printk: move printk sysctl to printk/sysctl.c

The 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.

So move printk sysctl from kernel/sysctl.c to kernel/printk/sysctl.c.
Use register_sysctl() to register the sysctl interface.

Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
[mcgrof: fixed compile issues when PRINTK is not set, commit log update]
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

5 files changed, 96 insertions, 69 deletions

diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile
index d118739874c0d..f5b388e810b9f 100644
--- a/kernel/printk/Makefile
+++ b/kernel/printk/Makefile
@@ -2,5 +2,8 @@
 obj-y	= printk.o
 obj-$(CONFIG_PRINTK)	+= printk_safe.o
 obj-$(CONFIG_A11Y_BRAILLE_CONSOLE)	+= braille.o
-obj-$(CONFIG_PRINTK)	+= printk_ringbuffer.o
 obj-$(CONFIG_PRINTK_INDEX)	+= index.o
+
+obj-$(CONFIG_PRINTK)                 += printk_support.o
+printk_support-y	             := printk_ringbuffer.o
+printk_support-$(CONFIG_SYSCTL)	     += sysctl.o
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 9f3ed2fdb7211..d072801fa1166 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -4,6 +4,12 @@
  */
 #include <linux/percpu.h>
 
+#ifdef CONFIG_SYSCTL
+void __init printk_sysctl_init(void);
+#else
+#define printk_sysctl_init() do { } while (0)
+#endif
+
 #ifdef CONFIG_PRINTK
 
 /* Flags for a single printk record. */
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index cbc35d586afb6..dbb44086ba652 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3202,6 +3202,7 @@ static int __init printk_late_init(void)
 	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online",
 					console_cpu_notify, NULL);
 	WARN_ON(ret < 0);
+	printk_sysctl_init();
 	return 0;
 }
 late_initcall(printk_late_init);
diff --git a/kernel/printk/sysctl.c b/kernel/printk/sysctl.c
new file mode 100644
index 0000000000000..e321c46229a6f
--- /dev/null
+++ b/kernel/printk/sysctl.c
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * sysctl.c: General linux system control interface
+ */
+
+#include <linux/sysctl.h>
+#include <linux/printk.h>
+#include <linux/capability.h>
+#include <linux/ratelimit.h>
+#include "internal.h"
+
+static const int ten_thousand = 10000;
+
+static int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
+				void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	if (write && !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+}
+
+static struct ctl_table printk_sysctls[] = {
+	{
+		.procname	= "printk",
+		.data		= &console_loglevel,
+		.maxlen		= 4*sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "printk_ratelimit",
+		.data		= &printk_ratelimit_state.interval,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_jiffies,
+	},
+	{
+		.procname	= "printk_ratelimit_burst",
+		.data		= &printk_ratelimit_state.burst,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "printk_delay",
+		.data		= &printk_delay_msec,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= (void *)&ten_thousand,
+	},
+	{
+		.procname	= "printk_devkmsg",
+		.data		= devkmsg_log_str,
+		.maxlen		= DEVKMSG_STR_MAX_SIZE,
+		.mode		= 0644,
+		.proc_handler	= devkmsg_sysctl_set_loglvl,
+	},
+	{
+		.procname	= "dmesg_restrict",
+		.data		= &dmesg_restrict,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax_sysadmin,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{
+		.procname	= "kptr_restrict",
+		.data		= &kptr_restrict,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax_sysadmin,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_TWO,
+	},
+	{}
+};
+
+void __init printk_sysctl_init(void)
+{
+	register_sysctl_init("kernel", printk_sysctls, "printk");
+}
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 7745c9b72bdaa..02ef278046011 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -907,17 +907,6 @@ static int proc_taint(struct ctl_table *table, int write,
 	return err;
 }
 
-#ifdef CONFIG_PRINTK
-static int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
-				void *buffer, size_t *lenp, loff_t *ppos)
-{
-	if (write && !capable(CAP_SYS_ADMIN))
-		return -EPERM;
-
-	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
-}
-#endif
-
 /**
  * struct do_proc_dointvec_minmax_conv_param - proc_dointvec_minmax() range checking structure
  * @min: pointer to minimum allowable value
@@ -2209,63 +2198,6 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_doulongvec_minmax,
 	},
-#if defined CONFIG_PRINTK
-	{
-		.procname	= "printk",
-		.data		= &console_loglevel,
-		.maxlen		= 4*sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-	{
-		.procname	= "printk_ratelimit",
-		.data		= &printk_ratelimit_state.interval,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_jiffies,
-	},
-	{
-		.procname	= "printk_ratelimit_burst",
-		.data		= &printk_ratelimit_state.burst,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-	{
-		.procname	= "printk_delay",
-		.data		= &printk_delay_msec,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= (void *)&ten_thousand,
-	},
-	{
-		.procname	= "printk_devkmsg",
-		.data		= devkmsg_log_str,
-		.maxlen		= DEVKMSG_STR_MAX_SIZE,
-		.mode		= 0644,
-		.proc_handler	= devkmsg_sysctl_set_loglvl,
-	},
-	{
-		.procname	= "dmesg_restrict",
-		.data		= &dmesg_restrict,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax_sysadmin,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
-	},
-	{
-		.procname	= "kptr_restrict",
-		.data		= &kptr_restrict,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax_sysadmin,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_TWO,
-	},
-#endif
 	{
 		.procname	= "ngroups_max",
 		.data		= (void *)&ngroups_max,