rdoff/rdfload.c

   1 /* rdfload.c    RDOFF Object File loader library
   2  *
   3  * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
   4  * Julian Hall. All rights reserved. The software is
   5  * redistributable under the licence given in the file "Licence"
   6  * distributed in the NASM archive.
   7  *
   8  * Permission to use this file in your own projects is granted, as long
   9  * as acknowledgement is given in an appropriate manner to its authors,
  10  * with instructions of how to obtain a copy via ftp.
  11  */
  12
  13 /*
  14  * TODO: this has been modified from previous version only in very
  15  * simplistic ways. Needs to be improved drastically, especially:
  16  *   - support for more than the 2 standard segments
  17  *   - support for segment relocations (hard to do in ANSI C)
  18  */
  19
  20 #include <stdlib.h>
  21 #include <stdio.h>
  22
  23 #include "rdfload.h"
  24 #include "symtab.h"
  25 #include "rdoff.h"
  26 #include "collectn.h"
  27
  28 extern int rdf_errno;
  29
  30 rdfmodule * rdfload(const char *filename)
  31 {
  32     rdfmodule   * f;
  33     long        bsslength = 0;
  34     char        * hdr;
  35     rdfheaderrec *r;
  36
  37     f = malloc(sizeof(rdfmodule));
  38     if (f == NULL)
  39     {
  40         rdf_errno = 6;          /* out of memory */
  41         return NULL;
  42     }
  43
  44     f->symtab = symtabNew();
  45     if (!f->symtab)
  46     {
  47         free(f);
  48         rdf_errno = 6;
  49         return NULL;
  50     }
  51
  52     /* open the file */
  53     if ( rdfopen( &(f->f), filename ) ) {
  54         free(f);
  55         return NULL;
  56     }
  57
  58     /* read in text and data segments, and header */
  59
  60     f->t = malloc (f->f.seg[0].length);
  61     f->d = malloc (f->f.seg[1].length); /* BSS seg allocated later */
  62     hdr = malloc (f->f.header_len);
  63
  64     if (! f->t || ! f->d || !hdr) {
  65         rdf_errno = 6;
  66         rdfclose(&f->f);
  67         if (f->t) free(f->t);
  68         if (f->d) free(f->d);
  69         free(f);
  70         return NULL;
  71     }
  72
  73     if ( rdfloadseg (&f->f,RDOFF_HEADER,hdr) ||
  74          rdfloadseg (&f->f,RDOFF_CODE,f->t) ||
  75          rdfloadseg (&f->f,RDOFF_DATA,f->d) )
  76     {
  77         rdfclose(&f->f);
  78         free(f->t);
  79         free(f->d);
  80         free(f);
  81         free(hdr);
  82         return NULL;
  83     }
  84
  85     rdfclose(&f->f);
  86
  87     /* Allocate BSS segment; step through header and count BSS records */
  88
  89     while ( ( r = rdfgetheaderrec (&f->f) ) )
  90     {
  91         if (r->type == 5)
  92             bsslength += r->b.amount;
  93     }
  94
  95     f->b = malloc ( bsslength );
  96     if (bsslength && (!f->b))
  97     {
  98         free(f->t);
  99         free(f->d);
 100         free(f);
 101         free(hdr);
 102         rdf_errno = 6;
 103         return NULL;
 104     }
 105
 106     rdfheaderrewind (&f->f);
 107
 108     f->textrel = (long)f->t;
 109     f->datarel = (long)f->d;
 110     f->bssrel  = (long)f->b;
 111
 112     return f;
 113 }
 114
 115 int rdf_relocate(rdfmodule * m)
 116 {
 117     rdfheaderrec        * r;
 118     Collection          imports;
 119     symtabEnt           e;
 120     long                rel;
 121     unsigned char       * seg;
 122
 123     rdfheaderrewind ( & m->f );
 124     collection_init(&imports);
 125
 126     while ( (r = rdfgetheaderrec ( & m->f ) ) )
 127     {
 128         switch (r->type)
 129         {
 130         case 1:         /* Relocation record */
 131
 132             /* calculate relocation factor */
 133
 134             if (r->r.refseg == 0) rel = m->textrel;
 135             else if (r->r.refseg == 1) rel = m->datarel;
 136             else if (r->r.refseg == 2) rel = m->bssrel;
 137             else
 138                 /* We currently do not support load-time linkage.
 139                    This should be added some time soon... */
 140
 141                 return 1;       /* return error code */
 142
 143             if ((r->r.segment & 63) == 0) seg = m->t;
 144             else if ((r->r.segment & 63) == 1) seg = m->d;
 145             else
 146                 continue;       /* relocation not in a loaded segment */
 147
 148             /* it doesn't matter in this case that the code is non-portable,
 149                as the entire concept of executing a module like this is
 150                non-portable */
 151             switch(r->r.length) {
 152             case 1:
 153                 seg[r->r.offset] += (char) rel;
 154                 break;
 155             case 2:
 156                 *(int16 *)(seg + r->r.offset) += (int16) rel;
 157                 break;
 158             case 4:
 159                 *(long *)(seg + r->r.offset) += rel;
 160                 break;
 161             }
 162             break;
 163
 164         case 3:                 /* export record - add to symtab */
 165             e.segment = r->e.segment;
 166             e.offset = r->e.offset +
 167                        (e.segment == 0 ? m->textrel : /* 0 -> code */
 168                         e.segment == 1 ? m->datarel : /* 1 -> data */
 169                                          m->bssrel) ; /* 2 -> bss  */
 170             e.flags = 0;
 171             e.name = malloc(strlen(r->e.label) + 1);
 172             if (! e.name)
 173                 return 1;
 174
 175             strcpy(e.name,r->e.label);
 176             symtabInsert(m->symtab,&e);
 177             break;
 178
 179         case 6:                 /* segment relocation */
 180             fprintf(stderr, "%s: segment relocation not supported by this "
 181                     "loader\n", m->f.name);
 182             return 1;
 183         }
 184     }
 185     return 0;
 186 }