kernel/reboot: move reboot sysctls to its own file

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.

All filesystem syctls now get reviewed by fs folks. This commit
follows the commit of fs, move the poweroff_cmd and ctrl-alt-del
sysctls to its own file, kernel/reboot.c.

Signed-off-by: tangmeng <[email protected]>
Signed-off-by: Luis Chamberlain <[email protected]>

Author: imtangmeng

include/linux/reboot.h

@@ -71,12 +71,8 @@ extern void kernel_restart(char *cmd);
 extern void kernel_halt(void);
 extern void kernel_power_off(void);
 
-extern int C_A_D; /* for sysctl */
 void ctrl_alt_del(void);
 
-#define POWEROFF_CMD_PATH_LEN	256
-extern char poweroff_cmd[POWEROFF_CMD_PATH_LEN];
-
 extern void orderly_poweroff(bool force);
 extern void orderly_reboot(void);
 void hw_protection_shutdown(const char *reason, int ms_until_forced);

kernel/reboot.c

@@ -23,7 +23,7 @@
  * this indicates whether you can reboot with ctrl-alt-del: the default is yes
  */
 
-int C_A_D = 1;
+static int C_A_D = 1;
 struct pid *cad_pid;
 EXPORT_SYMBOL(cad_pid);
 
@@ -417,9 +417,37 @@ void ctrl_alt_del(void)
 		kill_cad_pid(SIGINT, 1);
 }
 
-char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
+#define POWEROFF_CMD_PATH_LEN  256
+static char poweroff_cmd[POWEROFF_CMD_PATH_LEN] = "/sbin/poweroff";
 static const char reboot_cmd[] = "/sbin/reboot";
 
+#ifdef CONFIG_SYSCTL
+static struct ctl_table kern_reboot_table[] = {
+	{
+		.procname       = "poweroff_cmd",
+		.data           = &poweroff_cmd,
+		.maxlen         = POWEROFF_CMD_PATH_LEN,
+		.mode           = 0644,
+		.proc_handler   = proc_dostring,
+	},
+	{
+		.procname       = "ctrl-alt-del",
+		.data           = &C_A_D,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec,
+	},
+	{ }
+};
+
+static void __init kernel_reboot_sysctls_init(void)
+{
+	register_sysctl_init("kernel", kern_reboot_table);
+}
+#else
+#define kernel_reboot_sysctls_init() do { } while (0)
+#endif /* CONFIG_SYSCTL */
+
 static int run_cmd(const char *cmd)
 {
 	char **argv;
@@ -886,6 +914,8 @@ static int __init reboot_ksysfs_init(void)
 		return ret;
 	}
 
+	kernel_reboot_sysctls_init();
+
 	return 0;
 }
 late_initcall(reboot_ksysfs_init);

kernel/sysctl.c

@@ -1798,13 +1798,6 @@ static struct ctl_table kern_table[] = {
 		.proc_handler	= proc_dointvec,
 	},
 #endif
-	{
-		.procname	= "ctrl-alt-del",
-		.data		= &C_A_D,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
 #ifdef CONFIG_FUNCTION_TRACER
 	{
 		.procname	= "ftrace_enabled",
@@ -2111,13 +2104,6 @@ static struct ctl_table kern_table[] = {
 		.proc_handler	= proc_dointvec,
 	},
 #endif
-	{
-		.procname	= "poweroff_cmd",
-		.data		= &poweroff_cmd,
-		.maxlen		= POWEROFF_CMD_PATH_LEN,
-		.mode		= 0644,
-		.proc_handler	= proc_dostring,
-	},
 #ifdef CONFIG_KEYS
 	{
 		.procname	= "keys",