Merge branch 'bpf_random32'

Daniel Borkmann says:

====================
BPF/random32 updates

BPF update to split the prandom state apart, and to move the
*once helpers to the core. For details, please see individual
patches. Given the changes and since it's in the tree for
quite some time, net-next is a better choice in our opinion.

v1 -> v2:
 - Make DO_ONCE() type-safe, remove the kvec helper. Credits
   go to Alexei Starovoitov for the __VA_ARGS__ hint, thanks!
 - Add a comment to the DO_ONCE() helper as suggested by Alexei.
 - Rework prandom_init_once() helper to the new API.
 - Keep Alexei's Acked-by on the last patch.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 71 insertions, 17 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c915a6b54570..3697ad563899 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -200,4 +200,8 @@ extern const struct bpf_func_proto bpf_get_current_comm_proto;
 extern const struct bpf_func_proto bpf_skb_vlan_push_proto;
 extern const struct bpf_func_proto bpf_skb_vlan_pop_proto;
 
+/* Shared helpers among cBPF and eBPF. */
+void bpf_user_rnd_init_once(void);
+u64 bpf_user_rnd_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
+
 #endif /* _LINUX_BPF_H */
diff --git a/include/linux/net.h b/include/linux/net.h
index 049d4b03c4c4..70ac5e28e6b7 100644
--- a/include/linux/net.h
+++ b/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;							\
-	})
+#define net_get_random_once(buf, nbytes)			\
+	get_random_once((buf), (nbytes))
 
 int kernel_sendmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec,
 		   size_t num, size_t len);
diff --git a/include/linux/once.h b/include/linux/once.h
new file mode 100644
index 000000000000..285f12cb40e6
--- /dev/null
+++ b/include/linux/once.h
@@ -0,0 +1,57 @@
+#ifndef _LINUX_ONCE_H
+#define _LINUX_ONCE_H
+
+#include <linux/types.h>
+#include <linux/jump_label.h>
+
+bool __do_once_start(bool *done, unsigned long *flags);
+void __do_once_done(bool *done, struct static_key *once_key,
+		    unsigned long *flags);
+
+/* Call a function exactly once. The idea of DO_ONCE() is to perform
+ * a function call such as initialization of random seeds, etc, only
+ * once, where DO_ONCE() can live in the fast-path. After @func has
+ * been called with the passed arguments, the static key will patch
+ * out the condition into a nop. DO_ONCE() guarantees type safety of
+ * arguments!
+ *
+ * Not that the following is not equivalent ...
+ *
+ *   DO_ONCE(func, arg);
+ *   DO_ONCE(func, arg);
+ *
+ * ... to this version:
+ *
+ *   void foo(void)
+ *   {
+ *     DO_ONCE(func, arg);
+ *   }
+ *
+ *   foo();
+ *   foo();
+ *
+ * In case the one-time invocation could be triggered from multiple
+ * places, then a common helper function must be defined, so that only
+ * a single static key will be placed there!
+ */
+#define DO_ONCE(func, ...)						     \
+	({								     \
+		bool ___ret = false;					     \
+		static bool ___done = false;				     \
+		static struct static_key ___once_key = STATIC_KEY_INIT_TRUE; \
+		if (static_key_true(&___once_key)) {			     \
+			unsigned long ___flags;				     \
+			___ret = __do_once_start(&___done, &___flags);	     \
+			if (unlikely(___ret)) {				     \
+				func(__VA_ARGS__);			     \
+				__do_once_done(&___done, &___once_key,	     \
+					       &___flags);		     \
+			}						     \
+		}							     \
+		___ret;							     \
+	})
+
+#define get_random_once(buf, nbytes)					     \
+	DO_ONCE(get_random_bytes, (buf), (nbytes))
+
+#endif /* _LINUX_ONCE_H */
diff --git a/include/linux/random.h b/include/linux/random.h
index e651874df2c9..a75840c1aa71 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -7,6 +7,8 @@
 #define _LINUX_RANDOM_H
 
 #include <linux/list.h>
+#include <linux/once.h>
+
 #include <uapi/linux/random.h>
 
 struct random_ready_callback {
@@ -45,6 +47,10 @@ struct rnd_state {
 
 u32 prandom_u32_state(struct rnd_state *state);
 void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
+void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);
+
+#define prandom_init_once(pcpu_state)			\
+	DO_ONCE(prandom_seed_full_state, (pcpu_state))
 
 /**
  * prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro)