gold/script.h

   1 // script.h -- handle linker scripts 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 // We implement a subset of the original GNU ld linker script language
  24 // for compatibility.  The goal is not to implement the entire
  25 // language.  It is merely to implement enough to handle common uses.
  26 // In particular we need to handle /usr/lib/libc.so on a typical
  27 // GNU/Linux system, and we want to handle linker scripts used by the
  28 // Linux kernel build.
  29
  30 #ifndef GOLD_SCRIPT_H
  31 #define GOLD_SCRIPT_H
  32
  33 #include <cstdio>
  34 #include <string>
  35 #include <vector>
  36
  37 #include "script-sections.h"
  38
  39 namespace gold
  40 {
  41
  42 class General_options;
  43 class Command_line;
  44 class Symbol_table;
  45 class Layout;
  46 class Mapfile;
  47 class Input_argument;
  48 class Input_objects;
  49 class Input_group;
  50 class Input_file;
  51 class Output_segment;
  52 class Task_token;
  53 class Workqueue;
  54 struct Version_dependency_list;
  55 struct Version_expression_list;
  56 struct Version_tree;
  57
  58 // This class represents an expression in a linker script.
  59
  60 class Expression
  61 {
  62  protected:
  63   // These should only be created by child classes.
  64   Expression()
  65   { }
  66
  67  public:
  68   virtual ~Expression()
  69   { }
  70
  71   // Return the value of the expression which is not permitted to
  72   // refer to the dot symbol.  CHECK_ASSERTIONS is true if we should
  73   // check whether assertions are true.
  74   uint64_t
  75   eval(const Symbol_table*, const Layout*, bool check_assertions);
  76
  77   // Return the value of an expression which is permitted to refer to
  78   // the dot symbol.  DOT_VALUE is the absolute value of the dot
  79   // symbol.  DOT_SECTION is the section in which dot is defined; it
  80   // should be NULL if the dot symbol has an absolute value (e.g., is
  81   // defined in a SECTIONS clause outside of any output section
  82   // definition).  This sets *RESULT_SECTION to indicate where the
  83   // value is defined.  If the value is absolute *RESULT_SECTION will
  84   // be NULL.  Note that the returned value is still an absolute
  85   // value; to get a section relative value the caller must subtract
  86   // the section address.
  87   uint64_t
  88   eval_with_dot(const Symbol_table*, const Layout*, bool check_assertions,
  89                 uint64_t dot_value, Output_section* dot_section,
  90                 Output_section** result_section);
  91
  92   // Return the value of an expression which may or may not be
  93   // permitted to refer to the dot symbol, depending on
  94   // is_dot_available.
  95   uint64_t
  96   eval_maybe_dot(const Symbol_table*, const Layout*, bool check_assertions,
  97                  bool is_dot_available, uint64_t dot_value,
  98                  Output_section* dot_section,
  99                  Output_section** result_section);
 100
 101   // Print the expression to the FILE.  This is for debugging.
 102   virtual void
 103   print(FILE*) const = 0;
 104
 105  protected:
 106   struct Expression_eval_info;
 107
 108  public:
 109   // Compute the value of the expression (implemented by child class).
 110   // This is public rather than protected because it is called
 111   // directly by children of Expression on other Expression objects.
 112   virtual uint64_t
 113   value(const Expression_eval_info*) = 0;
 114
 115  private:
 116   // May not be copied.
 117   Expression(const Expression&);
 118   Expression& operator=(const Expression&);
 119 };
 120
 121
 122 // Version_script_info stores information parsed from the version
 123 // script, either provided by --version-script or as part of a linker
 124 // script.  A single Version_script_info object per target is owned by
 125 // Script_options.
 126
 127 class Version_script_info
 128 {
 129  public:
 130   ~Version_script_info();
 131
 132   // Clear everything.
 133   void
 134   clear();
 135
 136   // Return whether any version were defined in the version script.
 137   bool
 138   empty() const
 139   { return this->version_trees_.empty(); }
 140
 141   // If there is a version associated with SYMBOL, return true, and
 142   // set *VERSION to the version.  Otherwise, return false.
 143   bool
 144   get_symbol_version(const char* symbol, std::string* version) const
 145   { return this->get_symbol_version_helper(symbol, true, version); }
 146
 147   // Return whether this symbol matches the local: section of some
 148   // version.
 149   bool
 150   symbol_is_local(const char* symbol) const
 151   { return this->get_symbol_version_helper(symbol, false, NULL); }
 152
 153   // Return the names of versions defined in the version script.
 154   // Strings are allocated out of the stringpool given in the
 155   // constructor.
 156   std::vector<std::string>
 157   get_versions() const;
 158
 159   // Return the list of dependencies for this version.
 160   std::vector<std::string>
 161   get_dependencies(const char* version) const;
 162
 163   // The following functions should only be used by the bison helper
 164   // functions.  They allocate new structs whose memory belongs to
 165   // Version_script_info.  The bison functions copy the information
 166   // from the version script into these structs.
 167   struct Version_dependency_list*
 168   allocate_dependency_list();
 169
 170   struct Version_expression_list*
 171   allocate_expression_list();
 172
 173   struct Version_tree*
 174   allocate_version_tree();
 175
 176   // Print contents to the FILE.  This is for debugging.
 177   void
 178   print(FILE*) const;
 179
 180  private:
 181   void
 182   print_expression_list(FILE* f, const Version_expression_list*) const;
 183
 184   bool get_symbol_version_helper(const char* symbol,
 185                                  bool check_global,
 186                                  std::string* pversion) const;
 187
 188   std::vector<struct Version_dependency_list*> dependency_lists_;
 189   std::vector<struct Version_expression_list*> expression_lists_;
 190   std::vector<struct Version_tree*> version_trees_;
 191 };
 192
 193 // This class manages assignments to symbols.  These can appear in
 194 // three different locations in scripts: outside of a SECTIONS clause,
 195 // within a SECTIONS clause, and within an output section definition
 196 // within a SECTIONS clause.  This can also appear on the command line
 197 // via the --defsym command line option.
 198
 199 class Symbol_assignment
 200 {
 201  public:
 202   Symbol_assignment(const char* name, size_t namelen, Expression* val,
 203                     bool provide, bool hidden)
 204     : name_(name, namelen), val_(val), provide_(provide), hidden_(hidden),
 205       sym_(NULL)
 206   { }
 207
 208   // Add the symbol to the symbol table.
 209   void
 210   add_to_table(Symbol_table*);
 211
 212   // Finalize the symbol value.
 213   void
 214   finalize(Symbol_table*, const Layout*);
 215
 216   // Finalize the symbol value when it can refer to the dot symbol.
 217   void
 218   finalize_with_dot(Symbol_table*, const Layout*, uint64_t dot_value,
 219                     Output_section* dot_section);
 220
 221   // Set the symbol value, but only if the value is absolute.  This is
 222   // used while processing a SECTIONS clause.  We assume that dot is
 223   // an absolute value here.  We do not check assertions.
 224   void
 225   set_if_absolute(Symbol_table*, const Layout*, bool is_dot_available,
 226                   uint64_t dot_value);
 227
 228   // Print the assignment to the FILE.  This is for debugging.
 229   void
 230   print(FILE*) const;
 231
 232  private:
 233   // Shared by finalize and finalize_with_dot.
 234   void
 235   finalize_maybe_dot(Symbol_table*, const Layout*, bool is_dot_available,
 236                      uint64_t dot_value, Output_section* dot_section);
 237
 238   // Sized version of finalize.
 239   template<int size>
 240   void
 241   sized_finalize(Symbol_table*, const Layout*, bool is_dot_available,
 242                  uint64_t dot_value, Output_section*);
 243
 244   // Symbol name.
 245   std::string name_;
 246   // Expression to assign to symbol.
 247   Expression* val_;
 248   // Whether the assignment should be provided (only set if there is
 249   // an undefined reference to the symbol.
 250   bool provide_;
 251   // Whether the assignment should be hidden.
 252   bool hidden_;
 253   // The entry in the symbol table.
 254   Symbol* sym_;
 255 };
 256
 257 // This class manages assertions in linker scripts.  These can appear
 258 // in all the places where a Symbol_assignment can appear.
 259
 260 class Script_assertion
 261 {
 262  public:
 263   Script_assertion(Expression* check, const char* message,
 264                    size_t messagelen)
 265     : check_(check), message_(message, messagelen)
 266   { }
 267
 268   // Check the assertion.
 269   void
 270   check(const Symbol_table*, const Layout*);
 271
 272   // Print the assertion to the FILE.  This is for debugging.
 273   void
 274   print(FILE*) const;
 275
 276  private:
 277   // The expression to check.
 278   Expression* check_;
 279   // The message to issue if the expression fails.
 280   std::string message_;
 281 };
 282
 283 // We can read a linker script in two different contexts: when
 284 // initially parsing the command line, and when we find an input file
 285 // which is actually a linker script.  Also some of the data which can
 286 // be set by a linker script can also be set via command line options
 287 // like -e and --defsym.  This means that we have a type of data which
 288 // can be set both during command line option parsing and while
 289 // reading input files.  We store that data in an instance of this
 290 // object.  We will keep pointers to that instance in both the
 291 // Command_line and Layout objects.
 292
 293 class Script_options
 294 {
 295  public:
 296   Script_options();
 297
 298   // Add a symbol to be defined.
 299   void
 300   add_symbol_assignment(const char* name, size_t length, Expression* value,
 301                         bool provide, bool hidden);
 302
 303   // Add an assertion.
 304   void
 305   add_assertion(Expression* check, const char* message, size_t messagelen);
 306
 307   // Define a symbol from the command line.
 308   bool
 309   define_symbol(const char* definition);
 310
 311   // Create sections required by any linker scripts.
 312   void
 313   create_script_sections(Layout*);
 314
 315   // Add all symbol definitions to the symbol table.
 316   void
 317   add_symbols_to_table(Symbol_table*);
 318
 319   // Finalize the symbol values.  Also check assertions.
 320   void
 321   finalize_symbols(Symbol_table*, const Layout*);
 322
 323   // Version information parsed from a version script.  Everything
 324   // else has a pointer to this object.
 325   Version_script_info*
 326   version_script_info()
 327   { return &this->version_script_info_; }
 328
 329   const Version_script_info*
 330   version_script_info() const
 331   { return &this->version_script_info_; }
 332
 333   // A SECTIONS clause parsed from a linker script.  Everything else
 334   // has a pointer to this object.
 335   Script_sections*
 336   script_sections()
 337   { return &this->script_sections_; }
 338
 339   const Script_sections*
 340   script_sections() const
 341   { return &this->script_sections_; }
 342
 343   // Whether we saw a SECTIONS clause.
 344   bool
 345   saw_sections_clause() const
 346   { return this->script_sections_.saw_sections_clause(); }
 347
 348   // Whether we saw a PHDRS clause.
 349   bool
 350   saw_phdrs_clause() const
 351   { return this->script_sections_.saw_phdrs_clause(); }
 352
 353   // Set section addresses using a SECTIONS clause.  Return the
 354   // segment which should hold the file header and segment headers;
 355   // this may return NULL, in which case the headers are not in a
 356   // loadable segment.
 357   Output_segment*
 358   set_section_addresses(Symbol_table*, Layout*);
 359
 360   // Print the script to the FILE.  This is for debugging.
 361   void
 362   print(FILE*) const;
 363
 364  private:
 365   // We keep a list of symbol assignments which occur outside of a
 366   // SECTIONS clause.
 367   typedef std::vector<Symbol_assignment*> Symbol_assignments;
 368
 369   // We keep a list of all assertions whcih occur outside of a
 370   // SECTIONS clause.
 371   typedef std::vector<Script_assertion*> Assertions;
 372
 373   // The entry address.  This will be empty if not set.
 374   std::string entry_;
 375   // Symbols to set.
 376   Symbol_assignments symbol_assignments_;
 377   // Assertions to check.
 378   Assertions assertions_;
 379   // Version information parsed from a version script.
 380   Version_script_info version_script_info_;
 381   // Information from any SECTIONS clauses.
 382   Script_sections script_sections_;
 383 };
 384
 385 // FILE was found as an argument on the command line, but was not
 386 // recognized as an ELF file.  Try to read it as a script.  Return
 387 // true if the file was handled.  This has to handle /usr/lib/libc.so
 388 // on a GNU/Linux system.  *USED_NEXT_BLOCKER is set to indicate
 389 // whether the function took over NEXT_BLOCKER.
 390
 391 bool
 392 read_input_script(Workqueue*, Symbol_table*, Layout*, Dirsearch*, int,
 393                   Input_objects*, Mapfile*, Input_group*,
 394                   const Input_argument*, Input_file*,
 395                   Task_token* next_blocker, bool* used_next_blocker);
 396
 397 // FILE was found as an argument to --script (-T).
 398 // Read it as a script, and execute its contents immediately.
 399
 400 bool
 401 read_commandline_script(const char* filename, Command_line* cmdline);
 402
 403 // FILE was found as an argument to --version-script.  Read it as a
 404 // version script, and store its contents in
 405 // cmdline->script_options()->version_script_info().
 406
 407 bool
 408 read_version_script(const char* filename, Command_line* cmdline);
 409
 410 // FILENAME was found as an argument to --dynamic-list.  Read it as a
 411 // version script (actually, a versym_node from a version script), and
 412 // store its contents in DYNAMIC_LIST.
 413
 414 bool
 415 read_dynamic_list(const char* filename, Command_line* cmdline,
 416                   Script_options* dynamic_list);
 417
 418 } // End namespace gold.
 419
 420 #endif // !defined(GOLD_SCRIPT_H)