gdb/debuginfod: Add debuginfod_section_query

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

Approved-By: Andrew Burgess <aburgess@redhat.com>

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
@@ -412,6 +421,57 @@ 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".  */

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 */