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