endian>
 399   bool
 400   read_cie(Sized_relobj<size, big_endian>* object,
 401            unsigned int shndx,
 402            const unsigned char* symbols,
 403            section_size_type symbols_size,
 404            const unsigned char* symbol_names,
 405            section_size_type symbol_names_size,
 406            const unsigned char* pcontents,
 407            const unsigned char* pcie,
 408            const unsigned char* pcieend,
 409            Track_relocs<size, big_endian>* relocs,
 410            Offsets_to_cie* cies,
 411            New_cies* new_cies);
 412
 413   // Read an FDE.
 414   template<int size, bool big_endian>
 415   bool
 416   read_fde(Sized_relobj<size, big_endian>* object,
 417            unsigned int shndx,
 418            const unsigned char* symbols,
 419            section_size_type symbols_size,
 420            const unsigned char* pcontents,
 421            unsigned int offset,
 422            const unsigned char* pfde,
 423            const unsigned char* pfdeend,
 424            Track_relocs<size, big_endian>* relocs,
 425            Offsets_to_cie* cies);
 426
 427   // Template version of write function.
 428   template<int size, bool big_endian>
 429   void
 430   do_sized_write(unsigned char* oview);
 431
 432   // The exception frame header, if any.
 433   Eh_frame_hdr* eh_frame_hdr_;
 434   // A mapping from all unique CIEs to their offset in the output
 435   // file.
 436   Cie_offsets cie_offsets_;
 437   // A mapping from unmergeable CIEs to their offset in the output
 438   // file.
 439   Unmergeable_cie_offsets unmergeable_cie_offsets_;
 440   // A mapping from input sections to the output section.
 441   Merge_map merge_map_;
 442   // Whether we have created the mappings to the output section.
 443   bool mappings_are_done_;
 444   // The final data size.  This is only set if mappings_are_done_ is
 445   // true.
 446   section_size_type final_data_size_;
 447 };
 448
 449 } // End namespace gold.
 450
 451 #endif // !defined(GOLD_EHFRAME_H)