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 namespace gold
  36 {
  37
  38 class General_options;
  39 class Command_line;
  40 class Symbol_table;
  41 class Layout;
  42 class Input_argument;
  43 class Input_objects;
  44 class Input_group;
  45 class Input_file;
  46 class Target;
  47 class Task_token;
  48 class Workqueue;
  49
  50 // This class represents an expression in a linker script.
  51
  52 class Expression
  53 {
  54  protected:
  55   // These should only be created by child classes.
  56   Expression()
  57   { }
  58
  59  public:
  60   virtual ~Expression()
  61   { }
  62
  63   // Return the value of the expression.
  64   uint64_t
  65   eval(const Symbol_table*, const Layout*);
  66
  67  protected:
  68   struct Expression_eval_info;
  69
  70  public:
  71   // Compute the value of the expression (implemented by child class).
  72   // This is public rather than protected because it is called
  73   // directly by children of Expression on other Expression objects.
  74   virtual uint64_t
  75   value(const Expression_eval_info*) = 0;
  76
  77  private:
  78   // May not be copied.
  79   Expression(const Expression&);
  80   Expression& operator=(const Expression&);
  81 };
  82
  83 // We can read a linker script in two different contexts: when
  84 // initially parsing the command line, and when we find an input file
  85 // which is actually a linker script.  Also some of the data which can
  86 // be set by a linker script can also be set via command line options
  87 // like -e and --defsym.  This means that we have a type of data which
  88 // can be set both during command line option parsing and while
  89 // reading input files.  We store that data in an instance of this
  90 // object.  We will keep pointers to that instance in both the
  91 // Command_line and Layout objects.
  92
  93 class Script_options
  94 {
  95  public:
  96   Script_options();
  97
  98   // The entry address.
  99   const char*
 100   entry() const
 101   { return this->entry_.empty() ? NULL : this->entry_.c_str(); }
 102
 103   // Set the entry address.
 104   void
 105   set_entry(const char* entry, size_t length)
 106   { this->entry_.assign(entry, length); }
 107
 108   // Add a symbol to be defined.  These are for symbol definitions
 109   // which appear outside of a SECTIONS clause.
 110   void
 111   add_symbol_assignment(const char* name, size_t length, Expression* value,
 112                         bool provided, bool hidden)
 113   {
 114     this->symbol_assignments_.push_back(Symbol_assignment(name, length, value,
 115                                                           provided, hidden));
 116   }
 117
 118   // Define a symbol from the command line.
 119   bool
 120   define_symbol(const char* definition);
 121
 122   // Add all symbol definitions to the symbol table.
 123   void
 124   add_symbols_to_table(Symbol_table*, const Target*);
 125
 126   // Finalize the symbol values.
 127   void
 128   finalize_symbols(Symbol_table*, const Layout*);
 129
 130  private:
 131   // We keep a list of symbol assignments.
 132   struct Symbol_assignment
 133   {
 134     // Symbol name.
 135     std::string name;
 136     // Expression to assign to symbol.
 137     Expression* value;
 138     // Whether the assignment should be provided (only set if there is
 139     // an undefined reference to the symbol.
 140     bool provide;
 141     // Whether the assignment should be hidden.
 142     bool hidden;
 143     // The entry in the symbol table.
 144     Symbol* sym;
 145
 146     Symbol_assignment(const char* namea, size_t lengtha, Expression* valuea,
 147                       bool providea, bool hiddena)
 148       : name(namea, lengtha), value(valuea), provide(providea),
 149         hidden(hiddena), sym(NULL)
 150     { }
 151   };
 152
 153   typedef std::vector<Symbol_assignment> Symbol_assignments;
 154
 155   template<int size>
 156   void
 157   sized_finalize_symbols(Symbol_table*, const Layout*);
 158
 159   // The entry address.  This will be empty if not set.
 160   std::string entry_;
 161   // Symbols to set.
 162   Symbol_assignments symbol_assignments_;
 163 };
 164
 165 // FILE was found as an argument on the command line, but was not
 166 // recognized as an ELF file.  Try to read it as a script.  We've
 167 // already read BYTES of data into P.  Return true if the file was
 168 // handled.  This has to handle /usr/lib/libc.so on a GNU/Linux
 169 // system.
 170
 171 bool
 172 read_input_script(Workqueue*, const General_options&, Symbol_table*, Layout*,
 173                   Dirsearch*, Input_objects*, Input_group*,
 174                   const Input_argument*, Input_file*, const unsigned char* p,
 175                   off_t bytes, Task_token* this_blocker,
 176                   Task_token* next_blocker);
 177
 178 // FILE was found as an argument to --script (-T).
 179 // Read it as a script, and execute its contents immediately.
 180
 181 bool
 182 read_commandline_script(const char* filename, Command_line*);
 183
 184 } // End namespace gold.
 185
 186 #endif // !defined(GOLD_SCRIPT_H)