gold/expression.cc

   1 // expression.cc -- expressions in linker scripts for gold
   2
   3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011 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, false);
  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                           bool is_section_dot_assignment)
  92 {
  93   return this->eval_maybe_dot(symtab, layout, check_assertions, true,
  94                               dot_value, dot_section, result_section_pointer,
  95                               result_alignment_pointer,
  96                               is_section_dot_assignment);
  97 }
  98
  99 // Evaluate an expression which may or may not refer to the dot
 100 // symbol.
 101
 102 uint64_t
 103 Expression::eval_maybe_dot(const Symbol_table* symtab, const Layout* layout,
 104                            bool check_assertions, bool is_dot_available,
 105                            uint64_t dot_value, Output_section* dot_section,
 106                            Output_section** result_section_pointer,
 107                            uint64_t* result_alignment_pointer,
 108                            bool is_section_dot_assignment)
 109 {
 110   Expression_eval_info eei;
 111   eei.symtab = symtab;
 112   eei.layout = layout;
 113   eei.check_assertions = check_assertions;
 114   eei.is_dot_available = is_dot_available;
 115   eei.dot_value = dot_value;
 116   eei.dot_section = dot_section;
 117
 118   // We assume the value is absolute, and only set this to a section
 119   // if we find a section-relative reference.
 120   if (result_section_pointer != NULL)
 121     *result_section_pointer = NULL;
 122   eei.result_section_pointer = result_section_pointer;
 123
 124   eei.result_alignment_pointer = result_alignment_pointer;
 125
 126   uint64_t val = this->value(&eei);
 127
 128   // If this is an assignment to dot within a section, and the value
 129   // is absolute, treat it as a section-relative offset.
 130   if (is_section_dot_assignment && *result_section_pointer == NULL)
 131     {
 132       gold_assert(dot_section != NULL);
 133       val += dot_section->address();
 134       *result_section_pointer = dot_section;
 135     }
 136   return val;
 137 }
 138
 139 // A number.
 140
 141 class Integer_expression : public Expression
 142 {
 143  public:
 144   Integer_expression(uint64_t val)
 145     : val_(val)
 146   { }
 147
 148   uint64_t
 149   value(const Expression_eval_info*)
 150   { return this->val_; }
 151
 152   void
 153   print(FILE* f) const
 154   { fprintf(f, "0x%llx", static_cast<unsigned long long>(this->val_)); }
 155
 156  private:
 157   uint64_t val_;
 158 };
 159
 160 extern "C" Expression*
 161 script_exp_integer(uint64_t val)
 162 {
 163   return new Integer_expression(val);
 164 }
 165
 166 // An expression whose value is the value of a symbol.
 167
 168 class Symbol_expression : public Expression
 169 {
 170  public:
 171   Symbol_expression(const char* name, size_t length)
 172     : name_(name, length)
 173   { }
 174
 175   uint64_t
 176   value(const Expression_eval_info*);
 177
 178   void
 179   print(FILE* f) const
 180   { fprintf(f, "%s", this->name_.c_str()); }
 181
 182  private:
 183   std::string name_;
 184 };
 185
 186 uint64_t
 187 Symbol_expression::value(const Expression_eval_info* eei)
 188 {
 189   Symbol* sym = eei->symtab->lookup(this->name_.c_str());
 190   if (sym == NULL || !sym->is_defined())
 191     {
 192       gold_error(_("undefined symbol '%s' referenced in expression"),
 193                  this->name_.c_str());
 194       return 0;
 195     }
 196
 197   if (eei->result_section_pointer != NULL)
 198     *eei->result_section_pointer = sym->output_section();
 199
 200   if (parameters->target().get_size() == 32)
 201     return eei->symtab->get_sized_symbol<32>(sym)->value();
 202   else if (parameters->target().get_size() == 64)
 203     return eei->symtab->get_sized_symbol<64>(sym)->value();
 204   else
 205     gold_unreachable();
 206 }
 207
 208 // An expression whose value is the value of the special symbol ".".
 209 // This is only valid within a SECTIONS clause.
 210
 211 class Dot_expression : public Expression
 212 {
 213  public:
 214   Dot_expression()
 215   { }
 216
 217   uint64_t
 218   value(const Expression_eval_info*);
 219
 220   void
 221   print(FILE* f) const
 222   { fprintf(f, "."); }
 223 };
 224
 225 uint64_t
 226 Dot_expression::value(const Expression_eval_info* eei)
 227 {
 228   if (!eei->is_dot_available)
 229     {
 230       gold_error(_("invalid reference to dot symbol outside of "
 231                    "SECTIONS clause"));
 232       return 0;
 233     }
 234   if (eei->result_section_pointer != NULL)
 235     *eei->result_section_pointer = eei->dot_section;
 236   return eei->dot_value;
 237 }
 238
 239 // A string.  This is either the name of a symbol, or ".".
 240
 241 extern "C" Expression*
 242 script_exp_string(const char* name, size_t length)
 243 {
 244   if (length == 1 && name[0] == '.')
 245     return new Dot_expression();
 246   else
 247     return new Symbol_expression(name, length);
 248 }
 249
 250 // A unary expression.
 251
 252 class Unary_expression : public Expression
 253 {
 254  public:
 255   Unary_expression(Expression* arg)
 256     : arg_(arg)
 257   { }
 258
 259   ~Unary_expression()
 260   { delete this->arg_; }
 261
 262  protected:
 263   uint64_t
 264   arg_value(const Expression_eval_info* eei,
 265             Output_section** arg_section_pointer) const
 266   {
 267     return this->arg_->eval_maybe_dot(eei->symtab, eei->layout,
 268                                       eei->check_assertions,
 269                                       eei->is_dot_available,
 270                                       eei->dot_value,
 271                                       eei->dot_section,
 272                                       arg_section_pointer,
 273                                       eei->result_alignment_pointer,
 274                                       false);
 275   }
 276
 277   void
 278   arg_print(FILE* f) const
 279   { this->arg_->print(f); }
 280
 281  private:
 282   Expression* arg_;
 283 };
 284
 285 // Handle unary operators.  We use a preprocessor macro as a hack to
 286 // capture the C operator.
 287
 288 #define UNARY_EXPRESSION(NAME, OPERATOR)                                \
 289   class Unary_ ## NAME : public Unary_expression                        \
 290   {                                                                     \
 291   public:                                                               \
 292     Unary_ ## NAME(Expression* arg)                                     \
 293       : Unary_expression(arg)                                           \
 294     { }                                                                 \
 295                                                                         \
 296     uint64_t                                                            \
 297     value(const Expression_eval_info* eei)                              \
 298     {                                                                   \
 299       Output_section* arg_section;                                      \
 300       uint64_t ret = OPERATOR this->arg_value(eei, &arg_section);       \
 301       if (arg_section != NULL && parameters->options().relocatable())   \
 302         gold_warning(_("unary " #NAME " applied to section "            \
 303                        "relative value"));                              \
 304       return ret;                                                       \
 305     }                                                                   \
 306                                                                         \
 307     void                                                                \
 308     print(FILE* f) const                                                \
 309     {                                                                   \
 310       fprintf(f, "(%s ", #OPERATOR);                                    \
 311       this->arg_print(f);                                               \
 312       fprintf(f, ")");                                                  \
 313     }                                                                   \
 314   };                                                                    \
 315                                                                         \
 316   extern "C" Expression*                                                \
 317   script_exp_unary_ ## NAME(Expression* arg)                            \
 318   {                                                                     \
 319       return new Unary_ ## NAME(arg);                                   \
 320   }
 321
 322 UNARY_EXPRESSION(minus, -)
 323 UNARY_EXPRESSION(logical_not, !)
 324 UNARY_EXPRESSION(bitwise_not, ~)
 325
 326 // A binary expression.
 327
 328 class Binary_expression : public Expression
 329 {
 330  public:
 331   Binary_expression(Expression* left, Expression* right)
 332     : left_(left), right_(right)
 333   { }
 334
 335   ~Binary_expression()
 336   {
 337     delete this->left_;
 338     delete this->right_;
 339   }
 340
 341  protected:
 342   uint64_t
 343   left_value(const Expression_eval_info* eei,
 344              Output_section** section_pointer,
 345              uint64_t* alignment_pointer) const
 346   {
 347     return this->left_->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                                        false);
 355   }
 356
 357   uint64_t
 358   right_value(const Expression_eval_info* eei,
 359               Output_section** section_pointer,
 360               uint64_t* alignment_pointer) const
 361   {
 362     return this->right_->eval_maybe_dot(eei->symtab, eei->layout,
 363                                         eei->check_assertions,
 364                                         eei->is_dot_available,
 365                                         eei->dot_value,
 366                                         eei->dot_section,
 367                                         section_pointer,
 368                                         alignment_pointer,
 369                                         false);
 370   }
 371
 372   void
 373   left_print(FILE* f) const
 374   { this->left_->print(f); }
 375
 376   void
 377   right_print(FILE* f) const
 378   { this->right_->print(f); }
 379
 380   // This is a call to function FUNCTION_NAME.  Print it.  This is for
 381   // debugging.
 382   void
 383   print_function(FILE* f, const char* function_name) const
 384   {
 385     fprintf(f, "%s(", function_name);
 386     this->left_print(f);
 387     fprintf(f, ", ");
 388     this->right_print(f);
 389     fprintf(f, ")");
 390   }
 391
 392  private:
 393   Expression* left_;
 394   Expression* right_;
 395 };
 396
 397 // Handle binary operators.  We use a preprocessor macro as a hack to
 398 // capture the C operator.  KEEP_LEFT means that if the left operand
 399 // is section relative and the right operand is not, the result uses
 400 // the same section as the left operand.  KEEP_RIGHT is the same with
 401 // left and right swapped.  IS_DIV means that we need to give an error
 402 // if the right operand is zero.  WARN means that we should warn if
 403 // used on section relative values in a relocatable link.  We always
 404 // warn if used on values in different sections in a relocatable link.
 405
 406 #define BINARY_EXPRESSION(NAME, OPERATOR, KEEP_LEFT, KEEP_RIGHT, IS_DIV, WARN) \
 407   class Binary_ ## NAME : public Binary_expression                      \
 408   {                                                                     \
 409   public:                                                               \
 410     Binary_ ## NAME(Expression* left, Expression* right)                \
 411       : Binary_expression(left, right)                                  \
 412     { }                                                                 \
 413                                                                         \
 414     uint64_t                                                            \
 415     value(const Expression_eval_info* eei)                              \
 416     {                                                                   \
 417       Output_section* left_section;                                     \
 418       uint64_t left_alignment = 0;                                      \
 419       uint64_t left = this->left_value(eei, &left_section,              \
 420                                        &left_alignment);                \
 421       Output_section* right_section;                                    \
 422       uint64_t right_alignment = 0;                                     \
 423       uint64_t right = this->right_value(eei, &right_section,           \
 424                                          &right_alignment);             \
 425       if (KEEP_RIGHT && left_section == NULL && right_section != NULL)  \
 426         {                                                               \
 427           if (eei->result_section_pointer != NULL)                      \
 428             *eei->result_section_pointer = right_section;               \
 429           if (eei->result_alignment_pointer != NULL                     \
 430               && right_alignment > *eei->result_alignment_pointer)      \
 431             *eei->result_alignment_pointer = right_alignment;           \
 432         }                                                               \
 433       else if (KEEP_LEFT                                                \
 434                && left_section != NULL                                  \
 435                && right_section == NULL)                                \
 436         {                                                               \
 437           if (eei->result_section_pointer != NULL)                      \
 438             *eei->result_section_pointer = left_section;                \
 439           if (eei->result_alignment_pointer != NULL                     \
 440               && left_alignment > *eei->result_alignment_pointer)       \
 441             *eei->result_alignment_pointer = left_alignment;            \
 442         }                                                               \
 443       else if ((WARN || left_section != right_section)                  \
 444                && (left_section != NULL || right_section != NULL)       \
 445                && parameters->options().relocatable())                  \
 446         gold_warning(_("binary " #NAME " applied to section "           \
 447                        "relative value"));                              \
 448       if (IS_DIV && right == 0)                                         \
 449         {                                                               \
 450           gold_error(_(#NAME " by zero"));                              \
 451           return 0;                                                     \
 452         }                                                               \
 453       return left OPERATOR right;                                       \
 454     }                                                                   \
 455                                                                         \
 456     void                                                                \
 457     print(FILE* f) const                                                \
 458     {                                                                   \
 459       fprintf(f, "(");                                                  \
 460       this->left_print(f);                                              \
 461       fprintf(f, " %s ", #OPERATOR);                                    \
 462       this->right_print(f);                                             \
 463       fprintf(f, ")");                                                  \
 464     }                                                                   \
 465   };                                                                    \
 466                                                                         \
 467   extern "C" Expression*                                                \
 468   script_exp_binary_ ## NAME(Expression* left, Expression* right)       \
 469   {                                                                     \
 470     return new Binary_ ## NAME(left, right);                            \
 471   }
 472
 473 BINARY_EXPRESSION(mult, *, false, false, false, true)
 474 BINARY_EXPRESSION(div, /, false, false, true, true)
 475 BINARY_EXPRESSION(mod, %, false, false, true, true)
 476 BINARY_EXPRESSION(add, +, true, true, false, true)
 477 BINARY_EXPRESSION(sub, -, true, false, false, false)
 478 BINARY_EXPRESSION(lshift, <<, false, false, false, true)
 479 BINARY_EXPRESSION(rshift, >>, false, false, false, true)
 480 BINARY_EXPRESSION(eq, ==, false, false, false, false)
 481 BINARY_EXPRESSION(ne, !=, false, false, false, false)
 482 BINARY_EXPRESSION(le, <=, false, false, false, false)
 483 BINARY_EXPRESSION(ge, >=, false, false, false, false)
 484 BINARY_EXPRESSION(lt, <, false, false, false, false)
 485 BINARY_EXPRESSION(gt, >, false, false, false, false)
 486 BINARY_EXPRESSION(bitwise_and, &, true, true, false, true)
 487 BINARY_EXPRESSION(bitwise_xor, ^, true, true, false, true)
 488 BINARY_EXPRESSION(bitwise_or, |, true, true, false, true)
 489 BINARY_EXPRESSION(logical_and, &&, false, false, false, true)
 490 BINARY_EXPRESSION(logical_or, ||, false, false, false, true)
 491
 492 // A trinary expression.
 493
 494 class Trinary_expression : public Expression
 495 {
 496  public:
 497   Trinary_expression(Expression* arg1, Expression* arg2, Expression* arg3)
 498     : arg1_(arg1), arg2_(arg2), arg3_(arg3)
 499   { }
 500
 501   ~Trinary_expression()
 502   {
 503     delete this->arg1_;
 504     delete this->arg2_;
 505     delete this->arg3_;
 506   }
 507
 508  protected:
 509   uint64_t
 510   arg1_value(const Expression_eval_info* eei,
 511              Output_section** section_pointer) const
 512   {
 513     return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
 514                                        eei->check_assertions,
 515                                        eei->is_dot_available,
 516                                        eei->dot_value,
 517                                        eei->dot_section,
 518                                        section_pointer,
 519                                        NULL,
 520                                        false);
 521   }
 522
 523   uint64_t
 524   arg2_value(const Expression_eval_info* eei,
 525              Output_section** section_pointer,
 526              uint64_t* alignment_pointer) const
 527   {
 528     return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
 529                                        eei->check_assertions,
 530                                        eei->is_dot_available,
 531                                        eei->dot_value,
 532                                        eei->dot_section,
 533                                        section_pointer,
 534                                        alignment_pointer,
 535                                        false);
 536   }
 537
 538   uint64_t
 539   arg3_value(const Expression_eval_info* eei,
 540              Output_section** section_pointer,
 541              uint64_t* alignment_pointer) const
 542   {
 543     return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
 544                                        eei->check_assertions,
 545                                        eei->is_dot_available,
 546                                        eei->dot_value,
 547                                        eei->dot_section,
 548                                        section_pointer,
 549                                        alignment_pointer,
 550                                        false);
 551   }
 552
 553   void
 554   arg1_print(FILE* f) const
 555   { this->arg1_->print(f); }
 556
 557   void
 558   arg2_print(FILE* f) const
 559   { this->arg2_->print(f); }
 560
 561   void
 562   arg3_print(FILE* f) const
 563   { this->arg3_->print(f); }
 564
 565  private:
 566   Expression* arg1_;
 567   Expression* arg2_;
 568   Expression* arg3_;
 569 };
 570
 571 // The conditional operator.
 572
 573 class Trinary_cond : public Trinary_expression
 574 {
 575  public:
 576   Trinary_cond(Expression* arg1, Expression* arg2, Expression* arg3)
 577     : Trinary_expression(arg1, arg2, arg3)
 578   { }
 579
 580   uint64_t
 581   value(const Expression_eval_info* eei)
 582   {
 583     Output_section* arg1_section;
 584     uint64_t arg1 = this->arg1_value(eei, &arg1_section);
 585     return (arg1
 586             ? this->arg2_value(eei, eei->result_section_pointer,
 587                                eei->result_alignment_pointer)
 588             : this->arg3_value(eei, eei->result_section_pointer,
 589                                eei->result_alignment_pointer));
 590   }
 591
 592   void
 593   print(FILE* f) const
 594   {
 595     fprintf(f, "(");
 596     this->arg1_print(f);
 597     fprintf(f, " ? ");
 598     this->arg2_print(f);
 599     fprintf(f, " : ");
 600     this->arg3_print(f);
 601     fprintf(f, ")");
 602   }
 603 };
 604
 605 extern "C" Expression*
 606 script_exp_trinary_cond(Expression* arg1, Expression* arg2, Expression* arg3)
 607 {
 608   return new Trinary_cond(arg1, arg2, arg3);
 609 }
 610
 611 // Max function.
 612
 613 class Max_expression : public Binary_expression
 614 {
 615  public:
 616   Max_expression(Expression* left, Expression* right)
 617     : Binary_expression(left, right)
 618   { }
 619
 620   uint64_t
 621   value(const Expression_eval_info* eei)
 622   {
 623     Output_section* left_section;
 624     uint64_t left_alignment;
 625     uint64_t left = this->left_value(eei, &left_section, &left_alignment);
 626     Output_section* right_section;
 627     uint64_t right_alignment;
 628     uint64_t right = this->right_value(eei, &right_section, &right_alignment);
 629     if (left_section == right_section)
 630       {
 631         if (eei->result_section_pointer != NULL)
 632           *eei->result_section_pointer = left_section;
 633       }
 634     else if ((left_section != NULL || right_section != NULL)
 635              && parameters->options().relocatable())
 636       gold_warning(_("max applied to section relative value"));
 637     if (eei->result_alignment_pointer != NULL)
 638       {
 639         uint64_t ra = *eei->result_alignment_pointer;
 640         if (left > right)
 641           ra = std::max(ra, left_alignment);
 642         else if (right > left)
 643           ra = std::max(ra, right_alignment);
 644         else
 645           ra = std::max(ra, std::max(left_alignment, right_alignment));
 646         *eei->result_alignment_pointer = ra;
 647       }
 648     return std::max(left, right);
 649   }
 650
 651   void
 652   print(FILE* f) const
 653   { this->print_function(f, "MAX"); }
 654 };
 655
 656 extern "C" Expression*
 657 script_exp_function_max(Expression* left, Expression* right)
 658 {
 659   return new Max_expression(left, right);
 660 }
 661
 662 // Min function.
 663
 664 class Min_expression : public Binary_expression
 665 {
 666  public:
 667   Min_expression(Expression* left, Expression* right)
 668     : Binary_expression(left, right)
 669   { }
 670
 671   uint64_t
 672   value(const Expression_eval_info* eei)
 673   {
 674     Output_section* left_section;
 675     uint64_t left_alignment;
 676     uint64_t left = this->left_value(eei, &left_section, &left_alignment);
 677     Output_section* right_section;
 678     uint64_t right_alignment;
 679     uint64_t right = this->right_value(eei, &right_section, &right_alignment);
 680     if (left_section == right_section)
 681       {
 682         if (eei->result_section_pointer != NULL)
 683           *eei->result_section_pointer = left_section;
 684       }
 685     else if ((left_section != NULL || right_section != NULL)
 686              && parameters->options().relocatable())
 687       gold_warning(_("min applied to section relative value"));
 688     if (eei->result_alignment_pointer != NULL)
 689       {
 690         uint64_t ra = *eei->result_alignment_pointer;
 691         if (left < right)
 692           ra = std::max(ra, left_alignment);
 693         else if (right < left)
 694           ra = std::max(ra, right_alignment);
 695         else
 696           ra = std::max(ra, std::max(left_alignment, right_alignment));
 697         *eei->result_alignment_pointer = ra;
 698       }
 699     return std::min(left, right);
 700   }
 701
 702   void
 703   print(FILE* f) const
 704   { this->print_function(f, "MIN"); }
 705 };
 706
 707 extern "C" Expression*
 708 script_exp_function_min(Expression* left, Expression* right)
 709 {
 710   return new Min_expression(left, right);
 711 }
 712
 713 // Class Section_expression.  This is a parent class used for
 714 // functions which take the name of an output section.
 715
 716 class Section_expression : public Expression
 717 {
 718  public:
 719   Section_expression(const char* section_name, size_t section_name_len)
 720     : section_name_(section_name, section_name_len)
 721   { }
 722
 723   uint64_t
 724   value(const Expression_eval_info*);
 725
 726   void
 727   print(FILE* f) const
 728   { fprintf(f, "%s(%s)", this->function_name(), this->section_name_.c_str()); }
 729
 730  protected:
 731   // The child class must implement this.
 732   virtual uint64_t
 733   value_from_output_section(const Expression_eval_info*,
 734                             Output_section*) = 0;
 735
 736   // The child class must implement this.
 737   virtual uint64_t
 738   value_from_script_output_section(uint64_t address, uint64_t load_address,
 739                                    uint64_t addralign, uint64_t size) = 0;
 740
 741   // The child class must implement this.
 742   virtual const char*
 743   function_name() const = 0;
 744
 745  private:
 746   std::string section_name_;
 747 };
 748
 749 uint64_t
 750 Section_expression::value(const Expression_eval_info* eei)
 751 {
 752   const char* section_name = this->section_name_.c_str();
 753   Output_section* os = eei->layout->find_output_section(section_name);
 754   if (os != NULL)
 755     return this->value_from_output_section(eei, os);
 756
 757   uint64_t address;
 758   uint64_t load_address;
 759   uint64_t addralign;
 760   uint64_t size;
 761   const Script_options* ss = eei->layout->script_options();
 762   if (ss->saw_sections_clause())
 763     {
 764       if (ss->script_sections()->get_output_section_info(section_name,
 765                                                          &address,
 766                                                          &load_address,
 767                                                          &addralign,
 768                                                          &size))
 769         return this->value_from_script_output_section(address, load_address,
 770                                                       addralign, size);
 771     }
 772
 773   gold_error("%s called on nonexistent output section '%s'",
 774              this->function_name(), section_name);
 775   return 0;
 776 }
 777
 778 // ABSOLUTE function.
 779
 780 class Absolute_expression : public Unary_expression
 781 {
 782  public:
 783   Absolute_expression(Expression* arg)
 784     : Unary_expression(arg)
 785   { }
 786
 787   uint64_t
 788   value(const Expression_eval_info* eei)
 789   {
 790     uint64_t ret = this->arg_value(eei, NULL);
 791     // Force the value to be absolute.
 792     if (eei->result_section_pointer != NULL)
 793       *eei->result_section_pointer = NULL;
 794     return ret;
 795   }
 796
 797   void
 798   print(FILE* f) const
 799   {
 800     fprintf(f, "ABSOLUTE(");
 801     this->arg_print(f);
 802     fprintf(f, ")");
 803   }
 804 };
 805
 806 extern "C" Expression*
 807 script_exp_function_absolute(Expression* arg)
 808 {
 809   return new Absolute_expression(arg);
 810 }
 811
 812 // ALIGN function.
 813
 814 class Align_expression : public Binary_expression
 815 {
 816  public:
 817   Align_expression(Expression* left, Expression* right)
 818     : Binary_expression(left, right)
 819   { }
 820
 821   uint64_t
 822   value(const Expression_eval_info* eei)
 823   {
 824     Output_section* align_section;
 825     uint64_t align = this->right_value(eei, &align_section, NULL);
 826     if (align_section != NULL
 827         && parameters->options().relocatable())
 828       gold_warning(_("aligning to section relative value"));
 829
 830     if (eei->result_alignment_pointer != NULL
 831         && align > *eei->result_alignment_pointer)
 832       {
 833         uint64_t a = align;
 834         while ((a & (a - 1)) != 0)
 835           a &= a - 1;
 836         *eei->result_alignment_pointer = a;
 837       }
 838
 839     uint64_t value = this->left_value(eei, eei->result_section_pointer, NULL);
 840     if (align <= 1)
 841       return value;
 842     return ((value + align - 1) / align) * align;
 843   }
 844
 845   void
 846   print(FILE* f) const
 847   { this->print_function(f, "ALIGN"); }
 848 };
 849
 850 extern "C" Expression*
 851 script_exp_function_align(Expression* left, Expression* right)
 852 {
 853   return new Align_expression(left, right);
 854 }
 855
 856 // ASSERT function.
 857
 858 class Assert_expression : public Unary_expression
 859 {
 860  public:
 861   Assert_expression(Expression* arg, const char* message, size_t length)
 862     : Unary_expression(arg), message_(message, length)
 863   { }
 864
 865   uint64_t
 866   value(const Expression_eval_info* eei)
 867   {
 868     uint64_t value = this->arg_value(eei, eei->result_section_pointer);
 869     if (!value && eei->check_assertions)
 870       gold_error("%s", this->message_.c_str());
 871     return value;
 872   }
 873
 874   void
 875   print(FILE* f) const
 876   {
 877     fprintf(f, "ASSERT(");
 878     this->arg_print(f);
 879     fprintf(f, ", %s)", this->message_.c_str());
 880   }
 881
 882  private:
 883   std::string message_;
 884 };
 885
 886 extern "C" Expression*
 887 script_exp_function_assert(Expression* expr, const char* message,
 888                            size_t length)
 889 {
 890   return new Assert_expression(expr, message, length);
 891 }
 892
 893 // ADDR function.
 894
 895 class Addr_expression : public Section_expression
 896 {
 897  public:
 898   Addr_expression(const char* section_name, size_t section_name_len)
 899     : Section_expression(section_name, section_name_len)
 900   { }
 901
 902  protected:
 903   uint64_t
 904   value_from_output_section(const Expression_eval_info* eei,
 905                             Output_section* os)
 906   {
 907     if (eei->result_section_pointer != NULL)
 908       *eei->result_section_pointer = os;
 909     return os->address();
 910   }
 911
 912   uint64_t
 913   value_from_script_output_section(uint64_t address, uint64_t, uint64_t,
 914                                    uint64_t)
 915   { return address; }
 916
 917   const char*
 918   function_name() const
 919   { return "ADDR"; }
 920 };
 921
 922 extern "C" Expression*
 923 script_exp_function_addr(const char* section_name, size_t section_name_len)
 924 {
 925   return new Addr_expression(section_name, section_name_len);
 926 }
 927
 928 // ALIGNOF.
 929
 930 class Alignof_expression : public Section_expression
 931 {
 932  public:
 933   Alignof_expression(const char* section_name, size_t section_name_len)
 934     : Section_expression(section_name, section_name_len)
 935   { }
 936
 937  protected:
 938   uint64_t
 939   value_from_output_section(const Expression_eval_info*,
 940                             Output_section* os)
 941   { return os->addralign(); }
 942
 943   uint64_t
 944   value_from_script_output_section(uint64_t, uint64_t, uint64_t addralign,
 945                                    uint64_t)
 946   { return addralign; }
 947
 948   const char*
 949   function_name() const
 950   { return "ALIGNOF"; }
 951 };
 952
 953 extern "C" Expression*
 954 script_exp_function_alignof(const char* section_name, size_t section_name_len)
 955 {
 956   return new Alignof_expression(section_name, section_name_len);
 957 }
 958
 959 // CONSTANT.  It would be nice if we could simply evaluate this
 960 // immediately and return an Integer_expression, but unfortunately we
 961 // don't know the target.
 962
 963 class Constant_expression : public Expression
 964 {
 965  public:
 966   Constant_expression(const char* name, size_t length);
 967
 968   uint64_t
 969   value(const Expression_eval_info*);
 970
 971   void
 972   print(FILE* f) const;
 973
 974  private:
 975   enum Constant_function
 976   {
 977     CONSTANT_MAXPAGESIZE,
 978     CONSTANT_COMMONPAGESIZE
 979   };
 980
 981   Constant_function function_;
 982 };
 983
 984 Constant_expression::Constant_expression(const char* name, size_t length)
 985 {
 986   if (length == 11 && strncmp(name, "MAXPAGESIZE", length) == 0)
 987     this->function_ = CONSTANT_MAXPAGESIZE;
 988   else if (length == 14 && strncmp(name, "COMMONPAGESIZE", length) == 0)
 989     this->function_ = CONSTANT_COMMONPAGESIZE;
 990   else
 991     {
 992       std::string s(name, length);
 993       gold_error(_("unknown constant %s"), s.c_str());
 994       this->function_ = CONSTANT_MAXPAGESIZE;
 995     }
 996 }
 997
 998 uint64_t
 999 Constant_expression::value(const Expression_eval_info*)
1000 {
1001   switch (this->function_)
1002     {
1003     case CONSTANT_MAXPAGESIZE:
1004       return parameters->target().abi_pagesize();
1005     case CONSTANT_COMMONPAGESIZE:
1006       return parameters->target().common_pagesize();
1007     default:
1008       gold_unreachable();
1009     }
1010 }
1011
1012 void
1013 Constant_expression::print(FILE* f) const
1014 {
1015   const char* name;
1016   switch (this->function_)
1017     {
1018     case CONSTANT_MAXPAGESIZE:
1019       name = "MAXPAGESIZE";
1020       break;
1021     case CONSTANT_COMMONPAGESIZE:
1022       name = "COMMONPAGESIZE";
1023       break;
1024     default:
1025       gold_unreachable();
1026     }
1027   fprintf(f, "CONSTANT(%s)", name);
1028 }
1029
1030 extern "C" Expression*
1031 script_exp_function_constant(const char* name, size_t length)
1032 {
1033   return new Constant_expression(name, length);
1034 }
1035
1036 // DATA_SEGMENT_ALIGN.  FIXME: we don't implement this; we always fall
1037 // back to the general case.
1038
1039 extern "C" Expression*
1040 script_exp_function_data_segment_align(Expression* left, Expression*)
1041 {
1042   Expression* e1 = script_exp_function_align(script_exp_string(".", 1), left);
1043   Expression* e2 = script_exp_binary_sub(left, script_exp_integer(1));
1044   Expression* e3 = script_exp_binary_bitwise_and(script_exp_string(".", 1),
1045                                                  e2);
1046   return script_exp_binary_add(e1, e3);
1047 }
1048
1049 // DATA_SEGMENT_RELRO.  FIXME: This is not implemented.
1050
1051 extern "C" Expression*
1052 script_exp_function_data_segment_relro_end(Expression*, Expression* right)
1053 {
1054   return right;
1055 }
1056
1057 // DATA_SEGMENT_END.  FIXME: This is not implemented.
1058
1059 extern "C" Expression*
1060 script_exp_function_data_segment_end(Expression* val)
1061 {
1062   return val;
1063 }
1064
1065 // DEFINED function.
1066
1067 class Defined_expression : public Expression
1068 {
1069  public:
1070   Defined_expression(const char* symbol_name, size_t symbol_name_len)
1071     : symbol_name_(symbol_name, symbol_name_len)
1072   { }
1073
1074   uint64_t
1075   value(const Expression_eval_info* eei)
1076   {
1077     Symbol* sym = eei->symtab->lookup(this->symbol_name_.c_str());
1078     return sym != NULL && sym->is_defined();
1079   }
1080
1081   void
1082   print(FILE* f) const
1083   { fprintf(f, "DEFINED(%s)", this->symbol_name_.c_str()); }
1084
1085  private:
1086   std::string symbol_name_;
1087 };
1088
1089 extern "C" Expression*
1090 script_exp_function_defined(const char* symbol_name, size_t symbol_name_len)
1091 {
1092   return new Defined_expression(symbol_name, symbol_name_len);
1093 }
1094
1095 // LOADADDR function
1096
1097 class Loadaddr_expression : public Section_expression
1098 {
1099  public:
1100   Loadaddr_expression(const char* section_name, size_t section_name_len)
1101     : Section_expression(section_name, section_name_len)
1102   { }
1103
1104  protected:
1105   uint64_t
1106   value_from_output_section(const Expression_eval_info* eei,
1107                             Output_section* os)
1108   {
1109     if (os->has_load_address())
1110       return os->load_address();
1111     else
1112       {
1113         if (eei->result_section_pointer != NULL)
1114           *eei->result_section_pointer = os;
1115         return os->address();
1116       }
1117   }
1118
1119   uint64_t
1120   value_from_script_output_section(uint64_t, uint64_t load_address, uint64_t,
1121                                    uint64_t)
1122   { return load_address; }
1123
1124   const char*
1125   function_name() const
1126   { return "LOADADDR"; }
1127 };
1128
1129 extern "C" Expression*
1130 script_exp_function_loadaddr(const char* section_name, size_t section_name_len)
1131 {
1132   return new Loadaddr_expression(section_name, section_name_len);
1133 }
1134
1135 // SIZEOF function
1136
1137 class Sizeof_expression : public Section_expression
1138 {
1139  public:
1140   Sizeof_expression(const char* section_name, size_t section_name_len)
1141     : Section_expression(section_name, section_name_len)
1142   { }
1143
1144  protected:
1145   uint64_t
1146   value_from_output_section(const Expression_eval_info*,
1147                             Output_section* os)
1148   {
1149     // We can not use data_size here, as the size of the section may
1150     // not have been finalized.  Instead we get whatever the current
1151     // size is.  This will work correctly for backward references in
1152     // linker scripts.
1153     return os->current_data_size();
1154   }
1155
1156   uint64_t
1157   value_from_script_output_section(uint64_t, uint64_t, uint64_t,
1158                                    uint64_t size)
1159   { return size; }
1160
1161   const char*
1162   function_name() const
1163   { return "SIZEOF"; }
1164 };
1165
1166 extern "C" Expression*
1167 script_exp_function_sizeof(const char* section_name, size_t section_name_len)
1168 {
1169   return new Sizeof_expression(section_name, section_name_len);
1170 }
1171
1172 // SIZEOF_HEADERS.
1173
1174 class Sizeof_headers_expression : public Expression
1175 {
1176  public:
1177   Sizeof_headers_expression()
1178   { }
1179
1180   uint64_t
1181   value(const Expression_eval_info*);
1182
1183   void
1184   print(FILE* f) const
1185   { fprintf(f, "SIZEOF_HEADERS"); }
1186 };
1187
1188 uint64_t
1189 Sizeof_headers_expression::value(const Expression_eval_info* eei)
1190 {
1191   unsigned int ehdr_size;
1192   unsigned int phdr_size;
1193   if (parameters->target().get_size() == 32)
1194     {
1195       ehdr_size = elfcpp::Elf_sizes<32>::ehdr_size;
1196       phdr_size = elfcpp::Elf_sizes<32>::phdr_size;
1197     }
1198   else if (parameters->target().get_size() == 64)
1199     {
1200       ehdr_size = elfcpp::Elf_sizes<64>::ehdr_size;
1201       phdr_size = elfcpp::Elf_sizes<64>::phdr_size;
1202     }
1203   else
1204     gold_unreachable();
1205
1206   return ehdr_size + phdr_size * eei->layout->expected_segment_count();
1207 }
1208
1209 extern "C" Expression*
1210 script_exp_function_sizeof_headers()
1211 {
1212   return new Sizeof_headers_expression();
1213 }
1214
1215 // SEGMENT_START.
1216
1217 class Segment_start_expression : public Unary_expression
1218 {
1219  public:
1220   Segment_start_expression(const char* segment_name, size_t segment_name_len,
1221                            Expression* default_value)
1222     : Unary_expression(default_value),
1223       segment_name_(segment_name, segment_name_len)
1224   { }
1225
1226   uint64_t
1227   value(const Expression_eval_info*);
1228
1229   void
1230   print(FILE* f) const
1231   {
1232     fprintf(f, "SEGMENT_START(\"%s\", ", this->segment_name_.c_str());
1233     this->arg_print(f);
1234     fprintf(f, ")");
1235   }
1236
1237  private:
1238   std::string segment_name_;
1239 };
1240
1241 uint64_t
1242 Segment_start_expression::value(const Expression_eval_info* eei)
1243 {
1244   // Check for command line overrides.
1245   if (parameters->options().user_set_Ttext()
1246       && this->segment_name_ == ".text")
1247     return parameters->options().Ttext();
1248   else if (parameters->options().user_set_Tdata()
1249            && this->segment_name_ == ".data")
1250     return parameters->options().Tdata();
1251   else if (parameters->options().user_set_Tbss()
1252            && this->segment_name_ == ".bss")
1253     return parameters->options().Tbss();
1254   else
1255     {
1256       uint64_t ret = this->arg_value(eei, NULL);
1257       // Force the value to be absolute.
1258       if (eei->result_section_pointer != NULL)
1259         *eei->result_section_pointer = NULL;
1260       return ret;
1261     }
1262 }
1263
1264 extern "C" Expression*
1265 script_exp_function_segment_start(const char* segment_name,
1266                                   size_t segment_name_len,
1267                                   Expression* default_value)
1268 {
1269   return new Segment_start_expression(segment_name, segment_name_len,
1270                                       default_value);
1271 }
1272
1273 } // End namespace gold.