scripts/gdb: add helper and convenience function to look up tasks

Add the helper task_by_pid that can look up a task by its PID.  Also
export it as a convenience function.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/gdb/linux/tasks.py

@@ -44,3 +44,30 @@ class TaskList:
                 utils.container_of(t['thread_group']['next'],
                                    self.task_ptr_type, "thread_group")
         return t
+
+
+def get_task_by_pid(pid):
+    for task in TaskList():
+        if int(task['pid']) == pid:
+            return task
+    return None
+
+
+class LxTaskByPidFunc(gdb.Function):
+    """Find Linux task by PID and return the task_struct variable.
+
+$lx_task_by_pid(PID): Given PID, iterate over all tasks of the target and
+return that task_struct variable which PID matches."""
+
+    def __init__(self):
+        super(LxTaskByPidFunc, self).__init__("lx_task_by_pid")
+
+    def invoke(self, pid):
+        task = get_task_by_pid(pid)
+        if task:
+            return task.dereference()
+        else:
+            raise gdb.GdbError("No task of PID " + str(pid))
+
+
+LxTaskByPidFunc()

scripts/gdb/vmlinux-gdb.py

@@ -26,3 +26,4 @@ else:
     import linux.symbols
     import linux.modules
     import linux.dmesg
+    import linux.tasks