linux-kernel - [RFC][PATCH 11/14 v2] function_graph: Move graph depth stored data to shadow stack global var

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Message-Id: <20190520142158.231362726@goodmis.org>
Date:   Mon, 20 May 2019 10:20:12 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Andy Lutomirski <luto@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        "Frank Ch. Eigler" <fche@...hat.com>
Subject: [RFC][PATCH 11/14 v2] function_graph: Move graph depth stored data 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 depth 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>
---
 kernel/trace/trace.h | 63 ++++++++++++++++++++++----------------------
 1 file changed, 32 insertions(+), 31 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 08e79334c8ca..c466c8a1a8cf 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -567,25 +567,6 @@ enum {
  */
 	TRACE_IRQ_BIT,
 
-	/*
-	 * In the very unlikely case that an interrupt came in
-	 * at a start of graph tracing, and we want to trace
-	 * the function in that interrupt, the depth can be greater
-	 * than zero, because of the preempted start of a previous
-	 * trace. In an even more unlikely case, depth could be 2
-	 * if a softirq interrupted the start of graph tracing,
-	 * followed by an interrupt preempting a start of graph
-	 * tracing in the softirq, and depth can even be 3
-	 * if an NMI came in at the start of an interrupt function
-	 * that preempted a softirq start of a function that
-	 * preempted normal context!!!! Luckily, it can't be
-	 * greater than 3, so the next two bits are a mask
-	 * of what the depth is when we set TRACE_GRAPH_FL
-	 */
-
-	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
@@ -598,16 +579,6 @@ enum {
 #define trace_recursion_clear(bit)	do { (current)->trace_recursion &= ~(1<<(bit)); } while (0)
 #define trace_recursion_test(bit)	((current)->trace_recursion & (1<<(bit)))
 
-#define trace_recursion_depth() \
-	(((current)->trace_recursion >> TRACE_GRAPH_DEPTH_START_BIT) & 3)
-#define trace_recursion_set_depth(depth) \
-	do {								\
-		current->trace_recursion &=				\
-			~(3 << TRACE_GRAPH_DEPTH_START_BIT);		\
-		current->trace_recursion |=				\
-			((depth) & 3) << TRACE_GRAPH_DEPTH_START_BIT;	\
-	} while (0)
-
 #define TRACE_CONTEXT_BITS	4
 
 #define TRACE_FTRACE_START	TRACE_FTRACE_BIT
@@ -936,8 +907,38 @@ extern void free_fgraph_ops(struct trace_array *tr);
 
 enum {
 	TRACE_GRAPH_FL		= 1,
+
+	/*
+	 * In the very unlikely case that an interrupt came in
+	 * at a start of graph tracing, and we want to trace
+	 * the function in that interrupt, the depth can be greater
+	 * than zero, because of the preempted start of a previous
+	 * trace. In an even more unlikely case, depth could be 2
+	 * if a softirq interrupted the start of graph tracing,
+	 * followed by an interrupt preempting a start of graph
+	 * tracing in the softirq, and depth can even be 3
+	 * if an NMI came in at the start of an interrupt function
+	 * that preempted a softirq start of a function that
+	 * preempted normal context!!!! Luckily, it can't be
+	 * greater than 3, so the next two bits are a mask
+	 * of what the depth is when we set TRACE_GRAPH_FL
+	 */
+
+	TRACE_GRAPH_DEPTH_START_BIT,
+	TRACE_GRAPH_DEPTH_END_BIT,
 };
 
+static inline unsigned long ftrace_graph_depth(unsigned long *task_var)
+{
+	return (*task_var >> TRACE_GRAPH_DEPTH_START_BIT) & 3;
+}
+
+static inline void ftrace_graph_set_depth(unsigned long *task_var, int depth)
+{
+	*task_var &= ~(3 << TRACE_GRAPH_DEPTH_START_BIT);
+	*task_var |= (depth & 3) << TRACE_GRAPH_DEPTH_START_BIT;
+}
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 extern struct ftrace_hash *ftrace_graph_hash;
 extern struct ftrace_hash *ftrace_graph_notrace_hash;
@@ -961,7 +962,7 @@ ftrace_graph_addr(unsigned long *task_var, struct ftrace_graph_ent *trace)
 		 * when the depth is zero.
 		 */
 		*task_var |= TRACE_GRAPH_FL;
-		trace_recursion_set_depth(trace->depth);
+		ftrace_graph_set_depth(task_var, trace->depth);
 
 		/*
 		 * If no irqs are to be traced, but a set_graph_function
@@ -986,7 +987,7 @@ ftrace_graph_addr_finish(struct fgraph_ops *gops, struct ftrace_graph_ret *trace
 	unsigned long *task_var = fgraph_get_task_var(gops);
 
 	if ((*task_var & TRACE_GRAPH_FL) &&
-	    trace->depth == trace_recursion_depth())
+	    trace->depth == ftrace_graph_depth(task_var))
 		*task_var &= ~TRACE_GRAPH_FL;
 }
 
-- 
2.20.1