From: Eric Dumazet <edumazet@google.com>
Date: Fri, 6 Dec 2019 09:38:36 -0800
Subject: net: avoid an indirect call in ____sys_recvmsg()
Patch-mainline: v5.5-rc1
Git-commit: 1af66221a66de080274540a5c481ddacbe3574d2
References: bsc#1154353

CONFIG_RETPOLINE=y made indirect calls expensive.

gcc seems to add an indirect call in ____sys_recvmsg().

Rewriting the code slightly makes sure to avoid this indirection.

Alternative would be to not call sock_recvmsg() and instead
use security_socket_recvmsg() and sock_recvmsg_nosec(),
but this is less readable IMO.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: David Laight <David.Laight@aculab.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/socket.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/net/socket.c
+++ b/net/socket.c
@@ -2526,7 +2526,12 @@ static int ____sys_recvmsg(struct socket
 
 	if (sock->file->f_flags & O_NONBLOCK)
 		flags |= MSG_DONTWAIT;
-	err = (nosec ? sock_recvmsg_nosec : sock_recvmsg)(sock, msg_sys, flags);
+
+	if (unlikely(nosec))
+		err = sock_recvmsg_nosec(sock, msg_sys, flags);
+	else
+		err = sock_recvmsg(sock, msg_sys, flags);
+
 	if (err < 0)
 		goto out;
 	len = err;