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