asm/labels.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 1996-2016 The NASM Authors - All Rights Reserved
   4  *   See the file AUTHORS included with the NASM distribution for
   5  *   the specific copyright holders.
   6  *
   7  *   Redistribution and use in source and binary forms, with or without
   8  *   modification, are permitted provided that the following
   9  *   conditions are met:
  10  *
  11  *   * Redistributions of source code must retain the above copyright
  12  *     notice, this list of conditions and the following disclaimer.
  13  *   * Redistributions in binary form must reproduce the above
  14  *     copyright notice, this list of conditions and the following
  15  *     disclaimer in the documentation and/or other materials provided
  16  *     with the distribution.
  17  *
  18  *     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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  20  *     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  21  *     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  22  *     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  23  *     CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  *     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  25  *     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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  29  *     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
  30  *     EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  31  *
  32  * ----------------------------------------------------------------------- */
  33
  34 /*
  35  * labels.c  label handling for the Netwide Assembler
  36  */
  37
  38 #include "compiler.h"
  39
  40 #include <stdio.h>
  41 #include <string.h>
  42 #include <stdlib.h>
  43
  44 #include "nasm.h"
  45 #include "nasmlib.h"
  46 #include "hashtbl.h"
  47 #include "labels.h"
  48
  49 /*
  50  * A local label is one that begins with exactly one period. Things
  51  * that begin with _two_ periods are NASM-specific things.
  52  *
  53  * If TASM compatibility is enabled, a local label can also begin with
  54  * @@, so @@local is a TASM compatible local label. Note that we only
  55  * check for the first @ symbol, although TASM requires both.
  56  */
  57 #define islocal(l)                                                      \
  58         (tasm_compatible_mode ?                                         \
  59                 (((l)[0] == '.' || (l)[0] == '@') && (l)[1] != '.') :   \
  60                 ((l)[0] == '.' && (l)[1] != '.'))
  61 #define islocalchar(c)                                                  \
  62         (tasm_compatible_mode ?                                         \
  63                 ((c) == '.' || (c) == '@') :                            \
  64                 ((c) == '.'))
  65
  66 #define LABEL_BLOCK     128     /* no. of labels/block */
  67 #define LBLK_SIZE       (LABEL_BLOCK * sizeof(union label))
  68
  69 #define END_LIST        -3      /* don't clash with NO_SEG! */
  70 #define END_BLOCK       -2
  71 #define BOGUS_VALUE     -4
  72
  73 #define PERMTS_SIZE     16384   /* size of text blocks */
  74 #if (PERMTS_SIZE < IDLEN_MAX)
  75  #error "IPERMTS_SIZE must be greater than or equal to IDLEN_MAX"
  76 #endif
  77
  78 /* values for label.defn.is_global */
  79 #define DEFINED_BIT     1
  80 #define GLOBAL_BIT      2
  81 #define EXTERN_BIT      4
  82 #define COMMON_BIT      8
  83
  84 #define NOT_DEFINED_YET         0
  85 #define TYPE_MASK               3
  86 #define LOCAL_SYMBOL            (DEFINED_BIT)
  87 #define GLOBAL_PLACEHOLDER      (GLOBAL_BIT)
  88 #define GLOBAL_SYMBOL           (DEFINED_BIT | GLOBAL_BIT)
  89
  90 union label {                   /* actual label structures */
  91     struct {
  92         int32_t segment;
  93         int64_t offset;
  94         char *label, *special;
  95         int is_global, is_norm;
  96     } defn;
  97     struct {
  98         int32_t movingon;
  99         int64_t dummy;
 100         union label *next;
 101     } admin;
 102 };
 103
 104 struct permts {                 /* permanent text storage */
 105     struct permts *next;        /* for the linked list */
 106     int size, usage;            /* size and used space in ... */
 107     char data[PERMTS_SIZE];     /* ... the data block itself */
 108 };
 109
 110 extern int64_t global_offset_changed;   /* defined in nasm.c */
 111
 112 static struct hash_table ltab;          /* labels hash table */
 113 static union label *ldata;              /* all label data blocks */
 114 static union label *lfree;              /* labels free block */
 115 static struct permts *perm_head;        /* start of perm. text storage */
 116 static struct permts *perm_tail;        /* end of perm. text storage */
 117
 118 static void init_block(union label *blk);
 119 static char *perm_copy(const char *string);
 120
 121 static char *prevlabel;
 122
 123 static bool initialized = false;
 124
 125 char lprefix[PREFIX_MAX] = { 0 };
 126 char lpostfix[PREFIX_MAX] = { 0 };
 127
 128 /*
 129  * Emit a symdef to the output and the debug format backends.
 130  */
 131 static void out_symdef(char *name, int32_t segment, int64_t offset,
 132                        int is_global, char *special)
 133 {
 134     ofmt->symdef(name, segment, offset, is_global, special);
 135
 136     /*
 137      * NASM special symbols are not passed to the debug format; none
 138      * of the current backends want to see them.
 139      */
 140     if (!(name[0] == '.' && name[1] == '.' && name[2] != '@'))
 141         dfmt->debug_deflabel(name, segment, offset, is_global, special);
 142 }
 143
 144 /*
 145  * Internal routine: finds the `union label' corresponding to the
 146  * given label name. Creates a new one, if it isn't found, and if
 147  * `create' is true.
 148  */
 149 static union label *find_label(char *label, int create, int *created)
 150 {
 151     char *prev;
 152     int prevlen, len;
 153     union label *lptr, **lpp;
 154     char label_str[IDLEN_MAX];
 155     struct hash_insert ip;
 156
 157     if (islocal(label)) {
 158         prev = prevlabel;
 159         prevlen = strlen(prev);
 160         len = strlen(label);
 161         if (prevlen + len >= IDLEN_MAX) {
 162             nasm_error(ERR_NONFATAL, "identifier length exceed %i bytes",
 163                        IDLEN_MAX);
 164             return NULL;
 165         }
 166         memcpy(label_str, prev, prevlen);
 167         memcpy(label_str+prevlen, label, len+1);
 168         label = label_str;
 169     } else {
 170         prev = "";
 171         prevlen = 0;
 172     }
 173
 174     lpp = (union label **) hash_find(&ltab, label, &ip);
 175     lptr = lpp ? *lpp : NULL;
 176
 177     if (lptr || !create) {
 178         if (created)
 179             *created = 0;
 180         return lptr;
 181     }
 182
 183     /* Create a new label... */
 184     if (lfree->admin.movingon == END_BLOCK) {
 185         /*
 186          * must allocate a new block
 187          */
 188         lfree->admin.next = (union label *)nasm_malloc(LBLK_SIZE);
 189         lfree = lfree->admin.next;
 190         init_block(lfree);
 191     }
 192
 193     if (created)
 194         *created = 1;
 195
 196     lfree->admin.movingon = BOGUS_VALUE;
 197     lfree->defn.label = perm_copy(label);
 198     lfree->defn.special = NULL;
 199     lfree->defn.is_global = NOT_DEFINED_YET;
 200
 201     hash_add(&ip, lfree->defn.label, lfree);
 202     return lfree++;
 203 }
 204
 205 bool lookup_label(char *label, int32_t *segment, int64_t *offset)
 206 {
 207     union label *lptr;
 208
 209     if (!initialized)
 210         return false;
 211
 212     lptr = find_label(label, 0, NULL);
 213     if (lptr && (lptr->defn.is_global & DEFINED_BIT)) {
 214         *segment = lptr->defn.segment;
 215         *offset = lptr->defn.offset;
 216         return true;
 217     }
 218
 219     return false;
 220 }
 221
 222 bool is_extern(char *label)
 223 {
 224     union label *lptr;
 225
 226     if (!initialized)
 227         return false;
 228
 229     lptr = find_label(label, 0, NULL);
 230     return (lptr && (lptr->defn.is_global & EXTERN_BIT));
 231 }
 232
 233 void redefine_label(char *label, int32_t segment, int64_t offset, char *special,
 234                     bool is_norm, bool isextrn)
 235 {
 236     union label *lptr;
 237     int exi, created;
 238
 239     /* This routine possibly ought to check for phase errors.  Most assemblers
 240      * check for phase errors at this point.  I don't know whether phase errors
 241      * are even possible, nor whether they are checked somewhere else
 242      */
 243
 244     (void)special;              /* Don't warn that this parameter is unused */
 245     (void)is_norm;              /* Don't warn that this parameter is unused */
 246     (void)isextrn;              /* Don't warn that this parameter is unused */
 247
 248 #ifdef DEBUG
 249 #if DEBUG < 3
 250     if (!strncmp(label, "debugdump", 9))
 251 #endif
 252         nasm_error(ERR_DEBUG, "redefine_label (%s, %"PRIx32", %"PRIx64", %s, %d, %d)",
 253               label, segment, offset, special, is_norm, isextrn);
 254 #endif
 255
 256     lptr = find_label(label, 1, &created);
 257     if (!lptr)
 258         nasm_panic(0, "can't find label `%s' on pass two", label);
 259
 260     if (created)
 261             nasm_error(ERR_WARNING, "label `%s' defined on pass two", label);
 262
 263     if (!islocal(label)) {
 264         if (!islocalchar(*label) && lptr->defn.is_norm)
 265             prevlabel = lptr->defn.label;
 266     }
 267
 268     if (lptr->defn.offset != offset)
 269         global_offset_changed++;
 270
 271     lptr->defn.offset = offset;
 272     lptr->defn.segment = segment;
 273
 274     if (pass0 == 1) {
 275         exi = !!(lptr->defn.is_global & GLOBAL_BIT);
 276         if (exi) {
 277             char *xsymbol;
 278             int slen;
 279             slen = strlen(lprefix);
 280             slen += strlen(lptr->defn.label);
 281             slen += strlen(lpostfix);
 282             slen++;             /* room for that null char */
 283             xsymbol = nasm_malloc(slen);
 284             snprintf(xsymbol, slen, "%s%s%s", lprefix, lptr->defn.label,
 285                      lpostfix);
 286
 287             out_symdef(xsymbol, segment, offset, exi,
 288                        special ? special : lptr->defn.special);
 289             /** nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
 290         } else {
 291             if ((lptr->defn.is_global & (GLOBAL_BIT | EXTERN_BIT)) != EXTERN_BIT) {
 292                 out_symdef(lptr->defn.label, segment, offset, exi,
 293                            special ? special : lptr->defn.special);
 294             }
 295         }
 296     }   /* if (pass0 == 1) */
 297 }
 298
 299 void define_label(char *label, int32_t segment, int64_t offset, char *special,
 300                   bool is_norm, bool isextrn)
 301 {
 302     union label *lptr;
 303     int exi;
 304
 305 #ifdef DEBUG
 306 #if DEBUG<3
 307     if (!strncmp(label, "debugdump", 9))
 308 #endif
 309         nasm_error(ERR_DEBUG, "define_label (%s, %"PRIx32", %"PRIx64", %s, %d, %d)",
 310               label, segment, offset, special, is_norm, isextrn);
 311 #endif
 312     lptr = find_label(label, 1, NULL);
 313     if (!lptr)
 314         return;
 315     if (lptr->defn.is_global & DEFINED_BIT) {
 316         nasm_error(ERR_NONFATAL, "symbol `%s' redefined", label);
 317         return;
 318     }
 319     lptr->defn.is_global |= DEFINED_BIT;
 320     if (isextrn)
 321         lptr->defn.is_global |= EXTERN_BIT;
 322
 323     if (!islocalchar(label[0]) && is_norm) {
 324         /* not local, but not special either */
 325         prevlabel = lptr->defn.label;
 326     } else if (islocal(label) && !*prevlabel) {
 327         nasm_error(ERR_NONFATAL, "attempt to define a local label before any"
 328               " non-local labels");
 329     }
 330
 331     lptr->defn.segment = segment;
 332     lptr->defn.offset = offset;
 333     lptr->defn.is_norm = (!islocalchar(label[0]) && is_norm);
 334
 335     if (pass0 == 1 || (!is_norm && !isextrn && (segment > 0) && (segment & 1))) {
 336         exi = !!(lptr->defn.is_global & GLOBAL_BIT);
 337         if (exi) {
 338             char *xsymbol;
 339             int slen;
 340             slen = strlen(lprefix);
 341             slen += strlen(lptr->defn.label);
 342             slen += strlen(lpostfix);
 343             slen++;             /* room for that null char */
 344             xsymbol = nasm_malloc(slen);
 345             snprintf(xsymbol, slen, "%s%s%s", lprefix, lptr->defn.label,
 346                      lpostfix);
 347
 348             out_symdef(xsymbol, segment, offset, exi,
 349                        special ? special : lptr->defn.special);
 350             /** nasm_free(xsymbol);  ! outobj.c stores the pointer; ouch!!! **/
 351         } else {
 352             if ((lptr->defn.is_global & (GLOBAL_BIT | EXTERN_BIT)) != EXTERN_BIT) {
 353                 out_symdef(lptr->defn.label, segment, offset, exi,
 354                            special ? special : lptr->defn.special);
 355             }
 356         }
 357     }   /* if (pass0 == 1) */
 358 }
 359
 360 void define_common(char *label, int32_t segment, int32_t size, char *special)
 361 {
 362     union label *lptr;
 363
 364     lptr = find_label(label, 1, NULL);
 365     if (!lptr)
 366         return;
 367     if ((lptr->defn.is_global & DEFINED_BIT) &&
 368         (passn == 1 || !(lptr->defn.is_global & COMMON_BIT))) {
 369             nasm_error(ERR_NONFATAL, "symbol `%s' redefined", label);
 370             return;
 371     }
 372     lptr->defn.is_global |= DEFINED_BIT|COMMON_BIT;
 373
 374     if (!islocalchar(label[0])) {
 375         prevlabel = lptr->defn.label;
 376     } else {
 377         nasm_error(ERR_NONFATAL, "attempt to define a local label as a "
 378               "common variable");
 379         return;
 380     }
 381
 382     lptr->defn.segment = segment;
 383     lptr->defn.offset = 0;
 384
 385     if (pass0 == 0)
 386         return;
 387
 388     out_symdef(lptr->defn.label, segment, size, 2,
 389                special ? special : lptr->defn.special);
 390 }
 391
 392 void declare_as_global(char *label, char *special)
 393 {
 394     union label *lptr;
 395
 396     if (islocal(label)) {
 397         nasm_error(ERR_NONFATAL, "attempt to declare local symbol `%s' as"
 398               " global", label);
 399         return;
 400     }
 401     lptr = find_label(label, 1, NULL);
 402     if (!lptr)
 403         return;
 404     switch (lptr->defn.is_global & TYPE_MASK) {
 405     case NOT_DEFINED_YET:
 406         lptr->defn.is_global = GLOBAL_PLACEHOLDER;
 407         lptr->defn.special = special ? perm_copy(special) : NULL;
 408         break;
 409     case GLOBAL_PLACEHOLDER:   /* already done: silently ignore */
 410     case GLOBAL_SYMBOL:
 411         break;
 412     case LOCAL_SYMBOL:
 413         if (!(lptr->defn.is_global & EXTERN_BIT)) {
 414             nasm_error(ERR_WARNING, "symbol `%s': GLOBAL directive "
 415                   "after symbol definition is an experimental feature", label);
 416             lptr->defn.is_global = GLOBAL_SYMBOL;
 417         }
 418         break;
 419     }
 420 }
 421
 422 int init_labels(void)
 423 {
 424     hash_init(&ltab, HASH_LARGE);
 425
 426     ldata = lfree = (union label *)nasm_malloc(LBLK_SIZE);
 427     init_block(lfree);
 428
 429     perm_head = perm_tail =
 430         (struct permts *)nasm_malloc(sizeof(struct permts));
 431
 432     perm_head->next = NULL;
 433     perm_head->size = PERMTS_SIZE;
 434     perm_head->usage = 0;
 435
 436     prevlabel = "";
 437
 438     initialized = true;
 439
 440     return 0;
 441 }
 442
 443 void cleanup_labels(void)
 444 {
 445     union label *lptr, *lhold;
 446
 447     initialized = false;
 448
 449     hash_free(&ltab);
 450
 451     lptr = lhold = ldata;
 452     while (lptr) {
 453         lptr = &lptr[LABEL_BLOCK-1];
 454         lptr = lptr->admin.next;
 455         nasm_free(lhold);
 456         lhold = lptr;
 457     }
 458
 459     while (perm_head) {
 460         perm_tail = perm_head;
 461         perm_head = perm_head->next;
 462         nasm_free(perm_tail);
 463     }
 464 }
 465
 466 static void init_block(union label *blk)
 467 {
 468     int j;
 469
 470     for (j = 0; j < LABEL_BLOCK - 1; j++)
 471         blk[j].admin.movingon = END_LIST;
 472     blk[LABEL_BLOCK - 1].admin.movingon = END_BLOCK;
 473     blk[LABEL_BLOCK - 1].admin.next = NULL;
 474 }
 475
 476 static char *perm_copy(const char *string)
 477 {
 478     char *p;
 479     int len = strlen(string)+1;
 480
 481     nasm_assert(len <= PERMTS_SIZE);
 482
 483     if (perm_tail->size - perm_tail->usage < len) {
 484         perm_tail->next =
 485             (struct permts *)nasm_malloc(sizeof(struct permts));
 486         perm_tail = perm_tail->next;
 487         perm_tail->next = NULL;
 488         perm_tail->size = PERMTS_SIZE;
 489         perm_tail->usage = 0;
 490     }
 491     p = perm_tail->data + perm_tail->usage;
 492     memcpy(p, string, len);
 493     perm_tail->usage += len;
 494
 495     return p;
 496 }
 497
 498 char *local_scope(char *label)
 499 {
 500    return islocal(label) ? prevlabel : "";
 501 }
 502
 503 /*
 504  * Notes regarding bug involving redefinition of external segments.
 505  *
 506  * Up to and including v0.97, the following code didn't work. From 0.97
 507  * developers release 2 onwards, it will generate an error.
 508  *
 509  * EXTERN extlabel
 510  * newlabel EQU extlabel + 1
 511  *
 512  * The results of allowing this code through are that two import records
 513  * are generated, one for 'extlabel' and one for 'newlabel'.
 514  *
 515  * The reason for this is an inadequacy in the defined interface between
 516  * the label manager and the output formats. The problem lies in how the
 517  * output format driver tells that a label is an external label for which
 518  * a label import record must be produced. Most (all except bin?) produce
 519  * the record if the segment number of the label is not one of the internal
 520  * segments that the output driver is producing.
 521  *
 522  * A simple fix to this would be to make the output formats keep track of
 523  * which symbols they've produced import records for, and make them not
 524  * produce import records for segments that are already defined.
 525  *
 526  * The best way, which is slightly harder but reduces duplication of code
 527  * and should therefore make the entire system smaller and more stable is
 528  * to change the interface between assembler, define_label(), and
 529  * the output module. The changes that are needed are:
 530  *
 531  * The semantics of the 'isextern' flag passed to define_label() need
 532  * examining. This information may or may not tell us what we need to
 533  * know (ie should we be generating an import record at this point for this
 534  * label). If these aren't the semantics, the semantics should be changed
 535  * to this.
 536  *
 537  * The output module interface needs changing, so that the `isextern' flag
 538  * is passed to the module, so that it can be easily tested for.
 539  */