[RFC PATCH v3 18/19] tracing/boot: Add function-graph tracer options

[Masami Hiramatsu <mhiramat@kernel.org>]

Add following function-graph tracer related options

 - ftrace.fgraph.filters = FILTER[, FILTER2...];
   Add fgraph tracing function filters.

 - ftrace.fgraph.notraces = FILTER[, FILTER2...];
   Add fgraph non tracing function filters.

 - ftrace.fgraph.max_depth = MAX_DEPTH;
   Set MAX_DEPTH to maximum depth of fgraph tracer.

Note that these properties are available on ftrace global node
only, because these filters are globally applied.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 kernel/trace/ftrace.c     |   85 +++++++++++++++++++++++++++++----------------
 kernel/trace/trace_boot.c |   71 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 126 insertions(+), 30 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index eca34503f178..e016ce12e60a 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1241,7 +1241,7 @@ static void clear_ftrace_mod_list(struct list_head *head)
 	mutex_unlock(&ftrace_lock);
 }
 
-static void free_ftrace_hash(struct ftrace_hash *hash)
+void free_ftrace_hash(struct ftrace_hash *hash)
 {
 	if (!hash || hash == EMPTY_HASH)
 		return;
@@ -4897,7 +4897,7 @@ __setup("ftrace_filter=", set_ftrace_filter);
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 static char ftrace_graph_buf[FTRACE_FILTER_SIZE] __initdata;
 static char ftrace_graph_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
-static int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer);
+int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer);
 
 static int __init set_graph_function(char *str)
 {
@@ -5226,6 +5226,26 @@ __ftrace_graph_open(struct inode *inode, struct file *file,
 	return ret;
 }
 
+struct ftrace_hash *ftrace_graph_copy_hash(bool enable)
+{
+	struct ftrace_hash *hash;
+
+	mutex_lock(&graph_lock);
+
+	if (enable)
+		hash = rcu_dereference_protected(ftrace_graph_hash,
+					lockdep_is_held(&graph_lock));
+	else
+		hash = rcu_dereference_protected(ftrace_graph_notrace_hash,
+					lockdep_is_held(&graph_lock));
+
+	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, hash);
+
+	mutex_unlock(&graph_lock);
+
+	return hash;
+}
+
 static int
 ftrace_graph_open(struct inode *inode, struct file *file)
 {
@@ -5282,11 +5302,40 @@ ftrace_graph_notrace_open(struct inode *inode, struct file *file)
 	return ret;
 }
 
+int ftrace_graph_apply_hash(struct ftrace_hash *hash, bool enable)
+{
+	struct ftrace_hash *old_hash, *new_hash;
+
+	new_hash = __ftrace_hash_move(hash);
+	if (!new_hash)
+		return -ENOMEM;
+
+	mutex_lock(&graph_lock);
+
+	if (enable) {
+		old_hash = rcu_dereference_protected(ftrace_graph_hash,
+				lockdep_is_held(&graph_lock));
+		rcu_assign_pointer(ftrace_graph_hash, new_hash);
+	} else {
+		old_hash = rcu_dereference_protected(ftrace_graph_notrace_hash,
+				lockdep_is_held(&graph_lock));
+		rcu_assign_pointer(ftrace_graph_notrace_hash, new_hash);
+	}
+
+	mutex_unlock(&graph_lock);
+
+	/* Wait till all users are no longer using the old hash */
+	synchronize_rcu();
+
+	free_ftrace_hash(old_hash);
+
+	return 0;
+}
+
 static int
 ftrace_graph_release(struct inode *inode, struct file *file)
 {
 	struct ftrace_graph_data *fgd;
-	struct ftrace_hash *old_hash, *new_hash;
 	struct trace_parser *parser;
 	int ret = 0;
 
@@ -5311,41 +5360,17 @@ ftrace_graph_release(struct inode *inode, struct file *file)
 
 		trace_parser_put(parser);
 
-		new_hash = __ftrace_hash_move(fgd->new_hash);
-		if (!new_hash) {
-			ret = -ENOMEM;
-			goto out;
-		}
-
-		mutex_lock(&graph_lock);
-
-		if (fgd->type == GRAPH_FILTER_FUNCTION) {
-			old_hash = rcu_dereference_protected(ftrace_graph_hash,
-					lockdep_is_held(&graph_lock));
-			rcu_assign_pointer(ftrace_graph_hash, new_hash);
-		} else {
-			old_hash = rcu_dereference_protected(ftrace_graph_notrace_hash,
-					lockdep_is_held(&graph_lock));
-			rcu_assign_pointer(ftrace_graph_notrace_hash, new_hash);
-		}
-
-		mutex_unlock(&graph_lock);
-
-		/* Wait till all users are no longer using the old hash */
-		synchronize_rcu();
-
-		free_ftrace_hash(old_hash);
+		ret = ftrace_graph_apply_hash(fgd->new_hash,
+					fgd->type == GRAPH_FILTER_FUNCTION);
 	}
 
- out:
 	free_ftrace_hash(fgd->new_hash);
 	kfree(fgd);
 
 	return ret;
 }
 
-static int
-ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
+int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
 {
 	struct ftrace_glob func_g;
 	struct dyn_ftrace *rec;
diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 942ca8d3fcc8..b32688032d36 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -72,6 +72,75 @@ trace_boot_set_instance_options(struct trace_array *tr, struct skc_node *node)
 	}
 }
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+extern unsigned int fgraph_max_depth;
+extern struct ftrace_hash *ftrace_graph_copy_hash(bool enable);
+extern int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer);
+extern int ftrace_graph_apply_hash(struct ftrace_hash *hash, bool enable);
+extern void free_ftrace_hash(struct ftrace_hash *hash);
+
+static void __init
+trace_boot_set_fgraph_filter(struct skc_node *node, const char *option,
+			     bool enable)
+{
+	struct ftrace_hash *hash;
+	struct skc_node *anode;
+	const char *p;
+	char *q;
+	int err;
+	bool updated = false;
+
+	hash = ftrace_graph_copy_hash(enable);
+	if (!hash) {
+		pr_err("Failed to copy fgraph hash\n");
+		return;
+	}
+	skc_node_for_each_array_value(node, option, anode, p) {
+		q = kstrdup(p, GFP_KERNEL);
+		if (!q)
+			goto free_hash;
+		err = ftrace_graph_set_hash(hash, q);
+		kfree(q);
+		if (err)
+			pr_err("Failed to add %s: %s\n", option, p);
+		else
+			updated = true;
+	}
+	if (!updated)
+		goto free_hash;
+
+	if (ftrace_graph_apply_hash(hash, enable) < 0)
+		pr_err("Failed to apply new fgraph hash\n");
+	else {
+		/* If succeeded to apply new hash, old hash is released */
+		return;
+	}
+
+free_hash:
+	free_ftrace_hash(hash);
+}
+
+static void __init
+trace_boot_set_fgraph_options(struct skc_node *node)
+{
+	const char *p;
+	unsigned long v;
+
+	node = skc_node_find_child(node, "fgraph");
+	if (!node)
+		return;
+
+	trace_boot_set_fgraph_filter(node, "filters", true);
+	trace_boot_set_fgraph_filter(node, "notraces", false);
+
+	p = skc_node_find_value(node, "max_depth", NULL);
+	if (p && *p != '\0' && !kstrtoul(p, 0, &v))
+		fgraph_max_depth = (unsigned int)v;
+}
+#else
+#define trace_boot_set_fgraph_options(node)	do {} while (0)
+#endif
+
 static void __init
 trace_boot_set_global_options(struct trace_array *tr, struct skc_node *node)
 {
@@ -98,6 +167,8 @@ trace_boot_set_global_options(struct trace_array *tr, struct skc_node *node)
 	if (skc_node_find_value(node, "alloc_snapshot", NULL))
 		if (tracing_alloc_snapshot() < 0)
 			pr_err("Failed to allocate snapshot buffer\n");
+
+	trace_boot_set_fgraph_options(node);
 }
 
 #ifdef CONFIG_EVENT_TRACING