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 <vector>
  34
  35 struct Version_dependency_list;
  36 struct Version_expression_list;
  37 struct Version_tree;
  38
  39 namespace gold
  40 {
  41
  42 class General_options;
  43 class Command_line;
  44 class Symbol_table;
  45 class Layout;
  46 class Input_argument;
  47 class Input_objects;
  48 class Input_group;
  49 class Input_file;
  50 class Target;
  51 class Task_token;
  52 class Workqueue;
  53
  54 // This class represents an expression in a linker script.
  55
  56 class Expression
  57 {
  58  protected:
  59   // These should only be created by child classes.
  60   Expression()
  61   { }
  62
  63  public:
  64   virtual ~Expression()
  65   { }
  66
  67   // Return the value of the expression.
  68   uint64_t
  69   eval(const Symbol_table*, const Layout*);
  70
  71  protected:
  72   struct Expression_eval_info;
  73
  74  public:
  75   // Compute the value of the expression (implemented by child class).
  76   // This is public rather than protected because it is called
  77   // directly by children of Expression on other Expression objects.
  78   virtual uint64_t
  79   value(const Expression_eval_info*) = 0;
  80
  81  private:
  82   // May not be copied.
  83   Expression(const Expression&);
  84   Expression& operator=(const Expression&);
  85 };
  86
  87
  88 // Version_script_info stores information parsed from the version
  89 // script, either provided by --version-script or as part of a linker
  90 // script.  A single Version_script_info object per target is owned by
  91 // Script_options.
  92
  93 class Version_script_info {
  94  public:
  95   ~Version_script_info();
  96
  97   // Return whether any version were defined in the version script.
  98   bool
  99   empty() const
 100   { return this->version_trees_.empty(); }
 101
 102   // Return the version associated with the given symbol name.
 103   // Strings are allocated out of the stringpool given in the
 104   // constructor.  Strings are allocated out of the stringpool given
 105   // in the constructor.
 106   const std::string&
 107   get_symbol_version(const char* symbol) const
 108   { return get_symbol_version_helper(symbol, true); }
 109
 110   // Return whether this symbol matches the local: section of a
 111   // version script (it doesn't matter which).  This test is only
 112   // valid if get_symbol_version() returns the empty string, as we
 113   // don't test that here.
 114   bool
 115   symbol_is_local(const char* symbol) const
 116   { return !get_symbol_version_helper(symbol, false).empty(); }
 117
 118   // Return the names of versions defined in the version script.
 119   // Strings are allocated out of the stringpool given in the
 120   // constructor.
 121   std::vector<std::string>
 122   get_versions() const;
 123
 124   // Return the list of dependencies for this version.
 125   std::vector<std::string>
 126   get_dependencies(const char* version) const;
 127
 128   // The following functions should only be used by the bison helper
 129   // functions.  They allocate new structs whose memory belongs to
 130   // Version_script_info.  The bison functions copy the information
 131   // from the version script into these structs.
 132   struct Version_dependency_list*
 133   allocate_dependency_list();
 134
 135   struct Version_expression_list*
 136   allocate_expression_list();
 137
 138   struct Version_tree*
 139   allocate_version_tree();
 140
 141  private:
 142   const std::string& get_symbol_version_helper(const char* symbol,
 143                                                bool check_global) const;
 144
 145   std::vector<struct Version_dependency_list*> dependency_lists_;
 146   std::vector<struct Version_expression_list*> expression_lists_;
 147   std::vector<struct Version_tree*> version_trees_;
 148 };
 149
 150 // We can read a linker script in two different contexts: when
 151 // initially parsing the command line, and when we find an input file
 152 // which is actually a linker script.  Also some of the data which can
 153 // be set by a linker script can also be set via command line options
 154 // like -e and --defsym.  This means that we have a type of data which
 155 // can be set both during command line option parsing and while
 156 // reading input files.  We store that data in an instance of this
 157 // object.  We will keep pointers to that instance in both the
 158 // Command_line and Layout objects.
 159
 160 class Script_options
 161 {
 162  public:
 163   Script_options();
 164
 165   // The entry address.
 166   const char*
 167   entry() const
 168   { return this->entry_.empty() ? NULL : this->entry_.c_str(); }
 169
 170   // Set the entry address.
 171   void
 172   set_entry(const char* entry, size_t length)
 173   { this->entry_.assign(entry, length); }
 174
 175   // Add a symbol to be defined.  These are for symbol definitions
 176   // which appear outside of a SECTIONS clause.
 177   void
 178   add_symbol_assignment(const char* name, size_t length, Expression* value,
 179                         bool provided, bool hidden)
 180   {
 181     this->symbol_assignments_.push_back(Symbol_assignment(name, length, value,
 182                                                           provided, hidden));
 183   }
 184
 185   // Define a symbol from the command line.
 186   bool
 187   define_symbol(const char* definition);
 188
 189   // Add all symbol definitions to the symbol table.
 190   void
 191   add_symbols_to_table(Symbol_table*, const Target*);
 192
 193   // Finalize the symbol values.
 194   void
 195   finalize_symbols(Symbol_table*, const Layout*);
 196
 197   // Version information parsed from a version script.  Everything
 198   // else has a pointer to this object.
 199   Version_script_info*
 200   version_script_info()
 201   { return &version_script_info_; }
 202
 203  private:
 204   // We keep a list of symbol assignments.
 205   struct Symbol_assignment
 206   {
 207     // Symbol name.
 208     std::string name;
 209     // Expression to assign to symbol.
 210     Expression* value;
 211     // Whether the assignment should be provided (only set if there is
 212     // an undefined reference to the symbol.
 213     bool provide;
 214     // Whether the assignment should be hidden.
 215     bool hidden;
 216     // The entry in the symbol table.
 217     Symbol* sym;
 218
 219     Symbol_assignment(const char* namea, size_t lengtha, Expression* valuea,
 220                       bool providea, bool hiddena)
 221       : name(namea, lengtha), value(valuea), provide(providea),
 222         hidden(hiddena), sym(NULL)
 223     { }
 224   };
 225
 226   typedef std::vector<Symbol_assignment> Symbol_assignments;
 227
 228   template<int size>
 229   void
 230   sized_finalize_symbols(Symbol_table*, const Layout*);
 231
 232   // The entry address.  This will be empty if not set.
 233   std::string entry_;
 234   // Symbols to set.
 235   Symbol_assignments symbol_assignments_;
 236   // Version information parsed from a version script.
 237   Version_script_info version_script_info_;
 238 };
 239
 240 // FILE was found as an argument on the command line, but was not
 241 // recognized as an ELF file.  Try to read it as a script.  We've
 242 // already read BYTES of data into P.  Return true if the file was
 243 // handled.  This has to handle /usr/lib/libc.so on a GNU/Linux
 244 // system.
 245
 246 bool
 247 read_input_script(Workqueue*, const General_options&, Symbol_table*, Layout*,
 248                   Dirsearch*, Input_objects*, Input_group*,
 249                   const Input_argument*, Input_file*, const unsigned char* p,
 250                   off_t bytes, Task_token* this_blocker,
 251                   Task_token* next_blocker);
 252
 253 // FILE was found as an argument to --script (-T).
 254 // Read it as a script, and execute its contents immediately.
 255
 256 bool
 257 read_commandline_script(const char* filename, Command_line*);
 258
 259 // FILE was found as an argument to --version-script.  Read it as a
 260 // version script, and store its contents in
 261 // cmdline->script_options()->version_script_info().
 262
 263 bool
 264 read_version_script(const char* filename, Command_line* cmdline);
 265
 266
 267 } // End namespace gold.
 268
 269 #endif // !defined(GOLD_SCRIPT_H)