[PATCH 3/7 v3] gdb: Add command 'maint set/show debuginfod download-sections'

[Aaron Merey <amerey@redhat.com>]

v2: https://sourceware.org/pipermail/gdb-patches/2023-June/199983.html

v3 updates some of the doc text.

Commit message:

This setting controls whether GDB may attempt to download ELF/DWARF
sections from debuginfod servers.

This setting is enabled by default if gdb is built with debuginfod
section download support (requires libdebuginfod 0.188).

Also update debuginfod command help text and gdb.texinfo with
information on section downloading and the new command.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Reviewed-By: Andrew Burgess <aburgess@redhat.com>
---
 gdb/debuginfod-support.c | 63 ++++++++++++++++++++++++++++++++++++++--
 gdb/doc/gdb.texinfo      | 19 ++++++++++--
 2 files changed, 77 insertions(+), 5 deletions(-)

diff --git a/gdb/debuginfod-support.c b/gdb/debuginfod-support.c
index 33bb9d9b7bc..c0794212a31 100644
--- a/gdb/debuginfod-support.c
+++ b/gdb/debuginfod-support.c
@@ -31,6 +31,10 @@
 static cmd_list_element *set_debuginfod_prefix_list;
 static cmd_list_element *show_debuginfod_prefix_list;
 
+/* maint set/show debuginfod commands.  */
+static cmd_list_element *maint_set_debuginfod_cmdlist;
+static cmd_list_element *maint_show_debuginfod_cmdlist;
+
 static const char debuginfod_on[] = "on";
 static const char debuginfod_off[] = "off";
 static const char debuginfod_ask[] = "ask";
@@ -50,6 +54,14 @@ static const char *debuginfod_enabled =
   debuginfod_off;
 #endif
 
+/* Controls whether ELF/DWARF section downloading is enabled.  */
+static bool debuginfod_download_sections =
+#if defined(HAVE_LIBDEBUGINFOD_FIND_SECTION)
+  true;
+#else
+  false;
+#endif
+
 static unsigned int debuginfod_verbose = 1;
 
 #ifndef HAVE_LIBDEBUGINFOD
@@ -435,7 +447,7 @@ debuginfod_section_query (const unsigned char *build_id,
   return scoped_fd (-ENOSYS);
 #else
 
- if (!debuginfod_is_enabled ())
+ if (!debuginfod_download_sections || !debuginfod_is_enabled ())
     return scoped_fd (-ENOSYS);
 
   debuginfod_client *c = get_debuginfod_client ();
@@ -561,6 +573,28 @@ show_debuginfod_verbose_command (ui_file *file, int from_tty,
 	      value);
 }
 
+/* Set callback for "maint set debuginfod download-sections".  */
+
+static void
+maint_set_debuginfod_download_sections (bool value)
+{
+#if !defined(HAVE_LIBDEBUGINFOD_FIND_SECTION)
+  if (value)
+    error (_("Support for section downloading is not compiled into GDB. " \
+"Defaulting to \"off\"."));
+#endif
+
+  debuginfod_download_sections = value;
+}
+
+/* Get callback for "maint set debuginfod download-sections".  */
+
+static bool
+maint_get_debuginfod_download_sections ()
+{
+  return debuginfod_download_sections;
+}
+
 /* Register debuginfod commands.  */
 
 void _initialize_debuginfod ();
@@ -579,8 +613,10 @@ _initialize_debuginfod ()
 			_("Set whether to use debuginfod."),
 			_("Show whether to use debuginfod."),
 			_("\
-When on, enable the use of debuginfod to download missing debug info and\n\
-source files."),
+When set to \"on\", enable the use of debuginfod to download missing\n\
+debug info and source files.  GDB may also download components of debug\n\
+info instead of entire files.  \"off\" disables the use of debuginfod.\n\
+When set to \"ask\", prompt whether to enable or disable debuginfod." ),
 			set_debuginfod_enabled,
 			get_debuginfod_enabled,
 			show_debuginfod_enabled,
@@ -611,4 +647,25 @@ query.\nTo disable, set to zero.  Verbose output is displayed by default."),
 			     show_debuginfod_verbose_command,
 			     &set_debuginfod_prefix_list,
 			     &show_debuginfod_prefix_list);
+
+  /* maint set/show debuginfod.  */
+  add_setshow_prefix_cmd ("debuginfod", class_maintenance,
+			  _("Set debuginfod specific variables."),
+			  _("Show debuginfod specific variables."),
+			  &maint_set_debuginfod_cmdlist,
+			  &maint_show_debuginfod_cmdlist,
+			  &maintenance_set_cmdlist, &maintenance_show_cmdlist);
+
+  /* maint set/show debuginfod download-sections.  */
+  add_setshow_boolean_cmd ("download-sections", class_maintenance, _("\
+Set whether debuginfod may download individual ELF/DWARF sections."), _("\
+Show whether debuginfod may download individual ELF/DWARF sections."), _("\
+When enabled, debuginfod may attempt to download individual ELF/DWARF \
+sections from debug info files.\nIf disabled, only whole debug info files \
+may be downloaded."),
+			   maint_set_debuginfod_download_sections,
+			   maint_get_debuginfod_download_sections,
+			   nullptr,
+			   &maint_set_debuginfod_cmdlist,
+			   &maint_show_debuginfod_cmdlist);
 }
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 814cc6d714a..7ecf07e2820 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -40920,6 +40920,17 @@ Create a core file? (y or n) @kbd{n}
 (@value{GDBP})
 @end smallexample
 
+@kindex maint set debuginfod download-sections
+@kindex maint show debuginfod download-sections
+@cindex debuginfod, maintenance commands
+@item maint set debuginfod download-sections
+@itemx maint set debuginfod download-sections @r{[}on|off@r{]}
+@itemx maint show debuginfod download-sections
+Controls whether @value{GDBN} will attempt to download individual
+ELF/DWARF sections from @code{debuginfod}.  If disabled, only
+whole debug info files will be downloaded; this could result
+in @value{GDBN} downloading larger amounts of data.
+
 @cindex @value{GDBN} internal error
 @cindex internal errors, control of @value{GDBN} behavior
 @cindex demangler crashes
@@ -49430,8 +49441,12 @@ regarding @code{debuginfod}.
 @item set debuginfod enabled
 @itemx set debuginfod enabled on
 @cindex enable debuginfod
-@value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
-info or source files.
+@value{GDBN} may query @code{debuginfod} servers for missing debug info and
+source files.  @value{GDBN} may also download individual ELF/DWARF sections
+such as @code{.gdb_index} to help reduce the total amount of data downloaded
+from @code{debuginfod} servers; this can be controlled by @w{@code{maint
+set debuginfod download-sections}} (@pxref{Maintenance Commands, maint set
+debuginfod download-sections}).
 
 @item set debuginfod enabled off
 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
-- 
2.41.0