linux-kernel - [RFC PATCH 14/32] function_graph: Move graph notrace bit to shadow stack global var

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Message-Id: <169920056100.482486.10749804996506200504.stgit@devnote2>
Date:   Mon,  6 Nov 2023 01:09:21 +0900
From:   "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Florent Revest <revest@...omium.org>
Cc:     linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        bpf <bpf@...r.kernel.org>, Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alan Maguire <alan.maguire@...cle.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Guo Ren <guoren@...nel.org>
Subject: [RFC PATCH 14/32] function_graph: Move graph notrace bit to shadow stack global var

From: Steven Rostedt (VMware) <rostedt@...dmis.org>

The use of the task->trace_recursion for the logic used for the function
graph no-trace was a bit of an abuse of that variable. Now that there exists
global vars that are per stack for registered graph traces, use that instead.

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
 include/linux/trace_recursion.h      |    7 -------
 kernel/trace/trace.h                 |    9 +++++++++
 kernel/trace/trace_functions_graph.c |   10 ++++++----
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index 00e792bf148d..cc11b0e9d220 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -44,13 +44,6 @@ enum {
  */
 	TRACE_IRQ_BIT,
 
-	/*
-	 * To implement set_graph_notrace, if this bit is set, we ignore
-	 * function graph tracing of called functions, until the return
-	 * function is called to clear it.
-	 */
-	TRACE_GRAPH_NOTRACE_BIT,
-
 	/* Used to prevent recursion recording from recursing. */
 	TRACE_RECORD_RECURSION_BIT,
 };
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 8e5943d3d25c..350c889c2f1e 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -911,8 +911,17 @@ enum {
 
 	TRACE_GRAPH_DEPTH_START_BIT,
 	TRACE_GRAPH_DEPTH_END_BIT,
+
+	/*
+	 * To implement set_graph_notrace, if this bit is set, we ignore
+	 * function graph tracing of called functions, until the return
+	 * function is called to clear it.
+	 */
+	TRACE_GRAPH_NOTRACE_BIT,
 };
 
+#define TRACE_GRAPH_NOTRACE		(1 << TRACE_GRAPH_NOTRACE_BIT)
+
 static inline unsigned long ftrace_graph_depth(unsigned long *task_var)
 {
 	return (*task_var >> TRACE_GRAPH_DEPTH_START_BIT) & 3;
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 66cce73e94f8..13d0387ac6a6 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -130,6 +130,7 @@ static inline int ftrace_graph_ignore_irqs(void)
 int trace_graph_entry(struct ftrace_graph_ent *trace,
 		      struct fgraph_ops *gops)
 {
+	unsigned long *task_var = fgraph_get_task_var(gops);
 	struct trace_array *tr = gops->private;
 	struct trace_array_cpu *data;
 	unsigned long flags;
@@ -138,7 +139,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace,
 	int ret;
 	int cpu;
 
-	if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT))
+	if (*task_var & TRACE_GRAPH_NOTRACE)
 		return 0;
 
 	/*
@@ -149,7 +150,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace,
 	 * returning from the function.
 	 */
 	if (ftrace_graph_notrace_addr(trace->func)) {
-		trace_recursion_set(TRACE_GRAPH_NOTRACE_BIT);
+		*task_var |= TRACE_GRAPH_NOTRACE_BIT;
 		/*
 		 * Need to return 1 to have the return called
 		 * that will clear the NOTRACE bit.
@@ -240,6 +241,7 @@ void __trace_graph_return(struct trace_array *tr,
 void trace_graph_return(struct ftrace_graph_ret *trace,
 			struct fgraph_ops *gops)
 {
+	unsigned long *task_var = fgraph_get_task_var(gops);
 	struct trace_array *tr = gops->private;
 	struct trace_array_cpu *data;
 	unsigned long flags;
@@ -249,8 +251,8 @@ void trace_graph_return(struct ftrace_graph_ret *trace,
 
 	ftrace_graph_addr_finish(gops, trace);
 
-	if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
-		trace_recursion_clear(TRACE_GRAPH_NOTRACE_BIT);
+	if (*task_var & TRACE_GRAPH_NOTRACE) {
+		*task_var &= ~TRACE_GRAPH_NOTRACE;
 		return;
 	}