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