1 // ehframe.h -- handle exception frame sections for gold -*- C++ -*-
3 // Copyright (C) 2006-2015 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
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.
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.
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.
23 #ifndef GOLD_EHFRAME_H
24 #define GOLD_EHFRAME_H
36 template<int size, bool big_endian>
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.
48 class Eh_frame_hdr : public Output_section_data
51 Eh_frame_hdr(Output_section* eh_frame_section, const Eh_frame*);
53 // Record that we found an unrecognized .eh_frame section.
55 found_unrecognized_eh_frame_section()
56 { this->any_unrecognized_eh_frame_sections_ = true; }
60 record_fde(section_offset_type fde_offset, unsigned char fde_encoding)
62 if (!this->any_unrecognized_eh_frame_sections_)
63 this->fde_offsets_.push_back(std::make_pair(fde_offset, fde_encoding));
67 // Set the final data size.
69 set_final_data_size();
71 // Write the data to the file.
73 do_write(Output_file*);
75 // Write to a map file.
77 do_print_to_mapfile(Mapfile* mapfile) const
78 { mapfile->print_output_data(this, _("** eh_frame_hdr")); }
81 // Write the data to the file with the right endianness.
82 template<int size, bool big_endian>
84 do_sized_write(Output_file*);
86 // The data we record for one FDE: the offset of the FDE within the
87 // .eh_frame section, and the FDE encoding.
88 typedef std::pair<section_offset_type, unsigned char> Fde_offset;
90 // The list of information we record for an FDE.
91 typedef std::vector<Fde_offset> Fde_offsets;
93 // When writing out the header, we convert the FDE offsets into FDE
94 // addresses. This is a list of pairs of the offset from the header
95 // to the FDE PC and to the FDE itself.
100 typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
101 typedef typename std::pair<Address, Address> Fde_address;
102 typedef typename std::vector<Fde_address> Fde_address_list;
103 typedef typename Fde_address_list::iterator iterator;
105 Fde_addresses(unsigned int reserve)
107 { this->fde_addresses_.reserve(reserve); }
110 push_back(Address pc_address, Address fde_address)
112 this->fde_addresses_.push_back(std::make_pair(pc_address, fde_address));
117 { return this->fde_addresses_.begin(); }
121 { return this->fde_addresses_.end(); }
124 Fde_address_list fde_addresses_;
127 // Compare Fde_address objects.
129 struct Fde_address_compare
132 operator()(const typename Fde_addresses<size>::Fde_address& f1,
133 const typename Fde_addresses<size>::Fde_address& f2) const
134 { return f1.first < f2.first; }
137 // Return the PC to which an FDE refers.
138 template<int size, bool big_endian>
139 typename elfcpp::Elf_types<size>::Elf_Addr
140 get_fde_pc(typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address,
141 const unsigned char* eh_frame_contents,
142 section_offset_type fde_offset, unsigned char fde_encoding);
144 // Convert Fde_offsets to Fde_addresses.
145 template<int size, bool big_endian>
147 get_fde_addresses(Output_file* of,
148 const Fde_offsets* fde_offsets,
149 Fde_addresses<size>* fde_addresses);
151 // The .eh_frame section.
152 Output_section* eh_frame_section_;
153 // The .eh_frame section data.
154 const Eh_frame* eh_frame_data_;
155 // Data from the FDEs in the .eh_frame sections.
156 Fde_offsets fde_offsets_;
157 // Whether we found any .eh_frame sections which we could not
159 bool any_unrecognized_eh_frame_sections_;
162 // This class holds an FDE.
167 Fde(Relobj* object, unsigned int shndx, section_offset_type input_offset,
168 const unsigned char* contents, size_t length)
170 contents_(reinterpret_cast<const char*>(contents), length)
172 this->u_.from_object.shndx = shndx;
173 this->u_.from_object.input_offset = input_offset;
176 // Create an FDE associated with a PLT.
177 Fde(Output_data* plt, const unsigned char* contents, size_t length,
180 contents_(reinterpret_cast<const char*>(contents), length)
182 this->u_.from_linker.plt = plt;
183 this->u_.from_linker.post_map = post_map;
186 // Return the length of this FDE. Add 4 for the length and 4 for
187 // the offset to the CIE.
190 { return this->contents_.length() + 8; }
192 // Add a mapping for this FDE to MERGE_MAP, so that relocations
193 // against the FDE are applied to right part of the output file.
195 add_mapping(section_offset_type output_offset,
196 Output_section_data* output_data) const
198 if (this->object_ != NULL)
199 this->object_->add_merge_mapping(output_data, this->u_.from_object.shndx,
200 this->u_.from_object.input_offset, this->length(),
204 // Return whether this FDE was added after merge mapping.
207 { return this->object_ == NULL && this->u_.from_linker.post_map; }
209 // Write the FDE to OVIEW starting at OFFSET. FDE_ENCODING is the
210 // encoding, from the CIE. Round up the bytes to ADDRALIGN if
211 // necessary. ADDRESS is the virtual address of OVIEW. Record the
212 // FDE in EH_FRAME_HDR. Return the new offset.
213 template<int size, bool big_endian>
215 write(unsigned char* oview, section_offset_type output_section_offset,
216 section_offset_type offset, uint64_t address, unsigned int addralign,
217 section_offset_type cie_offset, unsigned char fde_encoding,
218 Eh_frame_hdr* eh_frame_hdr);
221 // The object in which this FDE was seen. This will be NULL for a
222 // linker generated FDE.
226 // These fields are used if the FDE is from an input object (the
227 // object_ field is not NULL).
230 // Input section index for this FDE.
232 // Offset within the input section for this FDE.
233 section_offset_type input_offset;
235 // This field is used if the FDE is generated by the linker (the
236 // object_ field is NULL).
239 // The only linker generated FDEs are for PLT sections, and this
240 // points to the PLT section.
242 // Set if the FDE was added after merge mapping.
247 std::string contents_;
250 // A FDE plus some info from a CIE to allow later writing of the FDE.
254 Post_fde(Fde* f, section_offset_type cie_off, unsigned char encoding)
255 : fde(f), cie_offset(cie_off), fde_encoding(encoding)
259 section_offset_type cie_offset;
260 unsigned char fde_encoding;
263 typedef std::vector<Post_fde> Post_fdes;
265 // This class holds a CIE.
270 Cie(Relobj* object, unsigned int shndx, section_offset_type input_offset,
271 unsigned char fde_encoding, const char* personality_name,
272 const unsigned char* contents, size_t length)
275 input_offset_(input_offset),
276 fde_encoding_(fde_encoding),
277 personality_name_(personality_name),
279 contents_(reinterpret_cast<const char*>(contents), length)
284 // We permit copying a CIE when there are no FDEs. This is
285 // convenient in the code which creates them.
287 : object_(cie.object_),
289 input_offset_(cie.input_offset_),
290 fde_encoding_(cie.fde_encoding_),
291 personality_name_(cie.personality_name_),
293 contents_(cie.contents_)
294 { gold_assert(cie.fdes_.empty()); }
296 // Add an FDE associated with this CIE.
299 { this->fdes_.push_back(fde); }
301 // Return the number of FDEs.
304 { return this->fdes_.size(); }
306 // Set the output offset of this CIE to OUTPUT_OFFSET. It will be
307 // followed by all its FDEs. ADDRALIGN is the required address
308 // alignment, typically 4 or 8. This updates MERGE_MAP with the
309 // mapping. It returns the new output offset.
311 set_output_offset(section_offset_type output_offset, unsigned int addralign,
312 Output_section_data*);
314 // Write the CIE to OVIEW starting at OFFSET. Round up the bytes to
315 // ADDRALIGN. ADDRESS is the virtual address of OVIEW.
316 // EH_FRAME_HDR is the exception frame header for FDE recording.
317 // POST_FDES stashes FDEs created after mappings were done, for later
318 // writing. Return the new offset.
319 template<int size, bool big_endian>
321 write(unsigned char* oview, section_offset_type output_section_offset,
322 section_offset_type offset, uint64_t address,
323 unsigned int addralign, Eh_frame_hdr* eh_frame_hdr,
324 Post_fdes* post_fdes);
326 friend bool operator<(const Cie&, const Cie&);
327 friend bool operator==(const Cie&, const Cie&);
330 // The class is not assignable.
331 Cie& operator=(const Cie&);
333 // The object in which this CIE was first seen. This will be NULL
334 // for a linker generated CIE.
336 // Input section index for this CIE. This will be 0 for a linker
339 // Offset within the input section for this CIE. This will be 0 for
340 // a linker generated CIE.
341 section_offset_type input_offset_;
342 // The encoding of the FDE. This is a DW_EH_PE code.
343 unsigned char fde_encoding_;
344 // The name of the personality routine. This will be the name of a
345 // global symbol, or will be the empty string.
346 std::string personality_name_;
348 std::vector<Fde*> fdes_;
350 std::string contents_;
353 extern bool operator<(const Cie&, const Cie&);
354 extern bool operator==(const Cie&, const Cie&);
356 // This class manages .eh_frame sections. It discards duplicate
357 // exception information.
359 class Eh_frame : public Output_section_data
364 // Record the associated Eh_frame_hdr, if any.
366 set_eh_frame_hdr(Eh_frame_hdr* hdr)
367 { this->eh_frame_hdr_ = hdr; }
369 // Add the input section SHNDX in OBJECT. SYMBOLS is the contents
370 // of the symbol table section (size SYMBOLS_SIZE), SYMBOL_NAMES is
371 // the symbol names section (size SYMBOL_NAMES_SIZE). RELOC_SHNDX
372 // is the relocation section if any (0 for none, -1U for multiple).
373 // RELOC_TYPE is the type of the relocation section if any. This
374 // returns whether the section was incorporated into the .eh_frame
376 template<int size, bool big_endian>
378 add_ehframe_input_section(Sized_relobj_file<size, big_endian>* object,
379 const unsigned char* symbols,
380 section_size_type symbols_size,
381 const unsigned char* symbol_names,
382 section_size_type symbol_names_size,
383 unsigned int shndx, unsigned int reloc_shndx,
384 unsigned int reloc_type);
386 // Add a CIE and an FDE for a PLT section, to permit unwinding
387 // through a PLT. The FDE data should start with 8 bytes of zero,
388 // which will be replaced by a 4 byte PC relative reference to the
389 // address of PLT and a 4 byte size of PLT.
391 add_ehframe_for_plt(Output_data* plt, const unsigned char* cie_data,
392 size_t cie_length, const unsigned char* fde_data,
395 // Return the number of FDEs.
400 // Set the final data size.
402 set_final_data_size();
404 // Return the output address for an input address.
406 do_output_offset(const Relobj*, unsigned int shndx,
407 section_offset_type offset,
408 section_offset_type* poutput) const;
410 // Write the data to the file.
412 do_write(Output_file*);
414 // Write to a map file.
416 do_print_to_mapfile(Mapfile* mapfile) const
417 { mapfile->print_output_data(this, _("** eh_frame")); }
420 // The comparison routine for the CIE map.
424 operator()(const Cie* cie1, const Cie* cie2) const
425 { return *cie1 < *cie2; }
428 // A set of unique CIEs.
429 typedef std::set<Cie*, Cie_less> Cie_offsets;
431 // A list of unmergeable CIEs.
432 typedef std::vector<Cie*> Unmergeable_cie_offsets;
434 // A mapping from offsets to CIEs. This is used while reading an
436 typedef std::map<uint64_t, Cie*> Offsets_to_cie;
438 // A list of CIEs, and a bool indicating whether the CIE is
440 typedef std::vector<std::pair<Cie*, bool> > New_cies;
444 skip_leb128(const unsigned char**, const unsigned char*);
446 // The implementation of add_ehframe_input_section.
447 template<int size, bool big_endian>
449 do_add_ehframe_input_section(Sized_relobj_file<size, big_endian>* object,
450 const unsigned char* symbols,
451 section_size_type symbols_size,
452 const unsigned char* symbol_names,
453 section_size_type symbol_names_size,
455 unsigned int reloc_shndx,
456 unsigned int reloc_type,
457 const unsigned char* pcontents,
458 section_size_type contents_len,
462 template<int size, bool big_endian>
464 read_cie(Sized_relobj_file<size, big_endian>* object,
466 const unsigned char* symbols,
467 section_size_type symbols_size,
468 const unsigned char* symbol_names,
469 section_size_type symbol_names_size,
470 const unsigned char* pcontents,
471 const unsigned char* pcie,
472 const unsigned char* pcieend,
473 Track_relocs<size, big_endian>* relocs,
474 Offsets_to_cie* cies,
478 template<int size, bool big_endian>
480 read_fde(Sized_relobj_file<size, big_endian>* object,
482 const unsigned char* symbols,
483 section_size_type symbols_size,
484 const unsigned char* pcontents,
486 const unsigned char* pfde,
487 const unsigned char* pfdeend,
488 Track_relocs<size, big_endian>* relocs,
489 Offsets_to_cie* cies);
491 // Template version of write function.
492 template<int size, bool big_endian>
494 do_sized_write(unsigned char* oview);
496 // The exception frame header, if any.
497 Eh_frame_hdr* eh_frame_hdr_;
498 // A mapping from all unique CIEs to their offset in the output
500 Cie_offsets cie_offsets_;
501 // A mapping from unmergeable CIEs to their offset in the output
503 Unmergeable_cie_offsets unmergeable_cie_offsets_;
504 // Whether we have created the mappings to the output section.
505 bool mappings_are_done_;
506 // The final data size. This is only set if mappings_are_done_ is
508 section_size_type final_data_size_;
511 } // End namespace gold.
513 #endif // !defined(GOLD_EHFRAME_H)