gold/script-sections.h

   1 // script-sections.h -- linker script SECTIONS for gold   -*- C++ -*-
   2
   3 // Copyright (C) 2008-2016 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 // This is for the support of the SECTIONS clause in linker scripts.
  24
  25 #ifndef GOLD_SCRIPT_SECTIONS_H
  26 #define GOLD_SCRIPT_SECTIONS_H
  27
  28 #include <cstdio>
  29 #include <list>
  30 #include <vector>
  31
  32 namespace gold
  33 {
  34
  35 struct Parser_output_section_header;
  36 struct Parser_output_section_trailer;
  37 struct Input_section_spec;
  38 class Expression;
  39 class Sections_element;
  40 class Memory_region;
  41 class Phdrs_element;
  42 class Output_data;
  43 class Output_section_definition;
  44 class Output_section;
  45 class Output_segment;
  46 class Orphan_section_placement;
  47
  48 class Script_sections
  49 {
  50  public:
  51   // This is a list, not a vector, because we insert orphan sections
  52   // in the middle.
  53   typedef std::list<Sections_element*> Sections_elements;
  54
  55   // Logical script section types.  We map section types returned by the
  56   // parser into these since some section types have the same semantics.
  57   enum Section_type
  58   {
  59     // No section type specified.
  60     ST_NONE,
  61     // Section is NOLOAD.  We allocate space in the output but section
  62     // is not loaded in runtime.
  63     ST_NOLOAD,
  64     // No space is allocated to section.
  65     ST_NOALLOC
  66   };
  67
  68   Script_sections();
  69
  70   // Start a SECTIONS clause.
  71   void
  72   start_sections();
  73
  74   // Finish a SECTIONS clause.
  75   void
  76   finish_sections();
  77
  78   // Return whether we ever saw a SECTIONS clause.  If we did, then
  79   // all section layout needs to go through this class.
  80   bool
  81   saw_sections_clause() const
  82   { return this->saw_sections_clause_; }
  83
  84   // Return whether we are currently processing a SECTIONS clause.
  85   bool
  86   in_sections_clause() const
  87   { return this->in_sections_clause_; }
  88
  89   // Return whether we ever saw a PHDRS clause.  We ignore the PHDRS
  90   // clause unless we also saw a SECTIONS clause.
  91   bool
  92   saw_phdrs_clause() const
  93   { return this->saw_sections_clause_ && this->phdrs_elements_ != NULL; }
  94
  95   // Start processing entries for an output section.
  96   void
  97   start_output_section(const char* name, size_t namelen,
  98                        const Parser_output_section_header*);
  99
 100   // Finish processing entries for an output section.
 101   void
 102   finish_output_section(const Parser_output_section_trailer*);
 103
 104   // Add a data item to the current output section.
 105   void
 106   add_data(int size, bool is_signed, Expression* val);
 107
 108   // Add a symbol to be defined.
 109   void
 110   add_symbol_assignment(const char* name, size_t length, Expression* value,
 111                         bool provide, bool hidden);
 112
 113   // Add an assignment to the special dot symbol.
 114   void
 115   add_dot_assignment(Expression* value);
 116
 117   // Add an assertion.
 118   void
 119   add_assertion(Expression* check, const char* message, size_t messagelen);
 120
 121   // Add a setting for the fill value.
 122   void
 123   add_fill(Expression* val);
 124
 125   // Add an input section specification.
 126   void
 127   add_input_section(const Input_section_spec* spec, bool keep);
 128
 129   // Saw DATA_SEGMENT_ALIGN.
 130   void
 131   data_segment_align();
 132
 133   // Saw DATA_SEGMENT_RELRO_END.
 134   void
 135   data_segment_relro_end();
 136
 137   // Create any required sections.
 138   void
 139   create_sections(Layout*);
 140
 141   // Add any symbols we are defining to the symbol table.
 142   void
 143   add_symbols_to_table(Symbol_table*);
 144
 145   // Finalize symbol values and check assertions.
 146   void
 147   finalize_symbols(Symbol_table* symtab, const Layout* layout);
 148
 149   // Find the name of the output section to use for an input file name
 150   // and section name.  This returns a name, and sets
 151   // *OUTPUT_SECTION_SLOT to point to the address where the actual
 152   // output section may be stored.
 153   // 1) If the input section should be discarded, this returns NULL
 154   //    and sets *OUTPUT_SECTION_SLOT to NULL.
 155   // 2) If the input section is mapped by the SECTIONS clause, this
 156   //    returns the name to use for the output section (in permanent
 157   //    storage), and sets *OUTPUT_SECTION_SLOT to point to where the
 158   //    output section should be stored.  **OUTPUT_SECTION_SLOT will be
 159   //    non-NULL if we have seen this output section already.
 160   // 3) If the input section is not mapped by the SECTIONS clause,
 161   //    this returns SECTION_NAME, and sets *OUTPUT_SECTION_SLOT to
 162   //    NULL.
 163   // PSCRIPT_SECTION_TYPE points to a location for returning the section
 164   // type specified in script.  This can be SCRIPT_SECTION_TYPE_NONE if
 165   // no type is specified.
 166   // *KEEP indicates whether the section should survive garbage collection.
 167   const char*
 168   output_section_name(const char* file_name, const char* section_name,
 169                       Output_section*** output_section_slot,
 170                       Section_type* pscript_section_type,
 171                       bool* keep);
 172
 173   // Place a marker for an orphan output section into the SECTIONS
 174   // clause.
 175   void
 176   place_orphan(Output_section* os);
 177
 178   // Set the addresses of all the output sections.  Return the segment
 179   // which holds the file header and segment headers, if any.
 180   Output_segment*
 181   set_section_addresses(Symbol_table*, Layout*);
 182
 183   // Add a program header definition.
 184   void
 185   add_phdr(const char* name, size_t namelen, unsigned int type,
 186            bool filehdr, bool phdrs, bool is_flags_valid, unsigned int flags,
 187            Expression* load_address);
 188
 189   // Return the number of segments we expect to create based on the
 190   // SECTIONS clause.
 191   size_t
 192   expected_segment_count(const Layout*) const;
 193
 194   // Add the file header and segment header to non-load segments as
 195   // specified by the PHDRS clause.
 196   void
 197   put_headers_in_phdrs(Output_data* file_header, Output_data* segment_headers);
 198
 199   // Look for an output section by name and return the address, the
 200   // load address, the alignment, and the size.  This is used when an
 201   // expression refers to an output section which was not actually
 202   // created.  This returns true if the section was found, false
 203   // otherwise.
 204   bool
 205   get_output_section_info(const char* name, uint64_t* address,
 206                           uint64_t* load_address, uint64_t* addralign,
 207                           uint64_t* size) const;
 208
 209   // Release all Output_segments.  This is used in relaxation.
 210   void
 211   release_segments();
 212
 213   // Whether we ever saw a SEGMENT_START expression, the presence of which
 214   // changes the behaviour of -Ttext, -Tdata and -Tbss options.
 215   bool
 216   saw_segment_start_expression() const
 217   { return this->saw_segment_start_expression_; }
 218
 219   // Set the flag which indicates whether we saw a SEGMENT_START expression.
 220   void
 221   set_saw_segment_start_expression(bool value)
 222   { this->saw_segment_start_expression_ = value; }
 223
 224   // Add a memory region.
 225   void
 226   add_memory_region(const char*, size_t, unsigned int,
 227                     Expression*, Expression*);
 228
 229   // Find a memory region's origin.
 230   Expression*
 231   find_memory_region_origin(const char*, size_t);
 232
 233   // Find a memory region's length.
 234   Expression*
 235   find_memory_region_length(const char*, size_t);
 236
 237   // Find a memory region by name.
 238   Memory_region*
 239   find_memory_region(const char*, size_t);
 240
 241   // Find a memory region that should be used by a given output section.
 242   Memory_region*
 243   find_memory_region(Output_section_definition*, bool, bool,
 244                      Output_section_definition**);
 245
 246   // Returns true if the provide block of memory is contained
 247   // within a memory region.
 248   bool
 249   block_in_region(Symbol_table*, Layout*, uint64_t, uint64_t) const;
 250
 251   // Set the memory region of the section.
 252   void
 253   set_memory_region(Memory_region*, bool);
 254
 255   // Print the contents to the FILE.  This is for debugging.
 256   void
 257   print(FILE*) const;
 258
 259   // Used for orphan sections.
 260   typedef Sections_elements::iterator Elements_iterator;
 261
 262  private:
 263   typedef std::vector<Memory_region*> Memory_regions;
 264   typedef std::vector<Phdrs_element*> Phdrs_elements;
 265
 266   // Create segments.
 267   Output_segment*
 268   create_segments(Layout*, uint64_t);
 269
 270   // Create PT_NOTE and PT_TLS segments.
 271   void
 272   create_note_and_tls_segments(Layout*, const std::vector<Output_section*>*);
 273
 274   // Return whether the section is a BSS section.
 275   static bool
 276   is_bss_section(const Output_section*);
 277
 278   // Return the total size of the headers.
 279   size_t
 280   total_header_size(Layout* layout) const;
 281
 282   // Return the amount we have to subtract from the LMA to accomodate
 283   // headers of the given size.
 284   uint64_t
 285   header_size_adjustment(uint64_t lma, size_t sizeof_headers) const;
 286
 287   // Create the segments from a PHDRS clause.
 288   Output_segment*
 289   create_segments_from_phdrs_clause(Layout* layout, uint64_t);
 290
 291   // Attach sections to segments from a PHDRS clause.
 292   void
 293   attach_sections_using_phdrs_clause(Layout*);
 294
 295   // Set addresses of segments from a PHDRS clause.
 296   Output_segment*
 297   set_phdrs_clause_addresses(Layout*, uint64_t);
 298
 299   // True if we ever saw a SECTIONS clause.
 300   bool saw_sections_clause_;
 301   // True if we are currently processing a SECTIONS clause.
 302   bool in_sections_clause_;
 303   // The list of elements in the SECTIONS clause.
 304   Sections_elements* sections_elements_;
 305   // The current output section, if there is one.
 306   Output_section_definition* output_section_;
 307   // The list of memory regions in the MEMORY clause.
 308   Memory_regions* memory_regions_;
 309   // The list of program headers in the PHDRS clause.
 310   Phdrs_elements* phdrs_elements_;
 311   // Where to put orphan sections.
 312   Orphan_section_placement* orphan_section_placement_;
 313   // A pointer to the last Sections_element when we see
 314   // DATA_SEGMENT_ALIGN.
 315   Sections_elements::iterator data_segment_align_start_;
 316   // Whether we have seen DATA_SEGMENT_ALIGN.
 317   bool saw_data_segment_align_;
 318   // Whether we have seen DATA_SEGMENT_RELRO_END.
 319   bool saw_relro_end_;
 320   // Whether we have seen SEGMENT_START.
 321   bool saw_segment_start_expression_;
 322   // Whether we have created all necessary segments.
 323   bool segments_created_;
 324 };
 325
 326 // Attributes for memory regions.
 327 enum
 328 {
 329   MEM_EXECUTABLE   = (1 << 0),
 330   MEM_WRITEABLE    = (1 << 1),
 331   MEM_READABLE     = (1 << 2),
 332   MEM_ALLOCATABLE  = (1 << 3),
 333   MEM_INITIALIZED  = (1 << 4),
 334   MEM_ATTR_MASK    = (1 << 5) - 1
 335 };
 336
 337 } // End namespace gold.
 338
 339 #endif // !defined(GOLD_SCRIPT_SECTIONS_H