Add a function to check for legal exclusions

Add a function check_exclusion_subsets() that checks the event name
against a given list of exclusion names. Report warnings and/or errors
if an exclusion is not a proper subset of the event.

Return a newly allocated list of newly allocated exclusion name strings,
the count of items in that list, and an error code.

diff --git a/src/bin/lttng/commands/enable_events.c b/src/bin/lttng/commands/enable_events.c
index 6ea3c919f1dc8806cb2de0e4515d81a0e06d34f2..231b7b38ee7750e8fd3d256a07b0c242f5ea59df 100644 (file)
--- a/src/bin/lttng/commands/enable_events.c
+++ b/src/bin/lttng/commands/enable_events.c
@@ -336,6 +336,94 @@ const char *print_raw_channel_name(const char *name)
        return name ? : "<default>";
 }
 
+/*
+ * Compare list of exclusions against an event name.
+ * Return a list of legal exclusion names.
+ * Produce an error or a warning about others (depending on the situation)
+ */
+static
+int check_exclusion_subsets(const char *event_name,
+               const char *exclusions,
+               int *exclusion_count_ptr,
+               char ***exclusion_list_ptr)
+{
+       const char *excluder_ptr;
+       const char *event_ptr;
+       const char *next_excluder;
+       int excluder_length;
+       int exclusion_count = 0;
+       char **exclusion_list = NULL;
+       int ret = CMD_SUCCESS;
+
+       if (event_name[strlen(event_name) - 1] != '*') {
+               ERR("Event %s: Excluders can only be used with wildcarded events", event_name);
+               goto error;
+       }
+
+       next_excluder = exclusions;
+       while (*next_excluder != 0) {
+               event_ptr = event_name;
+               excluder_ptr = next_excluder;
+               excluder_length = strcspn(next_excluder, ",");
+
+               /* Scan both the excluder and the event letter by letter */
+               while (1) {
+                       char e, x;
+
+                       e = *event_ptr;
+                       x = *excluder_ptr;
+
+                       if (x == '*') {
+                               /* Event is a subset of the excluder */
+                               ERR("Event %s: %.*s excludes all events from %s",
+                                               event_name,
+                                               excluder_length,
+                                               next_excluder,
+                                               event_name);
+                               goto error;
+                       }
+                       if (e == '*') {
+                               /* Excluder is a proper subset of event */
+                               exclusion_count++;
+                               exclusion_list = realloc(exclusion_list, sizeof(char **) * exclusion_count);
+                               exclusion_list[exclusion_count - 1] = strndup(next_excluder, excluder_length);
+
+                               break;
+                       }
+                       if (x != e) {
+                               /* Excluder and event sets have no common elements */
+                               WARN("Event %s: %.*s does not exclude any events from %s",
+                                               event_name,
+                                               excluder_length,
+                                               next_excluder,
+                                               event_name);
+                               break;
+                       }
+                       excluder_ptr++;
+                       event_ptr++;
+               }
+               /* next excluder */
+               next_excluder += excluder_length;
+               if (*next_excluder == ',') {
+                       next_excluder++;
+               }
+       }
+       goto end;
+error:
+       while (exclusion_count--) {
+               free(exclusion_list[exclusion_count]);
+       }
+       if (exclusion_list != NULL) {
+               free(exclusion_list);
+       }
+       exclusion_list = NULL;
+       exclusion_count = 0;
+       ret = CMD_ERROR;
+end:
+       *exclusion_count_ptr = exclusion_count;
+       *exclusion_list_ptr = exclusion_list;
+       return ret;
+}
 /*
  * Enabling event using the lttng API.
  */