output/outaout.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 1996-2009 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  * outaout.c    output routines for the Netwide Assembler to produce
  36  *              Linux a.out object files
  37  */
  38
  39 #include "compiler.h"
  40
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <ctype.h>
  45 #include <inttypes.h>
  46
  47 #include "nasm.h"
  48 #include "nasmlib.h"
  49 #include "saa.h"
  50 #include "raa.h"
  51 #include "stdscan.h"
  52 #include "eval.h"
  53 #include "output/outform.h"
  54 #include "output/outlib.h"
  55
  56 #if defined OF_AOUT || defined OF_AOUTB
  57
  58 #define RELTYPE_ABSOLUTE 0x00
  59 #define RELTYPE_RELATIVE 0x01
  60 #define RELTYPE_GOTPC    0x01   /* no explicit GOTPC in a.out */
  61 #define RELTYPE_GOTOFF   0x10
  62 #define RELTYPE_GOT      0x10   /* distinct from GOTOFF bcos sym not sect */
  63 #define RELTYPE_PLT      0x21
  64 #define RELTYPE_SYMFLAG  0x08
  65
  66 struct Reloc {
  67     struct Reloc *next;
  68     int32_t address;               /* relative to _start_ of section */
  69     int32_t symbol;                /* symbol number or -ve section id */
  70     int bytes;                  /* 2 or 4 */
  71     int reltype;                /* see above */
  72 };
  73
  74 struct Symbol {
  75     int32_t strpos;                /* string table position of name */
  76     int type;                   /* symbol type - see flags below */
  77     int32_t value;                 /* address, or COMMON variable size */
  78     int32_t size;                  /* size for data or function exports */
  79     int32_t segment;               /* back-reference used by gsym_reloc */
  80     struct Symbol *next;        /* list of globals in each section */
  81     struct Symbol *nextfwd;     /* list of unresolved-size symbols */
  82     char *name;                 /* for unresolved-size symbols */
  83     int32_t symnum;                /* index into symbol table */
  84 };
  85
  86 /*
  87  * Section IDs - used in Reloc.symbol when negative, and in
  88  * Symbol.type when positive.
  89  */
  90 #define SECT_ABS 2              /* absolute value */
  91 #define SECT_TEXT 4             /* text section */
  92 #define SECT_DATA 6             /* data section */
  93 #define SECT_BSS 8              /* bss section */
  94 #define SECT_MASK 0xE           /* mask out any of the above */
  95
  96 /*
  97  * More flags used in Symbol.type.
  98  */
  99 #define SYM_GLOBAL 1            /* it's a global symbol */
 100 #define SYM_DATA 0x100          /* used for shared libs */
 101 #define SYM_FUNCTION 0x200      /* used for shared libs */
 102 #define SYM_WITH_SIZE 0x4000    /* not output; internal only */
 103
 104 /*
 105  * Bit more explanation of symbol types: SECT_xxx denotes a local
 106  * symbol. SECT_xxx|SYM_GLOBAL denotes a global symbol, defined in
 107  * this module. Just SYM_GLOBAL, with zero value, denotes an
 108  * external symbol referenced in this module. And just SYM_GLOBAL,
 109  * but with a non-zero value, declares a C `common' variable, of
 110  * size `value'.
 111  */
 112
 113 struct Section {
 114     struct SAA *data;
 115     uint32_t len, size, nrelocs;
 116     int32_t index;
 117     struct Reloc *head, **tail;
 118     struct Symbol *gsyms, *asym;
 119 };
 120
 121 static struct Section stext, sdata, sbss;
 122
 123 static struct SAA *syms;
 124 static uint32_t nsyms;
 125
 126 static struct RAA *bsym;
 127
 128 static struct SAA *strs;
 129 static uint32_t strslen;
 130
 131 static struct Symbol *fwds;
 132
 133 static int bsd;
 134 static int is_pic;
 135
 136 static void aout_write(void);
 137 static void aout_write_relocs(struct Reloc *);
 138 static void aout_write_syms(void);
 139 static void aout_sect_write(struct Section *, const uint8_t *,
 140                             uint32_t);
 141 static void aout_pad_sections(void);
 142 static void aout_fixup_relocs(struct Section *);
 143
 144 /*
 145  * Special section numbers which are used to define special
 146  * symbols, which can be used with WRT to provide PIC relocation
 147  * types.
 148  */
 149 static int32_t aout_gotpc_sect, aout_gotoff_sect;
 150 static int32_t aout_got_sect, aout_plt_sect;
 151 static int32_t aout_sym_sect;
 152
 153 static void aoutg_init(void)
 154 {
 155     stext.data = saa_init(1L);
 156     stext.head = NULL;
 157     stext.tail = &stext.head;
 158     sdata.data = saa_init(1L);
 159     sdata.head = NULL;
 160     sdata.tail = &sdata.head;
 161     stext.len = stext.size = sdata.len = sdata.size = sbss.len = 0;
 162     stext.nrelocs = sdata.nrelocs = 0;
 163     stext.gsyms = sdata.gsyms = sbss.gsyms = NULL;
 164     stext.index = seg_alloc();
 165     sdata.index = seg_alloc();
 166     sbss.index = seg_alloc();
 167     stext.asym = sdata.asym = sbss.asym = NULL;
 168     syms = saa_init((int32_t)sizeof(struct Symbol));
 169     nsyms = 0;
 170     bsym = raa_init();
 171     strs = saa_init(1L);
 172     strslen = 0;
 173     fwds = NULL;
 174 }
 175
 176 #ifdef OF_AOUT
 177
 178 static void aout_init(void)
 179 {
 180     bsd = false;
 181     aoutg_init();
 182
 183     aout_gotpc_sect = aout_gotoff_sect = aout_got_sect =
 184         aout_plt_sect = aout_sym_sect = NO_SEG;
 185 }
 186
 187 #endif
 188
 189 #ifdef OF_AOUTB
 190
 191 extern struct ofmt of_aoutb;
 192
 193 static void aoutb_init(void)
 194 {
 195     bsd = true;
 196     aoutg_init();
 197
 198     is_pic = 0x00;              /* may become 0x40 */
 199
 200     aout_gotpc_sect = seg_alloc();
 201     define_label("..gotpc", aout_gotpc_sect + 1, 0L, NULL, false, false);
 202     aout_gotoff_sect = seg_alloc();
 203     define_label("..gotoff", aout_gotoff_sect + 1, 0L, NULL, false, false);
 204     aout_got_sect = seg_alloc();
 205     define_label("..got", aout_got_sect + 1, 0L, NULL, false, false);
 206     aout_plt_sect = seg_alloc();
 207     define_label("..plt", aout_plt_sect + 1, 0L, NULL, false, false);
 208     aout_sym_sect = seg_alloc();
 209     define_label("..sym", aout_sym_sect + 1, 0L, NULL, false, false);
 210 }
 211
 212 #endif
 213
 214 static void aout_cleanup(int debuginfo)
 215 {
 216     struct Reloc *r;
 217
 218     (void)debuginfo;
 219
 220     aout_pad_sections();
 221     aout_fixup_relocs(&stext);
 222     aout_fixup_relocs(&sdata);
 223     aout_write();
 224     saa_free(stext.data);
 225     while (stext.head) {
 226         r = stext.head;
 227         stext.head = stext.head->next;
 228         nasm_free(r);
 229     }
 230     saa_free(sdata.data);
 231     while (sdata.head) {
 232         r = sdata.head;
 233         sdata.head = sdata.head->next;
 234         nasm_free(r);
 235     }
 236     saa_free(syms);
 237     raa_free(bsym);
 238     saa_free(strs);
 239 }
 240
 241 static int32_t aout_section_names(char *name, int pass, int *bits)
 242 {
 243
 244     (void)pass;
 245
 246     /*
 247      * Default to 32 bits.
 248      */
 249     if (!name)
 250         *bits = 32;
 251
 252     if (!name)
 253         return stext.index;
 254
 255     if (!strcmp(name, ".text"))
 256         return stext.index;
 257     else if (!strcmp(name, ".data"))
 258         return sdata.index;
 259     else if (!strcmp(name, ".bss"))
 260         return sbss.index;
 261     else
 262         return NO_SEG;
 263 }
 264
 265 static void aout_deflabel(char *name, int32_t segment, int64_t offset,
 266                           int is_global, char *special)
 267 {
 268     int pos = strslen + 4;
 269     struct Symbol *sym;
 270     int special_used = false;
 271
 272     if (name[0] == '.' && name[1] == '.' && name[2] != '@') {
 273         /*
 274          * This is a NASM special symbol. We never allow it into
 275          * the a.out symbol table, even if it's a valid one. If it
 276          * _isn't_ a valid one, we should barf immediately.
 277          */
 278         if (strcmp(name, "..gotpc") && strcmp(name, "..gotoff") &&
 279             strcmp(name, "..got") && strcmp(name, "..plt") &&
 280             strcmp(name, "..sym"))
 281             nasm_error(ERR_NONFATAL, "unrecognised special symbol `%s'", name);
 282         return;
 283     }
 284
 285     if (is_global == 3) {
 286         struct Symbol **s;
 287         /*
 288          * Fix up a forward-reference symbol size from the first
 289          * pass.
 290          */
 291         for (s = &fwds; *s; s = &(*s)->nextfwd)
 292             if (!strcmp((*s)->name, name)) {
 293                 struct tokenval tokval;
 294                 expr *e;
 295                 char *p = special;
 296
 297                 while (*p && !nasm_isspace(*p))
 298                     p++;
 299                 while (*p && nasm_isspace(*p))
 300                     p++;
 301                 stdscan_reset();
 302                 stdscan_set(p);
 303                 tokval.t_type = TOKEN_INVALID;
 304                 e = evaluate(stdscan, NULL, &tokval, NULL, 1, nasm_error, NULL);
 305                 if (e) {
 306                     if (!is_simple(e))
 307                         nasm_error(ERR_NONFATAL, "cannot use relocatable"
 308                               " expression as symbol size");
 309                     else
 310                         (*s)->size = reloc_value(e);
 311                 }
 312
 313                 /*
 314                  * Remove it from the list of unresolved sizes.
 315                  */
 316                 nasm_free((*s)->name);
 317                 *s = (*s)->nextfwd;
 318                 return;
 319             }
 320         return;                 /* it wasn't an important one */
 321     }
 322
 323     saa_wbytes(strs, name, (int32_t)(1 + strlen(name)));
 324     strslen += 1 + strlen(name);
 325
 326     sym = saa_wstruct(syms);
 327
 328     sym->strpos = pos;
 329     sym->type = is_global ? SYM_GLOBAL : 0;
 330     sym->segment = segment;
 331     if (segment == NO_SEG)
 332         sym->type |= SECT_ABS;
 333     else if (segment == stext.index) {
 334         sym->type |= SECT_TEXT;
 335         if (is_global) {
 336             sym->next = stext.gsyms;
 337             stext.gsyms = sym;
 338         } else if (!stext.asym)
 339             stext.asym = sym;
 340     } else if (segment == sdata.index) {
 341         sym->type |= SECT_DATA;
 342         if (is_global) {
 343             sym->next = sdata.gsyms;
 344             sdata.gsyms = sym;
 345         } else if (!sdata.asym)
 346             sdata.asym = sym;
 347     } else if (segment == sbss.index) {
 348         sym->type |= SECT_BSS;
 349         if (is_global) {
 350             sym->next = sbss.gsyms;
 351             sbss.gsyms = sym;
 352         } else if (!sbss.asym)
 353             sbss.asym = sym;
 354     } else
 355         sym->type = SYM_GLOBAL;
 356     if (is_global == 2)
 357         sym->value = offset;
 358     else
 359         sym->value = (sym->type == SYM_GLOBAL ? 0 : offset);
 360
 361     if (is_global && sym->type != SYM_GLOBAL) {
 362         /*
 363          * Global symbol exported _from_ this module. We must check
 364          * the special text for type information.
 365          */
 366
 367         if (special) {
 368             int n = strcspn(special, " ");
 369
 370             if (!nasm_strnicmp(special, "function", n))
 371                 sym->type |= SYM_FUNCTION;
 372             else if (!nasm_strnicmp(special, "data", n) ||
 373                      !nasm_strnicmp(special, "object", n))
 374                 sym->type |= SYM_DATA;
 375             else
 376                 nasm_error(ERR_NONFATAL, "unrecognised symbol type `%.*s'",
 377                       n, special);
 378             if (special[n]) {
 379                 struct tokenval tokval;
 380                 expr *e;
 381                 int fwd = false;
 382                 char *saveme = stdscan_get();
 383
 384                 if (!bsd) {
 385                     nasm_error(ERR_NONFATAL, "Linux a.out does not support"
 386                           " symbol size information");
 387                 } else {
 388                     while (special[n] && nasm_isspace(special[n]))
 389                         n++;
 390                     /*
 391                      * We have a size expression; attempt to
 392                      * evaluate it.
 393                      */
 394                     sym->type |= SYM_WITH_SIZE;
 395                     stdscan_reset();
 396                     stdscan_set(special + n);
 397                     tokval.t_type = TOKEN_INVALID;
 398                     e = evaluate(stdscan, NULL, &tokval, &fwd, 0, nasm_error,
 399                                  NULL);
 400                     if (fwd) {
 401                         sym->nextfwd = fwds;
 402                         fwds = sym;
 403                         sym->name = nasm_strdup(name);
 404                     } else if (e) {
 405                         if (!is_simple(e))
 406                             nasm_error(ERR_NONFATAL, "cannot use relocatable"
 407                                   " expression as symbol size");
 408                         else
 409                             sym->size = reloc_value(e);
 410                     }
 411                 }
 412                 stdscan_set(saveme);
 413             }
 414             special_used = true;
 415         }
 416     }
 417
 418     /*
 419      * define the references from external-symbol segment numbers
 420      * to these symbol records.
 421      */
 422     if (segment != NO_SEG && segment != stext.index &&
 423         segment != sdata.index && segment != sbss.index)
 424         bsym = raa_write(bsym, segment, nsyms);
 425     sym->symnum = nsyms;
 426
 427     nsyms++;
 428     if (sym->type & SYM_WITH_SIZE)
 429         nsyms++;                /* and another for the size */
 430
 431     if (special && !special_used)
 432         nasm_error(ERR_NONFATAL, "no special symbol features supported here");
 433 }
 434
 435 static void aout_add_reloc(struct Section *sect, int32_t segment,
 436                            int reltype, int bytes)
 437 {
 438     struct Reloc *r;
 439
 440     r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
 441     sect->tail = &r->next;
 442     r->next = NULL;
 443
 444     r->address = sect->len;
 445     r->symbol = (segment == NO_SEG ? -SECT_ABS :
 446                  segment == stext.index ? -SECT_TEXT :
 447                  segment == sdata.index ? -SECT_DATA :
 448                  segment == sbss.index ? -SECT_BSS :
 449                  raa_read(bsym, segment));
 450     r->reltype = reltype;
 451     if (r->symbol >= 0)
 452         r->reltype |= RELTYPE_SYMFLAG;
 453     r->bytes = bytes;
 454
 455     sect->nrelocs++;
 456 }
 457
 458 /*
 459  * This routine deals with ..got and ..sym relocations: the more
 460  * complicated kinds. In shared-library writing, some relocations
 461  * with respect to global symbols must refer to the precise symbol
 462  * rather than referring to an offset from the base of the section
 463  * _containing_ the symbol. Such relocations call to this routine,
 464  * which searches the symbol list for the symbol in question.
 465  *
 466  * RELTYPE_GOT references require the _exact_ symbol address to be
 467  * used; RELTYPE_ABSOLUTE references can be at an offset from the
 468  * symbol. The boolean argument `exact' tells us this.
 469  *
 470  * Return value is the adjusted value of `addr', having become an
 471  * offset from the symbol rather than the section. Should always be
 472  * zero when returning from an exact call.
 473  *
 474  * Limitation: if you define two symbols at the same place,
 475  * confusion will occur.
 476  *
 477  * Inefficiency: we search, currently, using a linked list which
 478  * isn't even necessarily sorted.
 479  */
 480 static int32_t aout_add_gsym_reloc(struct Section *sect,
 481                                 int32_t segment, int32_t offset,
 482                                 int type, int bytes, int exact)
 483 {
 484     struct Symbol *sym, *sm, *shead;
 485     struct Reloc *r;
 486
 487     /*
 488      * First look up the segment to find whether it's text, data,
 489      * bss or an external symbol.
 490      */
 491     shead = NULL;
 492     if (segment == stext.index)
 493         shead = stext.gsyms;
 494     else if (segment == sdata.index)
 495         shead = sdata.gsyms;
 496     else if (segment == sbss.index)
 497         shead = sbss.gsyms;
 498     if (!shead) {
 499         if (exact && offset != 0)
 500             nasm_error(ERR_NONFATAL, "unable to find a suitable global symbol"
 501                   " for this reference");
 502         else
 503             aout_add_reloc(sect, segment, type, bytes);
 504         return offset;
 505     }
 506
 507     if (exact) {
 508         /*
 509          * Find a symbol pointing _exactly_ at this one.
 510          */
 511         list_for_each(sym, shead)
 512             if (sym->value == offset)
 513                 break;
 514     } else {
 515         /*
 516          * Find the nearest symbol below this one.
 517          */
 518         sym = NULL;
 519         list_for_each(sm, shead)
 520             if (sm->value <= offset && (!sym || sm->value > sym->value))
 521                 sym = sm;
 522     }
 523     if (!sym && exact) {
 524         nasm_error(ERR_NONFATAL, "unable to find a suitable global symbol"
 525               " for this reference");
 526         return 0;
 527     }
 528
 529     r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
 530     sect->tail = &r->next;
 531     r->next = NULL;
 532
 533     r->address = sect->len;
 534     r->symbol = sym->symnum;
 535     r->reltype = type | RELTYPE_SYMFLAG;
 536     r->bytes = bytes;
 537
 538     sect->nrelocs++;
 539
 540     return offset - sym->value;
 541 }
 542
 543 /*
 544  * This routine deals with ..gotoff relocations. These _must_ refer
 545  * to a symbol, due to a perversity of *BSD's PIC implementation,
 546  * and it must be a non-global one as well; so we store `asym', the
 547  * first nonglobal symbol defined in each section, and always work
 548  * from that. Relocation type is always RELTYPE_GOTOFF.
 549  *
 550  * Return value is the adjusted value of `addr', having become an
 551  * offset from the `asym' symbol rather than the section.
 552  */
 553 static int32_t aout_add_gotoff_reloc(struct Section *sect, int32_t segment,
 554                                   int32_t offset, int bytes)
 555 {
 556     struct Reloc *r;
 557     struct Symbol *asym;
 558
 559     /*
 560      * First look up the segment to find whether it's text, data,
 561      * bss or an external symbol.
 562      */
 563     asym = NULL;
 564     if (segment == stext.index)
 565         asym = stext.asym;
 566     else if (segment == sdata.index)
 567         asym = sdata.asym;
 568     else if (segment == sbss.index)
 569         asym = sbss.asym;
 570     if (!asym)
 571         nasm_error(ERR_NONFATAL, "`..gotoff' relocations require a non-global"
 572               " symbol in the section");
 573
 574     r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
 575     sect->tail = &r->next;
 576     r->next = NULL;
 577
 578     r->address = sect->len;
 579     r->symbol = asym->symnum;
 580     r->reltype = RELTYPE_GOTOFF;
 581     r->bytes = bytes;
 582
 583     sect->nrelocs++;
 584
 585     return offset - asym->value;
 586 }
 587
 588 static void aout_out(int32_t segto, const void *data,
 589                      enum out_type type, uint64_t size,
 590                      int32_t segment, int32_t wrt)
 591 {
 592     struct Section *s;
 593     int32_t addr;
 594     uint8_t mydata[4], *p;
 595
 596     /*
 597      * handle absolute-assembly (structure definitions)
 598      */
 599     if (segto == NO_SEG) {
 600         if (type != OUT_RESERVE)
 601             nasm_error(ERR_NONFATAL, "attempt to assemble code in [ABSOLUTE]"
 602                   " space");
 603         return;
 604     }
 605
 606     if (segto == stext.index)
 607         s = &stext;
 608     else if (segto == sdata.index)
 609         s = &sdata;
 610     else if (segto == sbss.index)
 611         s = NULL;
 612     else {
 613         nasm_error(ERR_WARNING, "attempt to assemble code in"
 614               " segment %d: defaulting to `.text'", segto);
 615         s = &stext;
 616     }
 617
 618     if (!s && type != OUT_RESERVE) {
 619         nasm_error(ERR_WARNING, "attempt to initialize memory in the"
 620               " BSS section: ignored");
 621         sbss.len += realsize(type, size);
 622         return;
 623     }
 624
 625     if (type == OUT_RESERVE) {
 626         if (s) {
 627             nasm_error(ERR_WARNING, "uninitialized space declared in"
 628                   " %s section: zeroing",
 629                   (segto == stext.index ? "code" : "data"));
 630             aout_sect_write(s, NULL, size);
 631         } else
 632             sbss.len += size;
 633     } else if (type == OUT_RAWDATA) {
 634         if (segment != NO_SEG)
 635             nasm_error(ERR_PANIC, "OUT_RAWDATA with other than NO_SEG");
 636         aout_sect_write(s, data, size);
 637     } else if (type == OUT_ADDRESS) {
 638         addr = *(int64_t *)data;
 639         if (segment != NO_SEG) {
 640             if (segment % 2) {
 641                 nasm_error(ERR_NONFATAL, "a.out format does not support"
 642                       " segment base references");
 643             } else {
 644                 if (wrt == NO_SEG) {
 645                     aout_add_reloc(s, segment, RELTYPE_ABSOLUTE,
 646                                    size);
 647                 } else if (!bsd) {
 648                     nasm_error(ERR_NONFATAL,
 649                           "Linux a.out format does not support"
 650                           " any use of WRT");
 651                     wrt = NO_SEG;       /* we can at least _try_ to continue */
 652                 } else if (wrt == aout_gotpc_sect + 1) {
 653                     is_pic = 0x40;
 654                     aout_add_reloc(s, segment, RELTYPE_GOTPC, size);
 655                 } else if (wrt == aout_gotoff_sect + 1) {
 656                     is_pic = 0x40;
 657                     addr = aout_add_gotoff_reloc(s, segment,
 658                                                  addr, size);
 659                 } else if (wrt == aout_got_sect + 1) {
 660                     is_pic = 0x40;
 661                     addr =
 662                         aout_add_gsym_reloc(s, segment, addr, RELTYPE_GOT,
 663                                             size, true);
 664                 } else if (wrt == aout_sym_sect + 1) {
 665                     addr = aout_add_gsym_reloc(s, segment, addr,
 666                                                RELTYPE_ABSOLUTE, size,
 667                                                false);
 668                 } else if (wrt == aout_plt_sect + 1) {
 669                     is_pic = 0x40;
 670                     nasm_error(ERR_NONFATAL,
 671                           "a.out format cannot produce non-PC-"
 672                           "relative PLT references");
 673                 } else {
 674                     nasm_error(ERR_NONFATAL,
 675                           "a.out format does not support this"
 676                           " use of WRT");
 677                     wrt = NO_SEG;       /* we can at least _try_ to continue */
 678                 }
 679             }
 680         }
 681         p = mydata;
 682         if (size == 2)
 683             WRITESHORT(p, addr);
 684         else
 685             WRITELONG(p, addr);
 686         aout_sect_write(s, mydata, size);
 687     } else if (type == OUT_REL2ADR) {
 688         if (segment == segto)
 689             nasm_error(ERR_PANIC, "intra-segment OUT_REL2ADR");
 690         if (segment != NO_SEG && segment % 2) {
 691             nasm_error(ERR_NONFATAL, "a.out format does not support"
 692                   " segment base references");
 693         } else {
 694             if (wrt == NO_SEG) {
 695                 aout_add_reloc(s, segment, RELTYPE_RELATIVE, 2);
 696             } else if (!bsd) {
 697                 nasm_error(ERR_NONFATAL, "Linux a.out format does not support"
 698                       " any use of WRT");
 699                 wrt = NO_SEG;   /* we can at least _try_ to continue */
 700             } else if (wrt == aout_plt_sect + 1) {
 701                 is_pic = 0x40;
 702                 aout_add_reloc(s, segment, RELTYPE_PLT, 2);
 703             } else if (wrt == aout_gotpc_sect + 1 ||
 704                        wrt == aout_gotoff_sect + 1 ||
 705                        wrt == aout_got_sect + 1) {
 706                 nasm_error(ERR_NONFATAL, "a.out format cannot produce PC-"
 707                       "relative GOT references");
 708             } else {
 709                 nasm_error(ERR_NONFATAL, "a.out format does not support this"
 710                       " use of WRT");
 711                 wrt = NO_SEG;   /* we can at least _try_ to continue */
 712             }
 713         }
 714         p = mydata;
 715         WRITESHORT(p, *(int64_t *)data - (size + s->len));
 716         aout_sect_write(s, mydata, 2L);
 717     } else if (type == OUT_REL4ADR) {
 718         if (segment == segto)
 719             nasm_error(ERR_PANIC, "intra-segment OUT_REL4ADR");
 720         if (segment != NO_SEG && segment % 2) {
 721             nasm_error(ERR_NONFATAL, "a.out format does not support"
 722                   " segment base references");
 723         } else {
 724             if (wrt == NO_SEG) {
 725                 aout_add_reloc(s, segment, RELTYPE_RELATIVE, 4);
 726             } else if (!bsd) {
 727                 nasm_error(ERR_NONFATAL, "Linux a.out format does not support"
 728                       " any use of WRT");
 729                 wrt = NO_SEG;   /* we can at least _try_ to continue */
 730             } else if (wrt == aout_plt_sect + 1) {
 731                 is_pic = 0x40;
 732                 aout_add_reloc(s, segment, RELTYPE_PLT, 4);
 733             } else if (wrt == aout_gotpc_sect + 1 ||
 734                        wrt == aout_gotoff_sect + 1 ||
 735                        wrt == aout_got_sect + 1) {
 736                 nasm_error(ERR_NONFATAL, "a.out format cannot produce PC-"
 737                       "relative GOT references");
 738             } else {
 739                 nasm_error(ERR_NONFATAL, "a.out format does not support this"
 740                       " use of WRT");
 741                 wrt = NO_SEG;   /* we can at least _try_ to continue */
 742             }
 743         }
 744         p = mydata;
 745         WRITELONG(p, *(int64_t *)data - (size + s->len));
 746         aout_sect_write(s, mydata, 4L);
 747     }
 748 }
 749
 750 static void aout_pad_sections(void)
 751 {
 752     static uint8_t pad[] = { 0x90, 0x90, 0x90, 0x90 };
 753     /*
 754      * Pad each of the text and data sections with NOPs until their
 755      * length is a multiple of four. (NOP == 0x90.) Also increase
 756      * the length of the BSS section similarly.
 757      */
 758     aout_sect_write(&stext, pad, (-(int32_t)stext.len) & 3);
 759     aout_sect_write(&sdata, pad, (-(int32_t)sdata.len) & 3);
 760     sbss.len = ALIGN(sbss.len, 4);
 761 }
 762
 763 /*
 764  * a.out files have the curious property that all references to
 765  * things in the data or bss sections are done by addresses which
 766  * are actually relative to the start of the _text_ section, in the
 767  * _file_. (No relation to what happens after linking. No idea why
 768  * this should be so. It's very strange.) So we have to go through
 769  * the relocation table, _after_ the final size of each section is
 770  * known, and fix up the relocations pointed to.
 771  */
 772 static void aout_fixup_relocs(struct Section *sect)
 773 {
 774     struct Reloc *r;
 775
 776     saa_rewind(sect->data);
 777     list_for_each(r, sect->head) {
 778         uint8_t *p, *q, blk[4];
 779         int32_t l;
 780
 781         saa_fread(sect->data, r->address, blk, (int32_t)r->bytes);
 782         p = q = blk;
 783         l = *p++;
 784         if (r->bytes > 1) {
 785             l += ((int32_t)*p++) << 8;
 786             if (r->bytes == 4) {
 787                 l += ((int32_t)*p++) << 16;
 788                 l += ((int32_t)*p++) << 24;
 789             }
 790         }
 791         if (r->symbol == -SECT_DATA)
 792             l += stext.len;
 793         else if (r->symbol == -SECT_BSS)
 794             l += stext.len + sdata.len;
 795         if (r->bytes == 4)
 796             WRITELONG(q, l);
 797         else if (r->bytes == 2)
 798             WRITESHORT(q, l);
 799         else
 800             *q++ = l & 0xFF;
 801         saa_fwrite(sect->data, r->address, blk, (int32_t)r->bytes);
 802     }
 803 }
 804
 805 static void aout_write(void)
 806 {
 807     /*
 808      * Emit the a.out header.
 809      */
 810     /* OMAGIC, M_386 or MID_I386, no flags */
 811     fwriteint32_t(bsd ? 0x07018600 | is_pic : 0x640107L, ofile);
 812     fwriteint32_t(stext.len, ofile);
 813     fwriteint32_t(sdata.len, ofile);
 814     fwriteint32_t(sbss.len, ofile);
 815     fwriteint32_t(nsyms * 12, ofile);     /* length of symbol table */
 816     fwriteint32_t(0L, ofile);     /* object files have no entry point */
 817     fwriteint32_t(stext.nrelocs * 8, ofile);      /* size of text relocs */
 818     fwriteint32_t(sdata.nrelocs * 8, ofile);      /* size of data relocs */
 819
 820     /*
 821      * Write out the code section and the data section.
 822      */
 823     saa_fpwrite(stext.data, ofile);
 824     saa_fpwrite(sdata.data, ofile);
 825
 826     /*
 827      * Write out the relocations.
 828      */
 829     aout_write_relocs(stext.head);
 830     aout_write_relocs(sdata.head);
 831
 832     /*
 833      * Write the symbol table.
 834      */
 835     aout_write_syms();
 836
 837     /*
 838      * And the string table.
 839      */
 840     fwriteint32_t(strslen + 4, ofile);    /* length includes length count */
 841     saa_fpwrite(strs, ofile);
 842 }
 843
 844 static void aout_write_relocs(struct Reloc *r)
 845 {
 846     list_for_each(r, r) {
 847         uint32_t word2;
 848
 849         fwriteint32_t(r->address, ofile);
 850
 851         if (r->symbol >= 0)
 852             word2 = r->symbol;
 853         else
 854             word2 = -r->symbol;
 855         word2 |= r->reltype << 24;
 856         word2 |= (r->bytes == 1 ? 0 :
 857                   r->bytes == 2 ? 0x2000000L : 0x4000000L);
 858         fwriteint32_t(word2, ofile);
 859     }
 860 }
 861
 862 static void aout_write_syms(void)
 863 {
 864     uint32_t i;
 865
 866     saa_rewind(syms);
 867     for (i = 0; i < nsyms; i++) {
 868         struct Symbol *sym = saa_rstruct(syms);
 869         fwriteint32_t(sym->strpos, ofile);
 870         fwriteint32_t((int32_t)sym->type & ~SYM_WITH_SIZE, ofile);
 871         /*
 872          * Fix up the symbol value now we know the final section
 873          * sizes.
 874          */
 875         if ((sym->type & SECT_MASK) == SECT_DATA)
 876             sym->value += stext.len;
 877         if ((sym->type & SECT_MASK) == SECT_BSS)
 878             sym->value += stext.len + sdata.len;
 879         fwriteint32_t(sym->value, ofile);
 880         /*
 881          * Output a size record if necessary.
 882          */
 883         if (sym->type & SYM_WITH_SIZE) {
 884             fwriteint32_t(sym->strpos, ofile);
 885             fwriteint32_t(0x0DL, ofile);  /* special value: means size */
 886             fwriteint32_t(sym->size, ofile);
 887             i++;                /* use up another of `nsyms' */
 888         }
 889     }
 890 }
 891
 892 static void aout_sect_write(struct Section *sect,
 893                             const uint8_t *data, uint32_t len)
 894 {
 895     saa_wbytes(sect->data, data, len);
 896     sect->len += len;
 897 }
 898
 899 static int32_t aout_segbase(int32_t segment)
 900 {
 901     return segment;
 902 }
 903
 904 static void aout_filename(char *inname, char *outname)
 905 {
 906     standard_extension(inname, outname, ".o");
 907 }
 908
 909 extern macros_t aout_stdmac[];
 910
 911 #endif                          /* OF_AOUT || OF_AOUTB */
 912
 913 #ifdef OF_AOUT
 914
 915 struct ofmt of_aout = {
 916     "Linux a.out object files",
 917     "aout",
 918     0,
 919     null_debug_arr,
 920     &null_debug_form,
 921     aout_stdmac,
 922     aout_init,
 923     null_setinfo,
 924     aout_out,
 925     aout_deflabel,
 926     aout_section_names,
 927     aout_segbase,
 928     null_directive,
 929     aout_filename,
 930     aout_cleanup
 931 };
 932
 933 #endif
 934
 935 #ifdef OF_AOUTB
 936
 937 struct ofmt of_aoutb = {
 938     "NetBSD/FreeBSD a.out object files",
 939     "aoutb",
 940     0,
 941     null_debug_arr,
 942     &null_debug_form,
 943     aout_stdmac,
 944     aoutb_init,
 945     null_setinfo,
 946     aout_out,
 947     aout_deflabel,
 948     aout_section_names,
 949     aout_segbase,
 950     null_directive,
 951     aout_filename,
 952     aout_cleanup
 953 };
 954
 955 #endif