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
msdos_mkobject(bfd * abfd)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
msdos_object_p(bfd * abfd)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
msdos_sizeof_headers(bfd * abfd ATTRIBUTE_UNUSED,struct bfd_link_info * info ATTRIBUTE_UNUSED)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
msdos_write_object_contents(bfd * abfd)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
msdos_set_section_contents(bfd * abfd,sec_ptr section,const void * location,file_ptr offset,bfd_size_type count)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
326