[PATCH v2 sysctl-next] ftrace: move sysctl_ftrace_enabled to ftrace.c

[Wei Xiao]

This moves ftrace_enabled to trace/ftrace.c.

We move sysctls to places where features actually belong to improve
the readability of the code and reduce the risk of code merge conflicts.
At the same time, the proc-sysctl maintainers do not want to know what
sysctl knobs you wish to add for your owner piece of code, we just care
about the core logic.

Signed-off-by: Wei Xiao <xiaowei66@xxxxxxxxxx>

---
v2:
Add subject-prefix of sysctl-next and add the explanation to the commit log 
to help patch review and subsystem maintainers better understand the context/logic 
behind the migration.

v1: https://lore.kernel.org/lkml/20220223012311.134314-1-xiaowei66@xxxxxxxxxx/
1. Lack subject-prefix of sysctl-next to avoid conflicts better.
2. Lack more informations in the commit log to help patch review better.
---
 include/linux/ftrace.h |  3 ---
 kernel/sysctl.c        |  9 ---------
 kernel/trace/ftrace.c  | 22 +++++++++++++++++++++-
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 9999e29187de..659b2840563a 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -94,9 +94,6 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
 #ifdef CONFIG_FUNCTION_TRACER
 
 extern int ftrace_enabled;
-extern int
-ftrace_enable_sysctl(struct ctl_table *table, int write,
-		     void *buffer, size_t *lenp, loff_t *ppos);
 
 #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5ae443b2882e..55279ec66b28 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1906,15 +1906,6 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
-#ifdef CONFIG_FUNCTION_TRACER
-	{
-		.procname	= "ftrace_enabled",
-		.data		= &ftrace_enabled,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= ftrace_enable_sysctl,
-	},
-#endif
 #ifdef CONFIG_STACK_TRACER
 	{
 		.procname	= "stack_tracer_enabled",
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f9feb197b2da..4a5b4d6996a4 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -7846,7 +7846,8 @@ static bool is_permanent_ops_registered(void)
 	return false;
 }
 
-int
+#ifdef CONFIG_SYSCTL
+static int
 ftrace_enable_sysctl(struct ctl_table *table, int write,
 		     void *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -7889,3 +7890,22 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 	mutex_unlock(&ftrace_lock);
 	return ret;
 }
+
+static struct ctl_table ftrace_sysctls[] = {
+	{
+		.procname       = "ftrace_enabled",
+		.data           = &ftrace_enabled,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = ftrace_enable_sysctl,
+	},
+	{}
+};
+
+static int __init ftrace_sysctl_init(void)
+{
+	register_sysctl_init("kernel", ftrace_sysctls);
+	return 0;
+}
+late_initcall(ftrace_sysctl_init);
+#endif
-- 
2.19.1