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