gas/stabs.c

   1 /* Generic stabs parsing for gas.
   2    Copyright (C) 1989-2022 Free Software Foundation, Inc.
   3
   4    This file is part of GAS, the GNU Assembler.
   5
   6    GAS is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as
   8    published by the Free Software Foundation; either version 3,
   9    or (at your option) any later version.
  10
  11    GAS is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
  14    the GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with GAS; see the file COPYING.  If not, write to the Free
  18    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  19    02110-1301, USA.  */
  20
  21 #include "as.h"
  22 #include "filenames.h"
  23 #include "obstack.h"
  24 #include "subsegs.h"
  25 #include "ecoff.h"
  26
  27 /* We need this, despite the apparent object format dependency, since
  28    it defines stab types, which all object formats can use now.  */
  29
  30 #include "aout/stab_gnu.h"
  31
  32 /* Holds whether the assembler is generating stabs line debugging
  33    information or not.  Potentially used by md_cleanup function.  */
  34
  35 int outputting_stabs_line_debug = 0;
  36
  37 static void generate_asm_file (int, const char *);
  38
  39 /* Allow backends to override the names used for the stab sections.  */
  40 #ifndef STAB_SECTION_NAME
  41 #define STAB_SECTION_NAME ".stab"
  42 #endif
  43
  44 #ifndef STAB_STRING_SECTION_NAME
  45 #define STAB_STRING_SECTION_NAME ".stabstr"
  46 #endif
  47
  48 /* True if we're in the middle of a .func function, in which case
  49    stabs_generate_asm_lineno emits function relative line number stabs.
  50    Otherwise it emits line number stabs with absolute addresses.  Note that
  51    both cases only apply to assembler code assembled with -gstabs.  */
  52 static bool in_dot_func_p = false;
  53
  54 /* Label at start of current function if in_dot_func_p != FALSE.  */
  55 static const char *current_function_label;
  56
  57 /*
  58  * Handle .stabX directives, which used to be open-coded.
  59  * So much creeping featurism overloaded the semantics that we decided
  60  * to put all .stabX thinking in one place. Here.
  61  *
  62  * We try to make any .stabX directive legal. Other people's AS will often
  63  * do assembly-time consistency checks: eg assigning meaning to n_type bits
  64  * and "protecting" you from setting them to certain values. (They also zero
  65  * certain bits before emitting symbols. Tut tut.)
  66  *
  67  * If an expression is not absolute we either gripe or use the relocation
  68  * information. Other people's assemblers silently forget information they
  69  * don't need and invent information they need that you didn't supply.
  70  */
  71
  72 /*
  73  * Build a string dictionary entry for a .stabX symbol.
  74  * The symbol is added to the .<secname>str section.
  75  */
  76
  77 #ifndef SEPARATE_STAB_SECTIONS
  78 #define SEPARATE_STAB_SECTIONS 0
  79 #endif
  80
  81 unsigned int
  82 get_stab_string_offset (const char *string, const char *stabstr_secname,
  83                         bool free_stabstr_secname)
  84 {
  85   unsigned int length;
  86   unsigned int retval;
  87   segT save_seg;
  88   subsegT save_subseg;
  89   segT seg;
  90   char *p;
  91
  92   if (! SEPARATE_STAB_SECTIONS)
  93     abort ();
  94
  95   length = strlen (string);
  96
  97   save_seg = now_seg;
  98   save_subseg = now_subseg;
  99
 100   /* Create the stab string section, if it doesn't already exist.  */
 101   seg = subseg_new (stabstr_secname, 0);
 102   if (free_stabstr_secname && seg->name != stabstr_secname)
 103     free ((char *) stabstr_secname);
 104
 105   retval = seg_info (seg)->stabu.stab_string_size;
 106   if (retval <= 0)
 107     {
 108       /* Make sure the first string is empty.  */
 109       p = frag_more (1);
 110       *p = 0;
 111       retval = seg_info (seg)->stabu.stab_string_size = 1;
 112       bfd_set_section_flags (seg, SEC_READONLY | SEC_DEBUGGING);
 113     }
 114
 115   if (length > 0)
 116     {                           /* Ordinary case.  */
 117       p = frag_more (length + 1);
 118       strcpy (p, string);
 119
 120       seg_info (seg)->stabu.stab_string_size += length + 1;
 121     }
 122   else
 123     retval = 0;
 124
 125   subseg_set (save_seg, save_subseg);
 126
 127   return retval;
 128 }
 129
 130 #ifdef AOUT_STABS
 131 #ifndef OBJ_PROCESS_STAB
 132 #define OBJ_PROCESS_STAB(SEG,W,S,T,O,D) aout_process_stab(W,S,T,O,D)
 133 #endif
 134
 135 /* Here instead of obj-aout.c because other formats use it too.  */
 136 void
 137 aout_process_stab (int what, const char *string, int type, int other, int desc)
 138 {
 139   /* Put the stab information in the symbol table.  */
 140   symbolS *symbol;
 141
 142   /* Create the symbol now, but only insert it into the symbol chain
 143      after any symbols mentioned in the value expression get into the
 144      symbol chain.  This is to avoid "continuation symbols" (where one
 145      ends in "\" and the debug info is continued in the next .stabs
 146      directive) from being separated by other random symbols.  */
 147   symbol = symbol_create (string, undefined_section, &zero_address_frag, 0);
 148   if (what == 's' || what == 'n')
 149     {
 150       /* Pick up the value from the input line.  */
 151       pseudo_set (symbol);
 152     }
 153   else
 154     {
 155       /* .stabd sets the name to NULL.  Why?  */
 156       S_SET_NAME (symbol, NULL);
 157       symbol_set_frag (symbol, frag_now);
 158       S_SET_VALUE (symbol, (valueT) frag_now_fix ());
 159     }
 160
 161   symbol_append (symbol, symbol_lastP, &symbol_rootP, &symbol_lastP);
 162
 163   symbol_get_bfdsym (symbol)->flags |= BSF_DEBUGGING;
 164
 165   S_SET_TYPE (symbol, type);
 166   S_SET_OTHER (symbol, other);
 167   S_SET_DESC (symbol, desc);
 168 }
 169 #endif
 170
 171 /* This can handle different kinds of stabs (s,n,d) and different
 172    kinds of stab sections.  If STAB_SECNAME_OBSTACK_END is non-NULL,
 173    then STAB_SECNAME and STABSTR_SECNAME will be freed if possible
 174    before this function returns (the former by obstack_free).  */
 175
 176 static void
 177 s_stab_generic (int what,
 178                 const char *stab_secname,
 179                 const char *stabstr_secname,
 180                 const char *stab_secname_obstack_end)
 181 {
 182   long longint;
 183   const char *string;
 184   char *saved_string_obstack_end;
 185   int type;
 186   int other;
 187   int desc;
 188
 189   /* The general format is:
 190      .stabs "STRING",TYPE,OTHER,DESC,VALUE
 191      .stabn TYPE,OTHER,DESC,VALUE
 192      .stabd TYPE,OTHER,DESC
 193      At this point input_line_pointer points after the pseudo-op and
 194      any trailing whitespace.  The argument what is one of 's', 'n' or
 195      'd' indicating which type of .stab this is.  */
 196
 197   if (what != 's')
 198     {
 199       string = "";
 200       saved_string_obstack_end = 0;
 201     }
 202   else
 203     {
 204       int length;
 205
 206       string = demand_copy_C_string (&length);
 207       if (string == NULL)
 208         {
 209           as_warn (_(".stab%c: missing string"), what);
 210           ignore_rest_of_line ();
 211           return;
 212         }
 213       /* FIXME: We should probably find some other temporary storage
 214          for string, rather than leaking memory if someone else
 215          happens to use the notes obstack.  */
 216       saved_string_obstack_end = obstack_next_free (&notes);
 217       SKIP_WHITESPACE ();
 218       if (*input_line_pointer == ',')
 219         input_line_pointer++;
 220       else
 221         {
 222           as_warn (_(".stab%c: missing comma"), what);
 223           ignore_rest_of_line ();
 224           return;
 225         }
 226     }
 227
 228   if (get_absolute_expression_and_terminator (&longint) != ',')
 229     {
 230       as_warn (_(".stab%c: missing comma"), what);
 231       ignore_rest_of_line ();
 232       return;
 233     }
 234   type = longint;
 235
 236   if (get_absolute_expression_and_terminator (&longint) != ',')
 237     {
 238       as_warn (_(".stab%c: missing comma"), what);
 239       ignore_rest_of_line ();
 240       return;
 241     }
 242   other = longint;
 243
 244   desc = get_absolute_expression ();
 245
 246   if ((desc > 0xffff) || (desc < -0x8000))
 247     /* This could happen for example with a source file with a huge
 248        number of lines.  The only cure is to use a different debug
 249        format, probably DWARF.  */
 250     as_warn (_(".stab%c: description field '%x' too big, try a different debug format"),
 251              what, desc);
 252
 253   if (what == 's' || what == 'n')
 254     {
 255       if (*input_line_pointer != ',')
 256         {
 257           as_warn (_(".stab%c: missing comma"), what);
 258           ignore_rest_of_line ();
 259           return;
 260         }
 261       input_line_pointer++;
 262       SKIP_WHITESPACE ();
 263     }
 264
 265 #ifdef TC_PPC
 266 #ifdef OBJ_ELF
 267   /* Solaris on PowerPC has decided that .stabd can take 4 arguments, so if we were
 268      given 4 arguments, make it a .stabn */
 269   else if (what == 'd')
 270     {
 271       char *save_location = input_line_pointer;
 272
 273       SKIP_WHITESPACE ();
 274       if (*input_line_pointer == ',')
 275         {
 276           input_line_pointer++;
 277           what = 'n';
 278         }
 279       else
 280         input_line_pointer = save_location;
 281     }
 282 #endif /* OBJ_ELF */
 283 #endif /* TC_PPC */
 284
 285 #ifndef NO_LISTING
 286   if (listing)
 287     {
 288       switch (type)
 289         {
 290         case N_SLINE:
 291           listing_source_line ((unsigned int) desc);
 292           break;
 293         case N_SO:
 294         case N_SOL:
 295           listing_source_file (string);
 296           break;
 297         }
 298     }
 299 #endif /* ! NO_LISTING */
 300
 301   /* We have now gathered the type, other, and desc information.  For
 302      .stabs or .stabn, input_line_pointer is now pointing at the
 303      value.  */
 304
 305   if (SEPARATE_STAB_SECTIONS)
 306     /* Output the stab information in a separate section.  This is used
 307        at least for COFF and ELF.  */
 308     {
 309       segT saved_seg = now_seg;
 310       subsegT saved_subseg = now_subseg;
 311       fragS *saved_frag = frag_now;
 312       valueT dot;
 313       segT seg;
 314       unsigned int stroff;
 315       char *p;
 316
 317       static segT cached_sec;
 318
 319       dot = frag_now_fix ();
 320
 321 #ifdef md_flush_pending_output
 322       md_flush_pending_output ();
 323 #endif
 324
 325       if (cached_sec && strcmp (cached_sec->name, stab_secname) == 0)
 326         {
 327           seg = cached_sec;
 328           subseg_set (seg, 0);
 329         }
 330       else
 331         {
 332           seg = subseg_new (stab_secname, 0);
 333           cached_sec = seg;
 334         }
 335
 336       if (! seg_info (seg)->hadone)
 337         {
 338           bfd_set_section_flags (seg,
 339                                  SEC_READONLY | SEC_RELOC | SEC_DEBUGGING);
 340 #ifdef INIT_STAB_SECTION
 341           INIT_STAB_SECTION (seg);
 342 #endif
 343           seg_info (seg)->hadone = 1;
 344         }
 345
 346       stroff = get_stab_string_offset (string, stabstr_secname,
 347                                        stab_secname_obstack_end != NULL);
 348
 349       /* Release the string, if nobody else has used the obstack.  */
 350       if (saved_string_obstack_end != NULL
 351           && saved_string_obstack_end == obstack_next_free (&notes))
 352         obstack_free (&notes, string);
 353       /* Similarly for the section name.  This must be done before
 354          creating symbols below, which uses the notes obstack.  */
 355       if (seg->name != stab_secname
 356           && stab_secname_obstack_end != NULL
 357           && stab_secname_obstack_end == obstack_next_free (&notes))
 358         obstack_free (&notes, stab_secname);
 359
 360       /* At least for now, stabs in a special stab section are always
 361          output as 12 byte blocks of information.  */
 362       p = frag_more (8);
 363       md_number_to_chars (p, (valueT) stroff, 4);
 364       md_number_to_chars (p + 4, (valueT) type, 1);
 365       md_number_to_chars (p + 5, (valueT) other, 1);
 366       md_number_to_chars (p + 6, (valueT) desc, 2);
 367
 368       if (what == 's' || what == 'n')
 369         {
 370           /* Pick up the value from the input line.  */
 371           cons (4);
 372           input_line_pointer--;
 373         }
 374       else
 375         {
 376           symbolS *symbol;
 377           expressionS exp;
 378
 379           /* Arrange for a value representing the current location.  */
 380           symbol = symbol_temp_new (saved_seg, saved_frag, dot);
 381
 382           exp.X_op = O_symbol;
 383           exp.X_add_symbol = symbol;
 384           exp.X_add_number = 0;
 385
 386           emit_expr (&exp, 4);
 387         }
 388
 389 #ifdef OBJ_PROCESS_STAB
 390       OBJ_PROCESS_STAB (seg, what, string, type, other, desc);
 391 #endif
 392
 393       subseg_set (saved_seg, saved_subseg);
 394     }
 395   else
 396     {
 397       if (stab_secname_obstack_end != NULL)
 398         {
 399           free ((char *) stabstr_secname);
 400           if (stab_secname_obstack_end == obstack_next_free (&notes))
 401             obstack_free (&notes, stab_secname);
 402         }
 403 #ifdef OBJ_PROCESS_STAB
 404       OBJ_PROCESS_STAB (0, what, string, type, other, desc);
 405 #else
 406       abort ();
 407 #endif
 408     }
 409
 410   demand_empty_rest_of_line ();
 411 }
 412
 413 /* Regular stab directive.  */
 414
 415 void
 416 s_stab (int what)
 417 {
 418   s_stab_generic (what, STAB_SECTION_NAME, STAB_STRING_SECTION_NAME, NULL);
 419 }
 420
 421 /* "Extended stabs", used in Solaris only now.  */
 422
 423 void
 424 s_xstab (int what)
 425 {
 426   int length;
 427   char *stab_secname, *stabstr_secname, *stab_secname_obstack_end;
 428
 429   stab_secname = demand_copy_C_string (&length);
 430   stab_secname_obstack_end = obstack_next_free (&notes);
 431   SKIP_WHITESPACE ();
 432   if (*input_line_pointer == ',')
 433     input_line_pointer++;
 434   else
 435     {
 436       as_bad (_("comma missing in .xstabs"));
 437       ignore_rest_of_line ();
 438       return;
 439     }
 440
 441   /* To get the name of the stab string section, simply add "str" to
 442      the stab section name.  */
 443   stabstr_secname = concat (stab_secname, "str", (char *) NULL);
 444   s_stab_generic (what, stab_secname, stabstr_secname,
 445                   stab_secname_obstack_end);
 446 }
 447
 448 #ifdef S_SET_DESC
 449
 450 /* Frob invented at RMS' request. Set the n_desc of a symbol.  */
 451
 452 void
 453 s_desc (int ignore ATTRIBUTE_UNUSED)
 454 {
 455   char *name;
 456   char c;
 457   char *p;
 458   symbolS *symbolP;
 459   int temp;
 460
 461   c = get_symbol_name (&name);
 462   p = input_line_pointer;
 463   *p = c;
 464   SKIP_WHITESPACE_AFTER_NAME ();
 465   if (*input_line_pointer != ',')
 466     {
 467       *p = 0;
 468       as_bad (_("expected comma after \"%s\""), name);
 469       *p = c;
 470       ignore_rest_of_line ();
 471     }
 472   else
 473     {
 474       input_line_pointer++;
 475       temp = get_absolute_expression ();
 476       *p = 0;
 477       symbolP = symbol_find_or_make (name);
 478       *p = c;
 479       S_SET_DESC (symbolP, temp);
 480     }
 481   demand_empty_rest_of_line ();
 482 }                               /* s_desc() */
 483
 484 #endif /* defined (S_SET_DESC) */
 485
 486 /* Generate stabs debugging information to denote the main source file.  */
 487
 488 void
 489 stabs_generate_asm_file (void)
 490 {
 491   const char *file;
 492   unsigned int lineno;
 493
 494   file = as_where (&lineno);
 495   if (use_gnu_debug_info_extensions)
 496     {
 497       const char *dir;
 498       char *dir2;
 499
 500       dir = remap_debug_filename (getpwd ());
 501       dir2 = concat (dir, "/", NULL);
 502       generate_asm_file (N_SO, dir2);
 503       free (dir2);
 504       xfree ((char *) dir);
 505     }
 506   generate_asm_file (N_SO, file);
 507 }
 508
 509 /* Generate stabs debugging information to denote the source file.
 510    TYPE is one of N_SO, N_SOL.  */
 511
 512 static void
 513 generate_asm_file (int type, const char *file)
 514 {
 515   static char *last_file;
 516   static int label_count;
 517   char sym[30];
 518   char *buf;
 519   const char *tmp = file;
 520   const char *file_endp = file + strlen (file);
 521   char *bufp;
 522
 523   if (last_file != NULL
 524       && filename_cmp (last_file, file) == 0)
 525     return;
 526
 527   /* Rather than try to do this in some efficient fashion, we just
 528      generate a string and then parse it again.  That lets us use the
 529      existing stabs hook, which expect to see a string, rather than
 530      inventing new ones.  */
 531   sprintf (sym, "%sF%d", FAKE_LABEL_NAME, label_count);
 532   ++label_count;
 533
 534   /* Allocate enough space for the file name (possibly extended with
 535      doubled up backslashes), the symbol name, and the other characters
 536      that make up a stabs file directive.  */
 537   bufp = buf = XNEWVEC (char, 2 * strlen (file) + strlen (sym) + 12);
 538
 539   *bufp++ = '"';
 540
 541   while (tmp < file_endp)
 542     {
 543       const char *bslash = strchr (tmp, '\\');
 544       size_t len = bslash != NULL ? bslash - tmp + 1 : file_endp - tmp;
 545
 546       /* Double all backslashes, since demand_copy_C_string (used by
 547          s_stab to extract the part in quotes) will try to replace them as
 548          escape sequences.  backslash may appear in a filespec.  */
 549       memcpy (bufp, tmp, len);
 550
 551       tmp += len;
 552       bufp += len;
 553
 554       if (bslash != NULL)
 555         *bufp++ = '\\';
 556     }
 557
 558   sprintf (bufp, "\",%d,0,0,%s\n", type, sym);
 559
 560   temp_ilp (buf);
 561   s_stab ('s');
 562   restore_ilp ();
 563
 564   colon (sym);
 565
 566   free (last_file);
 567   last_file = xstrdup (file);
 568
 569   free (buf);
 570 }
 571
 572 /* Generate stabs debugging information for the current line.  This is
 573    used to produce debugging information for an assembler file.  */
 574
 575 void
 576 stabs_generate_asm_lineno (void)
 577 {
 578   static int label_count;
 579   const char *file;
 580   unsigned int lineno;
 581   char *buf;
 582   char sym[30];
 583   /* Remember the last file/line and avoid duplicates.  */
 584   static unsigned int prev_lineno = -1;
 585   static char *prev_file = NULL;
 586
 587   /* Rather than try to do this in some efficient fashion, we just
 588      generate a string and then parse it again.  That lets us use the
 589      existing stabs hook, which expect to see a string, rather than
 590      inventing new ones.  */
 591
 592   file = as_where (&lineno);
 593
 594   /* Don't emit sequences of stabs for the same line.  */
 595   if (prev_file == NULL)
 596     {
 597       /* First time through.  */
 598       prev_file = xstrdup (file);
 599       prev_lineno = lineno;
 600     }
 601   else if (lineno == prev_lineno
 602            && filename_cmp (file, prev_file) == 0)
 603     {
 604       /* Same file/line as last time.  */
 605       return;
 606     }
 607   else
 608     {
 609       /* Remember file/line for next time.  */
 610       prev_lineno = lineno;
 611       if (filename_cmp (file, prev_file) != 0)
 612         {
 613           free (prev_file);
 614           prev_file = xstrdup (file);
 615         }
 616     }
 617
 618   /* Let the world know that we are in the middle of generating a
 619      piece of stabs line debugging information.  */
 620   outputting_stabs_line_debug = 1;
 621
 622   generate_asm_file (N_SOL, file);
 623
 624   sprintf (sym, "%sL%d", FAKE_LABEL_NAME, label_count);
 625   ++label_count;
 626
 627   if (in_dot_func_p)
 628     {
 629       buf = XNEWVEC (char, 100 + strlen (current_function_label));
 630       sprintf (buf, "%d,0,%d,%s-%s\n", N_SLINE, lineno,
 631                sym, current_function_label);
 632     }
 633   else
 634     {
 635       buf = XNEWVEC (char, 100);
 636       sprintf (buf, "%d,0,%d,%s\n", N_SLINE, lineno, sym);
 637     }
 638
 639   temp_ilp (buf);
 640   s_stab ('n');
 641   restore_ilp ();
 642
 643   colon (sym);
 644
 645   outputting_stabs_line_debug = 0;
 646   free (buf);
 647 }
 648
 649 /* Emit a function stab.
 650    All assembler functions are assumed to have return type `void'.  */
 651
 652 void
 653 stabs_generate_asm_func (const char *funcname, const char *startlabname)
 654 {
 655   static bool void_emitted_p = false;
 656   char *buf;
 657   unsigned int lineno;
 658
 659   if (! void_emitted_p)
 660     {
 661       temp_ilp ((char *) "\"void:t1=1\",128,0,0,0");
 662       s_stab ('s');
 663       restore_ilp ();
 664       void_emitted_p = true;
 665     }
 666
 667   as_where (&lineno);
 668   if (asprintf (&buf, "\"%s:F1\",%d,0,%d,%s",
 669                 funcname, N_FUN, lineno + 1, startlabname) == -1)
 670     as_fatal ("%s", xstrerror (errno));
 671
 672   temp_ilp (buf);
 673   s_stab ('s');
 674   restore_ilp ();
 675   free (buf);
 676
 677   current_function_label = xstrdup (startlabname);
 678   in_dot_func_p = true;
 679 }
 680
 681 /* Emit a stab to record the end of a function.  */
 682
 683 void
 684 stabs_generate_asm_endfunc (const char *funcname ATTRIBUTE_UNUSED,
 685                             const char *startlabname)
 686 {
 687   static int label_count;
 688   char *buf;
 689   char sym[30];
 690
 691   sprintf (sym, "%sendfunc%d", FAKE_LABEL_NAME, label_count);
 692   ++label_count;
 693   colon (sym);
 694
 695   if (asprintf (&buf, "\"\",%d,0,0,%s-%s", N_FUN, sym, startlabname) == -1)
 696     as_fatal ("%s", xstrerror (errno));
 697
 698   temp_ilp (buf);
 699   s_stab ('s');
 700   restore_ilp ();
 701   free (buf);
 702
 703   in_dot_func_p = false;
 704   current_function_label = NULL;
 705 }