[PATCH 1/6 v2] gdb/debuginfod: Add debuginfod_section_query

[Aaron Merey <amerey@redhat.com>]

v1: https://sourceware.org/pipermail/gdb-patches/2023-February/197455.html

v2 improves the description of AC_DEBUGINFOD_SECTION and associated
macro names.  An if-statement in debuginfod_section_query is also
replaced with a gdb_assert.

Commit message:

Add new function debuginfod_section_query.  This function queries
debuginfod servers for an individual ELF/DWARF section associated with
a given build-id.

Also check for libdebuginfod version >= 0.188 at configure time.
debuginfod_section_query simply returns -ENOSYS if this condition
is not met.
---
 config/debuginfod.m4     |  33 +++++++++++
 gdb/config.in            |   3 +
 gdb/configure            | 116 +++++++++++++++++++++++++++++++++++++--
 gdb/configure.ac         |   2 +-
 gdb/debuginfod-support.c |  60 ++++++++++++++++++++
 gdb/debuginfod-support.h |  24 ++++++++
 6 files changed, 232 insertions(+), 6 deletions(-)

diff --git a/config/debuginfod.m4 b/config/debuginfod.m4
index 2c1bfbdb544..4c443b77d3a 100644
--- a/config/debuginfod.m4
+++ b/config/debuginfod.m4
@@ -26,3 +26,36 @@ else
   AC_MSG_WARN([debuginfod support disabled; some features may be unavailable.])
 fi
 ])
+
+AC_DEFUN([AC_DEBUGINFOD_SECTION],
+[
+# Handle optional debuginfod support as well as optional section
+# downloading support.
+#
+# Define HAVE_LIBDEBUGINFOD if libdebuginfod is found with version >= 0.179.
+#
+# Define HAVE_LIBDEBUGINFOD_FIND_SECTION if libdebuginfod is found with
+# version >= 0.188.
+AC_ARG_WITH([debuginfod],
+  AC_HELP_STRING([--with-debuginfod], [Enable debuginfo lookups with debuginfod (auto/yes/no)]),
+  [], [with_debuginfod=auto])
+AC_MSG_CHECKING([whether to use debuginfod])
+AC_MSG_RESULT([$with_debuginfod])
+
+if test "x$with_debuginfod" != xno; then
+  PKG_CHECK_MODULES([DEBUGINFOD], [libdebuginfod >= 0.188],
+    [AC_DEFINE([HAVE_LIBDEBUGINFOD_FIND_SECTION], [1],
+	       [Define to 1 if debuginfod section downloading is supported.])],
+    [AC_MSG_WARN([libdebuginfod is missing or some features may be unavailable.])])
+
+  PKG_CHECK_MODULES([DEBUGINFOD], [libdebuginfod >= 0.179],
+    [AC_DEFINE([HAVE_LIBDEBUGINFOD], [1], [Define to 1 if debuginfod is enabled.])],
+    [if test "x$with_debuginfod" = xyes; then
+      AC_MSG_ERROR(["--with-debuginfod was given, but libdebuginfod is missing or unusable."])
+     else
+      AC_MSG_WARN([libdebuginfod is missing or unusable; some features may be unavailable.])
+     fi])
+else
+  AC_MSG_WARN([debuginfod support disabled; some features may be unavailable.])
+fi
+])
diff --git a/gdb/config.in b/gdb/config.in
index a7da88b92d7..95dd2fa22cb 100644
--- a/gdb/config.in
+++ b/gdb/config.in
@@ -244,6 +244,9 @@
 /* Define to 1 if debuginfod is enabled. */
 #undef HAVE_LIBDEBUGINFOD
 
+/* Define to 1 if debuginfod section downloading is supported. */
+#undef HAVE_LIBDEBUGINFOD_FIND_SECTION
+
 /* Define if you have the expat library. */
 #undef HAVE_LIBEXPAT
 
diff --git a/gdb/configure b/gdb/configure
index 5bb2a0795e5..f58a2b6b92a 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -18349,7 +18349,13 @@ esac
 
 # Handle optional debuginfod support
 
-# Handle optional debuginfod support
+# Handle optional debuginfod support as well as optional section
+# downloading support.
+#
+# Define HAVE_LIBDEBUGINFOD if libdebuginfod is found with version >= 0.179.
+#
+# Define HAVE_LIBDEBUGINFOD_FIND_SECTION if libdebuginfod is found with
+# version >= 0.188.
 
 # Check whether --with-debuginfod was given.
 if test "${with_debuginfod+set}" = set; then :
@@ -18365,6 +18371,106 @@ $as_echo "$with_debuginfod" >&6; }
 
 if test "x$with_debuginfod" != xno; then
 
+pkg_failed=no
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for libdebuginfod >= 0.188" >&5
+$as_echo_n "checking for libdebuginfod >= 0.188... " >&6; }
+
+if test -n "$DEBUGINFOD_CFLAGS"; then
+    pkg_cv_DEBUGINFOD_CFLAGS="$DEBUGINFOD_CFLAGS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libdebuginfod >= 0.188\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libdebuginfod >= 0.188") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_DEBUGINFOD_CFLAGS=`$PKG_CONFIG --cflags "libdebuginfod >= 0.188" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+if test -n "$DEBUGINFOD_LIBS"; then
+    pkg_cv_DEBUGINFOD_LIBS="$DEBUGINFOD_LIBS"
+ elif test -n "$PKG_CONFIG"; then
+    if test -n "$PKG_CONFIG" && \
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"libdebuginfod >= 0.188\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "libdebuginfod >= 0.188") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; then
+  pkg_cv_DEBUGINFOD_LIBS=`$PKG_CONFIG --libs "libdebuginfod >= 0.188" 2>/dev/null`
+		      test "x$?" != "x0" && pkg_failed=yes
+else
+  pkg_failed=yes
+fi
+ else
+    pkg_failed=untried
+fi
+
+if test $pkg_failed = no; then
+  pkg_save_LDFLAGS="$LDFLAGS"
+  LDFLAGS="$LDFLAGS $pkg_cv_DEBUGINFOD_LIBS"
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+
+else
+  pkg_failed=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+  LDFLAGS=$pkg_save_LDFLAGS
+fi
+
+
+
+if test $pkg_failed = yes; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+if $PKG_CONFIG --atleast-pkgconfig-version 0.20; then
+        _pkg_short_errors_supported=yes
+else
+        _pkg_short_errors_supported=no
+fi
+        if test $_pkg_short_errors_supported = yes; then
+	        DEBUGINFOD_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "libdebuginfod >= 0.188" 2>&1`
+        else
+	        DEBUGINFOD_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "libdebuginfod >= 0.188" 2>&1`
+        fi
+	# Put the nasty error message in config.log where it belongs
+	echo "$DEBUGINFOD_PKG_ERRORS" >&5
+
+	{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: libdebuginfod is missing or some features may be unavailable." >&5
+$as_echo "$as_me: WARNING: libdebuginfod is missing or some features may be unavailable." >&2;}
+elif test $pkg_failed = untried; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+	{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: libdebuginfod is missing or some features may be unavailable." >&5
+$as_echo "$as_me: WARNING: libdebuginfod is missing or some features may be unavailable." >&2;}
+else
+	DEBUGINFOD_CFLAGS=$pkg_cv_DEBUGINFOD_CFLAGS
+	DEBUGINFOD_LIBS=$pkg_cv_DEBUGINFOD_LIBS
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+$as_echo "#define HAVE_LIBDEBUGINFOD_FIND_SECTION 1" >>confdefs.h
+
+fi
+
+
 pkg_failed=no
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for libdebuginfod >= 0.179" >&5
 $as_echo_n "checking for libdebuginfod >= 0.179... " >&6; }
@@ -18448,18 +18554,18 @@ fi
 	echo "$DEBUGINFOD_PKG_ERRORS" >&5
 
 	if test "x$with_debuginfod" = xyes; then
-       as_fn_error $? "\"--with-debuginfod was given, but libdebuginfod is missing or unusable.\"" "$LINENO" 5
+      as_fn_error $? "\"--with-debuginfod was given, but libdebuginfod is missing or unusable.\"" "$LINENO" 5
      else
-       { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: libdebuginfod is missing or unusable; some features may be unavailable." >&5
+      { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: libdebuginfod is missing or unusable; some features may be unavailable." >&5
 $as_echo "$as_me: WARNING: libdebuginfod is missing or unusable; some features may be unavailable." >&2;}
      fi
 elif test $pkg_failed = untried; then
         { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
 	if test "x$with_debuginfod" = xyes; then
-       as_fn_error $? "\"--with-debuginfod was given, but libdebuginfod is missing or unusable.\"" "$LINENO" 5
+      as_fn_error $? "\"--with-debuginfod was given, but libdebuginfod is missing or unusable.\"" "$LINENO" 5
      else
-       { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: libdebuginfod is missing or unusable; some features may be unavailable." >&5
+      { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: libdebuginfod is missing or unusable; some features may be unavailable." >&5
 $as_echo "$as_me: WARNING: libdebuginfod is missing or unusable; some features may be unavailable." >&2;}
      fi
 else
diff --git a/gdb/configure.ac b/gdb/configure.ac
index fb43cd10d6c..499802bb4c9 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -342,7 +342,7 @@ case $host_os in
 esac
 
 # Handle optional debuginfod support
-AC_DEBUGINFOD
+AC_DEBUGINFOD_SECTION
 
 # Libunwind support for ia64.
 AC_ARG_WITH(libunwind-ia64,
diff --git a/gdb/debuginfod-support.c b/gdb/debuginfod-support.c
index 5853f420a18..8be43a91dcc 100644
--- a/gdb/debuginfod-support.c
+++ b/gdb/debuginfod-support.c
@@ -80,6 +80,15 @@ debuginfod_exec_query (const unsigned char *build_id,
   return scoped_fd (-ENOSYS);
 }
 
+scoped_fd
+debuginfod_section_query (const unsigned char *build_id,
+			  int build_id_len,
+			  const char *filename,
+			  const char *section_name,
+			  gdb::unique_xmalloc_ptr<char> *destname)
+{
+  return scoped_fd (-ENOSYS);
+}
 #define NO_IMPL _("Support for debuginfod is not compiled into GDB.")
 
 #else
@@ -401,6 +410,57 @@ debuginfod_exec_query (const unsigned char *build_id,
 
   return fd;
 }
+
+/* See debuginfod-support.h  */
+
+scoped_fd
+debuginfod_section_query (const unsigned char *build_id,
+			  int build_id_len,
+			  const char *filename,
+			  const char *section_name,
+			  gdb::unique_xmalloc_ptr<char> *destname)
+{
+#if !defined (HAVE_LIBDEBUGINFOD_FIND_SECTION)
+  return scoped_fd (-ENOSYS);
+#else
+
+ if (!debuginfod_is_enabled ())
+    return scoped_fd (-ENOSYS);
+
+  debuginfod_client *c = get_debuginfod_client ();
+
+  if (c == nullptr)
+    return scoped_fd (-ENOMEM);
+
+  char *dname = nullptr;
+  std::string desc = std::string ("section ") + section_name + " for";
+  scoped_fd fd;
+  gdb::optional<target_terminal::scoped_restore_terminal_state> term_state;
+
+  {
+    user_data data (desc.c_str (), filename);
+    debuginfod_set_user_data (c, &data);
+    if (target_supports_terminal_ours ())
+      {
+	term_state.emplace ();
+	target_terminal::ours ();
+      }
+
+    fd = scoped_fd (debuginfod_find_section (c, build_id, build_id_len,
+					     section_name, &dname));
+    debuginfod_set_user_data (c, nullptr);
+  }
+
+  print_outcome (fd.get (), desc.c_str (), filename);
+  gdb_assert (destname != nullptr);
+
+  if (fd.get () >= 0)
+    destname->reset (dname);
+
+  return fd;
+#endif /* HAVE_LIBDEBUGINFOD_FIND_SECTION */
+}
+
 #endif
 
 /* Set callback for "set debuginfod enabled".  */
diff --git a/gdb/debuginfod-support.h b/gdb/debuginfod-support.h
index 633600a79da..9701e3b4685 100644
--- a/gdb/debuginfod-support.h
+++ b/gdb/debuginfod-support.h
@@ -81,4 +81,28 @@ extern scoped_fd debuginfod_exec_query (const unsigned char *build_id,
 					const char *filename,
 					gdb::unique_xmalloc_ptr<char>
 					  *destname);
+
+/* Query debuginfod servers for the binary contents of a ELF/DWARF section
+   from a file matching BUILD_ID.  BUILD_ID can be given as a binary blob
+   or a null-terminated string.  If given as a binary blob, BUILD_ID_LEN
+   should be the number of bytes.  If given as a null-terminated string,
+   BUILD_ID_LEN should be 0.
+
+   FILENAME should be the name or path associated with the file matching
+   BUILD_ID.  It is used for printing messages to the user.
+
+   SECTION_NAME should be the name of an ELF/DWARF section.
+
+   If the file is successfully retrieved, return a file descriptor and store
+   the file's local path in DESTNAME.  If unsuccessful, print an error message
+   and return a negative errno.  If GDB is not built with debuginfod or
+   libdebuginfod does not support section queries, this function returns
+   -ENOSYS.  */
+
+extern scoped_fd debuginfod_section_query (const unsigned char *build_id,
+					   int build_id_len,
+					   const char *filename,
+					   const char *section_name,
+					   gdb::unique_xmalloc_ptr<char>
+					     *destname);
 #endif /* DEBUGINFOD_SUPPORT_H */
-- 
2.40.1