gold/expression.cc

   1 // expression.cc -- expressions in linker scripts for gold
   2
   3 // Copyright (C) 2006-2018 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   // Pointer to where the type of the symbol on the RHS should be stored.
  72   elfcpp::STT* type_pointer;
  73   // Pointer to where the visibility of the symbol on the RHS should be stored.
  74   elfcpp::STV* vis_pointer;
  75   // Pointer to where the rest of the symbol's st_other field should be stored.
  76   unsigned char* nonvis_pointer;
  77   // Whether the value is valid.  In Symbol_assignment::set_if_absolute, we
  78   // may be trying to evaluate the address of a section whose address is not
  79   // yet finalized, and we need to fail the evaluation gracefully.
  80   bool *is_valid_pointer;
  81 };
  82
  83 // Evaluate an expression.
  84
  85 uint64_t
  86 Expression::eval(const Symbol_table* symtab, const Layout* layout,
  87                  bool check_assertions)
  88 {
  89   return this->eval_maybe_dot(symtab, layout, check_assertions, false, 0,
  90                               NULL, NULL, NULL, NULL, NULL, NULL, false, NULL);
  91 }
  92
  93 // Evaluate an expression which may refer to the dot symbol.
  94
  95 uint64_t
  96 Expression::eval_with_dot(const Symbol_table* symtab, const Layout* layout,
  97                           bool check_assertions, uint64_t dot_value,
  98                           Output_section* dot_section,
  99                           Output_section** result_section_pointer,
 100                           uint64_t* result_alignment_pointer,
 101                           bool is_section_dot_assignment)
 102 {
 103   return this->eval_maybe_dot(symtab, layout, check_assertions, true,
 104                               dot_value, dot_section, result_section_pointer,
 105                               result_alignment_pointer, NULL, NULL, NULL,
 106                               is_section_dot_assignment, NULL);
 107 }
 108
 109 // Evaluate an expression which may or may not refer to the dot
 110 // symbol.
 111
 112 uint64_t
 113 Expression::eval_maybe_dot(const Symbol_table* symtab, const Layout* layout,
 114                            bool check_assertions, bool is_dot_available,
 115                            uint64_t dot_value, Output_section* dot_section,
 116                            Output_section** result_section_pointer,
 117                            uint64_t* result_alignment_pointer,
 118                            elfcpp::STT* type_pointer,
 119                            elfcpp::STV* vis_pointer,
 120                            unsigned char* nonvis_pointer,
 121                            bool is_section_dot_assignment,
 122                            bool* is_valid_pointer)
 123 {
 124   Expression_eval_info eei;
 125   eei.symtab = symtab;
 126   eei.layout = layout;
 127   eei.check_assertions = check_assertions;
 128   eei.is_dot_available = is_dot_available;
 129   eei.dot_value = dot_value;
 130   eei.dot_section = dot_section;
 131
 132   // We assume the value is absolute, and only set this to a section
 133   // if we find a section-relative reference.
 134   if (result_section_pointer != NULL)
 135     *result_section_pointer = NULL;
 136   eei.result_section_pointer = result_section_pointer;
 137
 138   // For symbol=symbol assignments, we need to track the type, visibility,
 139   // and remaining st_other bits.
 140   eei.type_pointer = type_pointer;
 141   eei.vis_pointer = vis_pointer;
 142   eei.nonvis_pointer = nonvis_pointer;
 143
 144   eei.result_alignment_pointer = result_alignment_pointer;
 145
 146   // Assume the value is valid until we try to evaluate an expression
 147   // that can't be evaluated yet.
 148   bool is_valid = true;
 149   eei.is_valid_pointer = &is_valid;
 150
 151   uint64_t val = this->value(&eei);
 152
 153   if (is_valid_pointer != NULL)
 154     *is_valid_pointer = is_valid;
 155   else
 156     gold_assert(is_valid);
 157
 158   // If this is an assignment to dot within a section, and the value
 159   // is absolute, treat it as a section-relative offset.
 160   if (is_section_dot_assignment && *result_section_pointer == NULL)
 161     {
 162       gold_assert(dot_section != NULL);
 163       val += dot_section->address();
 164       *result_section_pointer = dot_section;
 165     }
 166   return val;
 167 }
 168
 169 // A number.
 170
 171 class Integer_expression : public Expression
 172 {
 173  public:
 174   Integer_expression(uint64_t val)
 175     : val_(val)
 176   { }
 177
 178   uint64_t
 179   value(const Expression_eval_info*)
 180   { return this->val_; }
 181
 182   void
 183   print(FILE* f) const
 184   { fprintf(f, "0x%llx", static_cast<unsigned long long>(this->val_)); }
 185
 186  private:
 187   uint64_t val_;
 188 };
 189
 190 extern "C" Expression*
 191 script_exp_integer(uint64_t val)
 192 {
 193   return new Integer_expression(val);
 194 }
 195
 196 // An expression whose value is the value of a symbol.
 197
 198 class Symbol_expression : public Expression
 199 {
 200  public:
 201   Symbol_expression(const char* name, size_t length)
 202     : name_(name, length)
 203   { }
 204
 205   uint64_t
 206   value(const Expression_eval_info*);
 207
 208   void
 209   print(FILE* f) const
 210   { fprintf(f, "%s", this->name_.c_str()); }
 211
 212  private:
 213   std::string name_;
 214 };
 215
 216 uint64_t
 217 Symbol_expression::value(const Expression_eval_info* eei)
 218 {
 219   Symbol* sym = eei->symtab->lookup(this->name_.c_str());
 220   if (sym == NULL || !sym->is_defined())
 221     {
 222       gold_error(_("undefined symbol '%s' referenced in expression"),
 223                  this->name_.c_str());
 224       return 0;
 225     }
 226
 227   if (eei->result_section_pointer != NULL)
 228     *eei->result_section_pointer = sym->output_section();
 229   if (eei->type_pointer != NULL)
 230     *eei->type_pointer = sym->type();
 231   if (eei->vis_pointer != NULL)
 232     *eei->vis_pointer = sym->visibility();
 233   if (eei->nonvis_pointer != NULL)
 234     *eei->nonvis_pointer = sym->nonvis();
 235
 236   if (parameters->target().get_size() == 32)
 237     return eei->symtab->get_sized_symbol<32>(sym)->value();
 238   else if (parameters->target().get_size() == 64)
 239     return eei->symtab->get_sized_symbol<64>(sym)->value();
 240   else
 241     gold_unreachable();
 242 }
 243
 244 // An expression whose value is the value of the special symbol ".".
 245 // This is only valid within a SECTIONS clause.
 246
 247 class Dot_expression : public Expression
 248 {
 249  public:
 250   Dot_expression()
 251   { }
 252
 253   uint64_t
 254   value(const Expression_eval_info*);
 255
 256   void
 257   print(FILE* f) const
 258   { fprintf(f, "."); }
 259 };
 260
 261 uint64_t
 262 Dot_expression::value(const Expression_eval_info* eei)
 263 {
 264   if (!eei->is_dot_available)
 265     {
 266       gold_error(_("invalid reference to dot symbol outside of "
 267                    "SECTIONS clause"));
 268       return 0;
 269     }
 270   if (eei->result_section_pointer != NULL)
 271     *eei->result_section_pointer = eei->dot_section;
 272   return eei->dot_value;
 273 }
 274
 275 // A string.  This is either the name of a symbol, or ".".
 276
 277 extern "C" Expression*
 278 script_exp_string(const char* name, size_t length)
 279 {
 280   if (length == 1 && name[0] == '.')
 281     return new Dot_expression();
 282   else
 283     return new Symbol_expression(name, length);
 284 }
 285
 286 // A unary expression.
 287
 288 class Unary_expression : public Expression
 289 {
 290  public:
 291   Unary_expression(Expression* arg)
 292     : arg_(arg)
 293   { }
 294
 295   ~Unary_expression()
 296   { delete this->arg_; }
 297
 298  protected:
 299   uint64_t
 300   arg_value(const Expression_eval_info* eei,
 301             Output_section** arg_section_pointer) const
 302   {
 303     return this->arg_->eval_maybe_dot(eei->symtab, eei->layout,
 304                                       eei->check_assertions,
 305                                       eei->is_dot_available,
 306                                       eei->dot_value,
 307                                       eei->dot_section,
 308                                       arg_section_pointer,
 309                                       eei->result_alignment_pointer,
 310                                       NULL,
 311                                       NULL,
 312                                       NULL,
 313                                       false,
 314                                       eei->is_valid_pointer);
 315   }
 316
 317   void
 318   arg_print(FILE* f) const
 319   { this->arg_->print(f); }
 320
 321  private:
 322   Expression* arg_;
 323 };
 324
 325 // Handle unary operators.  We use a preprocessor macro as a hack to
 326 // capture the C operator.
 327
 328 #define UNARY_EXPRESSION(NAME, OPERATOR)                                \
 329   class Unary_ ## NAME : public Unary_expression                        \
 330   {                                                                     \
 331   public:                                                               \
 332     Unary_ ## NAME(Expression* arg)                                     \
 333       : Unary_expression(arg)                                           \
 334     { }                                                                 \
 335                                                                         \
 336     uint64_t                                                            \
 337     value(const Expression_eval_info* eei)                              \
 338     {                                                                   \
 339       Output_section* arg_section;                                      \
 340       uint64_t ret = OPERATOR this->arg_value(eei, &arg_section);       \
 341       if (arg_section != NULL && parameters->options().relocatable())   \
 342         gold_warning(_("unary " #NAME " applied to section "            \
 343                        "relative value"));                              \
 344       return ret;                                                       \
 345     }                                                                   \
 346                                                                         \
 347     void                                                                \
 348     print(FILE* f) const                                                \
 349     {                                                                   \
 350       fprintf(f, "(%s ", #OPERATOR);                                    \
 351       this->arg_print(f);                                               \
 352       fprintf(f, ")");                                                  \
 353     }                                                                   \
 354   };                                                                    \
 355                                                                         \
 356   extern "C" Expression*                                                \
 357   script_exp_unary_ ## NAME(Expression* arg)                            \
 358   {                                                                     \
 359       return new Unary_ ## NAME(arg);                                   \
 360   }
 361
 362 UNARY_EXPRESSION(minus, -)
 363 UNARY_EXPRESSION(logical_not, !)
 364 UNARY_EXPRESSION(bitwise_not, ~)
 365
 366 // A binary expression.
 367
 368 class Binary_expression : public Expression
 369 {
 370  public:
 371   Binary_expression(Expression* left, Expression* right)
 372     : left_(left), right_(right)
 373   { }
 374
 375   ~Binary_expression()
 376   {
 377     delete this->left_;
 378     delete this->right_;
 379   }
 380
 381  protected:
 382   uint64_t
 383   left_value(const Expression_eval_info* eei,
 384              Output_section** section_pointer,
 385              uint64_t* alignment_pointer) const
 386   {
 387     return this->left_->eval_maybe_dot(eei->symtab, eei->layout,
 388                                        eei->check_assertions,
 389                                        eei->is_dot_available,
 390                                        eei->dot_value,
 391                                        eei->dot_section,
 392                                        section_pointer,
 393                                        alignment_pointer,
 394                                        NULL,
 395                                        NULL,
 396                                        NULL,
 397                                        false,
 398                                        eei->is_valid_pointer);
 399   }
 400
 401   uint64_t
 402   right_value(const Expression_eval_info* eei,
 403               Output_section** section_pointer,
 404               uint64_t* alignment_pointer) const
 405   {
 406     return this->right_->eval_maybe_dot(eei->symtab, eei->layout,
 407                                         eei->check_assertions,
 408                                         eei->is_dot_available,
 409                                         eei->dot_value,
 410                                         eei->dot_section,
 411                                         section_pointer,
 412                                         alignment_pointer,
 413                                         NULL,
 414                                         NULL,
 415                                         NULL,
 416                                         false,
 417                                         eei->is_valid_pointer);
 418   }
 419
 420   void
 421   left_print(FILE* f) const
 422   { this->left_->print(f); }
 423
 424   void
 425   right_print(FILE* f) const
 426   { this->right_->print(f); }
 427
 428   // This is a call to function FUNCTION_NAME.  Print it.  This is for
 429   // debugging.
 430   void
 431   print_function(FILE* f, const char* function_name) const
 432   {
 433     fprintf(f, "%s(", function_name);
 434     this->left_print(f);
 435     fprintf(f, ", ");
 436     this->right_print(f);
 437     fprintf(f, ")");
 438   }
 439
 440  private:
 441   Expression* left_;
 442   Expression* right_;
 443 };
 444
 445 // Handle binary operators.  We use a preprocessor macro as a hack to
 446 // capture the C operator.  KEEP_LEFT means that if the left operand
 447 // is section relative and the right operand is not, the result uses
 448 // the same section as the left operand.  KEEP_RIGHT is the same with
 449 // left and right swapped.  IS_DIV means that we need to give an error
 450 // if the right operand is zero.  WARN means that we should warn if
 451 // used on section relative values in a relocatable link.  We always
 452 // warn if used on values in different sections in a relocatable link.
 453
 454 #define BINARY_EXPRESSION(NAME, OPERATOR, KEEP_LEFT, KEEP_RIGHT, IS_DIV, WARN) \
 455   class Binary_ ## NAME : public Binary_expression                      \
 456   {                                                                     \
 457   public:                                                               \
 458     Binary_ ## NAME(Expression* left, Expression* right)                \
 459       : Binary_expression(left, right)                                  \
 460     { }                                                                 \
 461                                                                         \
 462     uint64_t                                                            \
 463     value(const Expression_eval_info* eei)                              \
 464     {                                                                   \
 465       Output_section* left_section;                                     \
 466       uint64_t left_alignment = 0;                                      \
 467       uint64_t left = this->left_value(eei, &left_section,              \
 468                                        &left_alignment);                \
 469       Output_section* right_section;                                    \
 470       uint64_t right_alignment = 0;                                     \
 471       uint64_t right = this->right_value(eei, &right_section,           \
 472                                          &right_alignment);             \
 473       if (KEEP_RIGHT && left_section == NULL && right_section != NULL)  \
 474         {                                                               \
 475           if (eei->result_section_pointer != NULL)                      \
 476             *eei->result_section_pointer = right_section;               \
 477           if (eei->result_alignment_pointer != NULL                     \
 478               && right_alignment > *eei->result_alignment_pointer)      \
 479             *eei->result_alignment_pointer = right_alignment;           \
 480         }                                                               \
 481       else if (KEEP_LEFT                                                \
 482                && left_section != NULL                                  \
 483                && right_section == NULL)                                \
 484         {                                                               \
 485           if (eei->result_section_pointer != NULL)                      \
 486             *eei->result_section_pointer = left_section;                \
 487           if (eei->result_alignment_pointer != NULL                     \
 488               && left_alignment > *eei->result_alignment_pointer)       \
 489             *eei->result_alignment_pointer = left_alignment;            \
 490         }                                                               \
 491       else if ((WARN || left_section != right_section)                  \
 492                && (left_section != NULL || right_section != NULL)       \
 493                && parameters->options().relocatable())                  \
 494         gold_warning(_("binary " #NAME " applied to section "           \
 495                        "relative value"));                              \
 496       if (IS_DIV && right == 0)                                         \
 497         {                                                               \
 498           gold_error(_(#NAME " by zero"));                              \
 499           return 0;                                                     \
 500         }                                                               \
 501       return left OPERATOR right;                                       \
 502     }                                                                   \
 503                                                                         \
 504     void                                                                \
 505     print(FILE* f) const                                                \
 506     {                                                                   \
 507       fprintf(f, "(");                                                  \
 508       this->left_print(f);                                              \
 509       fprintf(f, " %s ", #OPERATOR);                                    \
 510       this->right_print(f);                                             \
 511       fprintf(f, ")");                                                  \
 512     }                                                                   \
 513   };                                                                    \
 514                                                                         \
 515   extern "C" Expression*                                                \
 516   script_exp_binary_ ## NAME(Expression* left, Expression* right)       \
 517   {                                                                     \
 518     return new Binary_ ## NAME(left, right);                            \
 519   }
 520
 521 BINARY_EXPRESSION(mult, *, false, false, false, true)
 522 BINARY_EXPRESSION(div, /, false, false, true, true)
 523 BINARY_EXPRESSION(mod, %, false, false, true, true)
 524 BINARY_EXPRESSION(add, +, true, true, false, true)
 525 BINARY_EXPRESSION(sub, -, true, false, false, false)
 526 BINARY_EXPRESSION(lshift, <<, false, false, false, true)
 527 BINARY_EXPRESSION(rshift, >>, false, false, false, true)
 528 BINARY_EXPRESSION(eq, ==, false, false, false, false)
 529 BINARY_EXPRESSION(ne, !=, false, false, false, false)
 530 BINARY_EXPRESSION(le, <=, false, false, false, false)
 531 BINARY_EXPRESSION(ge, >=, false, false, false, false)
 532 BINARY_EXPRESSION(lt, <, false, false, false, false)
 533 BINARY_EXPRESSION(gt, >, false, false, false, false)
 534 BINARY_EXPRESSION(bitwise_and, &, true, true, false, true)
 535 BINARY_EXPRESSION(bitwise_xor, ^, true, true, false, true)
 536 BINARY_EXPRESSION(bitwise_or, |, true, true, false, true)
 537 BINARY_EXPRESSION(logical_and, &&, false, false, false, true)
 538 BINARY_EXPRESSION(logical_or, ||, false, false, false, true)
 539
 540 // A trinary expression.
 541
 542 class Trinary_expression : public Expression
 543 {
 544  public:
 545   Trinary_expression(Expression* arg1, Expression* arg2, Expression* arg3)
 546     : arg1_(arg1), arg2_(arg2), arg3_(arg3)
 547   { }
 548
 549   ~Trinary_expression()
 550   {
 551     delete this->arg1_;
 552     delete this->arg2_;
 553     delete this->arg3_;
 554   }
 555
 556  protected:
 557   uint64_t
 558   arg1_value(const Expression_eval_info* eei,
 559              Output_section** section_pointer) const
 560   {
 561     return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
 562                                        eei->check_assertions,
 563                                        eei->is_dot_available,
 564                                        eei->dot_value,
 565                                        eei->dot_section,
 566                                        section_pointer,
 567                                        NULL,
 568                                        NULL,
 569                                        NULL,
 570                                        NULL,
 571                                        false,
 572                                        eei->is_valid_pointer);
 573   }
 574
 575   uint64_t
 576   arg2_value(const Expression_eval_info* eei,
 577              Output_section** section_pointer,
 578              uint64_t* alignment_pointer) const
 579   {
 580     return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
 581                                        eei->check_assertions,
 582                                        eei->is_dot_available,
 583                                        eei->dot_value,
 584                                        eei->dot_section,
 585                                        section_pointer,
 586                                        alignment_pointer,
 587                                        NULL,
 588                                        NULL,
 589                                        NULL,
 590                                        false,
 591                                        eei->is_valid_pointer);
 592   }
 593
 594   uint64_t
 595   arg3_value(const Expression_eval_info* eei,
 596              Output_section** section_pointer,
 597              uint64_t* alignment_pointer) const
 598   {
 599     return this->arg1_->eval_maybe_dot(eei->symtab, eei->layout,
 600                                        eei->check_assertions,
 601                                        eei->is_dot_available,
 602                                        eei->dot_value,
 603                                        eei->dot_section,
 604                                        section_pointer,
 605                                        alignment_pointer,
 606                                        NULL,
 607                                        NULL,
 608                                        NULL,
 609                                        false,
 610                                        eei->is_valid_pointer);
 611   }
 612
 613   void
 614   arg1_print(FILE* f) const
 615   { this->arg1_->print(f); }
 616
 617   void
 618   arg2_print(FILE* f) const
 619   { this->arg2_->print(f); }
 620
 621   void
 622   arg3_print(FILE* f) const
 623   { this->arg3_->print(f); }
 624
 625  private:
 626   Expression* arg1_;
 627   Expression* arg2_;
 628   Expression* arg3_;
 629 };
 630
 631 // The conditional operator.
 632
 633 class Trinary_cond : public Trinary_expression
 634 {
 635  public:
 636   Trinary_cond(Expression* arg1, Expression* arg2, Expression* arg3)
 637     : Trinary_expression(arg1, arg2, arg3)
 638   { }
 639
 640   uint64_t
 641   value(const Expression_eval_info* eei)
 642   {
 643     Output_section* arg1_section;
 644     uint64_t arg1 = this->arg1_value(eei, &arg1_section);
 645     return (arg1
 646             ? this->arg2_value(eei, eei->result_section_pointer,
 647                                eei->result_alignment_pointer)
 648             : this->arg3_value(eei, eei->result_section_pointer,
 649                                eei->result_alignment_pointer));
 650   }
 651
 652   void
 653   print(FILE* f) const
 654   {
 655     fprintf(f, "(");
 656     this->arg1_print(f);
 657     fprintf(f, " ? ");
 658     this->arg2_print(f);
 659     fprintf(f, " : ");
 660     this->arg3_print(f);
 661     fprintf(f, ")");
 662   }
 663 };
 664
 665 extern "C" Expression*
 666 script_exp_trinary_cond(Expression* arg1, Expression* arg2, Expression* arg3)
 667 {
 668   return new Trinary_cond(arg1, arg2, arg3);
 669 }
 670
 671 // Max function.
 672
 673 class Max_expression : public Binary_expression
 674 {
 675  public:
 676   Max_expression(Expression* left, Expression* right)
 677     : Binary_expression(left, right)
 678   { }
 679
 680   uint64_t
 681   value(const Expression_eval_info* eei)
 682   {
 683     Output_section* left_section;
 684     uint64_t left_alignment;
 685     uint64_t left = this->left_value(eei, &left_section, &left_alignment);
 686     Output_section* right_section;
 687     uint64_t right_alignment;
 688     uint64_t right = this->right_value(eei, &right_section, &right_alignment);
 689     if (left_section == right_section)
 690       {
 691         if (eei->result_section_pointer != NULL)
 692           *eei->result_section_pointer = left_section;
 693       }
 694     else if ((left_section != NULL || right_section != NULL)
 695              && parameters->options().relocatable())
 696       gold_warning(_("max applied to section relative value"));
 697     if (eei->result_alignment_pointer != NULL)
 698       {
 699         uint64_t ra = *eei->result_alignment_pointer;
 700         if (left > right)
 701           ra = std::max(ra, left_alignment);
 702         else if (right > left)
 703           ra = std::max(ra, right_alignment);
 704         else
 705           ra = std::max(ra, std::max(left_alignment, right_alignment));
 706         *eei->result_alignment_pointer = ra;
 707       }
 708     return std::max(left, right);
 709   }
 710
 711   void
 712   print(FILE* f) const
 713   { this->print_function(f, "MAX"); }
 714 };
 715
 716 extern "C" Expression*
 717 script_exp_function_max(Expression* left, Expression* right)
 718 {
 719   return new Max_expression(left, right);
 720 }
 721
 722 // Min function.
 723
 724 class Min_expression : public Binary_expression
 725 {
 726  public:
 727   Min_expression(Expression* left, Expression* right)
 728     : Binary_expression(left, right)
 729   { }
 730
 731   uint64_t
 732   value(const Expression_eval_info* eei)
 733   {
 734     Output_section* left_section;
 735     uint64_t left_alignment;
 736     uint64_t left = this->left_value(eei, &left_section, &left_alignment);
 737     Output_section* right_section;
 738     uint64_t right_alignment;
 739     uint64_t right = this->right_value(eei, &right_section, &right_alignment);
 740     if (left_section == right_section)
 741       {
 742         if (eei->result_section_pointer != NULL)
 743           *eei->result_section_pointer = left_section;
 744       }
 745     else if ((left_section != NULL || right_section != NULL)
 746              && parameters->options().relocatable())
 747       gold_warning(_("min applied to section relative value"));
 748     if (eei->result_alignment_pointer != NULL)
 749       {
 750         uint64_t ra = *eei->result_alignment_pointer;
 751         if (left < right)
 752           ra = std::max(ra, left_alignment);
 753         else if (right < left)
 754           ra = std::max(ra, right_alignment);
 755         else
 756           ra = std::max(ra, std::max(left_alignment, right_alignment));
 757         *eei->result_alignment_pointer = ra;
 758       }
 759     return std::min(left, right);
 760   }
 761
 762   void
 763   print(FILE* f) const
 764   { this->print_function(f, "MIN"); }
 765 };
 766
 767 extern "C" Expression*
 768 script_exp_function_min(Expression* left, Expression* right)
 769 {
 770   return new Min_expression(left, right);
 771 }
 772
 773 // Class Section_expression.  This is a parent class used for
 774 // functions which take the name of an output section.
 775
 776 class Section_expression : public Expression
 777 {
 778  public:
 779   Section_expression(const char* section_name, size_t section_name_len)
 780     : section_name_(section_name, section_name_len)
 781   { }
 782
 783   uint64_t
 784   value(const Expression_eval_info*);
 785
 786   void
 787   print(FILE* f) const
 788   { fprintf(f, "%s(%s)", this->function_name(), this->section_name_.c_str()); }
 789
 790  protected:
 791   // The child class must implement this.
 792   virtual uint64_t
 793   value_from_output_section(const Expression_eval_info*,
 794                             Output_section*) = 0;
 795
 796   // The child class must implement this.
 797   virtual uint64_t
 798   value_from_script_output_section(uint64_t address, uint64_t load_address,
 799                                    uint64_t addralign, uint64_t size) = 0;
 800
 801   // The child class must implement this.
 802   virtual const char*
 803   function_name() const = 0;
 804
 805  private:
 806   std::string section_name_;
 807 };
 808
 809 uint64_t
 810 Section_expression::value(const Expression_eval_info* eei)
 811 {
 812   const char* section_name = this->section_name_.c_str();
 813   Output_section* os = eei->layout->find_output_section(section_name);
 814   if (os != NULL)
 815     return this->value_from_output_section(eei, os);
 816
 817   uint64_t address;
 818   uint64_t load_address;
 819   uint64_t addralign;
 820   uint64_t size;
 821   const Script_options* ss = eei->layout->script_options();
 822   if (ss->saw_sections_clause())
 823     {
 824       if (ss->script_sections()->get_output_section_info(section_name,
 825                                                          &address,
 826                                                          &load_address,
 827                                                          &addralign,
 828                                                          &size))
 829         return this->value_from_script_output_section(address, load_address,
 830                                                       addralign, size);
 831     }
 832
 833   gold_error("%s called on nonexistent output section '%s'",
 834              this->function_name(), section_name);
 835   return 0;
 836 }
 837
 838 // ABSOLUTE function.
 839
 840 class Absolute_expression : public Unary_expression
 841 {
 842  public:
 843   Absolute_expression(Expression* arg)
 844     : Unary_expression(arg)
 845   { }
 846
 847   uint64_t
 848   value(const Expression_eval_info* eei)
 849   {
 850     uint64_t ret = this->arg_value(eei, NULL);
 851     // Force the value to be absolute.
 852     if (eei->result_section_pointer != NULL)
 853       *eei->result_section_pointer = NULL;
 854     return ret;
 855   }
 856
 857   void
 858   print(FILE* f) const
 859   {
 860     fprintf(f, "ABSOLUTE(");
 861     this->arg_print(f);
 862     fprintf(f, ")");
 863   }
 864 };
 865
 866 extern "C" Expression*
 867 script_exp_function_absolute(Expression* arg)
 868 {
 869   return new Absolute_expression(arg);
 870 }
 871
 872 // ALIGN function.
 873
 874 class Align_expression : public Binary_expression
 875 {
 876  public:
 877   Align_expression(Expression* left, Expression* right)
 878     : Binary_expression(left, right)
 879   { }
 880
 881   uint64_t
 882   value(const Expression_eval_info* eei)
 883   {
 884     Output_section* align_section;
 885     uint64_t align = this->right_value(eei, &align_section, NULL);
 886     if (align_section != NULL
 887         && parameters->options().relocatable())
 888       gold_warning(_("aligning to section relative value"));
 889
 890     if (eei->result_alignment_pointer != NULL
 891         && align > *eei->result_alignment_pointer)
 892       {
 893         uint64_t a = align;
 894         while ((a & (a - 1)) != 0)
 895           a &= a - 1;
 896         *eei->result_alignment_pointer = a;
 897       }
 898
 899     uint64_t value = this->left_value(eei, eei->result_section_pointer, NULL);
 900     if (align <= 1)
 901       return value;
 902     return ((value + align - 1) / align) * align;
 903   }
 904
 905   void
 906   print(FILE* f) const
 907   { this->print_function(f, "ALIGN"); }
 908 };
 909
 910 extern "C" Expression*
 911 script_exp_function_align(Expression* left, Expression* right)
 912 {
 913   return new Align_expression(left, right);
 914 }
 915
 916 // ASSERT function.
 917
 918 class Assert_expression : public Unary_expression
 919 {
 920  public:
 921   Assert_expression(Expression* arg, const char* message, size_t length)
 922     : Unary_expression(arg), message_(message, length)
 923   { }
 924
 925   uint64_t
 926   value(const Expression_eval_info* eei)
 927   {
 928     uint64_t value = this->arg_value(eei, eei->result_section_pointer);
 929     if (!value && eei->check_assertions)
 930       gold_error("%s", this->message_.c_str());
 931     return value;
 932   }
 933
 934   void
 935   print(FILE* f) const
 936   {
 937     fprintf(f, "ASSERT(");
 938     this->arg_print(f);
 939     fprintf(f, ", %s)", this->message_.c_str());
 940   }
 941
 942  private:
 943   std::string message_;
 944 };
 945
 946 extern "C" Expression*
 947 script_exp_function_assert(Expression* expr, const char* message,
 948                            size_t length)
 949 {
 950   return new Assert_expression(expr, message, length);
 951 }
 952
 953 // ADDR function.
 954
 955 class Addr_expression : public Section_expression
 956 {
 957  public:
 958   Addr_expression(const char* section_name, size_t section_name_len)
 959     : Section_expression(section_name, section_name_len)
 960   { }
 961
 962  protected:
 963   uint64_t
 964   value_from_output_section(const Expression_eval_info* eei,
 965                             Output_section* os)
 966   {
 967     if (eei->result_section_pointer != NULL)
 968       *eei->result_section_pointer = os;
 969     if (os->is_address_valid())
 970       return os->address();
 971     *eei->is_valid_pointer = false;
 972     return 0;
 973   }
 974
 975   uint64_t
 976   value_from_script_output_section(uint64_t address, uint64_t, uint64_t,
 977                                    uint64_t)
 978   { return address; }
 979
 980   const char*
 981   function_name() const
 982   { return "ADDR"; }
 983 };
 984
 985 extern "C" Expression*
 986 script_exp_function_addr(const char* section_name, size_t section_name_len)
 987 {
 988   return new Addr_expression(section_name, section_name_len);
 989 }
 990
 991 // ALIGNOF.
 992
 993 class Alignof_expression : public Section_expression
 994 {
 995  public:
 996   Alignof_expression(const char* section_name, size_t section_name_len)
 997     : Section_expression(section_name, section_name_len)
 998   { }
 999
1000  protected:
1001   uint64_t
1002   value_from_output_section(const Expression_eval_info*,
1003                             Output_section* os)
1004   { return os->addralign(); }
1005
1006   uint64_t
1007   value_from_script_output_section(uint64_t, uint64_t, uint64_t addralign,
1008                                    uint64_t)
1009   { return addralign; }
1010
1011   const char*
1012   function_name() const
1013   { return "ALIGNOF"; }
1014 };
1015
1016 extern "C" Expression*
1017 script_exp_function_alignof(const char* section_name, size_t section_name_len)
1018 {
1019   return new Alignof_expression(section_name, section_name_len);
1020 }
1021
1022 // CONSTANT.  It would be nice if we could simply evaluate this
1023 // immediately and return an Integer_expression, but unfortunately we
1024 // don't know the target.
1025
1026 class Constant_expression : public Expression
1027 {
1028  public:
1029   Constant_expression(const char* name, size_t length);
1030
1031   uint64_t
1032   value(const Expression_eval_info*);
1033
1034   void
1035   print(FILE* f) const;
1036
1037  private:
1038   enum Constant_function
1039   {
1040     CONSTANT_MAXPAGESIZE,
1041     CONSTANT_COMMONPAGESIZE
1042   };
1043
1044   Constant_function function_;
1045 };
1046
1047 Constant_expression::Constant_expression(const char* name, size_t length)
1048 {
1049   if (length == 11 && strncmp(name, "MAXPAGESIZE", length) == 0)
1050     this->function_ = CONSTANT_MAXPAGESIZE;
1051   else if (length == 14 && strncmp(name, "COMMONPAGESIZE", length) == 0)
1052     this->function_ = CONSTANT_COMMONPAGESIZE;
1053   else
1054     {
1055       std::string s(name, length);
1056       gold_error(_("unknown constant %s"), s.c_str());
1057       this->function_ = CONSTANT_MAXPAGESIZE;
1058     }
1059 }
1060
1061 uint64_t
1062 Constant_expression::value(const Expression_eval_info*)
1063 {
1064   switch (this->function_)
1065     {
1066     case CONSTANT_MAXPAGESIZE:
1067       return parameters->target().abi_pagesize();
1068     case CONSTANT_COMMONPAGESIZE:
1069       return parameters->target().common_pagesize();
1070     default:
1071       gold_unreachable();
1072     }
1073 }
1074
1075 void
1076 Constant_expression::print(FILE* f) const
1077 {
1078   const char* name;
1079   switch (this->function_)
1080     {
1081     case CONSTANT_MAXPAGESIZE:
1082       name = "MAXPAGESIZE";
1083       break;
1084     case CONSTANT_COMMONPAGESIZE:
1085       name = "COMMONPAGESIZE";
1086       break;
1087     default:
1088       gold_unreachable();
1089     }
1090   fprintf(f, "CONSTANT(%s)", name);
1091 }
1092
1093 extern "C" Expression*
1094 script_exp_function_constant(const char* name, size_t length)
1095 {
1096   return new Constant_expression(name, length);
1097 }
1098
1099 // DATA_SEGMENT_ALIGN.  FIXME: we don't implement this; we always fall
1100 // back to the general case.
1101
1102 extern "C" Expression*
1103 script_exp_function_data_segment_align(Expression* left, Expression*)
1104 {
1105   Expression* e1 = script_exp_function_align(script_exp_string(".", 1), left);
1106   Expression* e2 = script_exp_binary_sub(left, script_exp_integer(1));
1107   Expression* e3 = script_exp_binary_bitwise_and(script_exp_string(".", 1),
1108                                                  e2);
1109   return script_exp_binary_add(e1, e3);
1110 }
1111
1112 // DATA_SEGMENT_RELRO.  FIXME: This is not implemented.
1113
1114 extern "C" Expression*
1115 script_exp_function_data_segment_relro_end(Expression*, Expression* right)
1116 {
1117   return right;
1118 }
1119
1120 // DATA_SEGMENT_END.  FIXME: This is not implemented.
1121
1122 extern "C" Expression*
1123 script_exp_function_data_segment_end(Expression* val)
1124 {
1125   return val;
1126 }
1127
1128 // DEFINED function.
1129
1130 class Defined_expression : public Expression
1131 {
1132  public:
1133   Defined_expression(const char* symbol_name, size_t symbol_name_len)
1134     : symbol_name_(symbol_name, symbol_name_len)
1135   { }
1136
1137   uint64_t
1138   value(const Expression_eval_info* eei)
1139   {
1140     Symbol* sym = eei->symtab->lookup(this->symbol_name_.c_str());
1141     return sym != NULL && sym->is_defined();
1142   }
1143
1144   void
1145   print(FILE* f) const
1146   { fprintf(f, "DEFINED(%s)", this->symbol_name_.c_str()); }
1147
1148  private:
1149   std::string symbol_name_;
1150 };
1151
1152 extern "C" Expression*
1153 script_exp_function_defined(const char* symbol_name, size_t symbol_name_len)
1154 {
1155   return new Defined_expression(symbol_name, symbol_name_len);
1156 }
1157
1158 // LOADADDR function
1159
1160 class Loadaddr_expression : public Section_expression
1161 {
1162  public:
1163   Loadaddr_expression(const char* section_name, size_t section_name_len)
1164     : Section_expression(section_name, section_name_len)
1165   { }
1166
1167  protected:
1168   uint64_t
1169   value_from_output_section(const Expression_eval_info* eei,
1170                             Output_section* os)
1171   {
1172     if (os->has_load_address())
1173       return os->load_address();
1174     else
1175       {
1176         if (eei->result_section_pointer != NULL)
1177           *eei->result_section_pointer = os;
1178         return os->address();
1179       }
1180   }
1181
1182   uint64_t
1183   value_from_script_output_section(uint64_t, uint64_t load_address, uint64_t,
1184                                    uint64_t)
1185   { return load_address; }
1186
1187   const char*
1188   function_name() const
1189   { return "LOADADDR"; }
1190 };
1191
1192 extern "C" Expression*
1193 script_exp_function_loadaddr(const char* section_name, size_t section_name_len)
1194 {
1195   return new Loadaddr_expression(section_name, section_name_len);
1196 }
1197
1198 // SIZEOF function
1199
1200 class Sizeof_expression : public Section_expression
1201 {
1202  public:
1203   Sizeof_expression(const char* section_name, size_t section_name_len)
1204     : Section_expression(section_name, section_name_len)
1205   { }
1206
1207  protected:
1208   uint64_t
1209   value_from_output_section(const Expression_eval_info*,
1210                             Output_section* os)
1211   {
1212     // We can not use data_size here, as the size of the section may
1213     // not have been finalized.  Instead we get whatever the current
1214     // size is.  This will work correctly for backward references in
1215     // linker scripts.
1216     return os->current_data_size();
1217   }
1218
1219   uint64_t
1220   value_from_script_output_section(uint64_t, uint64_t, uint64_t,
1221                                    uint64_t size)
1222   { return size; }
1223
1224   const char*
1225   function_name() const
1226   { return "SIZEOF"; }
1227 };
1228
1229 extern "C" Expression*
1230 script_exp_function_sizeof(const char* section_name, size_t section_name_len)
1231 {
1232   return new Sizeof_expression(section_name, section_name_len);
1233 }
1234
1235 // SIZEOF_HEADERS.
1236
1237 class Sizeof_headers_expression : public Expression
1238 {
1239  public:
1240   Sizeof_headers_expression()
1241   { }
1242
1243   uint64_t
1244   value(const Expression_eval_info*);
1245
1246   void
1247   print(FILE* f) const
1248   { fprintf(f, "SIZEOF_HEADERS"); }
1249 };
1250
1251 uint64_t
1252 Sizeof_headers_expression::value(const Expression_eval_info* eei)
1253 {
1254   unsigned int ehdr_size;
1255   unsigned int phdr_size;
1256   if (parameters->target().get_size() == 32)
1257     {
1258       ehdr_size = elfcpp::Elf_sizes<32>::ehdr_size;
1259       phdr_size = elfcpp::Elf_sizes<32>::phdr_size;
1260     }
1261   else if (parameters->target().get_size() == 64)
1262     {
1263       ehdr_size = elfcpp::Elf_sizes<64>::ehdr_size;
1264       phdr_size = elfcpp::Elf_sizes<64>::phdr_size;
1265     }
1266   else
1267     gold_unreachable();
1268
1269   return ehdr_size + phdr_size * eei->layout->expected_segment_count();
1270 }
1271
1272 extern "C" Expression*
1273 script_exp_function_sizeof_headers()
1274 {
1275   return new Sizeof_headers_expression();
1276 }
1277
1278 // SEGMENT_START.
1279
1280 class Segment_start_expression : public Unary_expression
1281 {
1282  public:
1283   Segment_start_expression(const char* segment_name, size_t segment_name_len,
1284                            Expression* default_value)
1285     : Unary_expression(default_value),
1286       segment_name_(segment_name, segment_name_len)
1287   { }
1288
1289   uint64_t
1290   value(const Expression_eval_info*);
1291
1292   void
1293   print(FILE* f) const
1294   {
1295     fprintf(f, "SEGMENT_START(\"%s\", ", this->segment_name_.c_str());
1296     this->arg_print(f);
1297     fprintf(f, ")");
1298   }
1299
1300  private:
1301   std::string segment_name_;
1302 };
1303
1304 uint64_t
1305 Segment_start_expression::value(const Expression_eval_info* eei)
1306 {
1307   // Check for command line overrides.
1308   if (parameters->options().user_set_Ttext()
1309       && this->segment_name_ == ".text")
1310     return parameters->options().Ttext();
1311   else if (parameters->options().user_set_Tdata()
1312            && this->segment_name_ == ".data")
1313     return parameters->options().Tdata();
1314   else if (parameters->options().user_set_Tbss()
1315            && this->segment_name_ == ".bss")
1316     return parameters->options().Tbss();
1317   else
1318     {
1319       uint64_t ret = this->arg_value(eei, NULL);
1320       // Force the value to be absolute.
1321       if (eei->result_section_pointer != NULL)
1322         *eei->result_section_pointer = NULL;
1323       return ret;
1324     }
1325 }
1326
1327 extern "C" Expression*
1328 script_exp_function_segment_start(const char* segment_name,
1329                                   size_t segment_name_len,
1330                                   Expression* default_value)
1331 {
1332   return new Segment_start_expression(segment_name, segment_name_len,
1333                                       default_value);
1334 }
1335
1336 } // End namespace gold.