gold/expression.cc

   1 // expression.cc -- expressions in linker scripts for gold
   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 #include "gold.h"
  24
  25 #include <string>
  26
  27 #include "elfcpp.h"
  28 #include "parameters.h"
  29 #include "symtab.h"
  30 #include "layout.h"
  31 #include "output.h"
  32 #include "script.h"
  33 #include "script-c.h"
  34
  35 namespace gold
  36 {
  37
  38 // This file holds the code which handles linker expressions.
  39
  40 // The dot symbol, which linker scripts refer to simply as ".",
  41 // requires special treatment.  The dot symbol is set several times,
  42 // section addresses will refer to it, output sections will change it,
  43 // and it can be set based on the value of other symbols.  We simplify
  44 // the handling by prohibiting setting the dot symbol to the value of
  45 // a non-absolute symbol.
  46
  47 // When evaluating the value of an expression, we pass in a pointer to
  48 // this struct, so that the expression evaluation can find the
  49 // information it needs.
  50
  51 struct Expression::Expression_eval_info
  52 {
  53   // The symbol table.
  54   const Symbol_table* symtab;
  55   // The layout--we use this to get section information.
  56   const Layout* layout;
  57   // Whether to check assertions.
  58   bool check_assertions;
  59   // Whether expressions can refer to the dot symbol.  The dot symbol
  60   // is only available within a SECTIONS clause.
  61   bool is_dot_available;
  62   // The current value of the dot symbol.
  63   uint64_t dot_value;
  64   // The section in which the dot symbol is defined; this is NULL if
  65   // it is absolute.
  66   Output_section* dot_section;
  67   // Points to where the section of the result should be stored.
  68   Output_section** result_section_pointer;
  69   // Pointer to where the alignment of the result should be stored.
  70   uint64_t* result_alignment_pointer;
  71 };
  72
  73 // Evaluate an expression.
  74
  75 uint64_t
  76 Expression::eval(const Symbol_table* symtab, const Layout* layout,
  77                  bool check_assertions)
  78 {
  79   return this->eval_maybe_dot(symtab, layout, check_assertions,
  80                               false, 0, NULL, NULL, NULL);
  81 }
  82
  83 // Evaluate an expression which may refer to the dot symbol.
  84
  85 uint64_t
  86 Expression::eval_with_dot(const Symbol_table* symtab, const Layout* layout,
  87                           bool check_assertions, uint64_t dot_value,
  88                           Output_section* dot_section,
  89                           Output_section** result_section_pointer,
  90                           uint64_t* result_alignment_pointer)
  91 {
  92   return this->eval_maybe_dot(symtab, layout, check_assertions, true,
  93                               dot_value, dot_section, result_section_pointer,
  94                               result_alignment_pointer);
  95 }
  96
  97 // Evaluate an expression which may or may not refer to the dot
  98 // symbol.
  99
 100 uint64_t
 101 Expression::eval_maybe_dot(const Symbol_table* symtab, const Layout* layout,
 102                            bool check_assertions, bool is_dot_available,
 103                            uint64_t dot_value, Output_section* dot_section,
 104                            Output_section** result_section_pointer,
 105                            uint64_t* result_alignment_pointer)
 106 {
 107   Expression_eval_info eei;
 108   eei.symtab = symtab;
 109   eei.layout = layout;
 110   eei.check_assertions = check_assertions;
 111   eei.is_dot_available = is_dot_available;
 112   eei.dot_value = dot_value;
 113   eei.dot_section = dot_section;
 114
 115   // We assume the value is absolute, and only set this to a section
 116   // if we find a section relative reference.
 117   if (result_section_pointer != NULL)
 118     *result_section_pointer = NULL;
 119   eei.result_section_pointer = result_section_pointer;
 120
 121   eei.result_alignment_pointer = result_alignment_pointer;
 122
 123   return this->value(&eei);
 124 }
 125
 126 // A number.
 127
 128 class Integer_expression : public Expression
 129 {
 130  public:
 131   Integer_expression(uint64_t val)
 132     : val_(val)
 133   { }
 134
 135   uint64_t
 136   value(const Expression_eval_info*)
 137   { return this->val_; }
 138
 139   void
 140   print(FILE* f) const
 141   { fprintf(f, "0x%llx", static_cast<unsigned long long>(this->val_)); }
 142
 143  private:
 144   uint64_t val_;
 145 };
 146
 147 extern "C" Expression*
 148 script_exp_integer(uint64_t val)
 149 {
 150   return new Integer_expression(val);
 151 }
 152
 153 // An expression whose value is the value of a symbol.
 154
 155 class Symbol_expression : public Expression
 156 {
 157  public:
 158   Symbol_expression(const char* name, size_t length)
 159     : name_(name, length)
 160   { }
 161
 162   uint64_t
 163   value(const Expression_eval_info*);
 164
 165   void
 166   print(FILE* f) const
 167   { fprintf(f, "%s", this->name_.c_str()); }
 168
 169  private:
 170   std::string name_;
 171 };
 172
 173 uint64_t
 174 Symbol_expression::value(const Expression_eval_info* eei)
 175 {
 176   Symbol* sym = eei->symtab->lookup(this->name_.c_str());
 177   if (sym == NULL || !sym->is_defined())
 178     {
 179       gold_error(_("undefined symbol '%s' referenced in expression"),
 180                  this->name_.c_str());
 181       return 0;
 182     }
 183
 184   if (eei->result_section_pointer != NULL)
 185     *eei->result_section_pointer = sym->output_section();
 186
 187   if (parameters->target().get_size() == 32)
 188     return eei->symtab->get_sized_symbol<32>(sym)->value();
 189   else if (parameters->target().get_size() == 64)
 190     return eei->symtab->get_sized_symbol<64>(sym)->value();
 191   else
 192     gold_unreachable();
 193 }
 194
 195 // An expression whose value is the value of the special symbol ".".
 196 // This is only valid within a SECTIONS clause.
 197
 198 class Dot_expression : public Expression
 199 {
 200  public:
 201   Dot_expression()
 202   { }
 203
 204   uint64_t
 205   value(const Expression_eval_info*);
 206
 207   void
 208   print(FILE* f) const
 209   { fprintf(f, "."); }
 210 };
 211
 212 uint64_t
 213 Dot_expression::value(const Expression_eval_info* eei)
 214 {
 215   if (!eei->is_dot_available)
 216     {
 217       gold_error(_("invalid reference to dot symbol outside of "
 218                    "SECTIONS clause"));
 219       return 0;
 220     }
 221   if (eei->result_section_pointer != NULL)
 222     *eei->result_section_pointer = eei->dot_section;
 223   return eei->dot_value;
 224 }
 225
 226 // A string.  This is either the name of a symbol, or ".".
 227
 228 extern "C" Expression*
 229 script_exp_string(const char* name, size_t length)
 230 {
 231   if (length == 1 && name[0] == '.')
 232     return new Dot_expression();
 233   else
 234     return new Symbol_expression(name, length);
 235 }
 236
 237 // A unary expression.
 238
 239 class Unary_expression : public Expression
 240 {
 241  public:
 242   Unary_expression(Expression* arg)
 243     : arg_(arg)
 244   { }
 245
 246   ~Unary_expression()
 247   { delete this->arg_; }
 248
 249  protected:
 250   uint64_t
 251   arg_value(const Expression_eval_info* eei,
 252             Output_section** arg_section_pointer) const
 253   {
 254     return this->arg_->eval_maybe_dot(eei->symtab, eei->layout,
 255                                       eei->check_assertions,
 256                                       eei->is_dot_available,
 257                                       eei->dot_value,
 258                                       eei->dot_section,
 259                                       arg_section_pointer,
 260                                       eei->result_alignment_pointer);
 261   }
 262
 263   void
 264   arg_print(FILE* f) const
 265   { this->arg_->print(f); }
 266
 267  private:
 268   Expression* arg_;
 269 };
 270
 271 // Handle unary operators.  We use a preprocessor macro as a hack to
 272 // capture the C operator.
 273
 274 #define UNARY_EXPRESSION(NAME, OPERATOR)                                \
 275   class Unary_ ## NAME : public Unary_expression                        \
 276   {                                                                     \
 277   public:                                                               \
 278     Unary_ ## NAME(Expression* arg)                                     \
 279       : Unary_expression(arg)                                           \
 280     { }                                                                 \
 281                                                                         \
 282     uint64_t                                                            \
 283     value(const Expression_eval_info* eei)                              \
 284     {                                                                   \
 285       Output_section* arg_section;                                      \
 286       uint64_t ret = OPERATOR this->arg_value(eei, &arg_section);       \
 287       if (arg_section != NULL && parameters->options().relocatable())   \
 288         gold_warning(_("unary " #NAME " applied to section "            \
 289                        "relative value"));                              \
 290       return ret;                                                       \
 291     }                                                                   \
 292                                                                         \
 293     void                                                                \
 294     print(FILE* f) const                                                \
 295     {                                                                   \
 296       fprintf(f, "(%s ", #OPERATOR);                                    \
 297       this->arg_print(f);                                               \
 298       fprintf(f, ")");                                                  \
 299     }                                                                   \
 300   };                                                                    \
 301                                                                         \
 302   extern "C" Expression*                                                \
 303   script_exp_unary_ ## NAME(Expression* arg)                            \
 304   {                                                                     \
 305       return new Unary_ ## NAME(arg);                                   \
 306   }
 307
 308 UNARY_EXPRESSION(minus, -)
 309 UNARY_EXPRESSION(logical_not, !)
 310 UNARY_EXPRESSION(bitwise_not, ~)
 311
 312 // A binary expression.
 313
 314 class Binary_expression : public Expression
 315 {
 316  public:
 317   Binary_expression(Expression* left, Expression* right)
 318     : left_(left), right_(right)
 319   { }
 320
 321   ~Binary_expression()
 322   {
 323     delete this->left_;
 324     delete this->right_;
 325   }
 326
 327  protected:
 328   uint64_t
 329   left_value(const Expression_eval_info* eei,
 330              Output_section** section_pointer,
 331              uint64_t* alignment_pointer) const
 332   {
 333     return this->left_->eval_maybe_dot(eei->symtab, eei->layout,
 334                                        eei->check_assertions,
 335                                        eei->is_dot_available,
 336                                        eei->dot_value,
 337                                        eei->dot_section,
 338                                        section_pointer,
 339                                        alignment_pointer);
 340   }
 341
 342   uint64_t
 343   right_value(const Expression_eval_info* eei,
 344               Output_section** section_pointer,
 345               uint64_t* alignment_pointer) const
 346   {
 347     return this->right_->eval_maybe_dot(eei->symtab, eei->layout,
 348                                         eei->check_assertions,
 349                                         eei->is_dot_available,
 350                                         eei->dot_value,
 351                                         eei->dot_section,
 352                                         section_pointer,
 353                                         alignment_pointer);
 354   }
 355
 356   void
 357   left_print(FILE* f) const
 358   { this->left_->print(f); }
 359
 360   void
 361   right_print(FILE* f) const
 362   { this->right_->print(f); }
 363
 364   // This is a call to function FUNCTION_NAME.  Print it.  This is for
 365   // debugging.
 366   void
 367   print_function(FILE* f, const char* function_name) const
 368   {
 369     fprintf(f, "%s(", function_name);
 370     this->left_print(f);
 371     fprintf(f, ", ");
 372     this->right_print(f);
 373     fprintf(f, ")");
 374   }
 375
 376  private:
 377   Expression* left_;
 378   Expression* right_;
 379 };
 380
 381 // Handle binary operators.  We use a preprocessor macro as a hack to
 382 // capture the C operator.  KEEP_LEFT means that if the left operand
 383 // is section relative and the right operand is not, the result uses
 384 // the same section as the left operand.  KEEP_RIGHT is the same with
 385 // left and right swapped.  IS_DIV means that we need to give an error
 386 // if the right operand is zero.  WARN means that we should warn if
 387 // used on section relative values in a relocatable link.  We always
 388 // warn if used on values in different sections in a relocatable link.
 389
 390 #define BINARY_EXPRESSION(NAME, OPERATOR, KEEP_LEFT, KEEP_RIGHT, IS_DIV, WARN) \
 391   class Binary_ ## NAME : public Binary_expression                      \
 392   {                                                                     \
 393   public:                                                               \
 394     Binary_ ## NAME(Expression* left, Expression* right)                \
 395       : Binary_expression(left, right)                                  \
 396     { }                                                                 \
 397                                                                         \
 398     uint64_t                                                            \
 399     value(const Expression_eval_info* eei)                              \
 400     {                                                                   \
 401       Output_section* left_section;                                     \
 402       uint64_t left_alignment = 0;                                      \
 403       uint64_t left = this->left_value(eei, &left_section,              \
 404                                        &left_alignment);                \
 405       Output_section* right_section;                                    \
 406       uint64_t right_alignment = 0;                                     \
 407       uint64_t right = this->right_value(eei, &right_section,           \
 408                                          &right_alignment);             \
 409       if (KEEP_RIGHT && left_section == NULL && right_section != NULL)  \
 410         {                                                               \
 411           if (eei->result_section_pointer != NULL)                      \
 412             *eei->result_section_pointer = right_section;               \
 413           if (eei->result_alignment_pointer != NULL                     \
 414               && right_alignment > *eei->result_alignment_pointer)      \
 415             *eei->result_alignment_pointer = right_alignment;           \
 416         }                                                               \
 417       else if (KEEP_LEFT                                                \
 418                && left_section != NULL                                  \
 419                && right_section == NULL)                                \
 420         {                                                               \
 421           if (eei->result_section_pointer != NULL)                      \
 422             *eei->result_section_pointer = left_section;                \
 423           if (eei->result_alignment_pointer != NULL                     \
 424               && left_alignment > *eei->result_alignment_pointer)       \
 425             *eei->result_alignment_pointer = left_alignment;            \
 426         }                                                               \
 427       else if ((WARN || left_section != right_section)                  \
 428                && (left_section != NULL || right_section != NULL)       \
 429                && parameters->options().relocatable())                  \
 430         gold_warning(_("binary " #NAME " applied to section "           \
 431                        "relative value"));                              \
 432       if (IS_DIV && right == 0)                                         \
 433         {                                                               \
 434           gold_error(_(#NAME " by zero"));                              \
 435           return 0;                                                     \
 436         }                                                               \
 437       return left OPERATOR right;                                       \
 438     }                                                                   \
 439                                                                         \
 440     void                                                                \
 441     print(FILE* f) const                                                \
 442     {                                                                   \
 443       fprintf(f, "(");                                                  \
 444       this->left_print(f);                                              \
 445       fprintf(f, " %s ", #OPERATOR);                                    \
 446       this->right_print(f);                                             \
 447       fprintf(f, ")");                                                  \
 448     }                                                                   \
 449   };                                                                    \
 450                                                                         \
 451   extern "C" Expression*                                                \
 452   script_exp_binary_ ## NAME(Expression* left, Expression* right)       \
 453   {                                                                     \
 454     return new Binary_ ## NAME(left, right);                            \
 455   }
 456
 457 BINARY_EXPRESSION(mult, *, false, false, false, true)
 458 BINARY_EXPRESSION(div, /, false, false, true, true)
 459 BINARY_EXPRESSION(mod, %, false, false, true, true)
 460 BINARY_EXPRESSION(add, +, true, true, false, true)
 461 BINARY_EXPRESSION(sub, -, true, false, false, false)
 462 BINARY_EXPRESSION(lshift, <<, false, false, false, true)
 463 BINARY_EXPRESSION(rshift, >>, false, false, false, true)
 464 BINARY_EXPRESSION(eq, ==, false, false, false, false)
 465 BINARY_EXPRESSION(ne, !=, false, false, false, false)
 466 BINARY_EXPRESSION(le, <=, false, false, false, false)
 467 BINARY_EXPRESSION(ge, >=, false, false, false, false)
 468 BINARY_EXPRESSION(lt, <, false, false, false, false)
 469 BINARY_EXPRESSION(gt, >, false, false, false, false)
 470 BINARY_EXPRESSION(bitwise_and, &, true, true, false, true)
 471 BINARY_EXPRESSION(bitwise_xor, ^, true, true, false, true)
 472 BINARY_EXPRESSION(bitwise_or, |, true, true, false, true)
 473 BINARY_EXPRESSION(logical_and, &&, false, false, false, true)
 474 BINARY_EXPRESSION(logical_or, ||, false, false, false, true)
 475
 476 // A trinary expression.
 477
 478 class Trinary_expression : public Expression
 479 {
 480  public:
 481   Trinary_expression(Expression* arg1, Expression* arg2, Expression* arg3)
 482     : arg1_(arg1), arg2_(arg2), arg3_(arg3)
 483   { }
 484
 485   ~Trinary_expression()
 486   {
 487     delete this->arg1_;
 488     delete this->arg2_;
 489     delete this->arg3_;
 490   }
 491
 492  protected:
 493   uint64_t
 494   arg1_value(const Expression_eval_info* eei,
 495              Output_section** section_pointer) const
 496   {
 497     return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
 498                                        eei->check_assertions,
 499                                        eei->is_dot_available,
 500                                        eei->dot_value,
 501                                        eei->dot_section,
 502                                        section_pointer,
 503                                        NULL);
 504   }
 505
 506   uint64_t
 507   arg2_value(const Expression_eval_info* eei,
 508              Output_section** section_pointer,
 509              uint64_t* alignment_pointer) const
 510   {
 511     return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
 512                                        eei->check_assertions,
 513                                        eei->is_dot_available,
 514                                        eei->dot_value,
 515                                        eei->dot_section,
 516                                        section_pointer,
 517                                        alignment_pointer);
 518   }
 519
 520   uint64_t
 521   arg3_value(const Expression_eval_info* eei,
 522              Output_section** section_pointer,
 523              uint64_t* alignment_pointer) const
 524   {
 525     return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
 526                                        eei->check_assertions,
 527                                        eei->is_dot_available,
 528                                        eei->dot_value,
 529                                        eei->dot_section,
 530                                        section_pointer,
 531                                        alignment_pointer);
 532   }
 533
 534   void
 535   arg1_print(FILE* f) const
 536   { this->arg1_->print(f); }
 537
 538   void
 539   arg2_print(FILE* f) const
 540   { this->arg2_->print(f); }
 541
 542   void
 543   arg3_print(FILE* f) const
 544   { this->arg3_->print(f); }
 545
 546  private:
 547   Expression* arg1_;
 548   Expression* arg2_;
 549   Expression* arg3_;
 550 };
 551
 552 // The conditional operator.
 553
 554 class Trinary_cond : public Trinary_expression
 555 {
 556  public:
 557   Trinary_cond(Expression* arg1, Expression* arg2, Expression* arg3)
 558     : Trinary_expression(arg1, arg2, arg3)
 559   { }
 560
 561   uint64_t
 562   value(const Expression_eval_info* eei)
 563   {
 564     Output_section* arg1_section;
 565     uint64_t arg1 = this->arg1_value(eei, &arg1_section);
 566     return (arg1
 567             ? this->arg2_value(eei, eei->result_section_pointer,
 568                                eei->result_alignment_pointer)
 569             : this->arg3_value(eei, eei->result_section_pointer,
 570                                eei->result_alignment_pointer));
 571   }
 572
 573   void
 574   print(FILE* f) const
 575   {
 576     fprintf(f, "(");
 577     this->arg1_print(f);
 578     fprintf(f, " ? ");
 579     this->arg2_print(f);
 580     fprintf(f, " : ");
 581     this->arg3_print(f);
 582     fprintf(f, ")");
 583   }
 584 };
 585
 586 extern "C" Expression*
 587 script_exp_trinary_cond(Expression* arg1, Expression* arg2, Expression* arg3)
 588 {
 589   return new Trinary_cond(arg1, arg2, arg3);
 590 }
 591
 592 // Max function.
 593
 594 class Max_expression : public Binary_expression
 595 {
 596  public:
 597   Max_expression(Expression* left, Expression* right)
 598     : Binary_expression(left, right)
 599   { }
 600
 601   uint64_t
 602   value(const Expression_eval_info* eei)
 603   {
 604     Output_section* left_section;
 605     uint64_t left_alignment;
 606     uint64_t left = this->left_value(eei, &left_section, &left_alignment);
 607     Output_section* right_section;
 608     uint64_t right_alignment;
 609     uint64_t right = this->right_value(eei, &right_section, &right_alignment);
 610     if (left_section == right_section)
 611       {
 612         if (eei->result_section_pointer != NULL)
 613           *eei->result_section_pointer = left_section;
 614       }
 615     else if ((left_section != NULL || right_section != NULL)
 616              && parameters->options().relocatable())
 617       gold_warning(_("max applied to section relative value"));
 618     if (eei->result_alignment_pointer != NULL)
 619       {
 620         uint64_t ra = *eei->result_alignment_pointer;
 621         if (left > right)
 622           ra = std::max(ra, left_alignment);
 623         else if (right > left)
 624           ra = std::max(ra, right_alignment);
 625         else
 626           ra = std::max(ra, std::max(left_alignment, right_alignment));
 627         *eei->result_alignment_pointer = ra;
 628       }
 629     return std::max(left, right);
 630   }
 631
 632   void
 633   print(FILE* f) const
 634   { this->print_function(f, "MAX"); }
 635 };
 636
 637 extern "C" Expression*
 638 script_exp_function_max(Expression* left, Expression* right)
 639 {
 640   return new Max_expression(left, right);
 641 }
 642
 643 // Min function.
 644
 645 class Min_expression : public Binary_expression
 646 {
 647  public:
 648   Min_expression(Expression* left, Expression* right)
 649     : Binary_expression(left, right)
 650   { }
 651
 652   uint64_t
 653   value(const Expression_eval_info* eei)
 654   {
 655     Output_section* left_section;
 656     uint64_t left_alignment;
 657     uint64_t left = this->left_value(eei, &left_section, &left_alignment);
 658     Output_section* right_section;
 659     uint64_t right_alignment;
 660     uint64_t right = this->right_value(eei, &right_section, &right_alignment);
 661     if (left_section == right_section)
 662       {
 663         if (eei->result_section_pointer != NULL)
 664           *eei->result_section_pointer = left_section;
 665       }
 666     else if ((left_section != NULL || right_section != NULL)
 667              && parameters->options().relocatable())
 668       gold_warning(_("min applied to section relative value"));
 669     if (eei->result_alignment_pointer != NULL)
 670       {
 671         uint64_t ra = *eei->result_alignment_pointer;
 672         if (left < right)
 673           ra = std::max(ra, left_alignment);
 674         else if (right < left)
 675           ra = std::max(ra, right_alignment);
 676         else
 677           ra = std::max(ra, std::max(left_alignment, right_alignment));
 678         *eei->result_alignment_pointer = ra;
 679       }
 680     return std::min(left, right);
 681   }
 682
 683   void
 684   print(FILE* f) const
 685   { this->print_function(f, "MIN"); }
 686 };
 687
 688 extern "C" Expression*
 689 script_exp_function_min(Expression* left, Expression* right)
 690 {
 691   return new Min_expression(left, right);
 692 }
 693
 694 // Class Section_expression.  This is a parent class used for
 695 // functions which take the name of an output section.
 696
 697 class Section_expression : public Expression
 698 {
 699  public:
 700   Section_expression(const char* section_name, size_t section_name_len)
 701     : section_name_(section_name, section_name_len)
 702   { }
 703
 704   uint64_t
 705   value(const Expression_eval_info*);
 706
 707   void
 708   print(FILE* f) const
 709   { fprintf(f, "%s(%s)", this->function_name(), this->section_name_.c_str()); }
 710
 711  protected:
 712   // The child class must implement this.
 713   virtual uint64_t
 714   value_from_output_section(const Expression_eval_info*,
 715                             Output_section*) = 0;
 716
 717   // The child class must implement this.
 718   virtual uint64_t
 719   value_from_script_output_section(uint64_t address, uint64_t load_address,
 720                                    uint64_t addralign, uint64_t size) = 0;
 721
 722   // The child class must implement this.
 723   virtual const char*
 724   function_name() const = 0;
 725
 726  private:
 727   std::string section_name_;
 728 };
 729
 730 uint64_t
 731 Section_expression::value(const Expression_eval_info* eei)
 732 {
 733   const char* section_name = this->section_name_.c_str();
 734   Output_section* os = eei->layout->find_output_section(section_name);
 735   if (os != NULL)
 736     return this->value_from_output_section(eei, os);
 737
 738   uint64_t address;
 739   uint64_t load_address;
 740   uint64_t addralign;
 741   uint64_t size;
 742   const Script_options* ss = eei->layout->script_options();
 743   if (ss->saw_sections_clause())
 744     {
 745       if (ss->script_sections()->get_output_section_info(section_name,
 746                                                          &address,
 747                                                          &load_address,
 748                                                          &addralign,
 749                                                          &size))
 750         return this->value_from_script_output_section(address, load_address,
 751                                                       addralign, size);
 752     }
 753
 754   gold_error("%s called on nonexistent output section '%s'",
 755              this->function_name(), section_name);
 756   return 0;
 757 }
 758
 759 // ABSOLUTE function.
 760
 761 class Absolute_expression : public Unary_expression
 762 {
 763  public:
 764   Absolute_expression(Expression* arg)
 765     : Unary_expression(arg)
 766   { }
 767
 768   uint64_t
 769   value(const Expression_eval_info* eei)
 770   {
 771     uint64_t ret = this->arg_value(eei, NULL);
 772     // Force the value to be absolute.
 773     if (eei->result_section_pointer != NULL)
 774       *eei->result_section_pointer = NULL;
 775     return ret;
 776   }
 777
 778   void
 779   print(FILE* f) const
 780   {
 781     fprintf(f, "ABSOLUTE(");
 782     this->arg_print(f);
 783     fprintf(f, ")");
 784   }
 785 };
 786
 787 extern "C" Expression*
 788 script_exp_function_absolute(Expression* arg)
 789 {
 790   return new Absolute_expression(arg);
 791 }
 792
 793 // ALIGN function.
 794
 795 class Align_expression : public Binary_expression
 796 {
 797  public:
 798   Align_expression(Expression* left, Expression* right)
 799     : Binary_expression(left, right)
 800   { }
 801
 802   uint64_t
 803   value(const Expression_eval_info* eei)
 804   {
 805     Output_section* align_section;
 806     uint64_t align = this->right_value(eei, &align_section, NULL);
 807     if (align_section != NULL
 808         && parameters->options().relocatable())
 809       gold_warning(_("aligning to section relative value"));
 810
 811     if (eei->result_alignment_pointer != NULL
 812         && align > *eei->result_alignment_pointer)
 813       {
 814         uint64_t a = align;
 815         while ((a & (a - 1)) != 0)
 816           a &= a - 1;
 817         *eei->result_alignment_pointer = a;
 818       }
 819
 820     uint64_t value = this->left_value(eei, eei->result_section_pointer, NULL);
 821     if (align <= 1)
 822       return value;
 823     return ((value + align - 1) / align) * align;
 824   }
 825
 826   void
 827   print(FILE* f) const
 828   { this->print_function(f, "ALIGN"); }
 829 };
 830
 831 extern "C" Expression*
 832 script_exp_function_align(Expression* left, Expression* right)
 833 {
 834   return new Align_expression(left, right);
 835 }
 836
 837 // ASSERT function.
 838
 839 class Assert_expression : public Unary_expression
 840 {
 841  public:
 842   Assert_expression(Expression* arg, const char* message, size_t length)
 843     : Unary_expression(arg), message_(message, length)
 844   { }
 845
 846   uint64_t
 847   value(const Expression_eval_info* eei)
 848   {
 849     uint64_t value = this->arg_value(eei, eei->result_section_pointer);
 850     if (!value && eei->check_assertions)
 851       gold_error("%s", this->message_.c_str());
 852     return value;
 853   }
 854
 855   void
 856   print(FILE* f) const
 857   {
 858     fprintf(f, "ASSERT(");
 859     this->arg_print(f);
 860     fprintf(f, ", %s)", this->message_.c_str());
 861   }
 862
 863  private:
 864   std::string message_;
 865 };
 866
 867 extern "C" Expression*
 868 script_exp_function_assert(Expression* expr, const char* message,
 869                            size_t length)
 870 {
 871   return new Assert_expression(expr, message, length);
 872 }
 873
 874 // ADDR function.
 875
 876 class Addr_expression : public Section_expression
 877 {
 878  public:
 879   Addr_expression(const char* section_name, size_t section_name_len)
 880     : Section_expression(section_name, section_name_len)
 881   { }
 882
 883  protected:
 884   uint64_t
 885   value_from_output_section(const Expression_eval_info* eei,
 886                             Output_section* os)
 887   {
 888     if (eei->result_section_pointer != NULL)
 889       *eei->result_section_pointer = os;
 890     return os->address();
 891   }
 892
 893   uint64_t
 894   value_from_script_output_section(uint64_t address, uint64_t, uint64_t,
 895                                    uint64_t)
 896   { return address; }
 897
 898   const char*
 899   function_name() const
 900   { return "ADDR"; }
 901 };
 902
 903 extern "C" Expression*
 904 script_exp_function_addr(const char* section_name, size_t section_name_len)
 905 {
 906   return new Addr_expression(section_name, section_name_len);
 907 }
 908
 909 // ALIGNOF.
 910
 911 class Alignof_expression : public Section_expression
 912 {
 913  public:
 914   Alignof_expression(const char* section_name, size_t section_name_len)
 915     : Section_expression(section_name, section_name_len)
 916   { }
 917
 918  protected:
 919   uint64_t
 920   value_from_output_section(const Expression_eval_info*,
 921                             Output_section* os)
 922   { return os->addralign(); }
 923
 924   uint64_t
 925   value_from_script_output_section(uint64_t, uint64_t, uint64_t addralign,
 926                                    uint64_t)
 927   { return addralign; }
 928
 929   const char*
 930   function_name() const
 931   { return "ALIGNOF"; }
 932 };
 933
 934 extern "C" Expression*
 935 script_exp_function_alignof(const char* section_name, size_t section_name_len)
 936 {
 937   return new Alignof_expression(section_name, section_name_len);
 938 }
 939
 940 // CONSTANT.  It would be nice if we could simply evaluate this
 941 // immediately and return an Integer_expression, but unfortunately we
 942 // don't know the target.
 943
 944 class Constant_expression : public Expression
 945 {
 946  public:
 947   Constant_expression(const char* name, size_t length);
 948
 949   uint64_t
 950   value(const Expression_eval_info*);
 951
 952   void
 953   print(FILE* f) const;
 954
 955  private:
 956   enum Constant_function
 957   {
 958     CONSTANT_MAXPAGESIZE,
 959     CONSTANT_COMMONPAGESIZE
 960   };
 961
 962   Constant_function function_;
 963 };
 964
 965 Constant_expression::Constant_expression(const char* name, size_t length)
 966 {
 967   if (length == 11 && strncmp(name, "MAXPAGESIZE", length) == 0)
 968     this->function_ = CONSTANT_MAXPAGESIZE;
 969   else if (length == 14 && strncmp(name, "COMMONPAGESIZE", length) == 0)
 970     this->function_ = CONSTANT_COMMONPAGESIZE;
 971   else
 972     {
 973       std::string s(name, length);
 974       gold_error(_("unknown constant %s"), s.c_str());
 975       this->function_ = CONSTANT_MAXPAGESIZE;
 976     }
 977 }
 978
 979 uint64_t
 980 Constant_expression::value(const Expression_eval_info*)
 981 {
 982   switch (this->function_)
 983     {
 984     case CONSTANT_MAXPAGESIZE:
 985       return parameters->target().abi_pagesize();
 986     case CONSTANT_COMMONPAGESIZE:
 987       return parameters->target().common_pagesize();
 988     default:
 989       gold_unreachable();
 990     }
 991 }
 992
 993 void
 994 Constant_expression::print(FILE* f) const
 995 {
 996   const char* name;
 997   switch (this->function_)
 998     {
 999     case CONSTANT_MAXPAGESIZE:
1000       name = "MAXPAGESIZE";
1001       break;
1002     case CONSTANT_COMMONPAGESIZE:
1003       name = "COMMONPAGESIZE";
1004       break;
1005     default:
1006       gold_unreachable();
1007     }
1008   fprintf(f, "CONSTANT(%s)", name);
1009 }
1010
1011 extern "C" Expression*
1012 script_exp_function_constant(const char* name, size_t length)
1013 {
1014   return new Constant_expression(name, length);
1015 }
1016
1017 // DATA_SEGMENT_ALIGN.  FIXME: we don't implement this; we always fall
1018 // back to the general case.
1019
1020 extern "C" Expression*
1021 script_exp_function_data_segment_align(Expression* left, Expression*)
1022 {
1023   Expression* e1 = script_exp_function_align(script_exp_string(".", 1), left);
1024   Expression* e2 = script_exp_binary_sub(left, script_exp_integer(1));
1025   Expression* e3 = script_exp_binary_bitwise_and(script_exp_string(".", 1),
1026                                                  e2);
1027   return script_exp_binary_add(e1, e3);
1028 }
1029
1030 // DATA_SEGMENT_RELRO.  FIXME: This is not implemented.
1031
1032 extern "C" Expression*
1033 script_exp_function_data_segment_relro_end(Expression*, Expression* right)
1034 {
1035   return right;
1036 }
1037
1038 // DATA_SEGMENT_END.  FIXME: This is not implemented.
1039
1040 extern "C" Expression*
1041 script_exp_function_data_segment_end(Expression* val)
1042 {
1043   return val;
1044 }
1045
1046 // DEFINED function.
1047
1048 class Defined_expression : public Expression
1049 {
1050  public:
1051   Defined_expression(const char* symbol_name, size_t symbol_name_len)
1052     : symbol_name_(symbol_name, symbol_name_len)
1053   { }
1054
1055   uint64_t
1056   value(const Expression_eval_info* eei)
1057   {
1058     Symbol* sym = eei->symtab->lookup(this->symbol_name_.c_str());
1059     return sym != NULL && sym->is_defined();
1060   }
1061
1062   void
1063   print(FILE* f) const
1064   { fprintf(f, "DEFINED(%s)", this->symbol_name_.c_str()); }
1065
1066  private:
1067   std::string symbol_name_;
1068 };
1069
1070 extern "C" Expression*
1071 script_exp_function_defined(const char* symbol_name, size_t symbol_name_len)
1072 {
1073   return new Defined_expression(symbol_name, symbol_name_len);
1074 }
1075
1076 // LOADADDR function
1077
1078 class Loadaddr_expression : public Section_expression
1079 {
1080  public:
1081   Loadaddr_expression(const char* section_name, size_t section_name_len)
1082     : Section_expression(section_name, section_name_len)
1083   { }
1084
1085  protected:
1086   uint64_t
1087   value_from_output_section(const Expression_eval_info* eei,
1088                             Output_section* os)
1089   {
1090     if (os->has_load_address())
1091       return os->load_address();
1092     else
1093       {
1094         if (eei->result_section_pointer != NULL)
1095           *eei->result_section_pointer = os;
1096         return os->address();
1097       }
1098   }
1099
1100   uint64_t
1101   value_from_script_output_section(uint64_t, uint64_t load_address, uint64_t,
1102                                    uint64_t)
1103   { return load_address; }
1104
1105   const char*
1106   function_name() const
1107   { return "LOADADDR"; }
1108 };
1109
1110 extern "C" Expression*
1111 script_exp_function_loadaddr(const char* section_name, size_t section_name_len)
1112 {
1113   return new Loadaddr_expression(section_name, section_name_len);
1114 }
1115
1116 // SIZEOF function
1117
1118 class Sizeof_expression : public Section_expression
1119 {
1120  public:
1121   Sizeof_expression(const char* section_name, size_t section_name_len)
1122     : Section_expression(section_name, section_name_len)
1123   { }
1124
1125  protected:
1126   uint64_t
1127   value_from_output_section(const Expression_eval_info*,
1128                             Output_section* os)
1129   {
1130     // We can not use data_size here, as the size of the section may
1131     // not have been finalized.  Instead we get whatever the current
1132     // size is.  This will work correctly for backward references in
1133     // linker scripts.
1134     return os->current_data_size();
1135   }
1136
1137   uint64_t
1138   value_from_script_output_section(uint64_t, uint64_t, uint64_t,
1139                                    uint64_t size)
1140   { return size; }
1141
1142   const char*
1143   function_name() const
1144   { return "SIZEOF"; }
1145 };
1146
1147 extern "C" Expression*
1148 script_exp_function_sizeof(const char* section_name, size_t section_name_len)
1149 {
1150   return new Sizeof_expression(section_name, section_name_len);
1151 }
1152
1153 // SIZEOF_HEADERS.
1154
1155 class Sizeof_headers_expression : public Expression
1156 {
1157  public:
1158   Sizeof_headers_expression()
1159   { }
1160
1161   uint64_t
1162   value(const Expression_eval_info*);
1163
1164   void
1165   print(FILE* f) const
1166   { fprintf(f, "SIZEOF_HEADERS"); }
1167 };
1168
1169 uint64_t
1170 Sizeof_headers_expression::value(const Expression_eval_info* eei)
1171 {
1172   unsigned int ehdr_size;
1173   unsigned int phdr_size;
1174   if (parameters->target().get_size() == 32)
1175     {
1176       ehdr_size = elfcpp::Elf_sizes<32>::ehdr_size;
1177       phdr_size = elfcpp::Elf_sizes<32>::phdr_size;
1178     }
1179   else if (parameters->target().get_size() == 64)
1180     {
1181       ehdr_size = elfcpp::Elf_sizes<64>::ehdr_size;
1182       phdr_size = elfcpp::Elf_sizes<64>::phdr_size;
1183     }
1184   else
1185     gold_unreachable();
1186
1187   return ehdr_size + phdr_size * eei->layout->expected_segment_count();
1188 }
1189
1190 extern "C" Expression*
1191 script_exp_function_sizeof_headers()
1192 {
1193   return new Sizeof_headers_expression();
1194 }
1195
1196 // SEGMENT_START.
1197
1198 class Segment_start_expression : public Unary_expression
1199 {
1200  public:
1201   Segment_start_expression(const char* segment_name, size_t segment_name_len,
1202                            Expression* default_value)
1203     : Unary_expression(default_value),
1204       segment_name_(segment_name, segment_name_len)
1205   { }
1206
1207   uint64_t
1208   value(const Expression_eval_info*);
1209
1210   void
1211   print(FILE* f) const
1212   {
1213     fprintf(f, "SEGMENT_START(\"%s\", ", this->segment_name_.c_str());
1214     this->arg_print(f);
1215     fprintf(f, ")");
1216   }
1217
1218  private:
1219   std::string segment_name_;
1220 };
1221
1222 uint64_t
1223 Segment_start_expression::value(const Expression_eval_info* eei)
1224 {
1225   // Check for command line overrides.
1226   if (parameters->options().user_set_Ttext()
1227       && this->segment_name_ == ".text")
1228     return parameters->options().Ttext();
1229   else if (parameters->options().user_set_Tdata()
1230            && this->segment_name_ == ".data")
1231     return parameters->options().Tdata();
1232   else if (parameters->options().user_set_Tbss()
1233            && this->segment_name_ == ".bss")
1234     return parameters->options().Tbss();
1235   else
1236     {
1237       uint64_t ret = this->arg_value(eei, NULL);
1238       // Force the value to be absolute.
1239       if (eei->result_section_pointer != NULL)
1240         *eei->result_section_pointer = NULL;
1241       return ret;
1242     }
1243 }
1244
1245 extern "C" Expression*
1246 script_exp_function_segment_start(const char* segment_name,
1247                                   size_t segment_name_len,
1248                                   Expression* default_value)
1249 {
1250   return new Segment_start_expression(segment_name, segment_name_len,
1251                                       default_value);
1252 }
1253
1254 } // End namespace gold.