debuginfod is a lightweight web service that indexes ELF/DWARF
debugging resources by build-id and serves them over HTTP. This patch
enables objdump and readelf to query debuginfod servers when they are
otherwise not able to find separate debug files. Binutils can be built
with debuginfod using the --with-debuginfod configure option. This
requires that libdebuginfod be installed and found at configure time.
debuginfod is packaged with elfutils, starting with version 0.178. For
more information see https://sourceware.org/elfutils/.
toplevel* config/debuginfod.m4: New file. Add macro AC_DEBUGINFOD. Adds
new configure option --with-debuginfod.
* configure: Regenerate.
* configure.ac: Call AC_DEBUGINFOD.
binutils* Makefile.am (readelf_LDADD, objdump_LDADD): Add libdebuginfod.
* Makefile.in: Regenerate.
* NEWS: Update.
* config.in: Regenerate.
* configure: Regenerate.
* configure.ac: Call AC_DEBUGINFOD.
* doc/Makefile.in: Regenerate.
* doc/binutils.texi: Add section on using binutils
with debuginfod.
* dwarf.c (debuginfod_fetch_separate_debug_info): New function.
Query debuginfod servers for the target debug file.
(load_separate_debug_info): Call
debuginfod_fetch_separate_debug_info if configured with
debuginfod.
(load_separate_debug_files): Add file argument to
load_separate_debug_info calls.
* dwarf.h (get_build_id): Add declaration.
* objdump.c (get_build_id): New function. Get build-id of file.
* readelf.c (get_build_id): Likewise.
* testsuite/binutils-all/debuginfod.exp: New tests.
* testsuite/binutils-all/linkdebug.s: Add .note.gnu.build-id
section.
* objdump.c (sym_ok): New function.
(find_symbol_for_address): Use new function.
(disassemble_section): Compare sections by name, not pointer.
(dump_dwarf): Move code to initialise byte_get pointer and iterate
over separate debug files from here to ...
(dump_bfd): ... here. Add parameter indicating that a separate
debug info file is being dumped. For main file, pull in the
symbol tables from all separate debug info files.
(display_object): Update call to dump_bfd.
* doc/binutils.texi: Document extened behaviour of the
--dwarf=follow-links option.
* NEWS: Mention this new feature.
* testsuite/binutils-all/objdump.WK2: Update expected output.
* testsuite/binutils-all/objdump.exp (test_follow_debuglink): Add
options and dump file parameters.
Add extra test.
* testsuite/binutils-all/objdump.WK3: New file.
* testsuite/binutils-all/readelf.exp: Change expected output for
readelf -wKis test.
* testsuite/binutils-all/readelf.wKis: New file.
Hi Guys,
I am applying the rather large patch attached to this email to enhance
the readelf and objdump programs so that they now have the ability to
follow links to separate debug info files. (As requested by PR
15152). So for example whereas before we had this output:
$ readelf -wi main.exe
Contents of the .debug_info section:
[...]
<15> DW_AT_comp_dir : (alt indirect string, offset: 0x30c)
[...]
With the new option enabled we get:
$ readelf -wiK main.exe
main.exe: Found separate debug info file: dwz.debug
Contents of the .debug_info section (loaded from main.exe):
[...]
<15> DW_AT_comp_dir : (alt indirect string, offset: 0x30c) /home/nickc/Downloads/dwzm
[...]
The link following feature also means that we can get two lots of
output if the same section exists in both the main file and the
separate debug info file:
$ readelf -wiK main.exe
main.exe: Found separate debug info file: dwz.debug
Contents of the .debug_info section (loaded from main.exe):
[...]
Contents of the .debug_info section (loaded from dwz.debug):
[...]
The patch also adds the ability to display the contents of debuglink
sections:
$ readelf -wk main.exe
Contents of the .gnu_debugaltlink section:
Separate debug info file: dwz.debug
Build-ID (0x14 bytes):
c4 a8 89 8d 64 cf 70 8a 35 68 21 f2 ed 24 45 3e 18 7a 7a 93
Naturally there are long versions of these options (=follow-links and
=links). The documentation has been updated as well, and since both
readelf and objdump use the same set of debug display options, I have
moved the text into a separate file. There are also a couple of new
binutils tests to exercise the new behaviour.
There are a couple of missing features in the current patch however,
although I do intend to address them in follow up submissions:
Firstly the code does not check the build-id inside separate debug
info files when it is searching for a file specified by a
.gnu_debugaltlink section. It just assumes that if the file is there,
then it contains the information being sought.
Secondly I have not checked the DWARF-5 version of these link
features, so there will probably be code to add there.
Thirdly I have only implemented link following for the
DW_FORM_GNU_strp_alt format. Other alternate formats (eg
DW_FORM_GNU_ref_alt) have yet to be implemented.
Lastly, whilst implementing this feature I found it necessary to move
some of the global variables used by readelf (eg section_headers) into
a structure that can be passed around. I have moved all of the global
variables that were necessary to get the patch working, but I need to
complete the operation and move the remaining, file-specific variables
(eg dynamic_strings).
Cheers
Nick
binutils PR 15152
* dwarf.h (enum dwarf_section_display_enum): Add gnu_debuglink,
gnu_debugaltlink and separate_debug_str.
(struct dwarf_section): Add filename field.
Add prototypes for load_separate_debug_file, close_debug_file and
open_debug_file.
* dwarf.c (do_debug_links): New.
(do_follow_links): New.
(separate_debug_file, separate_debug_filename): New.
(fetch_alt_indirect_string): New function. Retrieves a string
from the debug string table in the separate debug info file.
(read_and_display_attr_value): Use it with DW_FORM_GNU_strp_alt.
(load_debug_section_with_follow): New function. Like
load_debug_section, but if the first attempt fails, then tries
again in the separate debug info file.
(introduce): New function.
(process_debug_info): Use load_debug_section_with_follow and
introduce.
(load_debug_info): Likewise.
(display_debug_lines_raw): Likewise.
(display_debug_lines_decoded): Likewise.
(display_debug_macinfo): Likewise.
(display_debug_macro): Likewise.
(display_debug_abbrev): Likewise.
(display_debug_loc): Likewise.
(display_debug_str): Likewise.
(display_debug_aranges): Likewise.
(display_debug_addr); Likewise.
(display_debug_frames): Likewise.
(display_gdb_index): Likewise.
(process_cu_tu_index): Likewise.
(load_cu_tu_indexes): Likewise.
(display_debug_links): New function. Displays the contents of a
.gnu_debuglink or .gnu_debugaltlink section.
(calc_gnu_debuglink_ctc32):New function. Calculates a CRC32
value.
(check_gnu_debuglink): New function. Checks the CRC of a
potential separate debug info file.
(parse_gnu_debuglink): New function. Reads a CRC value out of a
.gnu_debuglink section.
(check_gnu_debugaltlink): New function.
(parse_gnu_debugaltlink): New function. Reads the build-id value
out of a .gnu_debugaltlink section.
(load_separate_debug_info): New function. Finds and loads a
separate debug info file.
(load_separate_debug_file): New function. Attempts to find and
follow a link to a separate debug info file.
(free_debug_memory): Free the separate debug info file
information.
(opts_table): Add "follow-links" and "links".
(dwarf_select_sections_by_letters): Add "k" and "K".
(debug_displays): Reformat. Add .gnu-debuglink and
.gnu_debugaltlink.
Add an extra entry for .debug_str in a separate debug info file.
* doc/binutils.texi: Move description of debug dump features
common to both readelf and objdump into...
* objdump.c (usage): Add -Wk and -WK.
(load_specific_debug_section): Initialise the filename field in
the dwarf_section structure.
(close_debug_file): New function.
(open_debug_file): New function.
(dump_dwarf): Load and dump the separate debug info sections.
* readelf.c (struct filedata): New structure. Contains various
variables that used to be global:
(current_file_size, string_table, string_table_length, elf_header)
(section_headers, program_headers, dump_sects, num_dump_sects):
Move into filedata structure.
(cmdline): New global variable. Contains list of sections to dump
by number, as specified on the command line.
Add filedata parameter to most functions.
(load_debug_section): Load the string table if it has not already
been retrieved.
(close_file): New function.
(close_debug_file): New function.
(open_file): New function.
(open_debug_file): New function.
(process_object): Process sections in any separate debug info files.
* doc/debug.options.texi: New file. Add description of =links and
=follow-links options.
* NEWS: Mention the new feature.
* elfcomm.c: Have the byte gte functions take a const pointer.
* elfcomm.h: Update prototypes.
* testsuite/binutils-all/dw5.W: Update expected output.
* testsuite/binutils-all/objdump.WL: Update expected output.
* testsuite/binutils-all/objdump.exp: Add test of -WK and -Wk.
* testsuite/binutils-all/readelf.exp: Add test of -wK and -wk.
* testsuite/binutils-all/readelf.k: New file.
* testsuite/binutils-all/objdump.Wk: New file.
* testsuite/binutils-all/objdump.WK2: New file.
* testsuite/binutils-all/linkdebug.s: New file.
* testsuite/binutils-all/debuglink.s: New file.
gas * testsuite/gas/avr/large-debug-line-table.d: Update expected
output.
* testsuite/gas/elf/dwarf2-11.d: Likewise.
* testsuite/gas/elf/dwarf2-12.d: Likewise.
* testsuite/gas/elf/dwarf2-13.d: Likewise.
* testsuite/gas/elf/dwarf2-14.d: Likewise.
* testsuite/gas/elf/dwarf2-15.d: Likewise.
* testsuite/gas/elf/dwarf2-16.d: Likewise.
* testsuite/gas/elf/dwarf2-17.d: Likewise.
* testsuite/gas/elf/dwarf2-18.d: Likewise.
* testsuite/gas/elf/dwarf2-5.d: Likewise.
* testsuite/gas/elf/dwarf2-6.d: Likewise.
* testsuite/gas/elf/dwarf2-7.d: Likewise.
ld * testsuite/ld-avr/gc-section-debugline.d: Update expected
output.
