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outaout.c

/* outaout.c      output routines for the Netwide Assembler to produce
 *          Linux a.out object files
 *
 * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
 * Julian Hall. All rights reserved. The software is
 * redistributable under the licence given in the file "Licence"
 * distributed in the NASM archive.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#include "nasm.h"
#include "nasmlib.h"
#include "outform.h"

#if defined OF_AOUT || defined OF_AOUTB

#define RELTYPE_ABSOLUTE 0x00
#define RELTYPE_RELATIVE 0x01
#define RELTYPE_GOTPC    0x01   /* no explicit GOTPC in a.out */
#define RELTYPE_GOTOFF   0x10
#define RELTYPE_GOT      0x10   /* distinct from GOTOFF bcos sym not sect */
#define RELTYPE_PLT      0x21
#define RELTYPE_SYMFLAG  0x08

struct Reloc {
    struct Reloc *next;
    long address;              /* relative to _start_ of section */
    long symbol;               /* symbol number or -ve section id */
    int bytes;                       /* 2 or 4 */
    int reltype;               /* see above */
};

struct Symbol {
    long strpos;               /* string table position of name */
    int type;                        /* symbol type - see flags below */
    long value;                      /* address, or COMMON variable size */
    long size;                       /* size for data or function exports */
    long segment;              /* back-reference used by gsym_reloc */
    struct Symbol *next;             /* list of globals in each section */
    struct Symbol *nextfwd;          /* list of unresolved-size symbols */
    char *name;                      /* for unresolved-size symbols */
    long symnum;               /* index into symbol table */
};

/*
 * Section IDs - used in Reloc.symbol when negative, and in
 * Symbol.type when positive.
 */
#define SECT_ABS 2                   /* absolute value */
#define SECT_TEXT 4                  /* text section */
#define SECT_DATA 6                  /* data section */
#define SECT_BSS 8                   /* bss section */
#define SECT_MASK 0xE                /* mask out any of the above */

/*
 * More flags used in Symbol.type.
 */
#define SYM_GLOBAL 1                 /* it's a global symbol */
#define SYM_DATA 0x100               /* used for shared libs */
#define SYM_FUNCTION 0x200           /* used for shared libs */
#define SYM_WITH_SIZE 0x4000         /* not output; internal only */

/*
 * Bit more explanation of symbol types: SECT_xxx denotes a local
 * symbol. SECT_xxx|SYM_GLOBAL denotes a global symbol, defined in
 * this module. Just SYM_GLOBAL, with zero value, denotes an
 * external symbol referenced in this module. And just SYM_GLOBAL,
 * but with a non-zero value, declares a C `common' variable, of
 * size `value'.
 */

struct Section {
    struct SAA *data;
    unsigned long len, size, nrelocs;
    long index;
    struct Reloc *head, **tail;
    struct Symbol *gsyms, *asym;
};

static struct Section stext, sdata, sbss;

static struct SAA *syms;
static unsigned long nsyms;

static struct RAA *bsym;

static struct SAA *strs;
static unsigned long strslen;

static struct Symbol *fwds;

static FILE *aoutfp;
static efunc error;
static evalfunc evaluate;

static int bsd;
static int is_pic;

static void aout_write(void);
static void aout_write_relocs(struct Reloc *);
static void aout_write_syms(void);
static void aout_sect_write(struct Section *, const unsigned char *, unsigned long);
static void aout_pad_sections(void);
static void aout_fixup_relocs(struct Section *);

/*
 * Special section numbers which are used to define special
 * symbols, which can be used with WRT to provide PIC relocation
 * types.
 */
static long aout_gotpc_sect, aout_gotoff_sect;
static long aout_got_sect, aout_plt_sect;
static long aout_sym_sect;

static void aoutg_init(FILE *fp, efunc errfunc, ldfunc ldef, evalfunc eval) 
{
    aoutfp = fp;
    error = errfunc;
    evaluate = eval;
    (void) ldef;               /* placate optimisers */
    stext.data = saa_init(1L); stext.head = NULL; stext.tail = &stext.head;
    sdata.data = saa_init(1L); sdata.head = NULL; sdata.tail = &sdata.head;
    stext.len = stext.size = sdata.len = sdata.size = sbss.len = 0;
    stext.nrelocs = sdata.nrelocs = 0;
    stext.gsyms = sdata.gsyms = sbss.gsyms = NULL;
    stext.index = seg_alloc();
    sdata.index = seg_alloc();
    sbss.index = seg_alloc();
    stext.asym = sdata.asym = sbss.asym = NULL;
    syms = saa_init((long)sizeof(struct Symbol));
    nsyms = 0;
    bsym = raa_init();
    strs = saa_init(1L);
    strslen = 0;
    fwds = NULL;
}

#ifdef OF_AOUT

static void aout_init(FILE *fp, efunc errfunc, ldfunc ldef, evalfunc eval) 
{
    bsd = FALSE;
    aoutg_init (fp, errfunc, ldef, eval);

    aout_gotpc_sect = aout_gotoff_sect = aout_got_sect =
      aout_plt_sect = aout_sym_sect = NO_SEG;
}

#endif

#ifdef OF_AOUTB

extern struct ofmt of_aoutb;

static void aoutb_init(FILE *fp, efunc errfunc, ldfunc ldef, evalfunc eval) 
{
    bsd = TRUE;
    aoutg_init (fp, errfunc, ldef, eval);

    is_pic = 0x00;                   /* may become 0x40 */

    aout_gotpc_sect = seg_alloc();
    ldef("..gotpc", aout_gotpc_sect+1, 0L, NULL, FALSE,FALSE,&of_aoutb,error);
    aout_gotoff_sect = seg_alloc();
    ldef("..gotoff", aout_gotoff_sect+1, 0L,NULL,FALSE,FALSE,&of_aoutb,error);
    aout_got_sect = seg_alloc();
    ldef("..got", aout_got_sect+1, 0L, NULL, FALSE,FALSE,&of_aoutb,error);
    aout_plt_sect = seg_alloc();
    ldef("..plt", aout_plt_sect+1, 0L, NULL, FALSE,FALSE,&of_aoutb,error);
    aout_sym_sect = seg_alloc();
    ldef("..sym", aout_sym_sect+1, 0L, NULL, FALSE,FALSE,&of_aoutb,error);
}

#endif

static void aout_cleanup(int debuginfo) 
{
    struct Reloc *r;

    (void) debuginfo;

    aout_pad_sections();
    aout_fixup_relocs(&stext);
    aout_fixup_relocs(&sdata);
    aout_write();
    fclose (aoutfp);
    saa_free (stext.data);
    while (stext.head) {
      r = stext.head;
      stext.head = stext.head->next;
      nasm_free (r);
    }
    saa_free (sdata.data);
    while (sdata.head) {
      r = sdata.head;
      sdata.head = sdata.head->next;
      nasm_free (r);
    }
    saa_free (syms);
    raa_free (bsym);
    saa_free (strs);
}

static long aout_section_names (char *name, int pass, int *bits) 
{
    /*
     * Default to 32 bits.
     */
    if (!name)
      *bits = 32;

    if (!name)
      return stext.index;

    if (!strcmp(name, ".text"))
      return stext.index;
    else if (!strcmp(name, ".data"))
      return sdata.index;
    else if (!strcmp(name, ".bss"))
      return sbss.index;
    else
      return NO_SEG;
}

static void aout_deflabel (char *name, long segment, long offset,
                     int is_global, char *special) 
{
    int pos = strslen+4;
    struct Symbol *sym;
    int special_used = FALSE;

    if (name[0] == '.' && name[1] == '.' && name[2] != '@') {
      /*
       * This is a NASM special symbol. We never allow it into
       * the a.out symbol table, even if it's a valid one. If it
       * _isn't_ a valid one, we should barf immediately.
       */
      if (strcmp(name, "..gotpc") && strcmp(name, "..gotoff") &&
          strcmp(name, "..got") && strcmp(name, "..plt") &&
          strcmp(name, "..sym"))
          error (ERR_NONFATAL, "unrecognised special symbol `%s'", name);
      return;
    }

    if (is_global == 3) {
      struct Symbol **s;
      /*
       * Fix up a forward-reference symbol size from the first
       * pass.
       */
      for (s = &fwds; *s; s = &(*s)->nextfwd)
          if (!strcmp((*s)->name, name)) {
            struct tokenval tokval;
            expr *e;
            char *p = special;

            while (*p && !isspace(*p)) p++;
            while (*p && isspace(*p)) p++;
            stdscan_reset();
            stdscan_bufptr = p;
            tokval.t_type = TOKEN_INVALID;
            e = evaluate(stdscan, NULL, &tokval, NULL, 1, error, NULL);
            if (e) {
                if (!is_simple(e))
                  error (ERR_NONFATAL, "cannot use relocatable"
                         " expression as symbol size");
                else
                  (*s)->size = reloc_value(e);
            }

            /*
             * Remove it from the list of unresolved sizes.
             */
            nasm_free ((*s)->name);
            *s = (*s)->nextfwd;
            return;
          }
      return;                        /* it wasn't an important one */
    }

    saa_wbytes (strs, name, (long)(1+strlen(name)));
    strslen += 1+strlen(name);

    sym = saa_wstruct (syms);

    sym->strpos = pos;
    sym->type = is_global ? SYM_GLOBAL : 0;
    sym->segment = segment;
    if (segment == NO_SEG)
      sym->type |= SECT_ABS;
    else if (segment == stext.index) {
      sym->type |= SECT_TEXT;
      if (is_global) {
          sym->next = stext.gsyms;
          stext.gsyms = sym;
      } else if (!stext.asym)
          stext.asym = sym;
    } else if (segment == sdata.index) {
      sym->type |= SECT_DATA;
      if (is_global) {
          sym->next = sdata.gsyms;
          sdata.gsyms = sym;
      } else if (!sdata.asym)
          sdata.asym = sym;
    } else if (segment == sbss.index) {
      sym->type |= SECT_BSS;
      if (is_global) {
          sym->next = sbss.gsyms;
          sbss.gsyms = sym;
      } else if (!sbss.asym)
          sbss.asym = sym;
    } else
      sym->type = SYM_GLOBAL;
    if (is_global == 2)
      sym->value = offset;
    else
      sym->value = (sym->type == SYM_GLOBAL ? 0 : offset);

    if (is_global && sym->type != SYM_GLOBAL) {
      /*
       * Global symbol exported _from_ this module. We must check
       * the special text for type information.
       */

      if (special) {
          int n = strcspn(special, " ");

          if (!nasm_strnicmp(special, "function", n))
            sym->type |= SYM_FUNCTION;
          else if (!nasm_strnicmp(special, "data", n) ||
                 !nasm_strnicmp(special, "object", n))
            sym->type |= SYM_DATA;
          else
            error(ERR_NONFATAL, "unrecognised symbol type `%.*s'",
                  n, special);
          if (special[n]) {
            struct tokenval tokval;
            expr *e;
            int fwd = FALSE;
            char *saveme=stdscan_bufptr;  /* bugfix? fbk 8/10/00 */

            if (!bsd) {
                error(ERR_NONFATAL, "Linux a.out does not support"
                    " symbol size information");
            } else {
                while (special[n] && isspace(special[n]))
                  n++;
                /*
                 * We have a size expression; attempt to
                 * evaluate it.
                 */
                sym->type |= SYM_WITH_SIZE;
                stdscan_reset();
                stdscan_bufptr = special+n;
                tokval.t_type = TOKEN_INVALID;
                e = evaluate(stdscan, NULL, &tokval, &fwd, 0, error, NULL);
                if (fwd) {
                  sym->nextfwd = fwds;
                  fwds = sym;
                  sym->name = nasm_strdup(name);
                } else if (e) {
                  if (!is_simple(e))
                      error (ERR_NONFATAL, "cannot use relocatable"
                           " expression as symbol size");
                  else
                      sym->size = reloc_value(e);
                }
            }
            stdscan_bufptr=saveme;     /* bugfix? fbk 8/10/00 */
          }
          special_used = TRUE;
      }
    }

    /*
     * define the references from external-symbol segment numbers
     * to these symbol records.
     */
    if (segment != NO_SEG && segment != stext.index &&
      segment != sdata.index && segment != sbss.index)
      bsym = raa_write (bsym, segment, nsyms);
    sym->symnum = nsyms;

    nsyms++;
    if (sym->type & SYM_WITH_SIZE)
      nsyms++;                 /* and another for the size */

    if (special && !special_used)
      error(ERR_NONFATAL, "no special symbol features supported here");
}

static void aout_add_reloc (struct Section *sect, long segment,
                      int reltype, int bytes) 
{
    struct Reloc *r;

    r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
    sect->tail = &r->next;
    r->next = NULL;

    r->address = sect->len;
    r->symbol = (segment == NO_SEG ? -SECT_ABS :
             segment == stext.index ? -SECT_TEXT :
             segment == sdata.index ? -SECT_DATA :
             segment == sbss.index ? -SECT_BSS :
             raa_read(bsym, segment));
    r->reltype = reltype;
    if (r->symbol >= 0)
      r->reltype |= RELTYPE_SYMFLAG;
    r->bytes = bytes;

    sect->nrelocs++;
}

/*
 * This routine deals with ..got and ..sym relocations: the more
 * complicated kinds. In shared-library writing, some relocations
 * with respect to global symbols must refer to the precise symbol
 * rather than referring to an offset from the base of the section
 * _containing_ the symbol. Such relocations call to this routine,
 * which searches the symbol list for the symbol in question.
 *
 * RELTYPE_GOT references require the _exact_ symbol address to be
 * used; RELTYPE_ABSOLUTE references can be at an offset from the
 * symbol. The boolean argument `exact' tells us this.
 *
 * Return value is the adjusted value of `addr', having become an
 * offset from the symbol rather than the section. Should always be
 * zero when returning from an exact call.
 *
 * Limitation: if you define two symbols at the same place,
 * confusion will occur.
 *
 * Inefficiency: we search, currently, using a linked list which
 * isn't even necessarily sorted.
 */
static long aout_add_gsym_reloc (struct Section *sect,
                         long segment, long offset,
                         int type, int bytes, int exact) 
{
    struct Symbol *sym, *sm, *shead;
    struct Reloc *r;

    /*
     * First look up the segment to find whether it's text, data,
     * bss or an external symbol.
     */
    shead = NULL;
    if (segment == stext.index)
      shead = stext.gsyms;
    else if (segment == sdata.index)
      shead = sdata.gsyms;
    else if (segment == sbss.index)
      shead = sbss.gsyms;
    if (!shead) {
      if (exact && offset != 0)
          error (ERR_NONFATAL, "unable to find a suitable global symbol"
               " for this reference");
      else
          aout_add_reloc (sect, segment, type, bytes);
      return offset;
    }

    if (exact) {
      /*
       * Find a symbol pointing _exactly_ at this one.
       */
      for (sym = shead; sym; sym = sym->next)
          if (sym->value == offset)
            break;
    } else {
      /*
       * Find the nearest symbol below this one.
       */
      sym = NULL;
      for (sm = shead; sm; sm = sm->next)
          if (sm->value <= offset && (!sym || sm->value > sym->value))
            sym = sm;
    }
    if (!sym && exact) {
      error (ERR_NONFATAL, "unable to find a suitable global symbol"
             " for this reference");
      return 0;
    }

    r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
    sect->tail = &r->next;
    r->next = NULL;

    r->address = sect->len;
    r->symbol = sym->symnum;
    r->reltype = type | RELTYPE_SYMFLAG;
    r->bytes = bytes;

    sect->nrelocs++;

    return offset - sym->value;
}

/*
 * This routine deals with ..gotoff relocations. These _must_ refer
 * to a symbol, due to a perversity of *BSD's PIC implementation,
 * and it must be a non-global one as well; so we store `asym', the
 * first nonglobal symbol defined in each section, and always work
 * from that. Relocation type is always RELTYPE_GOTOFF.
 *
 * Return value is the adjusted value of `addr', having become an
 * offset from the `asym' symbol rather than the section.
 */
static long aout_add_gotoff_reloc (struct Section *sect, long segment,
                           long offset, int bytes) 
{
    struct Reloc *r;
    struct Symbol *asym;

    /*
     * First look up the segment to find whether it's text, data,
     * bss or an external symbol.
     */
    asym = NULL;
    if (segment == stext.index)
      asym = stext.asym;
    else if (segment == sdata.index)
      asym = sdata.asym;
    else if (segment == sbss.index)
      asym = sbss.asym;
    if (!asym)
      error (ERR_NONFATAL, "`..gotoff' relocations require a non-global"
             " symbol in the section");

    r = *sect->tail = nasm_malloc(sizeof(struct Reloc));
    sect->tail = &r->next;
    r->next = NULL;

    r->address = sect->len;
    r->symbol = asym->symnum;
    r->reltype = RELTYPE_GOTOFF;
    r->bytes = bytes;

    sect->nrelocs++;

    return offset - asym->value;
}

static void aout_out (long segto, const void *data, unsigned long type,
                  long segment, long wrt) 
{
    struct Section *s;
    long realbytes = type & OUT_SIZMASK;
    long addr;
    unsigned char mydata[4], *p;

    type &= OUT_TYPMASK;

    /*
     * handle absolute-assembly (structure definitions)
     */
    if (segto == NO_SEG) {
      if (type != OUT_RESERVE)
          error (ERR_NONFATAL, "attempt to assemble code in [ABSOLUTE]"
               " space");
      return;
    }

    if (segto == stext.index)
      s = &stext;
    else if (segto == sdata.index)
      s = &sdata;
    else if (segto == sbss.index)
      s = NULL;
    else {
      error(ERR_WARNING, "attempt to assemble code in"
            " segment %d: defaulting to `.text'", segto);
      s = &stext;
    }

    if (!s && type != OUT_RESERVE) {
      error(ERR_WARNING, "attempt to initialise memory in the"
            " BSS section: ignored");
      if (type == OUT_REL2ADR)
          realbytes = 2;
      else if (type == OUT_REL4ADR)
          realbytes = 4;
      sbss.len += realbytes;
      return;
    }

    if (type == OUT_RESERVE) {
      if (s) {
          error(ERR_WARNING, "uninitialised space declared in"
              " %s section: zeroing",
              (segto == stext.index ? "code" : "data"));
          aout_sect_write (s, NULL, realbytes);
      } else
          sbss.len += realbytes;
    } else if (type == OUT_RAWDATA) {
      if (segment != NO_SEG)
          error(ERR_PANIC, "OUT_RAWDATA with other than NO_SEG");
      aout_sect_write (s, data, realbytes);
    } else if (type == OUT_ADDRESS) {
      addr = *(long *)data;
      if (segment != NO_SEG) {
          if (segment % 2) {
            error(ERR_NONFATAL, "a.out format does not support"
                  " segment base references");
          } else {
            if (wrt == NO_SEG) {
                aout_add_reloc (s, segment, RELTYPE_ABSOLUTE, realbytes);
            } else if (!bsd) {
                error (ERR_NONFATAL, "Linux a.out format does not support"
                     " any use of WRT");
                wrt = NO_SEG;      /* we can at least _try_ to continue */
            } else if (wrt == aout_gotpc_sect+1) {
                is_pic = 0x40;
                aout_add_reloc (s, segment, RELTYPE_GOTPC, realbytes);
            } else if (wrt == aout_gotoff_sect+1) {
                is_pic = 0x40;
                addr = aout_add_gotoff_reloc (s, segment,
                                      addr, realbytes);
            } else if (wrt == aout_got_sect+1) {
                is_pic = 0x40;
                addr = aout_add_gsym_reloc (s, segment, addr, RELTYPE_GOT,
                                    realbytes, TRUE);
            } else if (wrt == aout_sym_sect+1) {
                addr = aout_add_gsym_reloc (s, segment, addr,
                                    RELTYPE_ABSOLUTE, realbytes,
                                    FALSE);
            } else if (wrt == aout_plt_sect+1) {
                is_pic = 0x40;
                error(ERR_NONFATAL, "a.out format cannot produce non-PC-"
                    "relative PLT references");
            } else {
                error (ERR_NONFATAL, "a.out format does not support this"
                     " use of WRT");
                wrt = NO_SEG;      /* we can at least _try_ to continue */
            }
          }
      }
      p = mydata;
      if (realbytes == 2)
          WRITESHORT (p, addr);
      else
          WRITELONG (p, addr);
      aout_sect_write (s, mydata, realbytes);
    } else if (type == OUT_REL2ADR) {
      if (segment == segto)
          error(ERR_PANIC, "intra-segment OUT_REL2ADR");
      if (segment != NO_SEG && segment % 2) {
          error(ERR_NONFATAL, "a.out format does not support"
              " segment base references");
      } else {
          if (wrt == NO_SEG) {
            aout_add_reloc (s, segment, RELTYPE_RELATIVE, 2);
          } else if (!bsd) {
            error (ERR_NONFATAL, "Linux a.out format does not support"
                   " any use of WRT");
            wrt = NO_SEG;      /* we can at least _try_ to continue */
          } else if (wrt == aout_plt_sect+1) {
            is_pic = 0x40;
            aout_add_reloc (s, segment, RELTYPE_PLT, 2);
          } else if (wrt == aout_gotpc_sect+1 ||
                   wrt == aout_gotoff_sect+1 ||
                   wrt == aout_got_sect+1) {
            error(ERR_NONFATAL, "a.out format cannot produce PC-"
                  "relative GOT references");
          } else {
            error (ERR_NONFATAL, "a.out format does not support this"
                   " use of WRT");
            wrt = NO_SEG;      /* we can at least _try_ to continue */
          }
      }
      p = mydata;
      WRITESHORT (p, *(long*)data-(realbytes + s->len));
      aout_sect_write (s, mydata, 2L);
    } else if (type == OUT_REL4ADR) {
      if (segment == segto)
          error(ERR_PANIC, "intra-segment OUT_REL4ADR");
      if (segment != NO_SEG && segment % 2) {
          error(ERR_NONFATAL, "a.out format does not support"
              " segment base references");
      } else {
          if (wrt == NO_SEG) {
            aout_add_reloc (s, segment, RELTYPE_RELATIVE, 4);
          } else if (!bsd) {
            error (ERR_NONFATAL, "Linux a.out format does not support"
                   " any use of WRT");
            wrt = NO_SEG;      /* we can at least _try_ to continue */
          } else if (wrt == aout_plt_sect+1) {
            is_pic = 0x40;
            aout_add_reloc (s, segment, RELTYPE_PLT, 4);
          } else if (wrt == aout_gotpc_sect+1 ||
                   wrt == aout_gotoff_sect+1 ||
                   wrt == aout_got_sect+1) {
            error(ERR_NONFATAL, "a.out format cannot produce PC-"
                  "relative GOT references");
          } else {
            error (ERR_NONFATAL, "a.out format does not support this"
                   " use of WRT");
            wrt = NO_SEG;      /* we can at least _try_ to continue */
          }
      }
      p = mydata;
      WRITELONG (p, *(long*)data-(realbytes + s->len));
      aout_sect_write (s, mydata, 4L);
    }
}

static void aout_pad_sections(void) 
{
    static unsigned char pad[] = { 0x90, 0x90, 0x90, 0x90 };
    /*
     * Pad each of the text and data sections with NOPs until their
     * length is a multiple of four. (NOP == 0x90.) Also increase
     * the length of the BSS section similarly.
     */
    aout_sect_write (&stext, pad, (-(long)stext.len) & 3);
    aout_sect_write (&sdata, pad, (-(long)sdata.len) & 3);
    sbss.len = (sbss.len + 3) & ~3;
}

/*
 * a.out files have the curious property that all references to
 * things in the data or bss sections are done by addresses which
 * are actually relative to the start of the _text_ section, in the
 * _file_. (No relation to what happens after linking. No idea why
 * this should be so. It's very strange.) So we have to go through
 * the relocation table, _after_ the final size of each section is
 * known, and fix up the relocations pointed to.
 */
static void aout_fixup_relocs(struct Section *sect) 
{
    struct Reloc *r;

    saa_rewind (sect->data);
    for (r = sect->head; r; r = r->next) {
      unsigned char *p, *q, blk[4];
      long l;

      saa_fread (sect->data, r->address, blk, (long)r->bytes);
      p = q = blk;
      l = *p++;
      if (r->bytes > 1) {
          l += ((long)*p++) << 8;
          if (r->bytes == 4) {
            l += ((long)*p++) << 16;
            l += ((long)*p++) << 24;
          }
      }
      if (r->symbol == -SECT_DATA)
          l += stext.len;
      else if (r->symbol == -SECT_BSS)
          l += stext.len + sdata.len;
      if (r->bytes == 4)
          WRITELONG(q, l);
      else if (r->bytes == 2)
          WRITESHORT(q, l);
      else
          *q++ = l & 0xFF;
      saa_fwrite (sect->data, r->address, blk, (long)r->bytes);
    }
}

static void aout_write(void) 
{
    /*
     * Emit the a.out header.
     */
    /* OMAGIC, M_386 or MID_I386, no flags */
    fwritelong (bsd ? 0x07018600 | is_pic : 0x640107L, aoutfp);
    fwritelong (stext.len, aoutfp);
    fwritelong (sdata.len, aoutfp);
    fwritelong (sbss.len, aoutfp);
    fwritelong (nsyms * 12, aoutfp);   /* length of symbol table */
    fwritelong (0L, aoutfp);         /* object files have no entry point */
    fwritelong (stext.nrelocs * 8, aoutfp);   /* size of text relocs */
    fwritelong (sdata.nrelocs * 8, aoutfp);   /* size of data relocs */

    /*
     * Write out the code section and the data section.
     */
    saa_fpwrite (stext.data, aoutfp);
    saa_fpwrite (sdata.data, aoutfp);

    /*
     * Write out the relocations.
     */
    aout_write_relocs (stext.head);
    aout_write_relocs (sdata.head);

    /*
     * Write the symbol table.
     */
    aout_write_syms ();

    /*
     * And the string table.
     */
    fwritelong (strslen+4, aoutfp);    /* length includes length count */
    saa_fpwrite (strs, aoutfp);
}

static void aout_write_relocs (struct Reloc *r) 
{
    while (r) {
      unsigned long word2;

      fwritelong (r->address, aoutfp);

      if (r->symbol >= 0)
          word2 = r->symbol;
      else
          word2 = -r->symbol;
      word2 |= r->reltype << 24;
      word2 |= (r->bytes == 1 ? 0 :
              r->bytes == 2 ? 0x2000000L : 0x4000000L);
      fwritelong (word2, aoutfp);

      r = r->next;
    }
}

static void aout_write_syms (void) 
{
    unsigned long i;

    saa_rewind (syms);
    for (i = 0; i < nsyms; i++) {
      struct Symbol *sym = saa_rstruct(syms);
      fwritelong (sym->strpos, aoutfp);
      fwritelong ((long)sym->type & ~SYM_WITH_SIZE, aoutfp);
      /*
       * Fix up the symbol value now we know the final section
       * sizes.
       */
      if ((sym->type & SECT_MASK) == SECT_DATA)
          sym->value += stext.len;
      if ((sym->type & SECT_MASK) == SECT_BSS)
          sym->value += stext.len + sdata.len;
      fwritelong (sym->value, aoutfp);
      /*
       * Output a size record if necessary.
       */
      if (sym->type & SYM_WITH_SIZE) {
          fwritelong(sym->strpos, aoutfp);
          fwritelong(0x0DL, aoutfp);  /* special value: means size */
          fwritelong(sym->size, aoutfp);
          i++;                 /* use up another of `nsyms' */
      }
    }
}

static void aout_sect_write (struct Section *sect,
                       const unsigned char *data, unsigned long len) 
{
    saa_wbytes (sect->data, data, len);
    sect->len += len;
}

static long aout_segbase (long segment) 
{
    return segment;
}

static int aout_directive (char *directive, char *value, int pass) 
{
    return 0;
}

static void aout_filename (char *inname, char *outname, efunc error) 
{
    standard_extension (inname, outname, ".o", error);
}

static const char *aout_stdmac[] = {
    "%define __SECT__ [section .text]",
    "%macro __NASM_CDecl__ 1",
    "%endmacro",
    NULL
};

static int aout_set_info(enum geninfo type, char **val)
{
    return 0;
}
#endif /* OF_AOUT || OF_AOUTB */

#ifdef OF_AOUT

struct ofmt of_aout = {
    "Linux a.out object files",
    "aout",
    NULL,
    null_debug_arr,
    &null_debug_form,
    aout_stdmac,
    aout_init,
    aout_set_info,
    aout_out,
    aout_deflabel,
    aout_section_names,
    aout_segbase,
    aout_directive,
    aout_filename,
    aout_cleanup
};

#endif

#ifdef OF_AOUTB

struct ofmt of_aoutb = {
    "NetBSD/FreeBSD a.out object files",
    "aoutb",
    NULL,
    null_debug_arr,
    &null_debug_form,
    aout_stdmac,
    aoutb_init,
    aout_set_info,
    aout_out,
    aout_deflabel,
    aout_section_names,
    aout_segbase,
    aout_directive,
    aout_filename,
    aout_cleanup
};

#endif

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