kprobe: move sysctl_kprobes_optimization to kprobes.c

kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.

To help with this maintenance let's start by moving sysctls to places
where they actually belong.  The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we
just care about the core logic.

Move sysctl_kprobes_optimization from kernel/sysctl.c to
kernel/kprobes.c.  Use register_sysctl() to register the sysctl
interface.

[mcgrof@kernel.org: fix compile issue when CONFIG_OPTPROBES is disabled]

Link: https://lkml.kernel.org/r/20211129211943.640266-7-mcgrof@kernel.org
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Antti Palosaari <crope@iki.fi>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Lukas Middendorf <kernel@tuxforce.de>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Stephen Kitt <steve@sk2.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kprobes.h

@@ -348,12 +348,6 @@ extern void opt_pre_handler(struct kprobe *p, struct pt_regs *regs);
 
 DEFINE_INSN_CACHE_OPS(optinsn);
 
-#ifdef CONFIG_SYSCTL
-extern int sysctl_kprobes_optimization;
-extern int proc_kprobes_optimization_handler(struct ctl_table *table,
-					     int write, void *buffer,
-					     size_t *length, loff_t *ppos);
-#endif /* CONFIG_SYSCTL */
 extern void wait_for_kprobe_optimizer(void);
 #else /* !CONFIG_OPTPROBES */
 static inline void wait_for_kprobe_optimizer(void) { }

kernel/kprobes.c

@@ -48,6 +48,9 @@
 #define KPROBE_HASH_BITS 6
 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
 
+#if !defined(CONFIG_OPTPROBES) || !defined(CONFIG_SYSCTL)
+#define kprobe_sysctls_init() do { } while (0)
+#endif
 
 static int kprobes_initialized;
 /* kprobe_table can be accessed by
@@ -938,10 +941,10 @@ static void unoptimize_all_kprobes(void)
 }
 
 static DEFINE_MUTEX(kprobe_sysctl_mutex);
-int sysctl_kprobes_optimization;
-int proc_kprobes_optimization_handler(struct ctl_table *table, int write,
-				      void *buffer, size_t *length,
-				      loff_t *ppos)
+static int sysctl_kprobes_optimization;
+static int proc_kprobes_optimization_handler(struct ctl_table *table,
+					     int write, void *buffer,
+					     size_t *length, loff_t *ppos)
 {
 	int ret;
 
@@ -957,6 +960,24 @@ int proc_kprobes_optimization_handler(struct ctl_table *table, int write,
 
 	return ret;
 }
+
+static struct ctl_table kprobe_sysctls[] = {
+	{
+		.procname	= "kprobes-optimization",
+		.data		= &sysctl_kprobes_optimization,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_kprobes_optimization_handler,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{}
+};
+
+static void __init kprobe_sysctls_init(void)
+{
+	register_sysctl_init("debug", kprobe_sysctls);
+}
 #endif /* CONFIG_SYSCTL */
 
 /* Put a breakpoint for a probe. */
@@ -2584,6 +2605,7 @@ static int __init init_kprobes(void)
 		err = register_module_notifier(&kprobe_module_nb);
 
 	kprobes_initialized = (err == 0);
+	kprobe_sysctls_init();
 	return err;
 }
 early_initcall(init_kprobes);

kernel/sysctl.c

@@ -56,7 +56,6 @@
 #include <linux/reboot.h>
 #include <linux/ftrace.h>
 #include <linux/perf_event.h>
-#include <linux/kprobes.h>
 #include <linux/oom.h>
 #include <linux/kmod.h>
 #include <linux/capability.h>
@@ -2818,17 +2817,6 @@ static struct ctl_table debug_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
-#endif
-#if defined(CONFIG_OPTPROBES)
-	{
-		.procname	= "kprobes-optimization",
-		.data		= &sysctl_kprobes_optimization,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_kprobes_optimization_handler,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
-	},
 #endif
 	{ }
 };