gdb/minidebug.c

   1 /* Read MiniDebugInfo data from an objfile.
   2
   3    Copyright (C) 2012-2023 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 /* We stash a reference to the .gnu_debugdata BFD on the enclosing
  30    BFD.  */
  31 static const registry<bfd>::key<gdb_bfd_ref_ptr> gnu_debug_key;
  32
  33 #include <lzma.h>
  34
  35 /* Allocator function for LZMA.  */
  36
  37 static void *
  38 alloc_lzma (void *opaque, size_t nmemb, size_t size)
  39 {
  40   return xmalloc (nmemb * size);
  41 }
  42
  43 /* Free function for LZMA.  */
  44
  45 static void
  46 free_lzma (void *opaque, void *ptr)
  47 {
  48   xfree (ptr);
  49 }
  50
  51 /* The allocator object for LZMA.  Note that 'gdb_lzma_allocator'
  52    cannot be const due to the lzma library function prototypes.  */
  53
  54 static lzma_allocator gdb_lzma_allocator = { alloc_lzma, free_lzma, NULL };
  55
  56 /* Custom bfd_openr_iovec implementation to read compressed data from
  57    a section.  This keeps only the last decompressed block in memory
  58    to allow larger data without using to much memory.  */
  59
  60 struct gdb_lzma_stream
  61 {
  62   /* Section of input BFD from which we are decoding data.  */
  63   asection *section = nullptr;
  64
  65   /* lzma library decompression state.  */
  66   lzma_index *index = nullptr;
  67
  68   /* Currently decoded block.  */
  69   bfd_size_type data_start = 0;
  70   bfd_size_type data_end = 0;
  71   gdb::byte_vector data;
  72 };
  73
  74 /* bfd_openr_iovec OPEN_P implementation for
  75    find_separate_debug_file_in_section.  OPEN_CLOSURE is 'asection *'
  76    of the section to decompress.
  77
  78    Return 'struct gdb_lzma_stream *' must be freed by caller by delete,
  79    together with its INDEX lzma data.  */
  80
  81 static void *
  82 lzma_open (struct bfd *nbfd, void *open_closure)
  83 {
  84   asection *section = (asection *) open_closure;
  85   bfd_size_type size, offset;
  86   lzma_stream_flags options;
  87   gdb_byte footer[LZMA_STREAM_HEADER_SIZE];
  88   lzma_index *index;
  89   uint64_t memlimit = UINT64_MAX;
  90   struct gdb_lzma_stream *lstream;
  91   size_t pos;
  92
  93   size = bfd_section_size (section);
  94   offset = section->filepos + size - LZMA_STREAM_HEADER_SIZE;
  95   if (size < LZMA_STREAM_HEADER_SIZE
  96       || bfd_seek (section->owner, offset, SEEK_SET) != 0
  97       || bfd_read (footer, LZMA_STREAM_HEADER_SIZE, section->owner)
  98          != LZMA_STREAM_HEADER_SIZE
  99       || lzma_stream_footer_decode (&options, footer) != LZMA_OK
 100       || offset < options.backward_size)
 101     {
 102       bfd_set_error (bfd_error_wrong_format);
 103       return NULL;
 104     }
 105
 106   offset -= options.backward_size;
 107   gdb::byte_vector indexdata (options.backward_size);
 108   index = NULL;
 109   pos = 0;
 110   if (bfd_seek (section->owner, offset, SEEK_SET) != 0
 111       || bfd_read (indexdata.data (), options.backward_size, section->owner)
 112          != options.backward_size
 113       || lzma_index_buffer_decode (&index, &memlimit, &gdb_lzma_allocator,
 114                                    indexdata.data (), &pos,
 115                                    options.backward_size)
 116          != LZMA_OK
 117       || lzma_index_size (index) != options.backward_size)
 118     {
 119       bfd_set_error (bfd_error_wrong_format);
 120       return NULL;
 121     }
 122
 123   lstream = new struct gdb_lzma_stream;
 124   lstream->section = section;
 125   lstream->index = index;
 126
 127   return lstream;
 128 }
 129
 130 /* bfd_openr_iovec PREAD_P implementation for
 131    find_separate_debug_file_in_section.  Passed STREAM
 132    is 'struct gdb_lzma_stream *'.  */
 133
 134 static file_ptr
 135 lzma_pread (struct bfd *nbfd, void *stream, void *buf, file_ptr nbytes,
 136             file_ptr offset)
 137 {
 138   struct gdb_lzma_stream *lstream = (struct gdb_lzma_stream *) stream;
 139   bfd_size_type chunk_size;
 140   lzma_index_iter iter;
 141   file_ptr block_offset;
 142   lzma_filter filters[LZMA_FILTERS_MAX + 1];
 143   lzma_block block;
 144   size_t compressed_pos, uncompressed_pos;
 145   file_ptr res;
 146
 147   res = 0;
 148   while (nbytes > 0)
 149     {
 150       if (lstream->data.empty ()
 151           || lstream->data_start > offset || offset >= lstream->data_end)
 152         {
 153           asection *section = lstream->section;
 154
 155           lzma_index_iter_init (&iter, lstream->index);
 156           if (lzma_index_iter_locate (&iter, offset))
 157             break;
 158
 159           gdb::byte_vector compressed (iter.block.total_size);
 160           block_offset = section->filepos + iter.block.compressed_file_offset;
 161           if (bfd_seek (section->owner, block_offset, SEEK_SET) != 0
 162               || bfd_read (compressed.data (), iter.block.total_size,
 163                            section->owner) != iter.block.total_size)
 164             break;
 165
 166           gdb::byte_vector uncompressed (iter.block.uncompressed_size);
 167
 168           memset (&block, 0, sizeof (block));
 169           block.filters = filters;
 170           block.header_size = lzma_block_header_size_decode (compressed[0]);
 171           if (lzma_block_header_decode (&block, &gdb_lzma_allocator,
 172                                         compressed.data ())
 173               != LZMA_OK)
 174             break;
 175
 176           compressed_pos = block.header_size;
 177           uncompressed_pos = 0;
 178           if (lzma_block_buffer_decode (&block, &gdb_lzma_allocator,
 179                                         compressed.data (), &compressed_pos,
 180                                         iter.block.total_size,
 181                                         uncompressed.data (),
 182                                         &uncompressed_pos,
 183                                         iter.block.uncompressed_size)
 184               != LZMA_OK)
 185             break;
 186
 187           lstream->data = std::move (uncompressed);
 188           lstream->data_start = iter.block.uncompressed_file_offset;
 189           lstream->data_end = (iter.block.uncompressed_file_offset
 190                                + iter.block.uncompressed_size);
 191         }
 192
 193       chunk_size = std::min (nbytes, (file_ptr) lstream->data_end - offset);
 194       memcpy (buf, lstream->data.data () + offset - lstream->data_start,
 195               chunk_size);
 196       buf = (gdb_byte *) buf + chunk_size;
 197       offset += chunk_size;
 198       nbytes -= chunk_size;
 199       res += chunk_size;
 200     }
 201
 202   return res;
 203 }
 204
 205 /* bfd_openr_iovec CLOSE_P implementation for
 206    find_separate_debug_file_in_section.  Passed STREAM
 207    is 'struct gdb_lzma_stream *'.  */
 208
 209 static int
 210 lzma_close (struct bfd *nbfd,
 211             void *stream)
 212 {
 213   struct gdb_lzma_stream *lstream = (struct gdb_lzma_stream *) stream;
 214
 215   lzma_index_end (lstream->index, &gdb_lzma_allocator);
 216   delete lstream;
 217
 218   /* Zero means success.  */
 219   return 0;
 220 }
 221
 222 /* bfd_openr_iovec STAT_P implementation for
 223    find_separate_debug_file_in_section.  Passed STREAM
 224    is 'struct gdb_lzma_stream *'.  */
 225
 226 static int
 227 lzma_stat (struct bfd *abfd,
 228            void *stream,
 229            struct stat *sb)
 230 {
 231   struct gdb_lzma_stream *lstream = (struct gdb_lzma_stream *) stream;
 232
 233   memset (sb, 0, sizeof (struct stat));
 234   sb->st_size = lzma_index_uncompressed_size (lstream->index);
 235   return 0;
 236 }
 237
 238 #endif /* HAVE_LIBLZMA  */
 239
 240 /* This looks for a xz compressed separate debug info object file embedded
 241    in a section called .gnu_debugdata.  See
 242    http://fedoraproject.org/wiki/Features/MiniDebugInfo
 243    or the "Separate Debug Sections" of the manual for details.
 244    If we find one we create a iovec based bfd that decompresses the
 245    object data on demand.  If we don't find one, return NULL.  */
 246
 247 gdb_bfd_ref_ptr
 248 find_separate_debug_file_in_section (struct objfile *objfile)
 249 {
 250   asection *section;
 251   gdb_bfd_ref_ptr abfd;
 252
 253   if (objfile->obfd == NULL)
 254     return NULL;
 255
 256   section = bfd_get_section_by_name (objfile->obfd.get (), ".gnu_debugdata");
 257   if (section == NULL)
 258     return NULL;
 259
 260 #ifdef HAVE_LIBLZMA
 261   gdb_bfd_ref_ptr *shared = gnu_debug_key.get (objfile->obfd.get ());
 262   if (shared != nullptr)
 263     return *shared;
 264
 265   std::string filename = string_printf (_(".gnu_debugdata for %s"),
 266                                         objfile_name (objfile));
 267
 268   abfd = gdb_bfd_openr_iovec (filename.c_str (), gnutarget, lzma_open,
 269                               section, lzma_pread, lzma_close, lzma_stat);
 270   if (abfd == NULL)
 271     return NULL;
 272
 273   if (!bfd_check_format (abfd.get (), bfd_object))
 274     {
 275       warning (_("Cannot parse .gnu_debugdata section; not a BFD object"));
 276       return NULL;
 277     }
 278
 279   gnu_debug_key.emplace (objfile->obfd.get (), abfd);
 280
 281 #else
 282   warning (_("Cannot parse .gnu_debugdata section; LZMA support was "
 283              "disabled at compile time"));
 284 #endif /* !HAVE_LIBLZMA */
 285
 286   return abfd;
 287 }