linux-kernel - [for-next][PATCH 18/27] function_graph: Move graph notrace bit to shadow stack global var

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Date: Tue, 04 Jun 2024 10:41:21 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Alexei Starovoitov <alexei.starovoitov@...il.com>,
 Florent Revest <revest@...omium.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>,
 Peter Zijlstra <peterz@...radead.org>,
 Thomas Gleixner <tglx@...utronix.de>,
 Guo Ren <guoren@...nel.org>
Subject: [for-next][PATCH 18/27] 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.

Link: https://lore.kernel.org/linux-trace-kernel/171509107907.162236.6564679266777519065.stgit@devnote2
Link: https://lore.kernel.org/linux-trace-kernel/20240603190823.796709456@goodmis.org

Cc: Mark Rutland <mark.rutland@....com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Florent Revest <revest@...omium.org>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: bpf <bpf@...r.kernel.org>
Cc: Sven Schnelle <svens@...ux.ibm.com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Alan Maguire <alan.maguire@...cle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Guo Ren <guoren@...nel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.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 fdfb6f66718a..ae04054a1be3 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 82d879dc63ff..b37402e3f0c9 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -919,8 +919,17 @@ 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;
 	}
 
-- 
2.43.0