linux-kernel - [GIT PULL] ftrace: Fix function graph notrace setting

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Message-ID: <20250208093927.3be357ae@batman.local.home>
Date: Sat, 8 Feb 2025 09:39:27 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>, Mathieu
 Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [GIT PULL] ftrace: Fix function graph notrace setting



Linus,

function graph fix of notrace functions:

When the function graph tracer was restructured to use the global section
of the meta data in the shadow stack, the bit logic was changed. There's a
TRACE_GRAPH_NOTRACE_BIT that is the bit number in the mask that tells if
the function graph tracer is currently in the "notrace" mode. The
TRACE_GRAPH_NOTRACE is the mask with that bit set. But when the code was
restructured, the TRACE_GRAPH_NOTRACE_BIT was used when it should have
been the TRACE_GRAPH_NOTRACE mask. This made notrace not work properly.


Please pull the latest ftrace-v6.14-rc1 tree, which can be found at:


  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
ftrace-v6.14-rc1

Tag SHA1: 9f1894050febeedc75e6cbaef2bd02ea6094a9d9
Head SHA1: c8c9b1d2d5b4377c72a979f5a26e842a869aefc9


Steven Rostedt (1):
      fgraph: Fix set_graph_notrace with setting TRACE_GRAPH_NOTRACE_BIT

----
 kernel/trace/trace_functions_graph.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---------------------------
commit c8c9b1d2d5b4377c72a979f5a26e842a869aefc9
Author: Steven Rostedt <rostedt@...dmis.org>
Date:   Sat Feb 8 00:15:11 2025 -0500

    fgraph: Fix set_graph_notrace with setting TRACE_GRAPH_NOTRACE_BIT
    
    The code was restructured where the function graph notrace code, that
    would not trace a function and all its children is done by setting a
    NOTRACE flag when the function that is not to be traced is hit.
    
    There's a TRACE_GRAPH_NOTRACE_BIT which defines the bit in the flags and a
    TRACE_GRAPH_NOTRACE which is the mask with that bit set. But the
    restructuring used TRACE_GRAPH_NOTRACE_BIT when it should have used
    TRACE_GRAPH_NOTRACE.
    
    For example:
    
     # cd /sys/kernel/tracing
     # echo set_track_prepare stack_trace_save  > set_graph_notrace
     # echo function_graph > current_tracer
     # cat trace
    [..]
     0)               |                          __slab_free() {
     0)               |                            free_to_partial_list() {
     0)               |                                  arch_stack_walk() {
     0)               |                                    __unwind_start() {
     0)   0.501 us    |                                      get_stack_info();
    
    Where a non filter trace looks like:
    
     # echo > set_graph_notrace
     # cat trace
     0)               |                            free_to_partial_list() {
     0)               |                              set_track_prepare() {
     0)               |                                stack_trace_save() {
     0)               |                                  arch_stack_walk() {
     0)               |                                    __unwind_start() {
    
    Where the filter should look like:
    
     # cat trace
     0)               |                            free_to_partial_list() {
     0)               |                              _raw_spin_lock_irqsave() {
     0)   0.350 us    |                                preempt_count_add();
     0)   0.351 us    |                                do_raw_spin_lock();
     0)   2.440 us    |                              }
    
    Cc: stable@...r.kernel.org
    Cc: Masami Hiramatsu <mhiramat@...nel.org>
    Cc: Mark Rutland <mark.rutland@....com>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
    Link: https://lore.kernel.org/20250208001511.535be150@batman.local.home
    Fixes: b84214890a9bc ("function_graph: Move graph notrace bit to shadow stack global var")
    Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 54d850997c0a..136c750b0b4d 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -198,7 +198,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace,
 	 * returning from the function.
 	 */
 	if (ftrace_graph_notrace_addr(trace->func)) {
-		*task_var |= TRACE_GRAPH_NOTRACE_BIT;
+		*task_var |= TRACE_GRAPH_NOTRACE;
 		/*
 		 * Need to return 1 to have the return called
 		 * that will clear the NOTRACE bit.