Add debuginfod support to GDB

debuginfod is a lightweight web service that indexes ELF/DWARF debugging
resources by build-id and serves them over HTTP.

This patch enables GDB to query debuginfod servers for separate debug
files and source code when it is otherwise not able to find them.

GDB 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/.

Tested on x86_64 Fedora 31.

gdb/ChangeLog:
2020-02-26  Aaron Merey  <amerey@redhat.com>

        * Makefile.in: Handle optional debuginfod support.
        * NEWS: Update.
        * README: Add --with-debuginfod summary.
        * config.in: Regenerate.
        * configure: Regenerate.
        * configure.ac: Handle optional debuginfod support.
        * debuginfod-support.c: debuginfod helper functions.
        * debuginfod-support.h: Ditto.
        * doc/gdb.texinfo: Add --with-debuginfod to configure options
        summary.
        * dwarf2/read.c (dwarf2_get_dwz_file): Query debuginfod servers
        when a dwz file cannot be found.
        * elfread.c (elf_symfile_read): Query debuginfod servers when a
        debuginfo file cannot be found.
        * source.c (open_source_file): Query debuginfod servers when a
        source file cannot be found.
        * top.c (print_gdb_configuration): Include
        --{with,without}-debuginfod in the output.

gdb/testsuite/ChangeLog:
2020-02-26  Aaron Merey  <amerey@redhat.com>

        * gdb.debuginfod: New directory for debuginfod tests.
        * gdb.debuginfod/main.c: New test file.
        * gdb.debuginfod/fetch_src_and_symbols.exp: New tests.

1 files changed, 14 insertions, 0 deletions

diff --git a/gdb/NEWS b/gdb/NEWS
index e33d838..d3a3605 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,20 @@
 
 *** Changes since GDB 9
 
+* GDB now supports debuginfod, an HTTP server for distributing ELF/DWARF
+  debugging information as well as source code.
+
+  When built with debuginfod, GDB can automatically query debuginfod
+  servers for the separate debug files and source code of the executable
+  being debugged.
+
+  To build GDB with debuginfod, pass --with-debuginfod to configure (this
+  requires libdebuginfod, the debuginfod client library).
+
+  debuginfod is distributed with elfutils, starting with version 0.178.
+
+  You can get the latest version from https://sourceware.org/elfutils.
+
 * New features in the GDB remote stub, GDBserver
 
   ** GDBserver is now supported on RISC-V GNU/Linux.