net: move net_get_random_once to lib

There's no good reason why users outside of networking should not
be using this facility, f.e. for initializing their seeds.

Therefore, make it accessible from there as get_random_once().

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/net.h

@@ -24,7 +24,8 @@
 #include <linux/fcntl.h>	/* For O_CLOEXEC and O_NONBLOCK */
 #include <linux/kmemcheck.h>
 #include <linux/rcupdate.h>
-#include <linux/jump_label.h>
+#include <linux/once.h>
+
 #include <uapi/linux/net.h>
 
 struct poll_table_struct;
@@ -250,22 +251,8 @@ do {								\
 	} while (0)
 #endif
 
-bool __net_get_random_once(void *buf, int nbytes, bool *done,
-			   struct static_key *done_key);
-
 #define net_get_random_once(buf, nbytes)			\
-	({								\
-		bool ___ret = false;					\
-		static bool ___done = false;				\
-		static struct static_key ___once_key =			\
-			STATIC_KEY_INIT_TRUE;				\
-		if (static_key_true(&___once_key))			\
-			___ret = __net_get_random_once(buf,		\
-						       nbytes,		\
-						       &___done,	\
-						       &___once_key);	\
-		___ret;							\
-	})
+	get_random_once((buf), (nbytes))
 
 int kernel_sendmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec,
 		   size_t num, size_t len);

include/linux/once.h

@@ -0,0 +1,24 @@
+#ifndef _LINUX_ONCE_H
+#define _LINUX_ONCE_H
+
+#include <linux/types.h>
+#include <linux/jump_label.h>
+
+bool __get_random_once(void *buf, int nbytes, bool *done,
+		       struct static_key *once_key);
+
+#define get_random_once(buf, nbytes)					\
+	({								\
+		bool ___ret = false;					\
+		static bool ___done = false;				\
+		static struct static_key ___once_key =			\
+			STATIC_KEY_INIT_TRUE;				\
+		if (static_key_true(&___once_key))			\
+			___ret = __get_random_once((buf),		\
+						   (nbytes),		\
+						   &___done,		\
+						   &___once_key);	\
+		___ret;							\
+	})
+
+#endif /* _LINUX_ONCE_H */

lib/Makefile

@@ -26,7 +26,8 @@ obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
 	 bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \
 	 gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \
 	 bsearch.o find_bit.o llist.o memweight.o kfifo.o \
-	 percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o
+	 percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o \
+	 once.o
 obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
 obj-y += hexdump.o

lib/once.c

@@ -0,0 +1,54 @@
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/once.h>
+#include <linux/random.h>
+
+struct __random_once_work {
+	struct work_struct work;
+	struct static_key *key;
+};
+
+static void __random_once_deferred(struct work_struct *w)
+{
+	struct __random_once_work *work;
+
+	work = container_of(w, struct __random_once_work, work);
+	BUG_ON(!static_key_enabled(work->key));
+	static_key_slow_dec(work->key);
+	kfree(work);
+}
+
+static void __random_once_disable_jump(struct static_key *key)
+{
+	struct __random_once_work *w;
+
+	w = kmalloc(sizeof(*w), GFP_ATOMIC);
+	if (!w)
+		return;
+
+	INIT_WORK(&w->work, __random_once_deferred);
+	w->key = key;
+	schedule_work(&w->work);
+}
+
+bool __get_random_once(void *buf, int nbytes, bool *done,
+		       struct static_key *once_key)
+{
+	static DEFINE_SPINLOCK(lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&lock, flags);
+	if (*done) {
+		spin_unlock_irqrestore(&lock, flags);
+		return false;
+	}
+
+	get_random_bytes(buf, nbytes);
+	*done = true;
+	spin_unlock_irqrestore(&lock, flags);
+
+	__random_once_disable_jump(once_key);
+
+	return true;
+}
+EXPORT_SYMBOL(__get_random_once);

net/core/utils.c

@@ -348,52 +348,3 @@ void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
 	}
 }
 EXPORT_SYMBOL(inet_proto_csum_replace_by_diff);
-
-struct __net_random_once_work {
-	struct work_struct work;
-	struct static_key *key;
-};
-
-static void __net_random_once_deferred(struct work_struct *w)
-{
-	struct __net_random_once_work *work =
-		container_of(w, struct __net_random_once_work, work);
-	BUG_ON(!static_key_enabled(work->key));
-	static_key_slow_dec(work->key);
-	kfree(work);
-}
-
-static void __net_random_once_disable_jump(struct static_key *key)
-{
-	struct __net_random_once_work *w;
-
-	w = kmalloc(sizeof(*w), GFP_ATOMIC);
-	if (!w)
-		return;
-
-	INIT_WORK(&w->work, __net_random_once_deferred);
-	w->key = key;
-	schedule_work(&w->work);
-}
-
-bool __net_get_random_once(void *buf, int nbytes, bool *done,
-			   struct static_key *once_key)
-{
-	static DEFINE_SPINLOCK(lock);
-	unsigned long flags;
-
-	spin_lock_irqsave(&lock, flags);
-	if (*done) {
-		spin_unlock_irqrestore(&lock, flags);
-		return false;
-	}
-
-	get_random_bytes(buf, nbytes);
-	*done = true;
-	spin_unlock_irqrestore(&lock, flags);
-
-	__net_random_once_disable_jump(once_key);
-
-	return true;
-}
-EXPORT_SYMBOL(__net_get_random_once);