gdb/gdb_bfd.c

   1 /* Definitions for BFD wrappers used by GDB.
   2
   3    Copyright (C) 2011, 2012
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "gdb_bfd.h"
  23 #include "gdb_assert.h"
  24 #include "gdb_string.h"
  25 #include "hashtab.h"
  26 #ifdef HAVE_ZLIB_H
  27 #include <zlib.h>
  28 #endif
  29 #ifdef HAVE_MMAP
  30 #include <sys/mman.h>
  31 #ifndef MAP_FAILED
  32 #define MAP_FAILED ((void *) -1)
  33 #endif
  34 #endif
  35
  36 /* An object of this type is stored in the section's user data when
  37    mapping a section.  */
  38
  39 struct gdb_bfd_section_data
  40 {
  41   /* Size of the data.  */
  42   bfd_size_type size;
  43   /* If the data was mmapped, this is the length of the map.  */
  44   bfd_size_type map_len;
  45   /* The data.  If NULL, the section data has not been read.  */
  46   void *data;
  47   /* If the data was mmapped, this is the map address.  */
  48   void *map_addr;
  49 };
  50
  51 /* See gdb_bfd.h.  */
  52
  53 void
  54 gdb_bfd_stash_filename (struct bfd *abfd)
  55 {
  56   char *name = bfd_get_filename (abfd);
  57   char *data;
  58
  59   data = bfd_alloc (abfd, strlen (name) + 1);
  60   strcpy (data, name);
  61
  62   /* Unwarranted chumminess with BFD.  */
  63   abfd->filename = data;
  64 }
  65
  66 /* An object of this type is stored in each BFD's user data.  */
  67
  68 struct gdb_bfd_data
  69 {
  70   /* The reference count.  */
  71   int refc;
  72
  73   /* The mtime of the BFD at the point the cache entry was made.  */
  74   time_t mtime;
  75 };
  76
  77 /* A hash table storing all the BFDs maintained in the cache.  */
  78
  79 static htab_t gdb_bfd_cache;
  80
  81 /* The type of an object being looked up in gdb_bfd_cache.  We use
  82    htab's capability of storing one kind of object (BFD in this case)
  83    and using a different sort of object for searching.  */
  84
  85 struct gdb_bfd_cache_search
  86 {
  87   /* The filename.  */
  88   const char *filename;
  89   /* The mtime.  */
  90   time_t mtime;
  91 };
  92
  93 /* A hash function for BFDs.  */
  94
  95 static hashval_t
  96 hash_bfd (const void *b)
  97 {
  98   const bfd *abfd = b;
  99
 100   /* It is simplest to just hash the filename.  */
 101   return htab_hash_string (bfd_get_filename (abfd));
 102 }
 103
 104 /* An equality function for BFDs.  Note that this expects the caller
 105    to search using struct gdb_bfd_cache_search only, not BFDs.  */
 106
 107 static int
 108 eq_bfd (const void *a, const void *b)
 109 {
 110   const bfd *abfd = a;
 111   const struct gdb_bfd_cache_search *s = b;
 112   struct gdb_bfd_data *gdata = bfd_usrdata (abfd);
 113
 114   return (gdata->mtime == s->mtime
 115           && strcmp (bfd_get_filename (abfd), s->filename) == 0);
 116 }
 117
 118 /* See gdb_bfd.h.  */
 119
 120 struct bfd *
 121 gdb_bfd_open (const char *name, const char *target, int fd)
 122 {
 123   hashval_t hash;
 124   void **slot;
 125   bfd *abfd;
 126   struct gdb_bfd_cache_search search;
 127   struct stat st;
 128
 129   if (gdb_bfd_cache == NULL)
 130     gdb_bfd_cache = htab_create_alloc (1, hash_bfd, eq_bfd, NULL,
 131                                        xcalloc, xfree);
 132
 133   if (fd == -1)
 134     {
 135       fd = open (name, O_RDONLY | O_BINARY);
 136       if (fd == -1)
 137         {
 138           bfd_set_error (bfd_error_system_call);
 139           return NULL;
 140         }
 141     }
 142
 143   search.filename = name;
 144   if (fstat (fd, &st) < 0)
 145     {
 146       /* Weird situation here.  */
 147       search.mtime = 0;
 148     }
 149   else
 150     search.mtime = st.st_mtime;
 151
 152   /* Note that this must compute the same result as hash_bfd.  */
 153   hash = htab_hash_string (name);
 154   /* Note that we cannot use htab_find_slot_with_hash here, because
 155      opening the BFD may fail; and this would violate hashtab
 156      invariants.  */
 157   abfd = htab_find_with_hash (gdb_bfd_cache, &search, hash);
 158   if (abfd != NULL)
 159     {
 160       close (fd);
 161       return gdb_bfd_ref (abfd);
 162     }
 163
 164   abfd = bfd_fopen (name, target, FOPEN_RB, fd);
 165   if (abfd == NULL)
 166     return NULL;
 167
 168   slot = htab_find_slot_with_hash (gdb_bfd_cache, &search, hash, INSERT);
 169   gdb_assert (!*slot);
 170   *slot = abfd;
 171
 172   gdb_bfd_stash_filename (abfd);
 173   return gdb_bfd_ref (abfd);
 174 }
 175
 176 /* A helper function that releases any section data attached to the
 177    BFD.  */
 178
 179 static void
 180 free_one_bfd_section (bfd *abfd, asection *sectp, void *ignore)
 181 {
 182   struct gdb_bfd_section_data *sect = bfd_get_section_userdata (abfd, sectp);
 183
 184   if (sect != NULL && sect->data != NULL)
 185     {
 186 #ifdef HAVE_MMAP
 187       if (sect->map_addr != NULL)
 188         {
 189           int res;
 190
 191           res = munmap (sect->map_addr, sect->map_len);
 192           gdb_assert (res == 0);
 193         }
 194       else
 195 #endif
 196         xfree (sect->data);
 197     }
 198 }
 199
 200 /* Close ABFD, and warn if that fails.  */
 201
 202 static int
 203 gdb_bfd_close_or_warn (struct bfd *abfd)
 204 {
 205   int ret;
 206   char *name = bfd_get_filename (abfd);
 207
 208   bfd_map_over_sections (abfd, free_one_bfd_section, NULL);
 209
 210   ret = bfd_close (abfd);
 211
 212   if (!ret)
 213     warning (_("cannot close \"%s\": %s"),
 214              name, bfd_errmsg (bfd_get_error ()));
 215
 216   return ret;
 217 }
 218
 219 /* Add reference to ABFD.  Returns ABFD.  */
 220
 221 struct bfd *
 222 gdb_bfd_ref (struct bfd *abfd)
 223 {
 224   struct gdb_bfd_data *gdata;
 225
 226   if (abfd == NULL)
 227     return NULL;
 228
 229   gdata = bfd_usrdata (abfd);
 230
 231   if (gdata != NULL)
 232     {
 233       gdata->refc += 1;
 234       return abfd;
 235     }
 236
 237   gdata = bfd_zalloc (abfd, sizeof (struct gdb_bfd_data));
 238   gdata->refc = 1;
 239   gdata->mtime = bfd_get_mtime (abfd);
 240   bfd_usrdata (abfd) = gdata;
 241
 242   return abfd;
 243 }
 244
 245 /* Unreference and possibly close ABFD.  */
 246
 247 void
 248 gdb_bfd_unref (struct bfd *abfd)
 249 {
 250   struct gdb_bfd_data *gdata;
 251   struct gdb_bfd_cache_search search;
 252
 253   if (abfd == NULL)
 254     return;
 255
 256   gdata = bfd_usrdata (abfd);
 257   gdb_assert (gdata->refc >= 1);
 258
 259   gdata->refc -= 1;
 260   if (gdata->refc > 0)
 261     return;
 262
 263   search.filename = bfd_get_filename (abfd);
 264
 265   if (gdb_bfd_cache && search.filename)
 266     {
 267       hashval_t hash = htab_hash_string (search.filename);
 268       void **slot;
 269
 270       search.mtime = gdata->mtime;
 271       slot = htab_find_slot_with_hash (gdb_bfd_cache, &search, hash,
 272                                        NO_INSERT);
 273
 274       if (slot && *slot)
 275         htab_clear_slot (gdb_bfd_cache, slot);
 276     }
 277
 278   bfd_usrdata (abfd) = NULL;  /* Paranoia.  */
 279
 280   gdb_bfd_close_or_warn (abfd);
 281 }
 282
 283 /* A helper function that returns the section data descriptor
 284    associated with SECTION.  If no such descriptor exists, a new one
 285    is allocated and cleared.  */
 286
 287 static struct gdb_bfd_section_data *
 288 get_section_descriptor (asection *section)
 289 {
 290   struct gdb_bfd_section_data *result;
 291
 292   result = bfd_get_section_userdata (section->owner, section);
 293
 294   if (result == NULL)
 295     {
 296       result = bfd_zalloc (section->owner, sizeof (*result));
 297       bfd_set_section_userdata (section->owner, section, result);
 298     }
 299
 300   return result;
 301 }
 302
 303 /* Decompress a section that was compressed using zlib.  Store the
 304    decompressed buffer, and its size, in DESCRIPTOR.  */
 305
 306 static void
 307 zlib_decompress_section (asection *sectp,
 308                          struct gdb_bfd_section_data *descriptor)
 309 {
 310   bfd *abfd = sectp->owner;
 311 #ifndef HAVE_ZLIB_H
 312   error (_("Support for zlib-compressed data (from '%s', section '%s') "
 313            "is disabled in this copy of GDB"),
 314          bfd_get_filename (abfd),
 315          bfd_get_section_name (sectp));
 316 #else
 317   bfd_size_type compressed_size = bfd_get_section_size (sectp);
 318   gdb_byte *compressed_buffer = xmalloc (compressed_size);
 319   struct cleanup *cleanup = make_cleanup (xfree, compressed_buffer);
 320   struct cleanup *inner_cleanup;
 321   bfd_size_type uncompressed_size;
 322   gdb_byte *uncompressed_buffer;
 323   z_stream strm;
 324   int rc;
 325   int header_size = 12;
 326   struct dwarf2_per_bfd_section *section_data;
 327
 328   if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
 329       || bfd_bread (compressed_buffer,
 330                     compressed_size, abfd) != compressed_size)
 331     error (_("can't read data from '%s', section '%s'"),
 332            bfd_get_filename (abfd),
 333            bfd_get_section_name (abfd, sectp));
 334
 335   /* Read the zlib header.  In this case, it should be "ZLIB" followed
 336      by the uncompressed section size, 8 bytes in big-endian order.  */
 337   if (compressed_size < header_size
 338       || strncmp (compressed_buffer, "ZLIB", 4) != 0)
 339     error (_("corrupt ZLIB header from '%s', section '%s'"),
 340            bfd_get_filename (abfd),
 341            bfd_get_section_name (abfd, sectp));
 342   uncompressed_size = compressed_buffer[4]; uncompressed_size <<= 8;
 343   uncompressed_size += compressed_buffer[5]; uncompressed_size <<= 8;
 344   uncompressed_size += compressed_buffer[6]; uncompressed_size <<= 8;
 345   uncompressed_size += compressed_buffer[7]; uncompressed_size <<= 8;
 346   uncompressed_size += compressed_buffer[8]; uncompressed_size <<= 8;
 347   uncompressed_size += compressed_buffer[9]; uncompressed_size <<= 8;
 348   uncompressed_size += compressed_buffer[10]; uncompressed_size <<= 8;
 349   uncompressed_size += compressed_buffer[11];
 350
 351   /* It is possible the section consists of several compressed
 352      buffers concatenated together, so we uncompress in a loop.  */
 353   strm.zalloc = NULL;
 354   strm.zfree = NULL;
 355   strm.opaque = NULL;
 356   strm.avail_in = compressed_size - header_size;
 357   strm.next_in = (Bytef*) compressed_buffer + header_size;
 358   strm.avail_out = uncompressed_size;
 359   uncompressed_buffer = xmalloc (uncompressed_size);
 360   inner_cleanup = make_cleanup (xfree, uncompressed_buffer);
 361   rc = inflateInit (&strm);
 362   while (strm.avail_in > 0)
 363     {
 364       if (rc != Z_OK)
 365         error (_("setting up uncompression in '%s', section '%s': %d"),
 366                bfd_get_filename (abfd),
 367                bfd_get_section_name (abfd, sectp),
 368                rc);
 369       strm.next_out = ((Bytef*) uncompressed_buffer
 370                        + (uncompressed_size - strm.avail_out));
 371       rc = inflate (&strm, Z_FINISH);
 372       if (rc != Z_STREAM_END)
 373         error (_("zlib error uncompressing from '%s', section '%s': %d"),
 374                bfd_get_filename (abfd),
 375                bfd_get_section_name (abfd, sectp),
 376                rc);
 377       rc = inflateReset (&strm);
 378     }
 379   rc = inflateEnd (&strm);
 380   if (rc != Z_OK
 381       || strm.avail_out != 0)
 382     error (_("concluding uncompression in '%s', section '%s': %d"),
 383            bfd_get_filename (abfd),
 384            bfd_get_section_name (abfd, sectp),
 385            rc);
 386
 387   discard_cleanups (inner_cleanup);
 388   do_cleanups (cleanup);
 389
 390   /* Attach the data to the BFD section.  */
 391   descriptor->data = uncompressed_buffer;
 392   descriptor->size = uncompressed_size;
 393 #endif
 394 }
 395
 396 /* See gdb_bfd.h.  */
 397
 398 const gdb_byte *
 399 gdb_bfd_map_section (asection *sectp, bfd_size_type *size)
 400 {
 401   bfd *abfd;
 402   gdb_byte *buf, *retbuf;
 403   unsigned char header[4];
 404   struct gdb_bfd_section_data *descriptor;
 405
 406   gdb_assert ((sectp->flags & SEC_RELOC) == 0);
 407   gdb_assert (size != NULL);
 408
 409   abfd = sectp->owner;
 410
 411   descriptor = get_section_descriptor (sectp);
 412
 413   /* If the data was already read for this BFD, just reuse it.  */
 414   if (descriptor->data != NULL)
 415     goto done;
 416
 417   /* Check if the file has a 4-byte header indicating compression.  */
 418   if (bfd_get_section_size (sectp) > sizeof (header)
 419       && bfd_seek (abfd, sectp->filepos, SEEK_SET) == 0
 420       && bfd_bread (header, sizeof (header), abfd) == sizeof (header))
 421     {
 422       /* Upon decompression, update the buffer and its size.  */
 423       if (strncmp (header, "ZLIB", sizeof (header)) == 0)
 424         {
 425           zlib_decompress_section (sectp, descriptor);
 426           goto done;
 427         }
 428     }
 429
 430 #ifdef HAVE_MMAP
 431   {
 432     /* The page size, used when mmapping.  */
 433     static int pagesize;
 434
 435     if (pagesize == 0)
 436       pagesize = getpagesize ();
 437
 438     /* Only try to mmap sections which are large enough: we don't want
 439        to waste space due to fragmentation.  */
 440
 441     if (bfd_get_section_size (sectp) > 4 * pagesize)
 442       {
 443         descriptor->size = bfd_get_section_size (sectp);
 444         descriptor->data = bfd_mmap (abfd, 0, descriptor->size, PROT_READ,
 445                                      MAP_PRIVATE, sectp->filepos,
 446                                      &descriptor->map_addr,
 447                                      &descriptor->map_len);
 448
 449         if ((caddr_t)descriptor->data != MAP_FAILED)
 450           {
 451 #if HAVE_POSIX_MADVISE
 452             posix_madvise (descriptor->map_addr, descriptor->map_len,
 453                            POSIX_MADV_WILLNEED);
 454 #endif
 455             goto done;
 456           }
 457
 458         /* On failure, clear out the section data and try again.  */
 459         memset (descriptor, 0, sizeof (*descriptor));
 460       }
 461   }
 462 #endif /* HAVE_MMAP */
 463
 464   /* If we get here, we are a normal, not-compressed section.  */
 465
 466   descriptor->size = bfd_get_section_size (sectp);
 467   descriptor->data = xmalloc (descriptor->size);
 468
 469   if (bfd_seek (abfd, sectp->filepos, SEEK_SET) != 0
 470       || bfd_bread (descriptor->data, bfd_get_section_size (sectp),
 471                     abfd) != bfd_get_section_size (sectp))
 472     {
 473       xfree (descriptor->data);
 474       descriptor->data = NULL;
 475       error (_("Can't read data for section '%s'"),
 476              bfd_get_filename (abfd));
 477     }
 478
 479  done:
 480   gdb_assert (descriptor->data != NULL);
 481   *size = descriptor->size;
 482   return descriptor->data;
 483 }