net: socket: add __sys_recvfrom() helper; remove in-kernel call to syscall

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

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 9286a5a8c60c5d1971716340f9beaf2ffb064fd2..40cc93b916288c0237e8dc6a912f411eba293b9e 100644 (file)
--- 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 22381719718c4fbd5d63b8836e3161026b59a459..2d8186c277b28f7013df2cf852930b7ffc0fcf09 100644 (file)
--- 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 a93c99b518cab69b67d53a71298d15ce17c4d06b..712d99d8680f0d43f1c5244e128e1c15b13a10bf 100644 (file)
--- 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 @@ out:
        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 @@ out:
 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);