output/outaout.c

   1 /* outaout.c    output routines for the Netwide Assembler to produce
   2  *              Linux a.out object files
   3  *
   4  * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
   5  * Julian Hall. All rights reserved. The software is
   6  * redistributable under the licence given in the file "Licence"
   7  * distributed in the NASM archive.
   8  */
   9
  10 #include "compiler.h"
  11
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <string.h>
  15 #include <ctype.h>
  16 #include <inttypes.h>
  17
  18 #include "nasm.h"
  19 #include "nasmlib.h"
  20 #include "stdscan.h"
  21 #include "outform.h"
  22
  23 #if defined OF_AOUT || defined OF_AOUTB
  24
  25 #define RELTYPE_ABSOLUTE 0x00
  26 #define RELTYPE_RELATIVE 0x01
  27 #define RELTYPE_GOTPC    0x01   /* no explicit GOTPC in a.out */
  28 #define RELTYPE_GOTOFF   0x10
  29 #define RELTYPE_GOT      0x10   /* distinct from GOTOFF bcos sym not sect */
  30 #define RELTYPE_PLT      0x21
  31 #define RELTYPE_SYMFLAG  0x08
  32
  33 struct Reloc {
  34     struct Reloc *next;
  35     int32_t address;               /* relative to _start_ of section */
  36     int32_t symbol;                /* symbol number or -ve section id */
  37     int bytes;                  /* 2 or 4 */
  38     int reltype;                /* see above */
  39 };
  40
  41 struct Symbol {
  42     int32_t strpos;                /* string table position of name */
  43     int type;                   /* symbol type - see flags below */
  44     int32_t value;                 /* address, or COMMON variable size */
  45     int32_t size;                  /* size for data or function exports */
  46     int32_t segment;               /* back-reference used by gsym_reloc */
  47     struct Symbol *next;        /* list of globals in each section */
  48     struct Symbol *nextfwd;     /* list of unresolved-size symbols */
  49     char *name;                 /* for unresolved-size symbols */
  50     int32_t symnum;                /* index into symbol table */
  51 };
  52
  53 /*
  54  * Section IDs - used in Reloc.symbol when negative, and in
  55  * Symbol.type when positive.
  56  */
  57 #define SECT_ABS 2              /* absolute value */
  58 #define SECT_TEXT 4             /* text section */
  59 #define SECT_DATA 6             /* data section */
  60 #define SECT_BSS 8              /* bss section */
  61 #define SECT_MASK 0xE           /* mask out any of the above */
  62
  63 /*
  64  * More flags used in Symbol.type.
  65  */
  66 #define SYM_GLOBAL 1            /* it's a global symbol */
  67 #define SYM_DATA 0x100          /* used for shared libs */
  68 #define SYM_FUNCTION 0x200      /* used for shared libs */
  69 #define SYM_WITH_SIZE 0x4000    /* not output; internal only */
  70
  71 /*
  72  * Bit more explanation of symbol types: SECT_xxx denotes a local
  73  * symbol. SECT_xxx|SYM_GLOBAL denotes a global symbol, defined in
  74  * this module. Just SYM_GLOBAL, with zero value, denotes an
  75  * external symbol referenced in this module. And just SYM_GLOBAL,
  76  * but with a non-zero value, declares a C `common' variable, of
  77  * size `value'.
  78  */
  79
  80 struct Section {
  81     struct SAA *data;
  82     uint32_t len, size, nrelocs;
  83     int32_t index;
  84     struct Reloc *head, **tail;
  85     struct Symbol *gsyms, *asym;
  86 };
  87
  88 static struct Section stext, sdata, sbss;
  89
  90 static struct SAA *syms;
  91 static uint32_t nsyms;
  92
  93 static struct RAA *bsym;
  94
  95 static struct SAA *strs;
  96 static uint32_t strslen;
  97
  98 static struct Symbol *fwds;
  99
 100 static FILE *aoutfp;
 101 static efunc error;
 102 static evalfunc evaluate;
 103
 104 static int bsd;
 105 static int is_pic;
 106
 107 static void aout_write(void);
 108 static void aout_write_relocs(struct Reloc *);
 109 static void aout_write_syms(void);
 110 static void aout_sect_write(struct Section *, const uint8_t *,
 111                             uint32_t);
 112 static void aout_pad_sections(void);
 113 static void aout_fixup_relocs(struct Section *);
 114
 115 /*
 116  * Special section numbers which are used to define special
 117  * symbols, which can be used with WRT to provide PIC relocation
 118  * types.
 119  */
 120 static int32_t aout_gotpc_sect, aout_gotoff_sect;
 121 static int32_t aout_got_sect, aout_plt_sect;
 122 static int32_t aout_sym_sect;
 123
 124 static void aoutg_init(FILE * fp, efunc errfunc, ldfunc ldef,
 125                        evalfunc eval)
 126 {
 127     aoutfp = fp;
 128     error = errfunc;
 129     evaluate = eval;
 130     (void)ldef;                 /* placate optimisers */
 131     stext.data = saa_init(1L);
 132     stext.head = NULL;
 133     stext.tail = &stext.head;
 134     sdata.data = saa_init(1L);
 135     sdata.head = NULL;
 136     sdata.tail = &sdata.head;
 137     stext.len = stext.size = sdata.len = sdata.size = sbss.len = 0;
 138     stext.nrelocs = sdata.nrelocs = 0;
 139     stext.gsyms = sdata.gsyms = sbss.gsyms = NULL;
 140     stext.index = seg_alloc();
 141     sdata.index = seg_alloc();
 142     sbss.index = seg_alloc();
 143     stext.asym = sdata.asym = sbss.asym = NULL;
 144     syms = saa_init((int32_t)sizeof(struct Symbol));
 145     nsyms = 0;
 146     bsym = raa_init();
 147     strs = saa_init(1L);
 148     strslen = 0;
 149     fwds = NULL;
 150 }
 151
 152 #ifdef OF_AOUT
 153
 154 static void aout_init(FILE * fp, efunc errfunc, ldfunc ldef, evalfunc eval)
 155 {
 156     bsd = false;
 157     aoutg_init(fp, errfunc, ldef, eval);
 158
 159     aout_gotpc_sect = aout_gotoff_sect = aout_got_sect =
 160         aout_plt_sect = aout_sym_sect = NO_SEG;
 161 }
 162
 163 #endif
 164
 165 #ifdef OF_AOUTB
 166
 167 extern struct ofmt of_aoutb;
 168
 169 static void aoutb_init(FILE * fp, efunc errfunc, ldfunc ldef,
 170                        evalfunc eval)
 171 {
 172     bsd = true;
 173     aoutg_init(fp, errfunc, ldef, eval);
 174
 175     is_pic = 0x00;              /* may become 0x40 */
 176
 177     aout_gotpc_sect = seg_alloc();
 178     ldef("..gotpc", aout_gotpc_sect + 1, 0L, NULL, false, false, &of_aoutb,
 179          error);
 180     aout_gotoff_sect = seg_alloc();
 181     ldef("..gotoff", aout_gotoff_sect + 1, 0L, NULL, false, false,
 182          &of_aoutb, error);
 183     aout_got_sect = seg_alloc();
 184     ldef("..got", aout_got_sect + 1, 0L, NULL, false, false, &of_aoutb,
 185          error);
 186     aout_plt_sect = seg_alloc();
 187     ldef("..plt", aout_plt_sect + 1, 0L, NULL, false, false, &of_aoutb,
 188          error);
 189     aout_sym_sect = seg_alloc();
 190     ldef("..sym", aout_sym_sect + 1, 0L, NULL, false, false, &of_aoutb,
 191          error);
 192 }
 193
 194 #endif
 195
 196 static void aout_cleanup(int debuginfo)
 197 {
 198     struct Reloc *r;
 199
 200     (void)debuginfo;
 201
 202     aout_pad_sections();
 203     aout_fixup_relocs(&stext);
 204     aout_fixup_relocs(&sdata);
 205     aout_write();
 206     fclose(aoutfp);
 207     saa_free(stext.data);
 208     while (stext.head) {
 209         r = stext.head;
 210         stext.head = stext.head->next;
 211         nasm_free(r);
 212     }
 213     saa_free(sdata.data);
 214     while (sdata.head) {
 215         r = sdata.head;
 216         sdata.head = sdata.head->next;
 217         nasm_free(r);
 218     }
 219     saa_free(syms);
 220     raa_free(bsym);
 221     saa_free(strs);
 222 }
 223
 224 static int32_t aout_section_names(char *name, int pass, int *bits)
 225 {
 226
 227     (void)pass;
 228
 229     /*
 230      * Default to 32 bits.
 231      */
 232     if (!name)
 233         *bits = 32;
 234
 235     if (!name)
 236         return stext.index;
 237
 238     if (!strcmp(name, ".text"))
 239         return stext.index;
 240     else if (!strcmp(name, ".data"))
 241         return sdata.index;
 242     else if (!strcmp(name, ".bss"))
 243         return sbss.index;
 244     else
 245         return NO_SEG;
 246 }
 247
 248 static void aout_deflabel(char *name, int32_t segment, int32_t offset,
 249                           int is_global, char *special)
 250 {
 251     int pos = strslen + 4;
 252     struct Symbol *sym;
 253     int special_used = false;
 254
 255     if (name[0] == '.' && name[1] == '.' && name[2] != '@') {
 256         /*
 257          * This is a NASM special symbol. We never allow it into
 258          * the a.out symbol table, even if it's a valid one. If it
 259          * _isn't_ a valid one, we should barf immediately.
 260          */
 261         if (strcmp(name, "..gotpc") && strcmp(name, "..gotoff") &&
 262             strcmp(name, "..got") && strcmp(name, "..plt") &&
 263             strcmp(name, "..sym"))
 264             error(ERR_NONFATAL, "unrecognised special symbol `%s'", name);
 265         return;
 266     }
 267
 268     if (is_global == 3) {
 269         struct Symbol **s;
 270         /*
 271          * Fix up a forward-reference symbol size from the first
 272          * pass.
 273          */
 274         for (s = &fwds; *s; s = &(*s)->nextfwd)
 275             if (!strcmp((*s)->name, name)) {
 276                 struct tokenval tokval;
 277                 expr *e;
 278                 char *p = special;
 279
 280                 while (*p && !isspace(*p))
 281                     p++;
 282                 while (*p && isspace(*p))
 283                     p++;
 284                 stdscan_reset();
 285                 stdscan_bufptr = p;
 286                 tokval.t_type = TOKEN_INVALID;
 287                 e = evaluate(stdscan, NULL, &tokval, NULL, 1, error, NULL);
 288                 if (e) {
 289                     if (!is_simple(e))
 290                         error(ERR_NONFATAL, "cannot use relocatable"
 291                               " expression as symbol size");
 292                     else
 293                         (*s)->size = reloc_value(e);
 294                 }
 295
 296                 /*
 297                  * Remove it from the list of unresolved sizes.
 298                  */
 299                 nasm_free((*s)->name);
 300                 *s = (*s)->nextfwd;
 301                 return;
 302             }
 303         return;                 /* it wasn't an important one */
 304     }
 305
 306     saa_wbytes(strs, name, (int32_t)(1 + strlen(name)));
 307     strslen += 1 + strlen(name);
 308
 309     sym = saa_wstruct(syms);
 310
 311     sym->strpos = pos;
 312     sym->type = is_global ? SYM_GLOBAL : 0;
 313     sym->segment = segment;
 314     if (segment == NO_SEG)
 315         sym->type |= SECT_ABS;
 316     else if (segment == stext.index) {
 317         sym->type |= SECT_TEXT;
 318         if (is_global) {
 319             sym->next = stext.gsyms;
 320             stext.gsyms = sym;
 321         } else if (!stext.asym)
 322             stext.asym = sym;
 323     } else if (segment == sdata.index) {
 324         sym->type |= SECT_DATA;
 325         if (is_global) {
 326             sym->next = sdata.gsyms;
 327             sdata.gsyms = sym;
 328         } else if (!sdata.asym)
 329             sdata.asym = sym;
 330     } else if (segment == sbss.index) {
 331         sym->type |= SECT_BSS;
 332         if (is_global) {
 333             sym->next = sbss.gsyms;
 334             sbss.gsyms = sym;
 335         } else if (!sbss.asym)
 336             sbss.asym = sym;
 337     } else
 338         sym->type = SYM_GLOBAL;
 339     if (is_global == 2)
 340         sym->value = offset;
 341     else
 342         sym->value = (sym->type == SYM_GLOBAL ? 0 : offset);
 343
 344     if (is_global && sym->type != SYM_GLOBAL) {
 345         /*
 346          * Global symbol exported _from_ this module. We must check
 347          * the special text for type information.
 348          */
 349
 350         if (special) {
 351             int n = strcspn(special, " ");
 352
 353             if (!nasm_strnicmp(special, "function", n))
 354                 sym->type |= SYM_FUNCTION;
 355             else if (!nasm_strnicmp(special, "data", n) ||
 356                      !nasm_strnicmp(special, "object", n))
 357                 sym->type |= SYM_DATA;
 358             else
 359                 error(ERR_NONFATAL, "unrecognised symbol type `%.*s'",
 360                       n, special);
 361             if (special[n]) {
 362                 struct tokenval tokval;
 363                 expr *e;
 364                 int fwd = false;
 365                 char *saveme = stdscan_bufptr;  /* bugfix? fbk 8/10/00 */
 366
 367                 if (!bsd) {
 368                     error(ERR_NONFATAL, "Linux a.out does not support"
 369                           " symbol size information");
 370                 } else {
 371                     while (special[n] && isspace(special[n]))
 372                         n++;
 373                     /*
 374                      * We have a size expression; attempt to
 375                      * evaluate it.
 376                      */
 377                     sym->type |= SYM_WITH_SIZE;
 378                     stdscan_reset();
 379                     stdscan_bufptr = special + n;
 380                     tokval.t_type = TOKEN_INVALID;
 381                     e = evaluate(stdscan, NULL, &tokval, &fwd, 0, error,
 382                                  NULL);
 383                     if (fwd) {
 384                         sym->nextfwd = fwds;
 385                         fwds = sym;
 386                         sym->name = nasm_strdup(name);
 387                     } else if (e) {
 388                         if (!is_simple(e))
 389                             error(ERR_NONFATAL, "cannot use relocatable"
 390                                   " expression as symbol size");
 391                         else
 392                             sym->size = reloc_value(e);
 393                     }
 394                 }
 395                 stdscan_bufptr = saveme;        /* bugfix? fbk 8/10/00 */
 396             }
 397             special_used = true;
 398         }
 399     }
 400
 401     /*
 402      * define the references from external-symbol segment numbers
 403      * to these symbol records.
 404      */
 405     if (segment != NO_SEG && segment != stext.index &&
 406         segment != sdata.index && segment != sbss.index)
 407         bsym = raa_write(bsym, segment, nsyms);
 408     sym->symnum = nsyms;
 409
 410     nsyms++;
 411     if (sym->type & SYM_WITH_SIZE)
 412         nsyms++;                /* and another for the size */
 413
 414     if (special && !special_used)
 415         error(ERR_NONFATAL, "no special symbol features supported here");
 416 }
 417
 418 static void aout_add_reloc(struct Section *sect, int32_t segment,
 419                            int reltype, int bytes)
 420 {
 421     struct Reloc *r;
 422
 423     r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
 424     sect->tail = &r->next;
 425     r->next = NULL;
 426
 427     r->address = sect->len;
 428     r->symbol = (segment == NO_SEG ? -SECT_ABS :
 429                  segment == stext.index ? -SECT_TEXT :
 430                  segment == sdata.index ? -SECT_DATA :
 431                  segment == sbss.index ? -SECT_BSS :
 432                  raa_read(bsym, segment));
 433     r->reltype = reltype;
 434     if (r->symbol >= 0)
 435         r->reltype |= RELTYPE_SYMFLAG;
 436     r->bytes = bytes;
 437
 438     sect->nrelocs++;
 439 }
 440
 441 /*
 442  * This routine deals with ..got and ..sym relocations: the more
 443  * complicated kinds. In shared-library writing, some relocations
 444  * with respect to global symbols must refer to the precise symbol
 445  * rather than referring to an offset from the base of the section
 446  * _containing_ the symbol. Such relocations call to this routine,
 447  * which searches the symbol list for the symbol in question.
 448  *
 449  * RELTYPE_GOT references require the _exact_ symbol address to be
 450  * used; RELTYPE_ABSOLUTE references can be at an offset from the
 451  * symbol. The boolean argument `exact' tells us this.
 452  *
 453  * Return value is the adjusted value of `addr', having become an
 454  * offset from the symbol rather than the section. Should always be
 455  * zero when returning from an exact call.
 456  *
 457  * Limitation: if you define two symbols at the same place,
 458  * confusion will occur.
 459  *
 460  * Inefficiency: we search, currently, using a linked list which
 461  * isn't even necessarily sorted.
 462  */
 463 static int32_t aout_add_gsym_reloc(struct Section *sect,
 464                                 int32_t segment, int32_t offset,
 465                                 int type, int bytes, int exact)
 466 {
 467     struct Symbol *sym, *sm, *shead;
 468     struct Reloc *r;
 469
 470     /*
 471      * First look up the segment to find whether it's text, data,
 472      * bss or an external symbol.
 473      */
 474     shead = NULL;
 475     if (segment == stext.index)
 476         shead = stext.gsyms;
 477     else if (segment == sdata.index)
 478         shead = sdata.gsyms;
 479     else if (segment == sbss.index)
 480         shead = sbss.gsyms;
 481     if (!shead) {
 482         if (exact && offset != 0)
 483             error(ERR_NONFATAL, "unable to find a suitable global symbol"
 484                   " for this reference");
 485         else
 486             aout_add_reloc(sect, segment, type, bytes);
 487         return offset;
 488     }
 489
 490     if (exact) {
 491         /*
 492          * Find a symbol pointing _exactly_ at this one.
 493          */
 494         for (sym = shead; sym; sym = sym->next)
 495             if (sym->value == offset)
 496                 break;
 497     } else {
 498         /*
 499          * Find the nearest symbol below this one.
 500          */
 501         sym = NULL;
 502         for (sm = shead; sm; sm = sm->next)
 503             if (sm->value <= offset && (!sym || sm->value > sym->value))
 504                 sym = sm;
 505     }
 506     if (!sym && exact) {
 507         error(ERR_NONFATAL, "unable to find a suitable global symbol"
 508               " for this reference");
 509         return 0;
 510     }
 511
 512     r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
 513     sect->tail = &r->next;
 514     r->next = NULL;
 515
 516     r->address = sect->len;
 517     r->symbol = sym->symnum;
 518     r->reltype = type | RELTYPE_SYMFLAG;
 519     r->bytes = bytes;
 520
 521     sect->nrelocs++;
 522
 523     return offset - sym->value;
 524 }
 525
 526 /*
 527  * This routine deals with ..gotoff relocations. These _must_ refer
 528  * to a symbol, due to a perversity of *BSD's PIC implementation,
 529  * and it must be a non-global one as well; so we store `asym', the
 530  * first nonglobal symbol defined in each section, and always work
 531  * from that. Relocation type is always RELTYPE_GOTOFF.
 532  *
 533  * Return value is the adjusted value of `addr', having become an
 534  * offset from the `asym' symbol rather than the section.
 535  */
 536 static int32_t aout_add_gotoff_reloc(struct Section *sect, int32_t segment,
 537                                   int32_t offset, int bytes)
 538 {
 539     struct Reloc *r;
 540     struct Symbol *asym;
 541
 542     /*
 543      * First look up the segment to find whether it's text, data,
 544      * bss or an external symbol.
 545      */
 546     asym = NULL;
 547     if (segment == stext.index)
 548         asym = stext.asym;
 549     else if (segment == sdata.index)
 550         asym = sdata.asym;
 551     else if (segment == sbss.index)
 552         asym = sbss.asym;
 553     if (!asym)
 554         error(ERR_NONFATAL, "`..gotoff' relocations require a non-global"
 555               " symbol in the section");
 556
 557     r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
 558     sect->tail = &r->next;
 559     r->next = NULL;
 560
 561     r->address = sect->len;
 562     r->symbol = asym->symnum;
 563     r->reltype = RELTYPE_GOTOFF;
 564     r->bytes = bytes;
 565
 566     sect->nrelocs++;
 567
 568     return offset - asym->value;
 569 }
 570
 571 static void aout_out(int32_t segto, const void *data, uint32_t type,
 572                      int32_t segment, int32_t wrt)
 573 {
 574     struct Section *s;
 575     int32_t realbytes = type & OUT_SIZMASK;
 576     int32_t addr;
 577     uint8_t mydata[4], *p;
 578
 579     type &= OUT_TYPMASK;
 580
 581     /*
 582      * handle absolute-assembly (structure definitions)
 583      */
 584     if (segto == NO_SEG) {
 585         if (type != OUT_RESERVE)
 586             error(ERR_NONFATAL, "attempt to assemble code in [ABSOLUTE]"
 587                   " space");
 588         return;
 589     }
 590
 591     if (segto == stext.index)
 592         s = &stext;
 593     else if (segto == sdata.index)
 594         s = &sdata;
 595     else if (segto == sbss.index)
 596         s = NULL;
 597     else {
 598         error(ERR_WARNING, "attempt to assemble code in"
 599               " segment %d: defaulting to `.text'", segto);
 600         s = &stext;
 601     }
 602
 603     if (!s && type != OUT_RESERVE) {
 604         error(ERR_WARNING, "attempt to initialize memory in the"
 605               " BSS section: ignored");
 606         if (type == OUT_REL2ADR)
 607             realbytes = 2;
 608         else if (type == OUT_REL4ADR)
 609             realbytes = 4;
 610         sbss.len += realbytes;
 611         return;
 612     }
 613
 614     if (type == OUT_RESERVE) {
 615         if (s) {
 616             error(ERR_WARNING, "uninitialized space declared in"
 617                   " %s section: zeroing",
 618                   (segto == stext.index ? "code" : "data"));
 619             aout_sect_write(s, NULL, realbytes);
 620         } else
 621             sbss.len += realbytes;
 622     } else if (type == OUT_RAWDATA) {
 623         if (segment != NO_SEG)
 624             error(ERR_PANIC, "OUT_RAWDATA with other than NO_SEG");
 625         aout_sect_write(s, data, realbytes);
 626     } else if (type == OUT_ADDRESS) {
 627         addr = *(int32_t *)data;
 628         if (segment != NO_SEG) {
 629             if (segment % 2) {
 630                 error(ERR_NONFATAL, "a.out format does not support"
 631                       " segment base references");
 632             } else {
 633                 if (wrt == NO_SEG) {
 634                     aout_add_reloc(s, segment, RELTYPE_ABSOLUTE,
 635                                    realbytes);
 636                 } else if (!bsd) {
 637                     error(ERR_NONFATAL,
 638                           "Linux a.out format does not support"
 639                           " any use of WRT");
 640                     wrt = NO_SEG;       /* we can at least _try_ to continue */
 641                 } else if (wrt == aout_gotpc_sect + 1) {
 642                     is_pic = 0x40;
 643                     aout_add_reloc(s, segment, RELTYPE_GOTPC, realbytes);
 644                 } else if (wrt == aout_gotoff_sect + 1) {
 645                     is_pic = 0x40;
 646                     addr = aout_add_gotoff_reloc(s, segment,
 647                                                  addr, realbytes);
 648                 } else if (wrt == aout_got_sect + 1) {
 649                     is_pic = 0x40;
 650                     addr =
 651                         aout_add_gsym_reloc(s, segment, addr, RELTYPE_GOT,
 652                                             realbytes, true);
 653                 } else if (wrt == aout_sym_sect + 1) {
 654                     addr = aout_add_gsym_reloc(s, segment, addr,
 655                                                RELTYPE_ABSOLUTE, realbytes,
 656                                                false);
 657                 } else if (wrt == aout_plt_sect + 1) {
 658                     is_pic = 0x40;
 659                     error(ERR_NONFATAL,
 660                           "a.out format cannot produce non-PC-"
 661                           "relative PLT references");
 662                 } else {
 663                     error(ERR_NONFATAL,
 664                           "a.out format does not support this"
 665                           " use of WRT");
 666                     wrt = NO_SEG;       /* we can at least _try_ to continue */
 667                 }
 668             }
 669         }
 670         p = mydata;
 671         if (realbytes == 2)
 672             WRITESHORT(p, addr);
 673         else
 674             WRITELONG(p, addr);
 675         aout_sect_write(s, mydata, realbytes);
 676     } else if (type == OUT_REL2ADR) {
 677         if (segment == segto)
 678             error(ERR_PANIC, "intra-segment OUT_REL2ADR");
 679         if (segment != NO_SEG && segment % 2) {
 680             error(ERR_NONFATAL, "a.out format does not support"
 681                   " segment base references");
 682         } else {
 683             if (wrt == NO_SEG) {
 684                 aout_add_reloc(s, segment, RELTYPE_RELATIVE, 2);
 685             } else if (!bsd) {
 686                 error(ERR_NONFATAL, "Linux a.out format does not support"
 687                       " any use of WRT");
 688                 wrt = NO_SEG;   /* we can at least _try_ to continue */
 689             } else if (wrt == aout_plt_sect + 1) {
 690                 is_pic = 0x40;
 691                 aout_add_reloc(s, segment, RELTYPE_PLT, 2);
 692             } else if (wrt == aout_gotpc_sect + 1 ||
 693                        wrt == aout_gotoff_sect + 1 ||
 694                        wrt == aout_got_sect + 1) {
 695                 error(ERR_NONFATAL, "a.out format cannot produce PC-"
 696                       "relative GOT references");
 697             } else {
 698                 error(ERR_NONFATAL, "a.out format does not support this"
 699                       " use of WRT");
 700                 wrt = NO_SEG;   /* we can at least _try_ to continue */
 701             }
 702         }
 703         p = mydata;
 704         WRITESHORT(p, *(int32_t *)data - (realbytes + s->len));
 705         aout_sect_write(s, mydata, 2L);
 706     } else if (type == OUT_REL4ADR) {
 707         if (segment == segto)
 708             error(ERR_PANIC, "intra-segment OUT_REL4ADR");
 709         if (segment != NO_SEG && segment % 2) {
 710             error(ERR_NONFATAL, "a.out format does not support"
 711                   " segment base references");
 712         } else {
 713             if (wrt == NO_SEG) {
 714                 aout_add_reloc(s, segment, RELTYPE_RELATIVE, 4);
 715             } else if (!bsd) {
 716                 error(ERR_NONFATAL, "Linux a.out format does not support"
 717                       " any use of WRT");
 718                 wrt = NO_SEG;   /* we can at least _try_ to continue */
 719             } else if (wrt == aout_plt_sect + 1) {
 720                 is_pic = 0x40;
 721                 aout_add_reloc(s, segment, RELTYPE_PLT, 4);
 722             } else if (wrt == aout_gotpc_sect + 1 ||
 723                        wrt == aout_gotoff_sect + 1 ||
 724                        wrt == aout_got_sect + 1) {
 725                 error(ERR_NONFATAL, "a.out format cannot produce PC-"
 726                       "relative GOT references");
 727             } else {
 728                 error(ERR_NONFATAL, "a.out format does not support this"
 729                       " use of WRT");
 730                 wrt = NO_SEG;   /* we can at least _try_ to continue */
 731             }
 732         }
 733         p = mydata;
 734         WRITELONG(p, *(int32_t *)data - (realbytes + s->len));
 735         aout_sect_write(s, mydata, 4L);
 736     }
 737 }
 738
 739 static void aout_pad_sections(void)
 740 {
 741     static uint8_t pad[] = { 0x90, 0x90, 0x90, 0x90 };
 742     /*
 743      * Pad each of the text and data sections with NOPs until their
 744      * length is a multiple of four. (NOP == 0x90.) Also increase
 745      * the length of the BSS section similarly.
 746      */
 747     aout_sect_write(&stext, pad, (-(int32_t)stext.len) & 3);
 748     aout_sect_write(&sdata, pad, (-(int32_t)sdata.len) & 3);
 749     sbss.len = (sbss.len + 3) & ~3;
 750 }
 751
 752 /*
 753  * a.out files have the curious property that all references to
 754  * things in the data or bss sections are done by addresses which
 755  * are actually relative to the start of the _text_ section, in the
 756  * _file_. (No relation to what happens after linking. No idea why
 757  * this should be so. It's very strange.) So we have to go through
 758  * the relocation table, _after_ the final size of each section is
 759  * known, and fix up the relocations pointed to.
 760  */
 761 static void aout_fixup_relocs(struct Section *sect)
 762 {
 763     struct Reloc *r;
 764
 765     saa_rewind(sect->data);
 766     for (r = sect->head; r; r = r->next) {
 767         uint8_t *p, *q, blk[4];
 768         int32_t l;
 769
 770         saa_fread(sect->data, r->address, blk, (int32_t)r->bytes);
 771         p = q = blk;
 772         l = *p++;
 773         if (r->bytes > 1) {
 774             l += ((int32_t)*p++) << 8;
 775             if (r->bytes == 4) {
 776                 l += ((int32_t)*p++) << 16;
 777                 l += ((int32_t)*p++) << 24;
 778             }
 779         }
 780         if (r->symbol == -SECT_DATA)
 781             l += stext.len;
 782         else if (r->symbol == -SECT_BSS)
 783             l += stext.len + sdata.len;
 784         if (r->bytes == 4)
 785             WRITELONG(q, l);
 786         else if (r->bytes == 2)
 787             WRITESHORT(q, l);
 788         else
 789             *q++ = l & 0xFF;
 790         saa_fwrite(sect->data, r->address, blk, (int32_t)r->bytes);
 791     }
 792 }
 793
 794 static void aout_write(void)
 795 {
 796     /*
 797      * Emit the a.out header.
 798      */
 799     /* OMAGIC, M_386 or MID_I386, no flags */
 800     fwriteint32_t(bsd ? 0x07018600 | is_pic : 0x640107L, aoutfp);
 801     fwriteint32_t(stext.len, aoutfp);
 802     fwriteint32_t(sdata.len, aoutfp);
 803     fwriteint32_t(sbss.len, aoutfp);
 804     fwriteint32_t(nsyms * 12, aoutfp);     /* length of symbol table */
 805     fwriteint32_t(0L, aoutfp);     /* object files have no entry point */
 806     fwriteint32_t(stext.nrelocs * 8, aoutfp);      /* size of text relocs */
 807     fwriteint32_t(sdata.nrelocs * 8, aoutfp);      /* size of data relocs */
 808
 809     /*
 810      * Write out the code section and the data section.
 811      */
 812     saa_fpwrite(stext.data, aoutfp);
 813     saa_fpwrite(sdata.data, aoutfp);
 814
 815     /*
 816      * Write out the relocations.
 817      */
 818     aout_write_relocs(stext.head);
 819     aout_write_relocs(sdata.head);
 820
 821     /*
 822      * Write the symbol table.
 823      */
 824     aout_write_syms();
 825
 826     /*
 827      * And the string table.
 828      */
 829     fwriteint32_t(strslen + 4, aoutfp);    /* length includes length count */
 830     saa_fpwrite(strs, aoutfp);
 831 }
 832
 833 static void aout_write_relocs(struct Reloc *r)
 834 {
 835     while (r) {
 836         uint32_t word2;
 837
 838         fwriteint32_t(r->address, aoutfp);
 839
 840         if (r->symbol >= 0)
 841             word2 = r->symbol;
 842         else
 843             word2 = -r->symbol;
 844         word2 |= r->reltype << 24;
 845         word2 |= (r->bytes == 1 ? 0 :
 846                   r->bytes == 2 ? 0x2000000L : 0x4000000L);
 847         fwriteint32_t(word2, aoutfp);
 848
 849         r = r->next;
 850     }
 851 }
 852
 853 static void aout_write_syms(void)
 854 {
 855     uint32_t i;
 856
 857     saa_rewind(syms);
 858     for (i = 0; i < nsyms; i++) {
 859         struct Symbol *sym = saa_rstruct(syms);
 860         fwriteint32_t(sym->strpos, aoutfp);
 861         fwriteint32_t((int32_t)sym->type & ~SYM_WITH_SIZE, aoutfp);
 862         /*
 863          * Fix up the symbol value now we know the final section
 864          * sizes.
 865          */
 866         if ((sym->type & SECT_MASK) == SECT_DATA)
 867             sym->value += stext.len;
 868         if ((sym->type & SECT_MASK) == SECT_BSS)
 869             sym->value += stext.len + sdata.len;
 870         fwriteint32_t(sym->value, aoutfp);
 871         /*
 872          * Output a size record if necessary.
 873          */
 874         if (sym->type & SYM_WITH_SIZE) {
 875             fwriteint32_t(sym->strpos, aoutfp);
 876             fwriteint32_t(0x0DL, aoutfp);  /* special value: means size */
 877             fwriteint32_t(sym->size, aoutfp);
 878             i++;                /* use up another of `nsyms' */
 879         }
 880     }
 881 }
 882
 883 static void aout_sect_write(struct Section *sect,
 884                             const uint8_t *data, uint32_t len)
 885 {
 886     saa_wbytes(sect->data, data, len);
 887     sect->len += len;
 888 }
 889
 890 static int32_t aout_segbase(int32_t segment)
 891 {
 892     return segment;
 893 }
 894
 895 static int aout_directive(char *directive, char *value, int pass)
 896 {
 897     (void)directive;
 898     (void)value;
 899     (void)pass;
 900     return 0;
 901 }
 902
 903 static void aout_filename(char *inname, char *outname, efunc error)
 904 {
 905     standard_extension(inname, outname, ".o", error);
 906 }
 907
 908 static const char *aout_stdmac[] = {
 909     "%define __SECT__ [section .text]",
 910     "%macro __NASM_CDecl__ 1",
 911     "%endmacro",
 912     NULL
 913 };
 914
 915 static int aout_set_info(enum geninfo type, char **val)
 916 {
 917     (void)type;
 918     (void)val;
 919     return 0;
 920 }
 921 #endif                          /* OF_AOUT || OF_AOUTB */
 922
 923 #ifdef OF_AOUT
 924
 925 struct ofmt of_aout = {
 926     "Linux a.out object files",
 927     "aout",
 928     NULL,
 929     null_debug_arr,
 930     &null_debug_form,
 931     aout_stdmac,
 932     aout_init,
 933     aout_set_info,
 934     aout_out,
 935     aout_deflabel,
 936     aout_section_names,
 937     aout_segbase,
 938     aout_directive,
 939     aout_filename,
 940     aout_cleanup
 941 };
 942
 943 #endif
 944
 945 #ifdef OF_AOUTB
 946
 947 struct ofmt of_aoutb = {
 948     "NetBSD/FreeBSD a.out object files",
 949     "aoutb",
 950     NULL,
 951     null_debug_arr,
 952     &null_debug_form,
 953     aout_stdmac,
 954     aoutb_init,
 955     aout_set_info,
 956     aout_out,
 957     aout_deflabel,
 958     aout_section_names,
 959     aout_segbase,
 960     aout_directive,
 961     aout_filename,
 962     aout_cleanup
 963 };
 964
 965 #endif