bfd/i386msdos.c

   1 /* BFD back-end for MS-DOS executables.
   2    Copyright (C) 1990-2024 Free Software Foundation, Inc.
   3    Written by Bryan Ford of the University of Utah.
   4
   5    Contributed by the Center for Software Science at the
   6    University of Utah (pa-gdb-bugs@cs.utah.edu).
   7
   8    This file is part of BFD, the Binary File Descriptor library.
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 3 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program; if not, write to the Free Software
  22    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  23    MA 02110-1301, USA.  */
  24
  25
  26 #include "sysdep.h"
  27 #include "bfd.h"
  28 #include "libbfd.h"
  29 #include "libaout.h"
  30 #include "coff/msdos.h"
  31
  32 #define EXE_LOAD_HIGH   0x0000
  33 #define EXE_LOAD_LOW    0xffff
  34 #define EXE_PAGE_SIZE   512
  35
  36 static bool
  37 msdos_mkobject (bfd *abfd)
  38 {
  39   bfd_default_set_arch_mach (abfd, bfd_arch_i386, bfd_mach_i386_i8086);
  40
  41   return aout_32_mkobject (abfd);
  42 }
  43
  44 static bfd_cleanup
  45 msdos_object_p (bfd *abfd)
  46 {
  47   struct external_DOS_hdr hdr;
  48   bfd_byte buffer[2];
  49   asection *section;
  50   bfd_size_type size;
  51
  52   if (bfd_seek (abfd, 0, SEEK_SET) != 0
  53       || (size = bfd_read (&hdr, sizeof (hdr), abfd)) + 1 < DOS_HDR_SIZE + 1)
  54     {
  55       if (bfd_get_error () != bfd_error_system_call)
  56         bfd_set_error (bfd_error_wrong_format);
  57       return NULL;
  58     }
  59
  60   if (H_GET_16 (abfd, hdr.e_magic) != IMAGE_DOS_SIGNATURE)
  61     {
  62       bfd_set_error (bfd_error_wrong_format);
  63       return NULL;
  64     }
  65
  66   /* Check that this isn't actually a PE, NE, or LE file. If it is, the
  67      e_lfanew field will be valid and point to a header beginning with one of
  68      the relevant signatures.  If not, e_lfanew might point to anything, so
  69      don't bail if we can't read there.  */
  70   if (size < offsetof (struct external_DOS_hdr, e_lfanew) + 4
  71       || H_GET_16 (abfd, hdr.e_cparhdr) < 4)
  72     ;
  73   else if (bfd_seek (abfd, H_GET_32 (abfd, hdr.e_lfanew), SEEK_SET) != 0
  74            || bfd_read (buffer, 2, abfd) != 2)
  75     {
  76       if (bfd_get_error () == bfd_error_system_call)
  77         return NULL;
  78     }
  79   else
  80     {
  81       if (H_GET_16 (abfd, buffer) == IMAGE_NT_SIGNATURE
  82           || H_GET_16 (abfd, buffer) == IMAGE_OS2_SIGNATURE
  83           || H_GET_16 (abfd, buffer) == IMAGE_OS2_SIGNATURE_LE
  84           || H_GET_16 (abfd, buffer) == IMAGE_OS2_SIGNATURE_LX)
  85         {
  86           bfd_set_error (bfd_error_wrong_format);
  87           return NULL;
  88         }
  89     }
  90
  91   if (!msdos_mkobject (abfd))
  92     return NULL;
  93
  94   abfd->flags = EXEC_P;
  95   abfd->start_address = H_GET_16 (abfd, hdr.e_ip);
  96
  97   section = bfd_make_section (abfd, ".text");
  98   if (section == NULL)
  99     return NULL;
 100
 101   section->flags = (SEC_ALLOC | SEC_LOAD | SEC_CODE | SEC_HAS_CONTENTS);
 102   section->filepos = H_GET_16 (abfd, hdr.e_cparhdr) * 16;
 103   size = (H_GET_16 (abfd, hdr.e_cp) - 1) * EXE_PAGE_SIZE - section->filepos;
 104   size += H_GET_16 (abfd, hdr.e_cblp);
 105
 106   /* Check that the size is valid.  */
 107   if (bfd_seek (abfd, section->filepos + size, SEEK_SET) != 0)
 108     {
 109       if (bfd_get_error () != bfd_error_system_call)
 110         bfd_set_error (bfd_error_wrong_format);
 111       return NULL;
 112     }
 113
 114   bfd_set_section_size (section, size);
 115   section->alignment_power = 4;
 116
 117   return _bfd_no_cleanup;
 118 }
 119
 120 static int
 121 msdos_sizeof_headers (bfd *abfd ATTRIBUTE_UNUSED,
 122                       struct bfd_link_info *info ATTRIBUTE_UNUSED)
 123 {
 124   return 0;
 125 }
 126
 127 static bool
 128 msdos_write_object_contents (bfd *abfd)
 129 {
 130   static char hdr[EXE_PAGE_SIZE];
 131   file_ptr outfile_size = sizeof(hdr);
 132   bfd_vma high_vma = 0;
 133   asection *sec;
 134
 135   /* Find the total size of the program on disk and in memory.  */
 136   for (sec = abfd->sections; sec != (asection *) NULL; sec = sec->next)
 137     {
 138       if (sec->size == 0)
 139         continue;
 140       if (bfd_section_flags (sec) & SEC_ALLOC)
 141         {
 142           bfd_vma sec_vma = bfd_section_vma (sec) + sec->size;
 143           if (sec_vma > high_vma)
 144             high_vma = sec_vma;
 145         }
 146       if (bfd_section_flags (sec) & SEC_LOAD)
 147         {
 148           file_ptr sec_end = (sizeof (hdr)
 149                               + bfd_section_vma (sec)
 150                               + sec->size);
 151           if (sec_end > outfile_size)
 152             outfile_size = sec_end;
 153         }
 154     }
 155
 156   /* Make sure the program isn't too big.  */
 157   if (high_vma > (bfd_vma)0xffff)
 158     {
 159       bfd_set_error(bfd_error_file_too_big);
 160       return false;
 161     }
 162
 163   /* Constants.  */
 164   H_PUT_16 (abfd, IMAGE_DOS_SIGNATURE, &hdr[0]);
 165   H_PUT_16 (abfd, EXE_PAGE_SIZE / 16, &hdr[8]);
 166   H_PUT_16 (abfd, EXE_LOAD_LOW, &hdr[12]);
 167   H_PUT_16 (abfd, 0x3e, &hdr[24]);
 168   H_PUT_16 (abfd, 0x0001, &hdr[28]); /* XXX??? */
 169   H_PUT_16 (abfd, 0x30fb, &hdr[30]); /* XXX??? */
 170   H_PUT_16 (abfd, 0x726a, &hdr[32]); /* XXX??? */
 171
 172   /* Bytes in last page (0 = full page).  */
 173   H_PUT_16 (abfd, outfile_size & (EXE_PAGE_SIZE - 1), &hdr[2]);
 174
 175   /* Number of pages.  */
 176   H_PUT_16 (abfd, (outfile_size + EXE_PAGE_SIZE - 1) / EXE_PAGE_SIZE, &hdr[4]);
 177
 178   /* Set the initial stack pointer to the end of the bss.
 179      The program's crt0 code must relocate it to a real stack.  */
 180   H_PUT_16 (abfd, high_vma, &hdr[16]);
 181
 182   if (bfd_seek (abfd, 0, SEEK_SET) != 0
 183       || bfd_write (hdr, sizeof (hdr), abfd) != sizeof (hdr))
 184     return false;
 185
 186   return true;
 187 }
 188
 189 static bool
 190 msdos_set_section_contents (bfd *abfd,
 191                             sec_ptr section,
 192                             const void *location,
 193                             file_ptr offset,
 194                             bfd_size_type count)
 195 {
 196
 197   if (count == 0)
 198     return true;
 199
 200   section->filepos = EXE_PAGE_SIZE + bfd_section_vma (section);
 201
 202   if (bfd_section_flags (section) & SEC_LOAD)
 203     {
 204       if (bfd_seek (abfd, section->filepos + offset, SEEK_SET) != 0
 205           || bfd_write (location, count, abfd) != count)
 206         return false;
 207     }
 208
 209   return true;
 210 }
 211
 212
 213
 214 #define msdos_make_empty_symbol aout_32_make_empty_symbol
 215 #define msdos_bfd_reloc_type_lookup aout_32_reloc_type_lookup
 216 #define msdos_bfd_reloc_name_lookup aout_32_reloc_name_lookup
 217
 218 #define msdos_close_and_cleanup _bfd_generic_close_and_cleanup
 219 #define msdos_bfd_free_cached_info _bfd_generic_bfd_free_cached_info
 220 #define msdos_new_section_hook _bfd_generic_new_section_hook
 221 #define msdos_get_section_contents _bfd_generic_get_section_contents
 222 #define msdos_get_section_contents_in_window \
 223   _bfd_generic_get_section_contents_in_window
 224 #define msdos_bfd_get_relocated_section_contents \
 225   bfd_generic_get_relocated_section_contents
 226 #define msdos_bfd_relax_section bfd_generic_relax_section
 227 #define msdos_bfd_gc_sections bfd_generic_gc_sections
 228 #define msdos_bfd_lookup_section_flags bfd_generic_lookup_section_flags
 229 #define msdos_bfd_merge_sections bfd_generic_merge_sections
 230 #define msdos_bfd_is_group_section bfd_generic_is_group_section
 231 #define msdos_bfd_group_name bfd_generic_group_name
 232 #define msdos_bfd_discard_group bfd_generic_discard_group
 233 #define msdos_section_already_linked \
 234   _bfd_generic_section_already_linked
 235 #define msdos_bfd_define_common_symbol bfd_generic_define_common_symbol
 236 #define msdos_bfd_link_hide_symbol _bfd_generic_link_hide_symbol
 237 #define msdos_bfd_define_start_stop bfd_generic_define_start_stop
 238 #define msdos_bfd_link_hash_table_create _bfd_generic_link_hash_table_create
 239 #define msdos_bfd_link_add_symbols _bfd_generic_link_add_symbols
 240 #define msdos_bfd_link_just_syms _bfd_generic_link_just_syms
 241 #define msdos_bfd_copy_link_hash_symbol_type \
 242   _bfd_generic_copy_link_hash_symbol_type
 243 #define msdos_bfd_final_link _bfd_generic_final_link
 244 #define msdos_bfd_link_split_section _bfd_generic_link_split_section
 245 #define msdos_set_arch_mach _bfd_generic_set_arch_mach
 246 #define msdos_bfd_link_check_relocs _bfd_generic_link_check_relocs
 247
 248 #define msdos_get_symtab_upper_bound _bfd_nosymbols_get_symtab_upper_bound
 249 #define msdos_canonicalize_symtab _bfd_nosymbols_canonicalize_symtab
 250 #define msdos_print_symbol _bfd_nosymbols_print_symbol
 251 #define msdos_get_symbol_info _bfd_nosymbols_get_symbol_info
 252 #define msdos_get_symbol_version_string \
 253   _bfd_nosymbols_get_symbol_version_string
 254 #define msdos_find_nearest_line _bfd_nosymbols_find_nearest_line
 255 #define msdos_find_nearest_line_with_alt _bfd_nosymbols_find_nearest_line_with_alt
 256 #define msdos_find_line _bfd_nosymbols_find_line
 257 #define msdos_find_inliner_info _bfd_nosymbols_find_inliner_info
 258 #define msdos_get_lineno _bfd_nosymbols_get_lineno
 259 #define msdos_bfd_is_target_special_symbol _bfd_bool_bfd_asymbol_false
 260 #define msdos_bfd_is_local_label_name _bfd_nosymbols_bfd_is_local_label_name
 261 #define msdos_bfd_make_debug_symbol _bfd_nosymbols_bfd_make_debug_symbol
 262 #define msdos_read_minisymbols _bfd_nosymbols_read_minisymbols
 263 #define msdos_minisymbol_to_symbol _bfd_nosymbols_minisymbol_to_symbol
 264
 265 #define msdos_canonicalize_reloc _bfd_norelocs_canonicalize_reloc
 266 #define msdos_set_reloc _bfd_norelocs_set_reloc
 267 #define msdos_get_reloc_upper_bound _bfd_norelocs_get_reloc_upper_bound
 268 #define msdos_32_bfd_link_split_section  _bfd_generic_link_split_section
 269
 270 const bfd_target i386_msdos_vec =
 271   {
 272     "msdos",                    /* name */
 273     bfd_target_msdos_flavour,
 274     BFD_ENDIAN_LITTLE,          /* target byte order */
 275     BFD_ENDIAN_LITTLE,          /* target headers byte order */
 276     (EXEC_P),                   /* object flags */
 277     (SEC_CODE | SEC_DATA | SEC_HAS_CONTENTS
 278      | SEC_ALLOC | SEC_LOAD),   /* section flags */
 279     0,                          /* leading underscore */
 280     ' ',                                /* ar_pad_char */
 281     16,                         /* ar_max_namelen */
 282     0,                          /* match priority.  */
 283     TARGET_KEEP_UNUSED_SECTION_SYMBOLS, /* keep unused section symbols.  */
 284     bfd_getl64, bfd_getl_signed_64, bfd_putl64,
 285     bfd_getl32, bfd_getl_signed_32, bfd_putl32,
 286     bfd_getl16, bfd_getl_signed_16, bfd_putl16, /* data */
 287     bfd_getl64, bfd_getl_signed_64, bfd_putl64,
 288     bfd_getl32, bfd_getl_signed_32, bfd_putl32,
 289     bfd_getl16, bfd_getl_signed_16, bfd_putl16, /* hdrs */
 290
 291     {
 292       _bfd_dummy_target,
 293       msdos_object_p,           /* bfd_check_format */
 294       _bfd_dummy_target,
 295       _bfd_dummy_target,
 296     },
 297     {
 298       _bfd_bool_bfd_false_error,
 299       msdos_mkobject,
 300       _bfd_generic_mkarchive,
 301       _bfd_bool_bfd_false_error,
 302     },
 303     {                           /* bfd_write_contents */
 304       _bfd_bool_bfd_false_error,
 305       msdos_write_object_contents,
 306       _bfd_write_archive_contents,
 307       _bfd_bool_bfd_false_error,
 308     },
 309
 310     BFD_JUMP_TABLE_GENERIC (msdos),
 311     BFD_JUMP_TABLE_COPY (_bfd_generic),
 312     BFD_JUMP_TABLE_CORE (_bfd_nocore),
 313     BFD_JUMP_TABLE_ARCHIVE (_bfd_noarchive),
 314     BFD_JUMP_TABLE_SYMBOLS (msdos),
 315     BFD_JUMP_TABLE_RELOCS (msdos),
 316     BFD_JUMP_TABLE_WRITE (msdos),
 317     BFD_JUMP_TABLE_LINK (msdos),
 318     BFD_JUMP_TABLE_DYNAMIC (_bfd_nodynamic),
 319
 320     NULL,
 321
 322     NULL
 323   };
 324
 325