tracing: Move filtered_pid helper functions into trace.c

As the filtered_pid functions are going to be used by function tracer as
well as trace_events, move the code into the generic trace.c file.

The functions moved are:

 trace_find_filtered_pid()
 trace_ignore_this_task()
 trace_filter_add_remove_task()

Kernel Doc text was also added.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 78 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8a4bd6b68a0b..0b87fe8e6d0b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -319,6 +319,84 @@ int call_filter_check_discard(struct trace_event_call *call, void *rec,
         return 0;
 }
 
+/**
+ * trace_find_filtered_pid - check if a pid exists in a filtered_pid list
+ * @filtered_pids: The list of pids to check
+ * @search_pid: The PID to find in @filtered_pids
+ *
+ * Returns true if @search_pid is fonud in @filtered_pids, and false otherwis.
+ */
+bool
+trace_find_filtered_pid(struct trace_pid_list *filtered_pids, pid_t search_pid)
+{
+        /*
+         * If pid_max changed after filtered_pids was created, we
+         * by default ignore all pids greater than the previous pid_max.
+         */
+        if (search_pid >= filtered_pids->pid_max)
+                return false;
+
+        return test_bit(search_pid, filtered_pids->pids);
+}
+
+/**
+ * trace_ignore_this_task - should a task be ignored for tracing
+ * @filtered_pids: The list of pids to check
+ * @task: The task that should be ignored if not filtered
+ *
+ * Checks if @task should be traced or not from @filtered_pids.
+ * Returns true if @task should *NOT* be traced.
+ * Returns false if @task should be traced.
+ */
+bool
+trace_ignore_this_task(struct trace_pid_list *filtered_pids, struct task_struct *task)
+{
+        /*
+         * Return false, because if filtered_pids does not exist,
+         * all pids are good to trace.
+         */
+        if (!filtered_pids)
+                return false;
+
+        return !trace_find_filtered_pid(filtered_pids, task->pid);
+}
+
+/**
+ * trace_pid_filter_add_remove - Add or remove a task from a pid_list
+ * @pid_list: The list to modify
+ * @self: The current task for fork or NULL for exit
+ * @task: The task to add or remove
+ *
+ * If adding a task, if @self is defined, the task is only added if @self
+ * is also included in @pid_list. This happens on fork and tasks should
+ * only be added when the parent is listed. If @self is NULL, then the
+ * @task pid will be removed from the list, which would happen on exit
+ * of a task.
+ */
+void trace_filter_add_remove_task(struct trace_pid_list *pid_list,
+                                  struct task_struct *self,
+                                  struct task_struct *task)
+{
+        if (!pid_list)
+                return;
+
+        /* For forks, we only add if the forking task is listed */
+        if (self) {
+                if (!trace_find_filtered_pid(pid_list, self->pid))
+                        return;
+        }
+
+        /* Sorry, but we don't support pid_max changing after setting */
+        if (task->pid >= pid_list->pid_max)
+                return;
+
+        /* "self" is set for forks, and NULL for exits */
+        if (self)
+                set_bit(task->pid, pid_list->pids);
+        else
+                clear_bit(task->pid, pid_list->pids);
+}
+
 static cycle_t buffer_ftrace_now(struct trace_buffer *buf, int cpu)
 {
         u64 ts;