gdb/minidebug.c

   1 /* Read MiniDebugInfo data from an objfile.
   2
   3    Copyright (C) 2012-2020 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   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, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "gdb_bfd.h"
  22 #include "symfile.h"
  23 #include "objfiles.h"
  24 #include "gdbcore.h"
  25 #include <algorithm>
  26
  27 #ifdef HAVE_LIBLZMA
  28
  29 #include <lzma.h>
  30
  31 /* Allocator function for LZMA.  */
  32
  33 static void *
  34 alloc_lzma (void *opaque, size_t nmemb, size_t size)
  35 {
  36   return xmalloc (nmemb * size);
  37 }
  38
  39 /* Free function for LZMA.  */
  40
  41 static void
  42 free_lzma (void *opaque, void *ptr)
  43 {
  44   xfree (ptr);
  45 }
  46
  47 /* The allocator object for LZMA.  Note that 'gdb_lzma_allocator'
  48    cannot be const due to the lzma library function prototypes.  */
  49
  50 static lzma_allocator gdb_lzma_allocator = { alloc_lzma, free_lzma, NULL };
  51
  52 /* Custom bfd_openr_iovec implementation to read compressed data from
  53    a section.  This keeps only the last decompressed block in memory
  54    to allow larger data without using to much memory.  */
  55
  56 struct gdb_lzma_stream
  57 {
  58   /* Section of input BFD from which we are decoding data.  */
  59   asection *section;
  60
  61   /* lzma library decompression state.  */
  62   lzma_index *index;
  63
  64   /* Currently decoded block.  */
  65   bfd_size_type data_start;
  66   bfd_size_type data_end;
  67   gdb_byte *data;
  68 };
  69
  70 /* bfd_openr_iovec OPEN_P implementation for
  71    find_separate_debug_file_in_section.  OPEN_CLOSURE is 'asection *'
  72    of the section to decompress.
  73
  74    Return 'struct gdb_lzma_stream *' must be freed by caller by xfree,
  75    together with its INDEX lzma data.  */
  76
  77 static void *
  78 lzma_open (struct bfd *nbfd, void *open_closure)
  79 {
  80   asection *section = (asection *) open_closure;
  81   bfd_size_type size, offset;
  82   lzma_stream_flags options;
  83   gdb_byte footer[LZMA_STREAM_HEADER_SIZE];
  84   gdb_byte *indexdata;
  85   lzma_index *index;
  86   uint64_t memlimit = UINT64_MAX;
  87   struct gdb_lzma_stream *lstream;
  88   size_t pos;
  89
  90   size = bfd_section_size (section);
  91   offset = section->filepos + size - LZMA_STREAM_HEADER_SIZE;
  92   if (size < LZMA_STREAM_HEADER_SIZE
  93       || bfd_seek (section->owner, offset, SEEK_SET) != 0
  94       || bfd_bread (footer, LZMA_STREAM_HEADER_SIZE, section->owner)
  95          != LZMA_STREAM_HEADER_SIZE
  96       || lzma_stream_footer_decode (&options, footer) != LZMA_OK
  97       || offset < options.backward_size)
  98     {
  99       bfd_set_error (bfd_error_wrong_format);
 100       return NULL;
 101     }
 102
 103   offset -= options.backward_size;
 104   indexdata = (gdb_byte *) xmalloc (options.backward_size);
 105   index = NULL;
 106   pos = 0;
 107   if (bfd_seek (section->owner, offset, SEEK_SET) != 0
 108       || bfd_bread (indexdata, options.backward_size, section->owner)
 109          != options.backward_size
 110       || lzma_index_buffer_decode (&index, &memlimit, &gdb_lzma_allocator,
 111                                    indexdata, &pos, options.backward_size)
 112          != LZMA_OK
 113       || lzma_index_size (index) != options.backward_size)
 114     {
 115       xfree (indexdata);
 116       bfd_set_error (bfd_error_wrong_format);
 117       return NULL;
 118     }
 119   xfree (indexdata);
 120
 121   lstream = XCNEW (struct gdb_lzma_stream);
 122   lstream->section = section;
 123   lstream->index = index;
 124
 125   return lstream;
 126 }
 127
 128 /* bfd_openr_iovec PREAD_P implementation for
 129    find_separate_debug_file_in_section.  Passed STREAM
 130    is 'struct gdb_lzma_stream *'.  */
 131
 132 static file_ptr
 133 lzma_pread (struct bfd *nbfd, void *stream, void *buf, file_ptr nbytes,
 134             file_ptr offset)
 135 {
 136   struct gdb_lzma_stream *lstream = (struct gdb_lzma_stream *) stream;
 137   bfd_size_type chunk_size;
 138   lzma_index_iter iter;
 139   gdb_byte *compressed, *uncompressed;
 140   file_ptr block_offset;
 141   lzma_filter filters[LZMA_FILTERS_MAX + 1];
 142   lzma_block block;
 143   size_t compressed_pos, uncompressed_pos;
 144   file_ptr res;
 145
 146   res = 0;
 147   while (nbytes > 0)
 148     {
 149       if (lstream->data == NULL
 150           || lstream->data_start > offset || offset >= lstream->data_end)
 151         {
 152           asection *section = lstream->section;
 153
 154           lzma_index_iter_init (&iter, lstream->index);
 155           if (lzma_index_iter_locate (&iter, offset))
 156             break;
 157
 158           compressed = (gdb_byte *) xmalloc (iter.block.total_size);
 159           block_offset = section->filepos + iter.block.compressed_file_offset;
 160           if (bfd_seek (section->owner, block_offset, SEEK_SET) != 0
 161               || bfd_bread (compressed, iter.block.total_size, section->owner)
 162                  != iter.block.total_size)
 163             {
 164               xfree (compressed);
 165               break;
 166             }
 167
 168           uncompressed = (gdb_byte *) xmalloc (iter.block.uncompressed_size);
 169
 170           memset (&block, 0, sizeof (block));
 171           block.filters = filters;
 172           block.header_size = lzma_block_header_size_decode (compressed[0]);
 173           if (lzma_block_header_decode (&block, &gdb_lzma_allocator, compressed)
 174               != LZMA_OK)
 175             {
 176               xfree (compressed);
 177               xfree (uncompressed);
 178               break;
 179             }
 180
 181           compressed_pos = block.header_size;
 182           uncompressed_pos = 0;
 183           if (lzma_block_buffer_decode (&block, &gdb_lzma_allocator,
 184                                         compressed, &compressed_pos,
 185                                         iter.block.total_size,
 186                                         uncompressed, &uncompressed_pos,
 187                                         iter.block.uncompressed_size)
 188               != LZMA_OK)
 189             {
 190               xfree (compressed);
 191               xfree (uncompressed);
 192               break;
 193             }
 194
 195           xfree (compressed);
 196
 197           xfree (lstream->data);
 198           lstream->data = uncompressed;
 199           lstream->data_start = iter.block.uncompressed_file_offset;
 200           lstream->data_end = (iter.block.uncompressed_file_offset
 201                                + iter.block.uncompressed_size);
 202         }
 203
 204       chunk_size = std::min (nbytes, (file_ptr) lstream->data_end - offset);
 205       memcpy (buf, lstream->data + offset - lstream->data_start, chunk_size);
 206       buf = (gdb_byte *) buf + chunk_size;
 207       offset += chunk_size;
 208       nbytes -= chunk_size;
 209       res += chunk_size;
 210     }
 211
 212   return res;
 213 }
 214
 215 /* bfd_openr_iovec CLOSE_P implementation for
 216    find_separate_debug_file_in_section.  Passed STREAM
 217    is 'struct gdb_lzma_stream *'.  */
 218
 219 static int
 220 lzma_close (struct bfd *nbfd,
 221             void *stream)
 222 {
 223   struct gdb_lzma_stream *lstream = (struct gdb_lzma_stream *) stream;
 224
 225   lzma_index_end (lstream->index, &gdb_lzma_allocator);
 226   xfree (lstream->data);
 227   xfree (lstream);
 228
 229   /* Zero means success.  */
 230   return 0;
 231 }
 232
 233 /* bfd_openr_iovec STAT_P implementation for
 234    find_separate_debug_file_in_section.  Passed STREAM
 235    is 'struct gdb_lzma_stream *'.  */
 236
 237 static int
 238 lzma_stat (struct bfd *abfd,
 239            void *stream,
 240            struct stat *sb)
 241 {
 242   struct gdb_lzma_stream *lstream = (struct gdb_lzma_stream *) stream;
 243
 244   memset (sb, 0, sizeof (struct stat));
 245   sb->st_size = lzma_index_uncompressed_size (lstream->index);
 246   return 0;
 247 }
 248
 249 #endif /* HAVE_LIBLZMA  */
 250
 251 /* This looks for a xz compressed separate debug info object file embedded
 252    in a section called .gnu_debugdata.  See
 253    http://fedoraproject.org/wiki/Features/MiniDebugInfo
 254    or the "Separate Debug Sections" of the manual for details.
 255    If we find one we create a iovec based bfd that decompresses the
 256    object data on demand.  If we don't find one, return NULL.  */
 257
 258 gdb_bfd_ref_ptr
 259 find_separate_debug_file_in_section (struct objfile *objfile)
 260 {
 261   asection *section;
 262   gdb_bfd_ref_ptr abfd;
 263
 264   if (objfile->obfd == NULL)
 265     return NULL;
 266
 267   section = bfd_get_section_by_name (objfile->obfd, ".gnu_debugdata");
 268   if (section == NULL)
 269     return NULL;
 270
 271 #ifdef HAVE_LIBLZMA
 272   std::string filename = string_printf (_(".gnu_debugdata for %s"),
 273                                         objfile_name (objfile));
 274
 275   abfd = gdb_bfd_openr_iovec (filename.c_str (), gnutarget, lzma_open,
 276                               section, lzma_pread, lzma_close, lzma_stat);
 277   if (abfd == NULL)
 278     return NULL;
 279
 280   if (!bfd_check_format (abfd.get (), bfd_object))
 281     {
 282       warning (_("Cannot parse .gnu_debugdata section; not a BFD object"));
 283       return NULL;
 284     }
 285 #else
 286   warning (_("Cannot parse .gnu_debugdata section; LZMA support was "
 287              "disabled at compile time"));
 288 #endif /* !HAVE_LIBLZMA */
 289
 290   return abfd;
 291 }