bfd/coff-stgo32.c

   1 /* BFD back-end for Intel 386 COFF files (DJGPP variant with a stub).
   2    Copyright (C) 1997-2021 Free Software Foundation, Inc.
   3    Written by Robert Hoehne.
   4
   5    This file is part of BFD, the Binary File Descriptor library.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  20    MA 02110-1301, USA.  */
  21
  22 /* This file handles now also stubbed coff images. The stub is a small
  23    DOS executable program before the coff image to load it in memory
  24    and execute it. This is needed, because DOS cannot run coff files.
  25
  26    The COFF image is loaded in memory without the stub attached, so
  27    all offsets are relative to the beginning of the image, not the
  28    actual file.  We handle this in bfd by setting bfd->origin to where
  29    the COFF image starts.  */
  30
  31 #define TARGET_SYM              i386_coff_go32stubbed_vec
  32 #define TARGET_NAME             "coff-go32-exe"
  33 #define TARGET_UNDERSCORE       '_'
  34 #define COFF_GO32_EXE
  35 #define COFF_LONG_SECTION_NAMES
  36 #define COFF_SUPPORT_GNU_LINKONCE
  37 #define COFF_LONG_FILENAMES
  38
  39 #define COFF_SECTION_ALIGNMENT_ENTRIES \
  40 { COFF_SECTION_NAME_EXACT_MATCH (".data"), \
  41   COFF_ALIGNMENT_FIELD_EMPTY, COFF_ALIGNMENT_FIELD_EMPTY, 4 }, \
  42 { COFF_SECTION_NAME_EXACT_MATCH (".text"), \
  43   COFF_ALIGNMENT_FIELD_EMPTY, COFF_ALIGNMENT_FIELD_EMPTY, 4 }, \
  44 { COFF_SECTION_NAME_PARTIAL_MATCH (".debug"), \
  45   COFF_ALIGNMENT_FIELD_EMPTY, COFF_ALIGNMENT_FIELD_EMPTY, 0 }, \
  46 { COFF_SECTION_NAME_PARTIAL_MATCH (".gnu.linkonce.wi"), \
  47   COFF_ALIGNMENT_FIELD_EMPTY, COFF_ALIGNMENT_FIELD_EMPTY, 0 }
  48
  49 /* Section contains extended relocations. */
  50 #define IMAGE_SCN_LNK_NRELOC_OVFL (0x01000000)
  51
  52 #include "sysdep.h"
  53 #include "bfd.h"
  54 #include "coff/msdos.h"
  55
  56 static bfd_cleanup go32exe_check_format (bfd *);
  57 static bool go32exe_write_object_contents (bfd *);
  58 static bool go32exe_mkobject (bfd *);
  59 static bool go32exe_copy_private_bfd_data (bfd *, bfd *);
  60
  61 /* Defined in coff-go32.c.  */
  62 bool _bfd_go32_mkobject (bfd *);
  63 void _bfd_go32_swap_scnhdr_in (bfd *, void *, void *);
  64 unsigned int _bfd_go32_swap_scnhdr_out (bfd *, void *, void *);
  65
  66 #define COFF_CHECK_FORMAT go32exe_check_format
  67 #define COFF_WRITE_CONTENTS go32exe_write_object_contents
  68 #define coff_mkobject go32exe_mkobject
  69 #define coff_bfd_copy_private_bfd_data go32exe_copy_private_bfd_data
  70 #define coff_SWAP_scnhdr_in _bfd_go32_swap_scnhdr_in
  71 #define coff_SWAP_scnhdr_out _bfd_go32_swap_scnhdr_out
  72
  73 #include "coff-i386.c"
  74
  75 /* This macro is used, because I cannot assume the endianness of the
  76    host system.  */
  77 #define _H(index) (H_GET_16 (abfd, (header + index * 2)))
  78
  79 /* These bytes are a 2048-byte DOS executable, which loads the COFF
  80    image into memory and then runs it. It is called 'stub'.  */
  81 #define GO32EXE_DEFAULT_STUB_SIZE 2048
  82 static const unsigned char go32exe_default_stub[GO32EXE_DEFAULT_STUB_SIZE] =
  83 {
  84 #include "go32stub.h"
  85 };
  86
  87 /* Temporary location for stub read from input file.  */
  88 static char * go32exe_temp_stub = NULL;
  89 static bfd_size_type go32exe_temp_stub_size = 0;
  90
  91 /* That's the function, which creates the stub. There are
  92    different cases from where the stub is taken.
  93    At first the environment variable $(GO32STUB) is checked and then
  94    $(STUB) if it was not set.
  95    If it exists and points to a valid stub the stub is taken from
  96    that file. This file can be also a whole executable file, because
  97    the stub is computed from the exe information at the start of that
  98    file.
  99
 100    If there was any error, the standard stub (compiled in this file)
 101    is taken.
 102
 103    Ideally this function should exec '$(TARGET)-stubify' to generate
 104    a stub, like gcc does.  */
 105
 106 static void
 107 go32exe_create_stub (bfd *abfd)
 108 {
 109   /* Do it only once.  */
 110   if (coff_data (abfd)->stub == NULL)
 111     {
 112       char *stub;
 113       struct stat st;
 114       int f;
 115       unsigned char header[10];
 116       char magic[8];
 117       unsigned long coff_start;
 118       long exe_start;
 119
 120       /* If we read a stub from an input file, use that one.  */
 121       if (go32exe_temp_stub != NULL)
 122         {
 123           coff_data (abfd)->stub = bfd_alloc (abfd,
 124                                                   go32exe_temp_stub_size);
 125           if (coff_data (abfd)->stub == NULL)
 126             return;
 127           memcpy (coff_data (abfd)->stub, go32exe_temp_stub,
 128                   go32exe_temp_stub_size);
 129           coff_data (abfd)->stub_size = go32exe_temp_stub_size;
 130           free (go32exe_temp_stub);
 131           go32exe_temp_stub = NULL;
 132           go32exe_temp_stub_size = 0;
 133           return;
 134         }
 135
 136       /* Check at first the environment variable $(GO32STUB).  */
 137       stub = getenv ("GO32STUB");
 138       /* Now check the environment variable $(STUB).  */
 139       if (stub == NULL)
 140         stub = getenv ("STUB");
 141       if (stub == NULL)
 142         goto stub_end;
 143       if (stat (stub, &st) != 0)
 144         goto stub_end;
 145 #ifdef O_BINARY
 146       f = open (stub, O_RDONLY | O_BINARY);
 147 #else
 148       f = open (stub, O_RDONLY);
 149 #endif
 150       if (f < 0)
 151         goto stub_end;
 152       if (read (f, &header, sizeof (header)) < 0)
 153         {
 154           close (f);
 155           goto stub_end;
 156         }
 157       if (_H (0) != 0x5a4d)     /* It is not an exe file.  */
 158         {
 159           close (f);
 160           goto stub_end;
 161         }
 162       /* Compute the size of the stub (it is every thing up
 163          to the beginning of the coff image).  */
 164       coff_start = (long) _H (2) * 512L;
 165       if (_H (1))
 166         coff_start += (long) _H (1) - 512L;
 167
 168       exe_start = _H (4) * 16;
 169       if ((long) lseek (f, exe_start, SEEK_SET) != exe_start)
 170         {
 171           close (f);
 172           goto stub_end;
 173         }
 174       if (read (f, &magic, 8) != 8)
 175         {
 176           close (f);
 177           goto stub_end;
 178         }
 179       if (! startswith (magic, "go32stub"))
 180         {
 181           close (f);
 182           goto stub_end;
 183         }
 184       /* Now we found a correct stub (hopefully).  */
 185       coff_data (abfd)->stub = bfd_alloc (abfd, (bfd_size_type) coff_start);
 186       if (coff_data (abfd)->stub == NULL)
 187         {
 188           close (f);
 189           return;
 190         }
 191       lseek (f, 0L, SEEK_SET);
 192       if ((unsigned long) read (f, coff_data (abfd)->stub, coff_start)
 193           != coff_start)
 194         {
 195           bfd_release (abfd, coff_data (abfd)->stub);
 196           coff_data (abfd)->stub = NULL;
 197         }
 198       else
 199         coff_data (abfd)->stub_size = coff_start;
 200       close (f);
 201     }
 202  stub_end:
 203   /* There was something wrong above, so use now the standard builtin
 204      stub.  */
 205   if (coff_data (abfd)->stub == NULL)
 206     {
 207       coff_data (abfd)->stub
 208         = bfd_alloc (abfd, (bfd_size_type) GO32EXE_DEFAULT_STUB_SIZE);
 209       if (coff_data (abfd)->stub == NULL)
 210         return;
 211       memcpy (coff_data (abfd)->stub, go32exe_default_stub,
 212               GO32EXE_DEFAULT_STUB_SIZE);
 213       coff_data (abfd)->stub_size = GO32EXE_DEFAULT_STUB_SIZE;
 214     }
 215 }
 216
 217 /* If ibfd was a stubbed coff image, copy the stub from that bfd
 218    to the new obfd.  */
 219
 220 static bool
 221 go32exe_copy_private_bfd_data (bfd *ibfd, bfd *obfd)
 222 {
 223   /* Check if both are the same targets.  */
 224   if (ibfd->xvec != obfd->xvec)
 225     return true;
 226
 227   /* Make sure we have a source stub.  */
 228   BFD_ASSERT (coff_data (ibfd)->stub != NULL);
 229
 230   /* Reallocate the output stub if necessary.  */
 231   if (coff_data (ibfd)->stub_size > coff_data (obfd)->stub_size)
 232     coff_data (obfd)->stub = bfd_alloc (obfd, coff_data (ibfd)->stub_size);
 233   if (coff_data (obfd)->stub == NULL)
 234     return false;
 235
 236   /* Now copy the stub.  */
 237   memcpy (coff_data (obfd)->stub, coff_data (ibfd)->stub,
 238           coff_data (ibfd)->stub_size);
 239   coff_data (obfd)->stub_size = coff_data (ibfd)->stub_size;
 240   obfd->origin = coff_data (obfd)->stub_size;
 241
 242   return true;
 243 }
 244
 245 /* Cleanup function, returned from check_format hook.  */
 246
 247 static void
 248 go32exe_cleanup (bfd *abfd)
 249 {
 250   abfd->origin = 0;
 251
 252   free (go32exe_temp_stub);
 253   go32exe_temp_stub = NULL;
 254   go32exe_temp_stub_size = 0;
 255 }
 256
 257 /* Check that there is a GO32 stub and read it to go32exe_temp_stub.
 258    Then set abfd->origin so that the COFF image is read at the correct
 259    file offset.  */
 260
 261 static bfd_cleanup
 262 go32exe_check_format (bfd *abfd)
 263 {
 264   struct external_DOS_hdr filehdr_dos;
 265   uint16_t num_pages;
 266   uint16_t last_page_size;
 267   uint32_t header_end;
 268   bfd_size_type stubsize;
 269
 270   /* This format can not appear in an archive.  */
 271   if (abfd->origin != 0)
 272     {
 273       bfd_set_error (bfd_error_wrong_format);
 274       return NULL;
 275     }
 276
 277   bfd_set_error (bfd_error_system_call);
 278
 279   /* Read in the stub file header, which is a DOS MZ executable.  */
 280   if (bfd_bread (&filehdr_dos, DOS_HDR_SIZE, abfd) != DOS_HDR_SIZE)
 281     goto fail;
 282
 283   /* Make sure that this is an MZ executable.  */
 284   if (H_GET_16 (abfd, filehdr_dos.e_magic) != IMAGE_DOS_SIGNATURE)
 285     goto fail_format;
 286
 287   /* Determine the size of the stub  */
 288   num_pages = H_GET_16 (abfd, filehdr_dos.e_cp);
 289   last_page_size = H_GET_16 (abfd, filehdr_dos.e_cblp);
 290   stubsize = num_pages * 512;
 291   if (last_page_size != 0)
 292     stubsize += last_page_size - 512;
 293
 294   /* Save now the stub to be used later.  Put the stub data to a temporary
 295      location first as tdata still does not exist.  It may not even
 296      be ever created if we are just checking the file format of ABFD.  */
 297   bfd_seek (abfd, 0, SEEK_SET);
 298   go32exe_temp_stub = bfd_malloc (stubsize);
 299   if (go32exe_temp_stub == NULL)
 300     goto fail;
 301   if (bfd_bread (go32exe_temp_stub, stubsize, abfd) != stubsize)
 302     goto fail;
 303   go32exe_temp_stub_size = stubsize;
 304
 305   /* Confirm that this is a go32stub.  */
 306   header_end = H_GET_16 (abfd, filehdr_dos.e_cparhdr) * 16UL;
 307   if (go32exe_temp_stub_size < header_end
 308       || go32exe_temp_stub_size - header_end < sizeof "go32stub" - 1
 309       || !startswith (go32exe_temp_stub + header_end, "go32stub"))
 310     goto fail_format;
 311
 312   /* Set origin to where the COFF header starts and seek there.  */
 313   abfd->origin = stubsize;
 314   if (bfd_seek (abfd, 0, SEEK_SET) != 0)
 315     goto fail;
 316
 317   /* Call coff_object_p to read the COFF image.  If this fails then the file
 318      must be just a stub with no COFF data attached.  */
 319   bfd_cleanup cleanup = coff_object_p (abfd);
 320   if (cleanup == NULL)
 321     goto fail;
 322   BFD_ASSERT (cleanup == _bfd_no_cleanup);
 323
 324   return go32exe_cleanup;
 325
 326  fail_format:
 327   bfd_set_error (bfd_error_wrong_format);
 328  fail:
 329   go32exe_cleanup (abfd);
 330   return NULL;
 331 }
 332
 333 /* Write the stub to the output file, then call coff_write_object_contents.  */
 334
 335 static bool
 336 go32exe_write_object_contents (bfd *abfd)
 337 {
 338   const bfd_size_type pos = bfd_tell (abfd);
 339   const bfd_size_type stubsize = coff_data (abfd)->stub_size;
 340
 341   BFD_ASSERT (stubsize != 0);
 342
 343   bfd_set_error (bfd_error_system_call);
 344
 345   /* Write the stub.  */
 346   abfd->origin = 0;
 347   if (bfd_seek (abfd, 0, SEEK_SET) != 0)
 348     return false;
 349   if (bfd_bwrite (coff_data (abfd)->stub, stubsize, abfd) != stubsize)
 350     return false;
 351
 352   /* Seek back to where we were.  */
 353   abfd->origin = stubsize;
 354   if (bfd_seek (abfd, pos, SEEK_SET) != 0)
 355     return false;
 356
 357   return coff_write_object_contents (abfd);
 358 }
 359
 360 /* mkobject hook.  Called directly through bfd_set_format or via
 361    coff_mkobject_hook etc from bfd_check_format.  */
 362
 363 static bool
 364 go32exe_mkobject (bfd *abfd)
 365 {
 366   /* Don't output to an archive.  */
 367   if (abfd->my_archive != NULL)
 368     return false;
 369
 370   if (!_bfd_go32_mkobject (abfd))
 371     return false;
 372
 373   go32exe_create_stub (abfd);
 374   if (coff_data (abfd)->stub == NULL)
 375     {
 376       bfd_release (abfd, coff_data (abfd));
 377       return false;
 378     }
 379   abfd->origin = coff_data (abfd)->stub_size;
 380
 381   return true;
 382 }