Merge tag 'ftrace-v6.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull ftrace fixes from Steven Rostedt:

 - Always try to initialize the idle functions when graph tracer starts

   A bug was found that when a CPU is offline when graph tracing starts
   and then comes online, that CPU is not traced. The fix to that was to
   move the initialization of the idle shadow stack over to the hot plug
   online logic, which also handle onlined CPUs. The issue was that it
   removed the initialization of the shadow stack when graph tracing
   starts, but the callbacks to the hot plug logic do nothing if graph
   tracing isn't currently running. Although that fix fixed the onlining
   of a CPU during tracing, it broke the CPUs that were already online.

 - Have microblaze not try to get the "true parent" in function tracing

   If function tracing and graph tracing are both enabled at the same
   time the parent of the functions traced by the function tracer may
   sometimes be the graph tracing trampoline. The graph tracing hijacks
   the return pointer of the function to trace it, but that can
   interfere with the function tracing parent output.

   This was fixed by using the ftrace_graph_ret_addr() function passing
   in the kernel stack pointer using the ftrace_regs_get_stack_pointer()
   function. But Al Viro reported that Microblaze does not implement the
   kernel_stack_pointer(regs) helper function that
   ftrace_regs_get_stack_pointer() uses and fails to compile when
   function graph tracing is enabled.

   It was first thought that this was a microblaze issue, but the real
   cause is that this only works when an architecture implements
   HAVE_DYNAMIC_FTRACE_WITH_ARGS, as a requirement for that config is to
   have ftrace always pass a valid ftrace_regs to the callbacks. That
   also means that the architecture supports
   ftrace_regs_get_stack_pointer()

   Microblaze does not set HAVE_DYNAMIC_FTRACE_WITH_ARGS nor does it
   implement ftrace_regs_get_stack_pointer() which caused it to fail to
   build. Only implement the "true parent" logic if an architecture has
   that config set"

* tag 'ftrace-v6.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ftrace: Do not find "true_parent" if HAVE_DYNAMIC_FTRACE_WITH_ARGS is not set
  fgraph: Still initialize idle shadow stacks when starting

Author: torvalds

kernel/trace/fgraph.c

@@ -1215,14 +1215,20 @@ void fgraph_update_pid_func(void)
 static int start_graph_tracing(void)
 {
 	unsigned long **ret_stack_list;
-	int ret;
+	int ret, cpu;
 
 	ret_stack_list = kcalloc(FTRACE_RETSTACK_ALLOC_SIZE,
 				 sizeof(*ret_stack_list), GFP_KERNEL);
 
 	if (!ret_stack_list)
 		return -ENOMEM;
 
+	/* The cpu_boot init_task->ret_stack will never be freed */
+	for_each_online_cpu(cpu) {
+		if (!idle_task(cpu)->ret_stack)
+			ftrace_graph_init_idle_task(idle_task(cpu), cpu);
+	}
+
 	do {
 		ret = alloc_retstack_tasklist(ret_stack_list);
 	} while (ret == -EAGAIN);

kernel/trace/trace_functions.c

@@ -176,7 +176,8 @@ static void function_trace_start(struct trace_array *tr)
 	tracing_reset_online_cpus(&tr->array_buffer);
 }
 
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/* fregs are guaranteed not to be NULL if HAVE_DYNAMIC_FTRACE_WITH_ARGS is set */
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS)
 static __always_inline unsigned long
 function_get_true_parent_ip(unsigned long parent_ip, struct ftrace_regs *fregs)
 {