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Subject[PATCH 008/109] net: socket: add __sys_recvfrom() helper; remove in-kernel call to syscall
Date
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>
---
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);
--
2.16.3
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