gold/ehframe.h

   1 // ehframe.h -- handle exception frame sections for gold  -*- C++ -*-
   2
   3 // Copyright 2006, 2007 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 "output.h"
  27 #include "merge.h"
  28
  29 namespace gold
  30 {
  31
  32 template<int size, bool big_endian>
  33 class Track_relocs;
  34
  35 class Eh_frame;
  36
  37 // This class manages the .eh_frame_hdr section, which holds the data
  38 // for the PT_GNU_EH_FRAME segment.  gcc's unwind support code uses
  39 // the PT_GNU_EH_FRAME segment to find the list of FDEs.  This saves
  40 // the time required to register the exception handlers at startup
  41 // time and when a shared object is loaded, and the time required to
  42 // deregister the exception handlers when a shared object is unloaded.
  43
  44 // FIXME: gcc supports using storing a sorted lookup table for the
  45 // FDEs in the PT_GNU_EH_FRAME segment, but we do not yet generate
  46 // that.
  47
  48 class Eh_frame_hdr : public Output_section_data
  49 {
  50  public:
  51   Eh_frame_hdr(Output_section* eh_frame_section, const Eh_frame*);
  52
  53   // Record that we found an unrecognized .eh_frame section.
  54   void
  55   found_unrecognized_eh_frame_section()
  56   { this->any_unrecognized_eh_frame_sections_ = true; }
  57
  58   // Record an FDE.
  59   void
  60   record_fde(section_offset_type fde_offset, unsigned char fde_encoding)
  61   {
  62     if (!this->any_unrecognized_eh_frame_sections_)
  63       this->fde_offsets_.push_back(std::make_pair(fde_offset, fde_encoding));
  64   }
  65
  66   // Set the final data size.
  67   void
  68   set_final_data_size();
  69
  70   // Write the data to the file.
  71   void
  72   do_write(Output_file*);
  73
  74  private:
  75   // Write the data to the file with the right endianness.
  76   template<int size, bool big_endian>
  77   void
  78   do_sized_write(Output_file*);
  79
  80   // The data we record for one FDE: the offset of the FDE within the
  81   // .eh_frame section, and the FDE encoding.
  82   typedef std::pair<section_offset_type, unsigned char> Fde_offset;
  83
  84   // The list of information we record for an FDE.
  85   typedef std::vector<Fde_offset> Fde_offsets;
  86
  87   // When writing out the header, we convert the FDE offsets into FDE
  88   // addresses.  This is a list of pairs of the offset from the header
  89   // to the FDE PC and to the FDE itself.
  90   template<int size>
  91   class Fde_addresses
  92   {
  93    public:
  94     typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
  95     typedef typename std::pair<Address, Address> Fde_address;
  96     typedef typename std::vector<Fde_address> Fde_address_list;
  97     typedef typename Fde_address_list::iterator iterator;
  98
  99     Fde_addresses(unsigned int reserve)
 100       : fde_addresses_()
 101     { this->fde_addresses_.reserve(reserve); }
 102
 103     void
 104     push_back(Address pc_address, Address fde_address)
 105     {
 106       this->fde_addresses_.push_back(std::make_pair(pc_address, fde_address));
 107     }
 108
 109     iterator
 110     begin()
 111     { return this->fde_addresses_.begin(); }
 112
 113     iterator
 114     end()
 115     { return this->fde_addresses_.end(); }
 116
 117    private:
 118     Fde_address_list fde_addresses_;
 119   };
 120
 121   // Compare Fde_address objects.
 122   template<int size>
 123   struct Fde_address_compare
 124   {
 125     bool
 126     operator()(const typename Fde_addresses<size>::Fde_address& f1,
 127                const typename Fde_addresses<size>::Fde_address& f2) const
 128     { return f1.first < f2.first; }
 129   };
 130
 131   // Return the PC to which an FDE refers.
 132   template<int size, bool big_endian>
 133   typename elfcpp::Elf_types<size>::Elf_Addr
 134   get_fde_pc(typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address,
 135              const unsigned char* eh_frame_contents,
 136              section_offset_type fde_offset, unsigned char fde_encoding);
 137
 138   // Convert Fde_offsets to Fde_addresses.
 139   template<int size, bool big_endian>
 140   void
 141   get_fde_addresses(Output_file* of,
 142                     const Fde_offsets* fde_offsets,
 143                     Fde_addresses<size>* fde_addresses);
 144
 145   // The .eh_frame section.
 146   Output_section* eh_frame_section_;
 147   // The .eh_frame section data.
 148   const Eh_frame* eh_frame_data_;
 149   // Data from the FDEs in the .eh_frame sections.
 150   Fde_offsets fde_offsets_;
 151   // Whether we found any .eh_frame sections which we could not
 152   // process.
 153   bool any_unrecognized_eh_frame_sections_;
 154 };
 155
 156 // This class holds an FDE.
 157
 158 class Fde
 159 {
 160  public:
 161   Fde(Relobj* object, unsigned int shndx, section_offset_type input_offset,
 162       const unsigned char* contents, size_t length)
 163     : object_(object), shndx_(shndx), input_offset_(input_offset),
 164       contents_(reinterpret_cast<const char*>(contents), length)
 165   { }
 166
 167   // Return the length of this FDE.  Add 4 for the length and 4 for
 168   // the offset to the CIE.
 169   size_t
 170   length() const
 171   { return this->contents_.length() + 8; }
 172
 173   // Add a mapping for this FDE to MERGE_MAP.
 174   void
 175   add_mapping(section_offset_type output_offset, Merge_map* merge_map) const
 176   {
 177     merge_map->add_mapping(this->object_, this->shndx_,
 178                            this->input_offset_, this->length(),
 179                            output_offset);
 180   }
 181
 182   // Write the FDE to OVIEW starting at OFFSET.  FDE_ENCODING is the
 183   // encoding, from the CIE.  Record the FDE in EH_FRAME_HDR.  Return
 184   // the new offset.
 185   template<int size, bool big_endian>
 186   section_offset_type
 187   write(unsigned char* oview, section_offset_type offset,
 188         section_offset_type cie_offset, unsigned char fde_encoding,
 189         Eh_frame_hdr* eh_frame_hdr);
 190
 191  private:
 192   // The object in which this FDE was seen.
 193   Relobj* object_;
 194   // Input section index for this FDE.
 195   unsigned int shndx_;
 196   // Offset within the input section for this FDE.
 197   section_offset_type input_offset_;
 198   // FDE data.
 199   std::string contents_;
 200 };
 201
 202 // This class holds a CIE.
 203
 204 class Cie
 205 {
 206  public:
 207   Cie(Relobj* object, unsigned int shndx, section_offset_type input_offset,
 208       unsigned char fde_encoding, const char* personality_name,
 209       const unsigned char* contents, size_t length)
 210     : object_(object),
 211       shndx_(shndx),
 212       input_offset_(input_offset),
 213       fde_encoding_(fde_encoding),
 214       personality_name_(personality_name),
 215       fdes_(),
 216       contents_(reinterpret_cast<const char*>(contents), length)
 217   { }
 218
 219   ~Cie();
 220
 221   // We permit copying a CIE when there are no FDEs.  This is
 222   // convenient in the code which creates them.
 223   Cie(const Cie& cie)
 224     : object_(cie.object_),
 225       shndx_(cie.shndx_),
 226       input_offset_(cie.input_offset_),
 227       fde_encoding_(cie.fde_encoding_),
 228       personality_name_(cie.personality_name_),
 229       fdes_(),
 230       contents_(cie.contents_)
 231   { gold_assert(cie.fdes_.empty()); }
 232
 233   // Add an FDE associated with this CIE.
 234   void
 235   add_fde(Fde* fde)
 236   { this->fdes_.push_back(fde); }
 237
 238   // Return the number of FDEs.
 239   unsigned int
 240   fde_count() const
 241   { return this->fdes_.size(); }
 242
 243   // Set the output offset of this CIE to OUTPUT_OFFSET.  It will be
 244   // followed by all its FDEs.  ADDRALIGN is the required address
 245   // alignment, typically 4 or 8.  This updates MERGE_MAP with the
 246   // mapping.  It returns the new output offset.
 247   section_offset_type
 248   set_output_offset(section_offset_type output_offset, unsigned int addralign,
 249                     Merge_map*);
 250
 251   // Write the CIE to OVIEW starting at OFFSET.  EH_FRAME_HDR is the
 252   // exception frame header for FDE recording.  Return the new offset.
 253   template<int size, bool big_endian>
 254   section_offset_type
 255   write(unsigned char* oview, section_offset_type offset,
 256         Eh_frame_hdr* eh_frame_hdr);
 257
 258   friend bool operator<(const Cie&, const Cie&);
 259   friend bool operator==(const Cie&, const Cie&);
 260
 261  private:
 262   // The class is not assignable.
 263   Cie& operator=(const Cie&);
 264
 265   // The object in which this CIE was first seen.
 266   Relobj* object_;
 267   // Input section index for this CIE.
 268   unsigned int shndx_;
 269   // Offset within the input section for this CIE.
 270   section_offset_type input_offset_;
 271   // The encoding of the FDE.  This is a DW_EH_PE code.
 272   unsigned char fde_encoding_;
 273   // The name of the personality routine.  This will be the name of a
 274   // global symbol, or will be the empty string.
 275   std::string personality_name_;
 276   // List of FDEs.
 277   std::vector<Fde*> fdes_;
 278   // CIE data.
 279   std::string contents_;
 280 };
 281
 282 extern bool operator<(const Cie&, const Cie&);
 283 extern bool operator==(const Cie&, const Cie&);
 284
 285 // This class manages .eh_frame sections.  It discards duplicate
 286 // exception information.
 287
 288 class Eh_frame : public Output_section_data
 289 {
 290  public:
 291   Eh_frame();
 292
 293   // Record the associated Eh_frame_hdr, if any.
 294   void
 295   set_eh_frame_hdr(Eh_frame_hdr* hdr)
 296   { this->eh_frame_hdr_ = hdr; }
 297
 298   // Add the input section SHNDX in OBJECT.  SYMBOLS is the contents
 299   // of the symbol table section (size SYMBOLS_SIZE), SYMBOL_NAMES is
 300   // the symbol names section (size SYMBOL_NAMES_SIZE).  RELOC_SHNDX
 301   // is the relocation section if any (0 for none, -1U for multiple).
 302   // RELOC_TYPE is the type of the relocation section if any.  This
 303   // returns whether the section was incorporated into the .eh_frame
 304   // data.
 305   template<int size, bool big_endian>
 306   bool
 307   add_ehframe_input_section(Sized_relobj<size, big_endian>* object,
 308                             const unsigned char* symbols,
 309                             section_size_type symbols_size,
 310                             const unsigned char* symbol_names,
 311                             section_size_type symbol_names_size,
 312                             unsigned int shndx, unsigned int reloc_shndx,
 313                             unsigned int reloc_type);
 314
 315   // Return the number of FDEs.
 316   unsigned int
 317   fde_count() const;
 318
 319   // Set the final data size.
 320   void
 321   set_final_data_size();
 322
 323   // Return the output address for an input address.
 324   bool
 325   do_output_offset(const Relobj*, unsigned int shndx,
 326                    section_offset_type offset,
 327                    section_offset_type* poutput) const;
 328
 329   // Write the data to the file.
 330   void
 331   do_write(Output_file*);
 332
 333  private:
 334   // The comparison routine for the CIE map.
 335   struct Cie_less
 336   {
 337     bool
 338     operator()(const Cie* cie1, const Cie* cie2) const
 339     { return *cie1 < *cie2; }
 340   };
 341
 342   // A mapping from unique CIEs to their offset in the output file.
 343   typedef std::map<Cie*, uint64_t, Cie_less> Cie_offsets;
 344
 345   // A list of unmergeable CIEs with their offsets.
 346   typedef std::vector<std::pair<Cie*, uint64_t> > Unmergeable_cie_offsets;
 347
 348   // A mapping from offsets to CIEs.  This is used while reading an
 349   // input section.
 350   typedef std::map<uint64_t, Cie*> Offsets_to_cie;
 351
 352   // A list of CIEs, and a bool indicating whether the CIE is
 353   // mergeable.
 354   typedef std::vector<std::pair<Cie*, bool> > New_cies;
 355
 356   // Skip an LEB128.
 357   static bool
 358   skip_leb128(const unsigned char**, const unsigned char*);
 359
 360   // The implementation of add_ehframe_input_section.
 361   template<int size, bool big_endian>
 362   bool
 363   do_add_ehframe_input_section(Sized_relobj<size, big_endian>* object,
 364                                const unsigned char* symbols,
 365                                section_size_type symbols_size,
 366                                const unsigned char* symbol_names,
 367                                section_size_type symbol_names_size,
 368                                unsigned int shndx,
 369                                unsigned int reloc_shndx,
 370                                unsigned int reloc_type,
 371                                const unsigned char* pcontents,
 372                                section_size_type contents_len,
 373                                New_cies*);
 374
 375   // Read a CIE.
 376   template<int size, bool big_endian>
 377   bool
 378   read_cie(Sized_relobj<size, big_endian>* object,
 379            unsigned int shndx,
 380            const unsigned char* symbols,
 381            section_size_type symbols_size,
 382            const unsigned char* symbol_names,
 383            section_size_type symbol_names_size,
 384            const unsigned char* pcontents,
 385            const unsigned char* pcie,
 386            const unsigned char *pcieend,
 387            Track_relocs<size, big_endian>* relocs,
 388            Offsets_to_cie* cies,
 389            New_cies* new_cies);
 390
 391   // Read an FDE.
 392   template<int size, bool big_endian>
 393   bool
 394   read_fde(Sized_relobj<size, big_endian>* object,
 395            unsigned int shndx,
 396            const unsigned char* symbols,
 397            section_size_type symbols_size,
 398            const unsigned char* pcontents,
 399            unsigned int offset,
 400            const unsigned char* pfde,
 401            const unsigned char *pfdeend,
 402            Track_relocs<size, big_endian>* relocs,
 403            Offsets_to_cie* cies);
 404
 405   // Template version of write function.
 406   template<int size, bool big_endian>
 407   void
 408   do_sized_write(unsigned char* oview);
 409
 410   // The exception frame header, if any.
 411   Eh_frame_hdr* eh_frame_hdr_;
 412   // A mapping from all unique CIEs to their offset in the output
 413   // file.
 414   Cie_offsets cie_offsets_;
 415   // A mapping from unmergeable CIEs to their offset in the output
 416   // file.
 417   Unmergeable_cie_offsets unmergeable_cie_offsets_;
 418   // A mapping from input sections to the output section.
 419   Merge_map merge_map_;
 420 };
 421
 422 } // End namespace gold.
 423
 424 #endif // !defined(GOLD_EHFRAME_H)