bpf: Move BPF sysctls from kernel/sysctl.c to BPF core

We're moving sysctls out of kernel/sysctl.c as it is a mess. We
already moved all filesystem sysctls out. And with time the goal
is to move all sysctls out to their own subsystem/actual user.

kernel/sysctl.c has grown to an insane mess and its easy to run
into conflicts with it. The effort to move them out into various
subsystems is part of this.
Signed-off-by: Yan Zhu <zhuyan34@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/bpf/20220407070759.29506-1-zhuyan34@huawei.com

kernel/bpf/syscall.c

@@ -4908,3 +4908,90 @@ const struct bpf_verifier_ops bpf_syscall_verifier_ops = {
 const struct bpf_prog_ops bpf_syscall_prog_ops = {
 	.test_run = bpf_prog_test_run_syscall,
 };
+
+#ifdef CONFIG_SYSCTL
+static int bpf_stats_handler(struct ctl_table *table, int write,
+			     void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct static_key *key = (struct static_key *)table->data;
+	static int saved_val;
+	int val, ret;
+	struct ctl_table tmp = {
+		.data   = &val,
+		.maxlen = sizeof(val),
+		.mode   = table->mode,
+		.extra1 = SYSCTL_ZERO,
+		.extra2 = SYSCTL_ONE,
+	};
+
+	if (write && !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	mutex_lock(&bpf_stats_enabled_mutex);
+	val = saved_val;
+	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
+	if (write && !ret && val != saved_val) {
+		if (val)
+			static_key_slow_inc(key);
+		else
+			static_key_slow_dec(key);
+		saved_val = val;
+	}
+	mutex_unlock(&bpf_stats_enabled_mutex);
+	return ret;
+}
+
+void __weak unpriv_ebpf_notify(int new_state)
+{
+}
+
+static int bpf_unpriv_handler(struct ctl_table *table, int write,
+			      void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int ret, unpriv_enable = *(int *)table->data;
+	bool locked_state = unpriv_enable == 1;
+	struct ctl_table tmp = *table;
+
+	if (write && !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	tmp.data = &unpriv_enable;
+	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
+	if (write && !ret) {
+		if (locked_state && unpriv_enable != 1)
+			return -EPERM;
+		*(int *)table->data = unpriv_enable;
+	}
+
+	unpriv_ebpf_notify(unpriv_enable);
+
+	return ret;
+}
+
+static struct ctl_table bpf_syscall_table[] = {
+	{
+		.procname	= "unprivileged_bpf_disabled",
+		.data		= &sysctl_unprivileged_bpf_disabled,
+		.maxlen		= sizeof(sysctl_unprivileged_bpf_disabled),
+		.mode		= 0644,
+		.proc_handler	= bpf_unpriv_handler,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_TWO,
+	},
+	{
+		.procname	= "bpf_stats_enabled",
+		.data		= &bpf_stats_enabled_key.key,
+		.maxlen		= sizeof(bpf_stats_enabled_key),
+		.mode		= 0644,
+		.proc_handler	= bpf_stats_handler,
+	},
+	{ }
+};
+
+static int __init bpf_syscall_sysctl_init(void)
+{
+	register_sysctl_init("kernel", bpf_syscall_table);
+	return 0;
+}
+late_initcall(bpf_syscall_sysctl_init);
+#endif /* CONFIG_SYSCTL */

kernel/sysctl.c

@@ -62,7 +62,6 @@
 #include <linux/binfmts.h>
 #include <linux/sched/sysctl.h>
 #include <linux/kexec.h>
-#include <linux/bpf.h>
 #include <linux/mount.h>
 #include <linux/userfaultfd_k.h>
 #include <linux/latencytop.h>
@@ -148,66 +147,6 @@ static const int max_extfrag_threshold = 1000;
 
 #endif /* CONFIG_SYSCTL */
 
-#if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_SYSCTL)
-static int bpf_stats_handler(struct ctl_table *table, int write,
-			     void *buffer, size_t *lenp, loff_t *ppos)
-{
-	struct static_key *key = (struct static_key *)table->data;
-	static int saved_val;
-	int val, ret;
-	struct ctl_table tmp = {
-		.data   = &val,
-		.maxlen = sizeof(val),
-		.mode   = table->mode,
-		.extra1 = SYSCTL_ZERO,
-		.extra2 = SYSCTL_ONE,
-	};
-
-	if (write && !capable(CAP_SYS_ADMIN))
-		return -EPERM;
-
-	mutex_lock(&bpf_stats_enabled_mutex);
-	val = saved_val;
-	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
-	if (write && !ret && val != saved_val) {
-		if (val)
-			static_key_slow_inc(key);
-		else
-			static_key_slow_dec(key);
-		saved_val = val;
-	}
-	mutex_unlock(&bpf_stats_enabled_mutex);
-	return ret;
-}
-
-void __weak unpriv_ebpf_notify(int new_state)
-{
-}
-
-static int bpf_unpriv_handler(struct ctl_table *table, int write,
-			      void *buffer, size_t *lenp, loff_t *ppos)
-{
-	int ret, unpriv_enable = *(int *)table->data;
-	bool locked_state = unpriv_enable == 1;
-	struct ctl_table tmp = *table;
-
-	if (write && !capable(CAP_SYS_ADMIN))
-		return -EPERM;
-
-	tmp.data = &unpriv_enable;
-	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
-	if (write && !ret) {
-		if (locked_state && unpriv_enable != 1)
-			return -EPERM;
-		*(int *)table->data = unpriv_enable;
-	}
-
-	unpriv_ebpf_notify(unpriv_enable);
-
-	return ret;
-}
-#endif /* CONFIG_BPF_SYSCALL && CONFIG_SYSCTL */
-
 /*
  * /proc/sys support
  */
@@ -2299,24 +2238,6 @@ static struct ctl_table kern_table[] = {
 		.extra2		= SYSCTL_ONE,
 	},
 #endif
-#ifdef CONFIG_BPF_SYSCALL
-	{
-		.procname	= "unprivileged_bpf_disabled",
-		.data		= &sysctl_unprivileged_bpf_disabled,
-		.maxlen		= sizeof(sysctl_unprivileged_bpf_disabled),
-		.mode		= 0644,
-		.proc_handler	= bpf_unpriv_handler,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_TWO,
-	},
-	{
-		.procname	= "bpf_stats_enabled",
-		.data		= &bpf_stats_enabled_key.key,
-		.maxlen		= sizeof(bpf_stats_enabled_key),
-		.mode		= 0644,
-		.proc_handler	= bpf_stats_handler,
-	},
-#endif
 #if defined(CONFIG_TREE_RCU)
 	{
 		.procname	= "panic_on_rcu_stall",