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 int32_t
   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 <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23
  24 #include "rdfload.h"
  25 #include "symtab.h"
  26 #include "collectn.h"
  27
  28 extern int rdf_errno;
  29
  30 rdfmodule *rdfload(const char *filename)
  31 {
  32     rdfmodule *f;
  33     int32_t bsslength = 0;
  34     char *hdr;
  35     rdfheaderrec *r;
  36
  37     f = malloc(sizeof(rdfmodule));
  38     if (f == NULL) {
  39         rdf_errno = RDF_ERR_NOMEM;
  40         return NULL;
  41     }
  42
  43     f->symtab = symtabNew();
  44     if (!f->symtab) {
  45         free(f);
  46         rdf_errno = RDF_ERR_NOMEM;
  47         return NULL;
  48     }
  49
  50     /* open the file */
  51     if (rdfopen(&(f->f), filename)) {
  52         free(f);
  53         return NULL;
  54     }
  55
  56     /* read in text and data segments, and header */
  57
  58     f->t = malloc(f->f.seg[0].length);
  59     f->d = malloc(f->f.seg[1].length);  /* BSS seg allocated later */
  60     hdr = malloc(f->f.header_len);
  61
  62     if (!f->t || !f->d || !hdr) {
  63         rdf_errno = RDF_ERR_NOMEM;
  64         rdfclose(&f->f);
  65         if (f->t)
  66             free(f->t);
  67         if (f->d)
  68             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         rdfclose(&f->f);
  77         free(f->t);
  78         free(f->d);
  79         free(f);
  80         free(hdr);
  81         return NULL;
  82     }
  83
  84     rdfclose(&f->f);
  85
  86     /* Allocate BSS segment; step through header and count BSS records */
  87
  88     while ((r = rdfgetheaderrec(&f->f))) {
  89         if (r->type == 5)
  90             bsslength += r->b.amount;
  91     }
  92
  93     f->b = malloc(bsslength);
  94     if (bsslength && (!f->b)) {
  95         free(f->t);
  96         free(f->d);
  97         free(f);
  98         free(hdr);
  99         rdf_errno = RDF_ERR_NOMEM;
 100         return NULL;
 101     }
 102
 103     rdfheaderrewind(&f->f);
 104
 105     f->textrel = (int32_t)f->t;
 106     f->datarel = (int32_t)f->d;
 107     f->bssrel = (int32_t)f->b;
 108
 109     return f;
 110 }
 111
 112 int rdf_relocate(rdfmodule * m)
 113 {
 114     rdfheaderrec *r;
 115     Collection imports;
 116     symtabEnt e;
 117     int32_t rel;
 118     uint8_t *seg;
 119
 120     rdfheaderrewind(&m->f);
 121     collection_init(&imports);
 122
 123     while ((r = rdfgetheaderrec(&m->f))) {
 124         switch (r->type) {
 125         case 1:                /* Relocation record */
 126
 127             /* calculate relocation factor */
 128
 129             if (r->r.refseg == 0)
 130                 rel = m->textrel;
 131             else if (r->r.refseg == 1)
 132                 rel = m->datarel;
 133             else if (r->r.refseg == 2)
 134                 rel = m->bssrel;
 135             else
 136                 /* We currently do not support load-time linkage.
 137                    This should be added some time soon... */
 138
 139                 return 1;       /* return error code */
 140
 141             if ((r->r.segment & 63) == 0)
 142                 seg = m->t;
 143             else if ((r->r.segment & 63) == 1)
 144                 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                 *(uint16_t *) (seg + r->r.offset) += (uint16_t) rel;
 157                 break;
 158             case 4:
 159                 *(int32_t *)(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 + (e.segment == 0 ? m->textrel :     /* 0 -> code */
 167                                       e.segment == 1 ? m->datarel :     /* 1 -> data */
 168                                       m->bssrel);       /* 2 -> bss  */
 169             e.flags = 0;
 170             e.name = malloc(strlen(r->e.label) + 1);
 171             if (!e.name)
 172                 return 1;
 173
 174             strcpy(e.name, r->e.label);
 175             symtabInsert(m->symtab, &e);
 176             break;
 177
 178         case 6:                /* segment relocation */
 179             fprintf(stderr, "%s: segment relocation not supported by this "
 180                     "loader\n", m->f.name);
 181             return 1;
 182         }
 183     }
 184     return 0;
 185 }