[PATCH sysctl-testing v2] kernel/kexec_core: move kexec_core sysctls into its own file

[yingelin]

This move the kernel/kexec_core.c respective sysctls to its own file.

kernel/sysctl.c has grown to an insane mess, We move sysctls to places
where features actually belong to improve the readability and reduce
merge conflicts. At the same time, the proc-sysctl maintainers can easily
care about the core logic other than the sysctl knobs added for some feature.

We already moved all filesystem sysctls out. This patch is part of the effort
to move kexec related sysctls out.

Signed-off-by: yingelin <yingelin at huawei.com>

---
v2:
  1. Add the explanation to commit log to help patch review and subsystem
  maintainers better understand the context/logic behind the migration
  2. Add CONFIG_SYSCTL to to isolate the sysctl
  3. Change subject-prefix of sysctl-next to sysctl-testing

v1: https://lore.kernel.org/lkml/20220223030318.213093-1-yingelin@huawei.com/
  1. Lack more informations in the commit log to help patch review better
  2. Lack isolation of the sysctl
  3. Use subject-prefix of sysctl-next
---
 kernel/kexec_core.c | 22 ++++++++++++++++++++++
 kernel/sysctl.c     | 13 -------------
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 68480f731192..a0456baf52cc 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -936,6 +936,28 @@ int kimage_load_segment(struct kimage *image,
 struct kimage *kexec_image;
 struct kimage *kexec_crash_image;
 int kexec_load_disabled;
+#ifdef CONFIG_SYSCTL
+static struct ctl_table kexec_core_sysctls[] = {
+	{
+		.procname	= "kexec_load_disabled",
+		.data		= &kexec_load_disabled,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		/* only handle a transition from default "0" to "1" */
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ONE,
+		.extra2		= SYSCTL_ONE,
+	},
+	{ }
+};
+
+static int __init kexec_core_sysctl_init(void)
+{
+	register_sysctl_init("kernel", kexec_core_sysctls);
+	return 0;
+}
+late_initcall(kexec_core_sysctl_init);
+#endif
 
 /*
  * No panic_cpu check version of crash_kexec().  This function is called
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index b60345cbadf0..0f3cb61a2e39 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -61,7 +61,6 @@
 #include <linux/capability.h>
 #include <linux/binfmts.h>
 #include <linux/sched/sysctl.h>
-#include <linux/kexec.h>
 #include <linux/mount.h>
 #include <linux/userfaultfd_k.h>
 #include <linux/pid.h>
@@ -1712,18 +1711,6 @@ static struct ctl_table kern_table[] = {
 		.proc_handler	= tracepoint_printk_sysctl,
 	},
 #endif
-#ifdef CONFIG_KEXEC_CORE
-	{
-		.procname	= "kexec_load_disabled",
-		.data		= &kexec_load_disabled,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		/* only handle a transition from default "0" to "1" */
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ONE,
-		.extra2		= SYSCTL_ONE,
-	},
-#endif
 #ifdef CONFIG_MODULES
 	{
 		.procname	= "modprobe",
-- 
2.26.2