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