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ldrdf.c

/* ldrdf.c      RDOFF Object File linker/loader main program
 *
 * 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.
 */

/*
 * TODO:
 * - enhance search of required export symbols in libraries (now depends
 *   on modules order in library)
 * - keep a cache of symbol names in each library module so
 *   we don't have to constantly recheck the file
 * - general performance improvements
 *
 * BUGS & LIMITATIONS: this program doesn't support multiple code, data
 * or bss segments, therefore for 16 bit programs whose code, data or BSS
 * segment exceeds 64K in size, it will not work. This program probably
 * won't work if compiled by a 16 bit compiler. Try DJGPP if you're running
 * under DOS. '#define STINGY_MEMORY' may help a little.
 */

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

#include "rdoff.h"
#include "symtab.h"
#include "collectn.h"
#include "rdlib.h"
#include "segtab.h"

#define LDRDF_VERSION "1.05"

#define RDF_MAXSEGS 64
/* #define STINGY_MEMORY */

/* =======================================================================
 * Types & macros that are private to this program
 */

struct segment_infonode {
    int           dest_seg;   /* output segment to be placed into, -1 to 
                           skip linking this segment */
    long    reloc;            /* segment's relocation factor */
};


struct modulenode {
    rdffile f;          /* the RDOFF file structure */
    struct segment_infonode seginfo[RDF_MAXSEGS]; /* what are we doing
                                         with each segment? */
    void    * header;
    char    * name;
    struct modulenode * next;
    long    bss_reloc;
};

#include "ldsegs.h"

#define newstr(str) strcpy(malloc(strlen(str) + 1),str)
#define newstrcat(s1,s2) strcat(strcpy(malloc(strlen(s1)+strlen(s2)+1),s1),s2)

/* ==========================================================================
 * Function prototypes of private utility functions
 */

void processmodule(const char * filename, struct modulenode * mod);
int allocnewseg(int16 type,int16 reserved);
int findsegment(int16 type,int16 reserved);
void symtab_add(const char * symbol, int segment, long offset);
int symtab_get(const char * symbol, int * segment, long * offset);

/* =========================================================================
 * Global data structures.
 */

/* a linked list of modules that will be included in the output */
struct modulenode       * modules = NULL;
struct modulenode       * lastmodule = NULL;

/* a linked list of libraries to be searched for unresolved imported symbols */
struct librarynode      * libraries = NULL;
struct librarynode      * lastlib = NULL;

/* the symbol table */
void              * symtab = NULL;

/* objects search path */
char              * objpath = NULL;

/* libraries search path */
char              * libpath = NULL;

/* file to embed as a generic record */
char              * generic_rec_file = NULL;

/* error file */
static FILE       * error_file;

/* the header of the output file, built up stage by stage */
rdf_headerbuf           * newheader = NULL;

/* The current state of segment allocation, including information about
 * which output segment numbers have been allocated, and their types and
 * amount of data which has already been allocated inside them. 
 */
struct SegmentHeaderRec outputseg[RDF_MAXSEGS];
int               nsegs = 0;
long              bss_length;

/* global options which affect how the program behaves */
struct ldrdfoptions {
    int           verbose;
    int           align;
    int           warnUnresolved;
    int           strip;
    int         respfile;
    int         stderr_redir;
    int         objpath;
    int         libpath;
} options;

int errorcount = 0;     /* determines main program exit status */


/* =========================================================================
 * Utility functions
 */


/*
 * initsegments()
 *
 * sets up segments 0, 1, and 2, the initial code data and bss segments
 */

void initsegments()
{
    nsegs = 3;
    outputseg[0].type = 1;
    outputseg[0].number = 0;
    outputseg[0].reserved = 0;
    outputseg[0].length = 0;
    outputseg[1].type = 2;
    outputseg[1].number = 1;
    outputseg[1].reserved = 0;
    outputseg[1].length = 0;
    outputseg[2].type = 0xFFFF;     /* reserved segment type */
    outputseg[2].number = 2;
    outputseg[2].reserved = 0;
    outputseg[2].length = 0;
    bss_length = 0;
}

/*
 * loadmodule
 *
 * Determine the characteristics of a module, and decide what to do with
 * each segment it contains (including determining destination segments and
 * relocation factors for segments that   are kept).
 */

void loadmodule(const char * filename)
{
    if (options.verbose)
      printf("loading `%s'\n", filename);

    /* allocate a new module entry on the end of the modules list */
    if (!modules)
    {
      modules = malloc (sizeof(*modules));
      lastmodule = modules;
    }
    else
    {
      lastmodule->next = malloc (sizeof(*modules));
      lastmodule = lastmodule->next;
    }

    if ( ! lastmodule)
    {
      fprintf(stderr, "ldrdf: out of memory\n");
      exit(1);
    }

    /* open the file using 'rdfopen', which returns nonzero on error */

    if (rdfopen(&lastmodule->f, filename) != 0)
    {
      rdfperror("ldrdf", filename);
      exit(1);
    }

    /* 
     * store information about the module, and determine what segments
     * it contains, and what we should do with them (determine relocation
     * factor if we decide to keep them)
     */

    lastmodule->header = NULL;
    lastmodule->name = strdup(filename);
    lastmodule->next = NULL;

    processmodule(filename, lastmodule);
}
      
/*
 * processmodule()
 *
 * step through each segment, determine what exactly we're doing with
 * it, and if we intend to keep it, determine (a) which segment to
 * put it in and (b) whereabouts in that segment it will end up.
 * (b) is fairly easy, because we're now keeping track of how big each
 * segment in our output file is...
 */

void processmodule(const char * filename, struct modulenode * mod)
{
    struct segconfig sconf;
    int           seg, outseg;
    void    * header;
    rdfheaderrec * hr;
    long    bssamount = 0;
    int           bss_was_referenced = 0;

    for (seg = 0; seg < mod->f.nsegs; seg++)
    {
      /*
       * get the segment configuration for this type from the segment
       * table. getsegconfig() is a macro, defined in ldsegs.h.
       */
      getsegconfig(sconf, mod->f.seg[seg].type);

      if (options.verbose > 1) {
          printf ("%s %04x [%04x:%10s] ", filename, mod->f.seg[seg].number, 
                mod->f.seg[seg].type, sconf.typedesc);
      }
      /*
       * sconf->dowhat tells us what to do with a segment of this type.
       */
      switch (sconf.dowhat) {
      case SEG_IGNORE:
          /*
           * Set destination segment to -1, to indicate that this segment
           * should be ignored for the purpose of output, ie it is left
           * out of the linked executable.
           */
          mod->seginfo[seg].dest_seg = -1;
          if (options.verbose > 1) printf("IGNORED\n");
          break;

      case SEG_NEWSEG:
          /*
           * The configuration tells us to create a new segment for
           * each occurrence of this segment type.
           */
          outseg = allocnewseg(sconf.mergetype,
                         mod->f.seg[seg].reserved);
          mod->seginfo[seg].dest_seg = outseg;
          mod->seginfo[seg].reloc = 0;
          outputseg[outseg].length = mod->f.seg[seg].length;
          if (options.verbose > 1) 
            printf ("=> %04x:%08lx (+%04lx)\n", outseg,
                  mod->seginfo[seg].reloc,
                  mod->f.seg[seg].length);
          break;

      case SEG_MERGE:
          /*
           * The configuration tells us to merge the segment with
           * a previously existing segment of type 'sconf.mergetype',
           * if one exists. Otherwise a new segment is created.
           * This is handled transparently by 'findsegment()'.
           */
          outseg = findsegment(sconf.mergetype,
                         mod->f.seg[seg].reserved);
          mod->seginfo[seg].dest_seg = outseg;

          /*
           * We need to add alignment to these segments.
           */
          if (outputseg[outseg].length % options.align != 0)
            outputseg[outseg].length += 
                options.align - (outputseg[outseg].length % options.align);
          
          mod->seginfo[seg].reloc = outputseg[outseg].length;
          outputseg[outseg].length  += mod->f.seg[seg].length;

          if (options.verbose > 1) 
            printf ("=> %04x:%08lx (+%04lx)\n", outseg,
                  mod->seginfo[seg].reloc,
                  mod->f.seg[seg].length);
      }

    }

    /*
     * extract symbols from the header, and dump them into the
     * symbol table
     */
    header = malloc(mod->f.header_len);
    if (!header) {
      fprintf(stderr, "ldrdf: not enough memory\n");
      exit(1);
    }
    if (rdfloadseg(&mod->f, RDOFF_HEADER, header)) {
      rdfperror("ldrdf", filename);
      exit(1);
    }

    while ((hr = rdfgetheaderrec (&mod->f))) {
      switch(hr->type) {
          case RDFREC_IMPORT:       /* imported symbol */
          case RDFREC_FARIMPORT:
            /* Define with seg = -1 */
          symtab_add(hr->i.label, -1, 0);
          break;

          case RDFREC_GLOBAL: {     /* exported symbol */
            int destseg;
            long destreloc;

            if (hr->e.segment == 2) {
                bss_was_referenced = 1;
               destreloc = bss_length;
               if (destreloc % options.align != 0)
                  destreloc +=  options.align - (destreloc % options.align);
               destseg = 2;
                } else {
               if ((destseg = mod->seginfo[(int)hr->e.segment].dest_seg) == -1)
                  continue;
               destreloc = mod->seginfo[(int)hr->e.segment].reloc;
             }
          symtab_add(hr->e.label, destseg, destreloc + hr->e.offset);
          break;
           }

          case RDFREC_BSS:          /* BSS reservation */
          /*
           * first, amalgamate all BSS reservations in this module
           * into one, because we allow this in the output format.
           */
          bssamount += hr->b.amount;
          break;

          case RDFREC_COMMON: {     /* Common variable */
              symtabEnt *ste = symtabFind(symtab, hr->c.label);

            /* Is the symbol already in the table? */
            if (ste) break;
            
            /* Align the variable */
            if (bss_length % hr->c.align != 0)
                bss_length += hr->c.align - (bss_length % hr->c.align);
            if (options.verbose > 1) {
                printf ("%s %04x common '%s' => 0002:%08lx (+%04lx)\n",
                  filename, hr->c.segment, hr->c.label, bss_length, hr->c.size);
            }
            
            symtab_add(hr->c.label, 2, bss_length);
            mod->bss_reloc = bss_length;
            bss_length += hr->c.size;
            break;
          }
      }
    }

    if (bssamount != 0 || bss_was_referenced) {
      /*
       * handle the BSS segment - first pad the existing bss length
       * to the correct alignment, then store the length in bss_reloc
       * for this module. Then add this module's BSS length onto
       * bss_length.
       */
      if (bss_length % options.align != 0)
          bss_length +=  options.align - (bss_length % options.align);
    
      mod->bss_reloc = bss_length;
      if (options.verbose > 1) {
          printf ("%s 0002 [            BSS] => 0002:%08lx (+%04lx)\n",
                filename, bss_length, bssamount);
      }
      bss_length += bssamount;
    }

#ifdef STINGY_MEMORY
    /*
     * we free the header buffer here, to save memory later.
     * this isn't efficient, but probably halves the memory usage
     * of this program...
     */
    mod->f.header_loc = NULL;
    free(header);

#endif

}


/*
 * Look in the list for module by its name.
 */
int lookformodule(const char *name)
 {
  struct modulenode *curr=modules;

  while(curr) {
   if (!strcmp(name,curr->name)) return 1;
   curr = curr->next;
  }
  return 0;
 }


/*
 * allocnewseg()
 * findsegment()
 *
 * These functions manipulate the array of output segments, and are used
 * by processmodule(). allocnewseg() allocates a segment in the array,
 * initialising it to be empty. findsegment() first scans the array for
 * a segment of the type requested, and if one isn't found allocates a
 * new one.
 */
int allocnewseg(int16 type,int16 reserved)
{
    outputseg[nsegs].type = type;
    outputseg[nsegs].number = nsegs;
    outputseg[nsegs].reserved = reserved;
    outputseg[nsegs].length = 0;
    outputseg[nsegs].offset = 0;
    outputseg[nsegs].data = NULL;

    return nsegs++;
}

int findsegment(int16 type,int16 reserved)
{
    int i;

    for (i = 0; i < nsegs; i++)
      if (outputseg[i].type == type) return i;

    return allocnewseg(type,reserved);
}

/*
 * symtab_add()
 *
 * inserts a symbol into the global symbol table, which associates symbol
 * names either with addresses, or a marker that the symbol hasn't been
 * resolved yet, or possibly that the symbol has been defined as
 * contained in a dynamic [load time/run time] linked library.
 *
 * segment = -1 => not yet defined
 * segment = -2 => defined as dll symbol
 *
 * If the symbol is already defined, and the new segment >= 0, then
 * if the original segment was < 0 the symbol is redefined, otherwise
 * a duplicate symbol warning is issued. If new segment == -1, this
 * routine won't change a previously existing symbol. It will change
 * to segment = -2 only if the segment was previously < 0.
 */

void symtab_add(const char * symbol, int segment, long offset)
{
    symtabEnt * ste;

    ste = symtabFind(symtab, symbol);
    if (ste)
    {
      if (ste->segment >= 0) {
          /*
           * symbol previously defined
           */
          if (segment < 0) return;
          fprintf (error_file, "warning: `%s' redefined\n", symbol);
          return;
      }

      /*
       * somebody wanted the symbol, and put an undefined symbol
       * marker into the table
       */
      if (segment == -1) return;
      /*
       * we have more information now - update the symbol's entry
       */
      ste->segment = segment;
      ste->offset = offset;
      ste->flags = 0;
      return;
    }
    /*
     * this is the first declaration of this symbol
     */
    ste = malloc(sizeof(symtabEnt));
    if (!ste) {
      fprintf(stderr, "ldrdf: out of memory\n");
      exit(1);
    }
    ste->name = strdup(symbol);
    ste->segment = segment;
    ste->offset = offset;
    ste->flags = 0;
    symtabInsert(symtab, ste);
}

/*
 * symtab_get()
 *
 * Retrieves the values associated with a symbol. Undefined symbols
 * are assumed to have -1:0 associated. Returns 1 if the symbol was
 * successfully located.
 */

int symtab_get(const char * symbol, int * segment, long * offset)
{
    symtabEnt * ste = symtabFind(symtab, symbol);
    if (!ste) {
      *segment = -1;
      *offset = 0;
      return 0;
    }
    else
    {
      *segment = ste->segment;
      *offset = ste->offset;
      return 1;
    }
}

/*
 * add_library()
 *
 * checks that a library can be opened and is in the correct format,
 * then adds it to the linked list of libraries.
 */

void add_library(const char * name)
{
    if (rdl_verify(name)) {
      rdl_perror("ldrdf", name);
      errorcount++;
      return;
    }
    if (! libraries)
    {
      lastlib = libraries = malloc(sizeof(*libraries));
      if (! libraries) {
          fprintf(stderr, "ldrdf: out of memory\n");
          exit(1);
      }
    }
    else
    {
      lastlib->next = malloc(sizeof(*libraries));
      if (!lastlib->next) {
          fprintf(stderr, "ldrdf: out of memory\n");
          exit(1);
      }
      lastlib = lastlib->next;
    }
    lastlib->next = NULL;
    if (rdl_open(lastlib, name)) {
      rdl_perror("ldrdf", name);
      errorcount++;
      return;
    }
}

/*
 * search_libraries()
 *
 * scans through the list of libraries, attempting to match symbols
 * defined in library modules against symbols that are referenced but
 * not defined (segment = -1 in the symbol table)
 *
 * returns 1 if any extra library modules are included, indicating that
 * another pass through the library list should be made (possibly).
 */

int search_libraries()
{
    struct librarynode * cur;
    rdffile f;
    int     i;
    void    * header;
    int         segment;
    long    offset;
    int         doneanything = 0, pass = 1, keepfile;
    rdfheaderrec * hr;

    cur = libraries;

    while (cur)
    {
      if (options.verbose > 2)
          printf("scanning library `%s', pass %d...\n", cur->name, pass);
      
      for (i = 0; rdl_openmodule(cur, i, &f) == 0; i++)
      {
          if (pass == 2 && lookformodule(f.name)) continue;

          if (options.verbose > 3)
            printf("  looking in module `%s'\n", f.name);

          header = malloc(f.header_len);
          if (!header) {
            fprintf(stderr, "ldrdf: not enough memory\n");
            exit(1);
          }
          if (rdfloadseg(&f, RDOFF_HEADER, header)) {
            rdfperror("ldrdf", f.name);
            errorcount++;
            return 0;
          }
          
          keepfile = 0;

          while ((hr = rdfgetheaderrec (&f)))
          {
                /* We're only interested in exports, so skip others */
            if (hr->type != RDFREC_GLOBAL) continue; 

            /*
             * If the symbol is marked as SYM_GLOBAL, somebody will be
             * definitely interested in it..
             */
            if ((hr->e.flags & SYM_GLOBAL) == 0) {
                /*
                 * otherwise the symbol is just public. Find it in
                 * the symbol table. If the symbol isn't defined, we
                 * aren't interested, so go on to the next.
             * If it is defined as anything but -1, we're also not
             * interested. But if it is defined as -1, insert this
             * module into the list of modules to use, and go
             * immediately on to the next module...
             */
                if (!symtab_get(hr->e.label, &segment, &offset) || segment != -1)
                continue;    
            }
            
            doneanything = 1;
            keepfile = 1;

            /*
             * as there are undefined symbols, we can assume that
             * there are modules on the module list by the time
             * we get here.
             */
            lastmodule->next = malloc(sizeof(*lastmodule->next));
            if (!lastmodule->next) {
                fprintf(stderr, "ldrdf: not enough memory\n");
                exit(1);
            }
            lastmodule = lastmodule->next;
            memcpy(&lastmodule->f, &f, sizeof(f));
            lastmodule->name = strdup(f.name);
                lastmodule->next = NULL;
            processmodule(f.name, lastmodule);
            break;
          }
          if (!keepfile) {
              free(f.name);
              f.name = NULL;
              f.fp = NULL;
             }
      }
      if (rdl_error != 0 && rdl_error != RDL_ENOTFOUND)
          rdl_perror("ldrdf", cur->name);

      cur = cur->next;
      if (cur == NULL && pass == 1) {
          cur = libraries;
          pass++;
      }
    }

    return doneanything;
}

/*
 * write_output()
 *
 * this takes the linked list of modules, and walks through it, merging
 * all the modules into a single output module, and then writes this to a
 * file.
 */
void write_output(const char * filename)
{
    FILE          * f;
    rdf_headerbuf * rdfheader;
    struct modulenode * cur;
    int             i, availableseg, seg, localseg, isrelative;
    void      * header;
    rdfheaderrec  * hr, newrec;
    symtabEnt       * se;
    segtab    segs;
    long      offset;
    byte      * data;

    if ((f = fopen(filename, "wb"))==NULL) {
      fprintf(stderr, "ldrdf: couldn't open %s for output\n", filename);
      exit(1);
    }
    if ((rdfheader=rdfnewheader())==NULL) {
      fprintf(stderr, "ldrdf: out of memory\n");
      exit(1);
    }
    
    /*
     * If '-g' option was given, first record in output file will be a
     * `generic' record, filled with a given file content.
     * This can be useful, for example, when constructing multiboot
     * compliant kernels.
     */
    if (generic_rec_file) {
      FILE *ff;
    
      if (options.verbose)
          printf("\nadding generic record from binary file %s\n", generic_rec_file);
      
        hr = (rdfheaderrec *) malloc(sizeof(struct GenericRec));
      if ((ff = fopen(generic_rec_file, "r")) == NULL) {
          fprintf(stderr, "ldrdf: couldn't open %s for input\n", generic_rec_file);
          exit(1);
      }
      i = fread(hr->g.data, 1, sizeof(hr->g.data), ff);
      fseek(ff, 0, SEEK_END);
      if (ftell(ff) > sizeof(hr->g.data)) {
          fprintf (error_file, "warning: maximum generic record size is %d, rest of file ignored\n", sizeof(hr->g.data));
      }
      fclose(ff);
          
        hr->g.type = 0;
        hr->g.reclen = i;
        rdfaddheader(rdfheader,hr);
        free(hr);
    }

    if (options.verbose)
      printf ("\nbuilding output module (%d segments)\n", nsegs);

    /*
     * Allocate the memory for the segments. We may be better off
     * building the output module one segment at a time when running
     * under 16 bit DOS, but that would be a slower way of doing this.
     * And you could always use DJGPP...
     */
    for (i = 0; i < nsegs; i++)
    {
      outputseg[i].data=NULL;
      if(!outputseg[i].length) continue;
      outputseg[i].data = malloc(outputseg[i].length);
      if (!outputseg[i].data) {
          fprintf(stderr, "ldrdf: out of memory\n");
          exit(1);
      }
    }

    /*
     * initialise availableseg, used to allocate segment numbers for
     * imported and exported labels...
     */
    availableseg = nsegs;

    /*
     * Step through the modules, performing required actions on each one
     */
    for (cur = modules; cur; cur=cur->next)
    {
      /*
       * Read the actual segment contents into the correct places in
       * the newly allocated segments
       */

      for (i = 0; i < cur->f.nsegs; i++)
      {
          int dest = cur->seginfo[i].dest_seg;

          if (dest == -1) continue;
          if (rdfloadseg(&cur->f, i, 
                     outputseg[dest].data + cur->seginfo[i].reloc))
          {
            rdfperror("ldrdf", cur->name);
            exit(1);
          }
      }
 
      /*
       * Perform fixups, and add new header records where required
       */

      header = malloc(cur->f.header_len);
      if (!header) {
          fprintf(stderr, "ldrdf: out of memory\n");
          exit(1);
      }

      if (cur->f.header_loc)
          rdfheaderrewind(&cur->f);
      else
          if (rdfloadseg(&cur->f, RDOFF_HEADER, header))
          {
            rdfperror("ldrdf", cur->name);
            exit(1);
          }
      
      /*
       * we need to create a local segment number -> location
       * table for the segments in this module.
       */
      init_seglocations(&segs);
      for (i = 0; i < cur->f.nsegs; i++)
      {
          add_seglocation(&segs, cur->f.seg[i].number,
                      cur->seginfo[i].dest_seg, cur->seginfo[i].reloc);
      }
      /*
       * and the BSS segment (doh!)
       */
      add_seglocation (&segs, 2, 2, cur->bss_reloc);
      
      while ((hr = rdfgetheaderrec(&cur->f)))
      {
          switch(hr->type) {
          case RDFREC_RELOC: /* relocation record - need to do a fixup */
            /*
             * First correct the offset stored in the segment from
             * the start of the segment (which may well have changed).
             *
             * To do this we add to the number stored the relocation
             * factor associated with the segment that contains the
             * target segment.
             *
             * The relocation could be a relative relocation, in which
             * case we have to first subtract the amount we've relocated
             * the containing segment by.
             */
            
            if (!get_seglocation(&segs, hr->r.refseg, &seg, &offset))
            {
                fprintf(stderr, "%s: reloc to undefined segment %04x\n",
                      cur->name, (int) hr->r.refseg);
                errorcount++;
                break;
            }

            isrelative = (hr->r.segment & 64) == 64;
            hr->r.segment &= 63;

            if (hr->r.segment == 2 || 
                (localseg = rdffindsegment(&cur->f, hr->r.segment)) == -1)
            {
                fprintf(stderr, "%s: reloc from %s segment (%d)\n", 
                      cur->name,
                      hr->r.segment == 2 ? "BSS" : "unknown",
                      hr->r.segment);
                errorcount++;
                break;
            }

            if (hr->r.length != 1 && hr->r.length != 2 && hr->r.length!=4)
            {
                fprintf(stderr, "%s: nonstandard length reloc "
                      "(%d bytes)\n", cur->name, hr->r.length);
                errorcount++;
                break;
            }

            /* 
             * okay, now the relocation is in the segment pointed to by
             * cur->seginfo[localseg], and we know everything else is
             * okay to go ahead and do the relocation
             */
            data = outputseg[cur->seginfo[localseg].dest_seg].data;
            data += cur->seginfo[localseg].reloc + hr->r.offset;

            /*
             * data now points to the reference that needs
             * relocation. Calculate the relocation factor.
             * Factor is:
             *      offset of referred object in segment [in offset]
             *    (- relocation of localseg, if ref is relative)
             * For simplicity, the result is stored in 'offset'.
             * Then add 'offset' onto the value at data.
             */
            
            if (isrelative) offset -= cur->seginfo[localseg].reloc;
            switch (hr->r.length)
            {
            case 1:
                offset += *data;
                if (offset < -127 || offset > 128)
                  fprintf(error_file, "warning: relocation out of range "
                        "at %s(%02x:%08lx)\n", cur->name,
                        (int)hr->r.segment, hr->r.offset);
                *data = (char) offset;
                break;
            case 2:
                offset += * (short *)data;
                if (offset < -32767 || offset > 32768)
                  fprintf(error_file, "warning: relocation out of range "
                        "at %s(%02x:%08lx)\n", cur->name,
                        (int)hr->r.segment, hr->r.offset);
                * (short *)data = (short) offset;
                break;
            case 4:
                * (long *)data += offset;
                /* we can't easily detect overflow on this one */
                break;
            }

            /*
             * If the relocation was relative between two symbols in
             * the same segment, then we're done.
             *
             * Otherwise, we need to output a new relocation record
             * with the references updated segment and offset...
             */
            if (! isrelative || cur->seginfo[localseg].dest_seg != seg)
            {
                hr->r.segment = cur->seginfo[localseg].dest_seg;
                hr->r.offset += cur->seginfo[localseg].reloc;
                hr->r.refseg = seg;
                if (isrelative)
                  hr->r.segment += 64;
                rdfaddheader(rdfheader, hr);
            }
            break;

          case RDFREC_IMPORT:       /* import symbol */
          case RDFREC_FARIMPORT:
            /*
             * scan the global symbol table for the symbol
             * and associate its location with the segment number 
             * for this module
             */
            se = symtabFind(symtab, hr->i.label);
            if (!se || se->segment == -1) {
                if (options.warnUnresolved) {
                  switch (options.warnUnresolved) {
                      case 1:
                        fprintf(error_file, "warning");
                        break;
                      case 2:
                        fprintf(error_file, "error");
                        errorcount++;
                  }
                  fprintf(error_file, ": unresolved reference to `%s'"
                        " in module `%s'\n", hr->i.label, cur->name);
                }
                /*
                 * we need to allocate a segment number for this
                 * symbol, and store it in the symbol table for
                 * future reference
                 */ 
                if (!se) {
                  se=malloc(sizeof(*se));
                  if (!se) {
                      fprintf(stderr, "ldrdf: out of memory\n");
                      exit(1);
                  }
                  se->name = strdup(hr->i.label);
                  se->flags = 0;
                  se->segment = availableseg++;
                  se->offset = 0;
                  symtabInsert(symtab, se);
                }
                else {
                  se->segment = availableseg++;
                  se->offset = 0;
                }
                /*
                 * output a header record that imports it to the
                 * recently allocated segment number...
                 */
                newrec = *hr;
                newrec.i.segment = se->segment;
                rdfaddheader(rdfheader, &newrec);
            }

            add_seglocation(&segs, hr->i.segment, se->segment, se->offset);
            
            break;

          case RDFREC_GLOBAL:       /* export symbol */
            /*
             * need to insert an export for this symbol into the new
             * header, unless we're stripping symbols. Even if we're
             * stripping, put the symbol if it's marked as SYM_GLOBAL.
             */
            if (options.strip && !(hr->e.flags & SYM_GLOBAL))
                break;

            if (hr->e.segment == 2) {
                seg = 2;
                offset = cur->bss_reloc;
            }
            else {
                localseg = rdffindsegment(&cur->f, hr->e.segment);
                if (localseg == -1) {
                  fprintf(stderr, "%s: exported symbol `%s' from "
                        "unrecognised segment\n", cur->name,
                        hr->e.label);
                  errorcount++;
                  break;
                }
                offset = cur->seginfo[localseg].reloc;
                seg = cur->seginfo[localseg].dest_seg;
            }

            hr->e.segment = seg;    
            hr->e.offset += offset;
            rdfaddheader(rdfheader, hr);
            break;

          case RDFREC_MODNAME:       /* module name */
             /*
              * Insert module name record if export symbols
              * are not stripped.
              * If module name begins with '$' - insert it anyway.
              */
            if (options.strip && hr->m.modname[0] != '$') break;
            rdfaddheader(rdfheader, hr);
            break;

          case RDFREC_DLL:          /* DLL name */
             /*
              * Insert DLL name if it begins with '$'
              */
            if (hr->d.libname[0] != '$') break;
            rdfaddheader(rdfheader, hr);
            break;

          case RDFREC_SEGRELOC:      /* segment fixup */
            /*
             * modify the segment numbers if necessary, and
             * pass straight through to the output module header
             *
             * *** FIXME ***
             */
            if (hr->r.segment == 2) {
                fprintf(stderr, "%s: segment fixup in BSS section\n",
                      cur->name);
                errorcount++;
                break;
            }
            localseg = rdffindsegment(&cur->f, hr->r.segment);
            if (localseg == -1) {
                fprintf(stderr, "%s: segment fixup in unrecognised"
                      " segment (%d)\n", cur->name, hr->r.segment);
                errorcount++;
                break;
            }
            hr->r.segment = cur->seginfo[localseg].dest_seg;
            hr->r.offset += cur->seginfo[localseg].reloc;

            if (!get_seglocation(&segs, hr->r.refseg, &seg, &offset))
            {
                fprintf(stderr, "%s: segment fixup to undefined "
                      "segment %04x\n", cur->name, (int)hr->r.refseg);
                errorcount++;
                break;
            }
            hr->r.refseg = seg;
            rdfaddheader(rdfheader, hr);
            break;

          case RDFREC_COMMON:       /* Common variable */
            /* Is this symbol already in the table? */
            se = symtabFind(symtab, hr->c.label);
            if (!se) {
                printf("%s is not in symtab yet\n", hr->c.label);
                break;
            }
            /* Add segment location */
            add_seglocation(&segs, hr->c.segment, se->segment, se->offset);
            break;
          }
      }

      free(header);
      done_seglocations(&segs);

    }

    /*
     * combined BSS reservation for the entire results
     */
    newrec.type = RDFREC_BSS;
    newrec.b.reclen = 4;
    newrec.b.amount = bss_length;
    rdfaddheader(rdfheader, &newrec);

    /*
     * Write the header
     */
    for (i = 0; i < nsegs; i++)
    {
      if (i == 2) continue;
      rdfaddsegment (rdfheader, outputseg[i].length);
    }
    
    rdfwriteheader(f, rdfheader);
    rdfdoneheader(rdfheader);
    
    /*
     * Step through the segments, one at a time, writing out into
     * the output file
     */
    for (i = 0; i < nsegs; i++)
    {
      int16 s;
      long l;
      
      if (i == 2) continue;

      s = translateshort(outputseg[i].type);
      fwrite(&s, 2, 1, f);
      s = translateshort(outputseg[i].number);
      fwrite(&s, 2, 1, f);
      s = translateshort(outputseg[i].reserved);
      fwrite(&s, 2, 1, f);
      l = translatelong(outputseg[i].length);
      fwrite(&l, 4, 1, f);

      fwrite(outputseg[i].data, outputseg[i].length, 1, f);
    }

    fwrite("\0\0\0\0\0\0\0\0\0\0", 10, 1, f);
}

/* =========================================================================
 * Main program
 */

void usage()
{
    printf("usage:\n"
           "   ldrdf [options] object modules ... [-llibrary ...]\n"
           "   ldrdf -r\n"
           "options:\n"
           "   -v[=n]          increases verbosity by 1, or sets it to n\n"
           "   -a nn           sets segment alignment value (default 16)\n"
           "   -s              strips exported symbols\n"
           "   -x              warn about unresolved symbols\n"
           "   -o name         write output in file 'name'\n"
           "   -j path         specify objects search path\n"
           "   -L path         specify libraries search path\n"
           "   -g file         embed 'file' as a first header record with type 'generic'\n");
    exit(0);
}

int main(int argc, char ** argv)
{
    char * outname = "aout.rdf";
    int  moduleloaded = 0;
    char *respstrings[128] = {0, };

    options.verbose = 0;
    options.align = 16;
    options.warnUnresolved = 0;
    options.strip = 0;

    error_file = stderr;

    argc --, argv ++;
    if (argc == 0) usage();
    while (argc && *argv && **argv == '-' && argv[0][1] != 'l')
    {
      switch(argv[0][1]) {
      case 'r':
          printf("ldrdf (linker for RDF files) version " LDRDF_VERSION "\n");
          printf( _RDOFF_H "\n");
          exit(0);
      case 'v':
          if (argv[0][2] == '=') {
            options.verbose = argv[0][3] - '0';
            if (options.verbose < 0 || options.verbose > 9) {
                fprintf(stderr, "ldrdf: verbosity level must be a number"
                      " between 0 and 9\n");
                exit(1);
            }
          }
          else
            options.verbose++;
          break;
      case 'a':
          options.align = atoi(argv[1]);
          if (options.align <= 0) {
            fprintf(stderr,
                  "ldrdf: -a expects a positive number argument\n");
            exit(1);
          }
          argv++, argc--;
          break;
      case 's':
          options.strip = 1;
          break;
      case 'x':
          options.warnUnresolved = 1;
          if (argv[0][2]=='e')
            options.warnUnresolved++;
          break;
      case 'o':
          outname = argv[1];
          argv++, argc--;
          break;
      case 'j':
          if (!objpath) {
              options.objpath = 1;
            objpath = argv[1];
            argv++, argc--;
            break;
           } else {
            fprintf(stderr,"ldrdf: more than one objects search path specified\n");
            exit(1);
           }
      case 'L':
          if (!libpath) {
              options.libpath = 1;
            libpath = argv[1];
            argv++, argc--;
            break;
           } else {
            fprintf(stderr,"ldrdf: more than one libraries search path specified\n");
            exit(1);
           }
      case '@': {
            int i=0;
            char buf[256];
            FILE *f;

              options.respfile = 1;
            if (argv[1] != NULL) f = fopen(argv[1],"r");
          else {
            fprintf(stderr,"ldrdf: no response file name specified\n");
            exit(1);
             }

          if (f == NULL) {
            fprintf(stderr,"ldrdf: unable to open response file\n");
            exit(1);
             }
          
          argv++, argc--;
          while (fgets(buf, sizeof(buf), f) != NULL) {
            char *p;
            if (buf[0]=='\n') continue;
            if ((p = strchr(buf,'\n')) != NULL) *p = '\0';
            if (i >= 128) {
              fprintf(stderr,"ldrdf: too many input files\n");
              exit(1);
             }
            *(respstrings+i) = newstr(buf);
            argc++, i++;
             }
            break;
       }
      case '2':
            options.stderr_redir = 1;
          error_file = stdout;
          break;
      case 'g':
          generic_rec_file = argv[1];
          argv++, argc--;
            break;    
      default:
          usage();
      }
      argv++, argc--;
    }

    if (options.verbose > 4) {
      printf("ldrdf invoked with options:\n");
      printf("    section alignment: %d bytes\n", options.align);
      printf("    output name: `%s'\n", outname);
      if (options.strip)
          printf("    strip symbols\n");
      if (options.warnUnresolved == 1)
          printf("    warn about unresolved symbols\n");
      if (options.warnUnresolved == 2)
          printf("    error if unresolved symbols\n");    
        if (options.objpath)
            printf("    objects search path: %s\n",objpath);
        if (options.libpath)
            printf("    libraries search path: %s\n",libpath);
      printf("\n");
    }

    symtab = symtabNew();
    initsegments();

    if (!symtab) {
      fprintf(stderr, "ldrdf: out of memory\n");
      exit(1);
    }

    while (argc) {
      if (!*argv) argv = respstrings;
      if (!*argv) break;
      if (!strncmp(*argv, "-l", 2)) /* library */
         {
        if(libpath) add_library(newstrcat(libpath,*argv + 2));
          else add_library(*argv + 2);
         }
      else {
          if(objpath) loadmodule(newstrcat(objpath,*argv));
          else loadmodule(*argv);
          moduleloaded = 1;
      }
      argv++, argc--;
    }

    if (! moduleloaded) {
      printf("ldrdf: nothing to do. ldrdf -h for usage\n");
      return 0;
    }

    search_libraries();

    if (options.verbose > 2)
    {
      printf ("symbol table:\n");
      symtabDump(symtab, stdout);
    }

    write_output(outname);

    if (errorcount > 0) exit(1);
    return 0;
}

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