[PATCH -next 01/22] net: socket: add __sys_recvfrom() helper; remove in-kernel call to syscall

[Dominik Brodowski]

Using the net-internal helper __sys_recvfrom() allows us to avoid the
internal calls to the sys_recvfrom() syscall.

Cc: David S. Miller <da...@davemloft.net>
Cc: net...@vger.kernel.org
Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net>
---
 include/linux/socket.h |  6 ++++++
 net/compat.c           |  3 ++-
 net/socket.c           | 21 +++++++++++++--------
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 9286a5a8c60c..40cc93b91628 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -353,4 +353,10 @@ extern int __sys_recvmmsg(int fd, struct mmsghdr __user 
*mmsg, unsigned int vlen
                          unsigned int flags, struct timespec *timeout);
 extern int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg,
                          unsigned int vlen, unsigned int flags);
+
+/* helpers which do the actual work for syscalls */
+extern int __sys_recvfrom(int fd, void __user *ubuf, size_t size,
+                         unsigned int flags, struct sockaddr __user *addr,
+                         int __user *addr_len);
+
 #endif /* _LINUX_SOCKET_H */
diff --git a/net/compat.c b/net/compat.c
index 22381719718c..2d8186c277b2 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -760,7 +760,8 @@ COMPAT_SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, 
buf, compat_size_t, len
                       unsigned int, flags, struct sockaddr __user *, addr,
                       int __user *, addrlen)
 {
-       return sys_recvfrom(fd, buf, len, flags | MSG_CMSG_COMPAT, addr, 
addrlen);
+       return __sys_recvfrom(fd, buf, len, flags | MSG_CMSG_COMPAT, addr,
+                             addrlen);
 }
 
 COMPAT_SYSCALL_DEFINE5(recvmmsg, int, fd, struct compat_mmsghdr __user *, mmsg,
diff --git a/net/socket.c b/net/socket.c
index a93c99b518ca..712d99d8680f 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1767,10 +1767,8 @@ SYSCALL_DEFINE4(send, int, fd, void __user *, buff, 
size_t, len,
  *     sender. We verify the buffers are writable and if needed move the
  *     sender address from kernel to user space.
  */
-
-SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, ubuf, size_t, size,
-               unsigned int, flags, struct sockaddr __user *, addr,
-               int __user *, addr_len)
+int __sys_recvfrom(int fd, void __user *ubuf, size_t size, unsigned int flags,
+                  struct sockaddr __user *addr, int __user *addr_len)
 {
        struct socket *sock;
        struct iovec iov;
@@ -1810,6 +1808,13 @@ SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, ubuf, 
size_t, size,
        return err;
 }
 
+SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, ubuf, size_t, size,
+               unsigned int, flags, struct sockaddr __user *, addr,
+               int __user *, addr_len)
+{
+       return __sys_recvfrom(fd, ubuf, size, flags, addr, addr_len);
+}
+
 /*
  *     Receive a datagram from a socket.
  */
@@ -1817,7 +1822,7 @@ SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, ubuf, 
size_t, size,
 SYSCALL_DEFINE4(recv, int, fd, void __user *, ubuf, size_t, size,
                unsigned int, flags)
 {
-       return sys_recvfrom(fd, ubuf, size, flags, NULL, NULL);
+       return __sys_recvfrom(fd, ubuf, size, flags, NULL, NULL);
 }
 
 /*
@@ -2486,9 +2491,9 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long 
__user *, args)
                err = sys_recv(a0, (void __user *)a1, a[2], a[3]);
                break;
        case SYS_RECVFROM:
-               err = sys_recvfrom(a0, (void __user *)a1, a[2], a[3],
-                                  (struct sockaddr __user *)a[4],
-                                  (int __user *)a[5]);
+               err = __sys_recvfrom(a0, (void __user *)a1, a[2], a[3],
+                                    (struct sockaddr __user *)a[4],
+                                    (int __user *)a[5]);
                break;
        case SYS_SHUTDOWN:
                err = sys_shutdown(a0, a1);
-- 
2.16.2