util: allow displaying --command output if requested

Make `--debug` accept an optional argument, which allows fine-tuning of
which log handles/facilities we want to display.

man/dfuzzer.xml

@@ -200,10 +200,13 @@
 
             <varlistentry>
                 <term><option>-d</option></term>
-                <term><option>--debug</option></term>
+                <term><option>--debug<optional>=<replaceable>HANDLE</replaceable></optional></option></term>
 
-                <listitem><para>Enable debug logging. Implies <option>-v/--verbose</option>. This option should
-                not be normally used during testing.</para></listitem>
+                <listitem><para>Enable debug logging. Implies <option>-v/--verbose</option>. Takes an optional
+                argument specifying a log handle, where <replaceable>HANDLE</replaceable> is one of
+                <constant>all</constant>, <constant>general</constant>, or <constant>command</constant>.</para>
+
+                <para>This option should not be normally used during testing.</para></listitem>
             </varlistentry>
 
             <varlistentry>

src/dfuzzer.c

@@ -573,7 +573,9 @@ static void df_print_help(const char *name)
          "  -h --help                   Show this help text.\n"
          "  -l --list                   List all available services on both buses.\n"
          "  -v --verbose                Be more verbose.\n"
-         "  -d --debug                  Enable debug logging; implies -v.\n"
+         "  -d --debug[=HANDLE]         Enable debug logging; implies -v.\n"
+         "                              Takes an optional argument specifying a log handle,\n"
+         "                              where handle is one of 'all', 'general', or 'command'.\n"
          "  -L --log-dir=DIRNAME        Write full, parseable log into DIRNAME/BUS_NAME.\n"
          "                              The directory must already exist.\n"
          "  -s --no-suppressions        Don't load suppression file(s).\n"
@@ -626,7 +628,7 @@ static void df_parse_parameters(int argc, char **argv)
 
         static const struct option options[] = {
                 { "buffer-limit",       required_argument,  NULL,   'b'                 },
-                { "debug",              no_argument,        NULL,   'd'                 },
+                { "debug",              optional_argument,  NULL,   'd'                 },
                 { "command",            required_argument,  NULL,   'e'                 },
                 { "string-file",        required_argument,  NULL,   'f'                 },
                 { "help",               no_argument,        NULL,   'h'                 },
@@ -649,7 +651,7 @@ static void df_parse_parameters(int argc, char **argv)
                 {}
         };
 
-        while ((c = getopt_long(argc, argv, "n:o:i:m:b:t:e:L:x:y:f:I:p:sdvlhV", options, NULL)) >= 0) {
+        while ((c = getopt_long(argc, argv, "n:o:i:m:b:t:e:L:x:y:f:I:p:d::svlhV", options, NULL)) >= 0) {
                 switch (c) {
                         case 'n':
                                 if (strlen(optarg) >= MAX_OBJECT_PATH_LENGTH) {
@@ -712,7 +714,20 @@ static void df_parse_parameters(int argc, char **argv)
                                 df_supflg = 1;
                                 break;
                         case 'd':
-                                df_set_log_level(DF_LOG_HANDLE_GENERAL, DF_LOG_LEVEL_DEBUG);
+                                if (optarg) {
+                                        if (g_ascii_strcasecmp(optarg, "all") == 0)
+                                                df_set_log_level(DF_LOG_HANDLE_ALL, DF_LOG_LEVEL_DEBUG);
+                                        else if (g_ascii_strcasecmp(optarg, "general") == 0)
+                                                df_set_log_level(DF_LOG_HANDLE_GENERAL, DF_LOG_LEVEL_DEBUG);
+                                        else if (g_ascii_strcasecmp(optarg, "command") == 0)
+                                                df_set_log_level(DF_LOG_HANDLE_COMMAND, DF_LOG_LEVEL_DEBUG);
+                                        else {
+                                                df_fail("Invalid log handle '%s'\n", optarg);
+                                                exit(1);
+                                        }
+                                } else
+                                        df_set_log_level(DF_LOG_HANDLE_GENERAL, DF_LOG_LEVEL_DEBUG);
+
                                 break;
                         case 'v':
                                 df_set_log_level(DF_LOG_HANDLE_GENERAL, DF_LOG_LEVEL_VERBOSE);

src/log.c

@@ -7,11 +7,11 @@ static FILE *log_file;
 
 void df_set_log_level(guint8 log_handle, guint8 log_level)
 {
-        g_assert(log_handle < _DF_LOG_HANDLE_MAX);
+        g_assert(log_handle <= DF_LOG_HANDLE_ALL);
         g_assert(log_level < _DF_LOG_LEVEL_MAX);
 
         if (log_handle == DF_LOG_HANDLE_ALL)
-                for (guint8 i = 0; i < _DF_LOG_LEVEL_MAX; i++)
+                for (guint8 i = 0; i < _DF_LOG_HANDLE_MAX; i++)
                         log_level_max[i] = log_level;
         else
                 log_level_max[log_handle] = log_level;

src/util.c

@@ -104,6 +104,10 @@ int df_execute_external_command(const char *command)
                 return df_fail_ret(-1, "Failed to open /dev/null: %m\n");
 
         for (guint8 i = 0; i < 3; i++) {
+                /* Don't redirect stdout/stderr to /dev/null if the command log level
+                 * is set to debug */
+                if (i > 0 && df_get_log_level(DF_LOG_HANDLE_COMMAND) >= DF_LOG_LEVEL_DEBUG)
+                        break;
                 if (dup2(null_fd, i) < 0)
                         return df_fail_ret(-1, "Failed to replace fd %d with /dev/null: %m\n", i);
         }