[PATCH 021/109] net: socket: add do_sys_recvmmsg() helper; remove in-kernel call to syscall

From: Dominik Brodowski
Date: Thu Mar 29 2018 - 07:53:00 EST


Using the net-internal helper do_sys_recvmmsg() allows us to avoid the
internal calls to the sys_getsockopt() 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@xxxxxxxxxxxxxxxxxxxxxxxxxx

Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
---
net/socket.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index a05289b1f863..54d19b0edab1 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2445,9 +2445,9 @@ int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
return datagrams;
}

-SYSCALL_DEFINE5(recvmmsg, int, fd, struct mmsghdr __user *, mmsg,
- unsigned int, vlen, unsigned int, flags,
- struct timespec __user *, timeout)
+static int do_sys_recvmmsg(int fd, struct mmsghdr __user *mmsg,
+ unsigned int vlen, unsigned int flags,
+ struct timespec __user *timeout)
{
int datagrams;
struct timespec timeout_sys;
@@ -2470,6 +2470,13 @@ SYSCALL_DEFINE5(recvmmsg, int, fd, struct mmsghdr __user *, mmsg,
return datagrams;
}

+SYSCALL_DEFINE5(recvmmsg, int, fd, struct mmsghdr __user *, mmsg,
+ unsigned int, vlen, unsigned int, flags,
+ struct timespec __user *, timeout)
+{
+ return do_sys_recvmmsg(fd, mmsg, vlen, flags, timeout);
+}
+
#ifdef __ARCH_WANT_SYS_SOCKETCALL
/* Argument list sizes for sys_socketcall */
#define AL(x) ((x) * sizeof(unsigned long))
@@ -2582,8 +2589,8 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
err = sys_recvmsg(a0, (struct user_msghdr __user *)a1, a[2]);
break;
case SYS_RECVMMSG:
- err = sys_recvmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3],
- (struct timespec __user *)a[4]);
+ err = do_sys_recvmmsg(a0, (struct mmsghdr __user *)a1, a[2],
+ a[3], (struct timespec __user *)a[4]);
break;
case SYS_ACCEPT4:
err = __sys_accept4(a0, (struct sockaddr __user *)a1,
--
2.16.3