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.  DOT_VALUE is the absolute value of the dot
  76   // symbol.  DOT_SECTION is the section in which dot is defined; it
  77   // should be NULL if the dot symbol has an absolute value (e.g., is
  78   // defined in a SECTIONS clause outside of any output section
  79   // definition).  This sets *RESULT_SECTION to indicate where the
  80   // value is defined.  If the value is absolute *RESULT_SECTION will
  81   // be NULL.  Note that the returned value is still an absolute
  82   // value; to get a section relative value the caller must subtract
  83   // the section address.
  84   uint64_t
  85   eval_with_dot(const Symbol_table*, const Layout*, uint64_t dot_value,
  86                 Output_section* dot_section, Output_section** result_section);
  87
  88   // Return the value of an expression which may or may not be
  89   // permitted to refer to the dot symbol, depending on
  90   // is_dot_available.
  91   uint64_t
  92   eval_maybe_dot(const Symbol_table*, const Layout*, bool is_dot_available,
  93                  uint64_t dot_value, Output_section* dot_section,
  94                  Output_section** result_section);
  95
  96   // Print the expression to the FILE.  This is for debugging.
  97   virtual void
  98   print(FILE*) const = 0;
  99
 100  protected:
 101   struct Expression_eval_info;
 102
 103  public:
 104   // Compute the value of the expression (implemented by child class).
 105   // This is public rather than protected because it is called
 106   // directly by children of Expression on other Expression objects.
 107   virtual uint64_t
 108   value(const Expression_eval_info*) = 0;
 109
 110  private:
 111   // May not be copied.
 112   Expression(const Expression&);
 113   Expression& operator=(const Expression&);
 114 };
 115
 116
 117 // Version_script_info stores information parsed from the version
 118 // script, either provided by --version-script or as part of a linker
 119 // script.  A single Version_script_info object per target is owned by
 120 // Script_options.
 121
 122 class Version_script_info
 123 {
 124  public:
 125   ~Version_script_info();
 126
 127   // Clear everything.
 128   void
 129   clear();
 130
 131   // Return whether any version were defined in the version script.
 132   bool
 133   empty() const
 134   { return this->version_trees_.empty(); }
 135
 136   // Return the version associated with the given symbol name.
 137   // Strings are allocated out of the stringpool given in the
 138   // constructor.  Strings are allocated out of the stringpool given
 139   // in the constructor.
 140   const std::string&
 141   get_symbol_version(const char* symbol) const
 142   { return get_symbol_version_helper(symbol, true); }
 143
 144   // Return whether this symbol matches the local: section of a
 145   // version script (it doesn't matter which).
 146   bool
 147   symbol_is_local(const char* symbol) const
 148   {
 149     return (get_symbol_version(symbol).empty()
 150             && !get_symbol_version_helper(symbol, false).empty());
 151   }
 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   const std::string& get_symbol_version_helper(const char* symbol,
 185                                                bool check_global) const;
 186
 187   std::vector<struct Version_dependency_list*> dependency_lists_;
 188   std::vector<struct Version_expression_list*> expression_lists_;
 189   std::vector<struct Version_tree*> version_trees_;
 190 };
 191
 192 // This class manages assignments to symbols.  These can appear in
 193 // three different locations in scripts: outside of a SECTIONS clause,
 194 // within a SECTIONS clause, and within an output section definition
 195 // within a SECTIONS clause.  This can also appear on the command line
 196 // via the --defsym command line option.
 197
 198 class Symbol_assignment
 199 {
 200  public:
 201   Symbol_assignment(const char* name, size_t namelen, Expression* val,
 202                     bool provide, bool hidden)
 203     : name_(name, namelen), val_(val), provide_(provide), hidden_(hidden),
 204       sym_(NULL)
 205   { }
 206
 207   // Add the symbol to the symbol table.
 208   void
 209   add_to_table(Symbol_table*);
 210
 211   // Finalize the symbol value.
 212   void
 213   finalize(Symbol_table*, const Layout*);
 214
 215   // Finalize the symbol value when it can refer to the dot symbol.
 216   void
 217   finalize_with_dot(Symbol_table*, const Layout*, uint64_t dot_value,
 218                     Output_section* dot_section);
 219
 220   // Set the symbol value, but only if the value is absolute.  This is
 221   // used while processing a SECTIONS clause.  We assume that dot is
 222   // an absolute value here.
 223   void
 224   set_if_absolute(Symbol_table*, const Layout*, bool is_dot_available,
 225                   uint64_t dot_value);
 226
 227   // Print the assignment to the FILE.  This is for debugging.
 228   void
 229   print(FILE*) const;
 230
 231  private:
 232   // Shared by finalize and finalize_with_dot.
 233   void
 234   finalize_maybe_dot(Symbol_table*, const Layout*, bool is_dot_available,
 235                      uint64_t dot_value, Output_section* dot_section);
 236
 237   // Sized version of finalize.
 238   template<int size>
 239   void
 240   sized_finalize(Symbol_table*, const Layout*, bool is_dot_available,
 241                  uint64_t dot_value, Output_section*);
 242
 243   // Symbol name.
 244   std::string name_;
 245   // Expression to assign to symbol.
 246   Expression* val_;
 247   // Whether the assignment should be provided (only set if there is
 248   // an undefined reference to the symbol.
 249   bool provide_;
 250   // Whether the assignment should be hidden.
 251   bool hidden_;
 252   // The entry in the symbol table.
 253   Symbol* sym_;
 254 };
 255
 256 // This class manages assertions in linker scripts.  These can appear
 257 // in all the places where a Symbol_assignment can appear.
 258
 259 class Script_assertion
 260 {
 261  public:
 262   Script_assertion(Expression* check, const char* message,
 263                    size_t messagelen)
 264     : check_(check), message_(message, messagelen)
 265   { }
 266
 267   // Check the assertion.
 268   void
 269   check(const Symbol_table*, const Layout*);
 270
 271   // Print the assertion to the FILE.  This is for debugging.
 272   void
 273   print(FILE*) const;
 274
 275  private:
 276   // The expression to check.
 277   Expression* check_;
 278   // The message to issue if the expression fails.
 279   std::string message_;
 280 };
 281
 282 // We can read a linker script in two different contexts: when
 283 // initially parsing the command line, and when we find an input file
 284 // which is actually a linker script.  Also some of the data which can
 285 // be set by a linker script can also be set via command line options
 286 // like -e and --defsym.  This means that we have a type of data which
 287 // can be set both during command line option parsing and while
 288 // reading input files.  We store that data in an instance of this
 289 // object.  We will keep pointers to that instance in both the
 290 // Command_line and Layout objects.
 291
 292 class Script_options
 293 {
 294  public:
 295   Script_options();
 296
 297   // The entry address.
 298   const char*
 299   entry() const
 300   { return this->entry_.empty() ? NULL : this->entry_.c_str(); }
 301
 302   // Set the entry address.
 303   void
 304   set_entry(const char* entry, size_t length)
 305   { this->entry_.assign(entry, length); }
 306
 307   // Add a symbol to be defined.
 308   void
 309   add_symbol_assignment(const char* name, size_t length, Expression* value,
 310                         bool provide, bool hidden);
 311
 312   // Add an assertion.
 313   void
 314   add_assertion(Expression* check, const char* message, size_t messagelen);
 315
 316   // Define a symbol from the command line.
 317   bool
 318   define_symbol(const char* definition);
 319
 320   // Add all symbol definitions to the symbol table.
 321   void
 322   add_symbols_to_table(Symbol_table*);
 323
 324   // Finalize the symbol values.  Also check assertions.
 325   void
 326   finalize_symbols(Symbol_table*, const Layout*);
 327
 328   // Version information parsed from a version script.  Everything
 329   // else has a pointer to this object.
 330   Version_script_info*
 331   version_script_info()
 332   { return &this->version_script_info_; }
 333
 334   // A SECTIONS clause parsed from a linker script.  Everything else
 335   // has a pointer to this object.
 336   Script_sections*
 337   script_sections()
 338   { return &this->script_sections_; }
 339
 340   // Whether we saw a SECTIONS clause.
 341   bool
 342   saw_sections_clause() const
 343   { return this->script_sections_.saw_sections_clause(); }
 344
 345   // Whether we saw a PHDRS clause.
 346   bool
 347   saw_phdrs_clause() const
 348   { return this->script_sections_.saw_phdrs_clause(); }
 349
 350   // Set section addresses using a SECTIONS clause.  Return the
 351   // segment which should hold the file header and segment headers;
 352   // this may return NULL, in which case the headers are not in a
 353   // loadable segment.
 354   Output_segment*
 355   set_section_addresses(Symbol_table*, Layout*);
 356
 357   // Print the script to the FILE.  This is for debugging.
 358   void
 359   print(FILE*) const;
 360
 361  private:
 362   // We keep a list of symbol assignments which occur outside of a
 363   // SECTIONS clause.
 364   typedef std::vector<Symbol_assignment*> Symbol_assignments;
 365
 366   // We keep a list of all assertions whcih occur outside of a
 367   // SECTIONS clause.
 368   typedef std::vector<Script_assertion*> Assertions;
 369
 370   // The entry address.  This will be empty if not set.
 371   std::string entry_;
 372   // Symbols to set.
 373   Symbol_assignments symbol_assignments_;
 374   // Assertions to check.
 375   Assertions assertions_;
 376   // Version information parsed from a version script.
 377   Version_script_info version_script_info_;
 378   // Information from any SECTIONS clauses.
 379   Script_sections script_sections_;
 380 };
 381
 382 // FILE was found as an argument on the command line, but was not
 383 // recognized as an ELF file.  Try to read it as a script.  We've
 384 // already read BYTES of data into P.  Return true if the file was
 385 // handled.  This has to handle /usr/lib/libc.so on a GNU/Linux
 386 // system.
 387
 388 bool
 389 read_input_script(Workqueue*, const General_options&, Symbol_table*, Layout*,
 390                   Dirsearch*, Input_objects*, Input_group*,
 391                   const Input_argument*, Input_file*, const unsigned char* p,
 392                   off_t bytes, Task_token* this_blocker,
 393                   Task_token* next_blocker);
 394
 395 // FILE was found as an argument to --script (-T).
 396 // Read it as a script, and execute its contents immediately.
 397
 398 bool
 399 read_commandline_script(const char* filename, Command_line*);
 400
 401 // FILE was found as an argument to --version-script.  Read it as a
 402 // version script, and store its contents in
 403 // cmdline->script_options()->version_script_info().
 404
 405 bool
 406 read_version_script(const char* filename, Command_line* cmdline);
 407
 408
 409 } // End namespace gold.
 410
 411 #endif // !defined(GOLD_SCRIPT_H)