[PATCH 025/109] net: socket: add __compat_sys_recvfrom() helper; remove in-kernel call to compat syscall

From: Dominik Brodowski
Date: Thu Mar 29 2018 - 07:47:29 EST


Using the net-internal helper __compat_sys_recvfrom() allows us to avoid
the internal calls to the compat_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@xxxxxxxxxxxxxxxxxxxxxxxxxx

Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
---
net/compat.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/net/compat.c b/net/compat.c
index 9e0d030063ad..513adc8d0e0f 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -753,18 +753,25 @@ COMPAT_SYSCALL_DEFINE3(recvmsg, int, fd, struct compat_msghdr __user *, msg, uns
flags | MSG_CMSG_COMPAT, false);
}

+static inline long __compat_sys_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);
+}
+
COMPAT_SYSCALL_DEFINE4(recv, int, fd, void __user *, buf, compat_size_t, len, unsigned int, flags)
{
- return __sys_recvfrom(fd, buf, len, flags | MSG_CMSG_COMPAT, NULL,
- NULL);
+ return __compat_sys_recvfrom(fd, buf, len, flags, NULL, NULL);
}

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 __compat_sys_recvfrom(fd, buf, len, flags, addr, addrlen);
}

COMPAT_SYSCALL_DEFINE5(recvmmsg, int, fd, struct compat_mmsghdr __user *, mmsg,
@@ -845,11 +852,13 @@ COMPAT_SYSCALL_DEFINE2(socketcall, int, call, u32 __user *, args)
compat_ptr(a[4]), a[5]);
break;
case SYS_RECV:
- ret = compat_sys_recv(a0, compat_ptr(a1), a[2], a[3]);
+ ret = __compat_sys_recvfrom(a0, compat_ptr(a1), a[2], a[3],
+ NULL, NULL);
break;
case SYS_RECVFROM:
- ret = compat_sys_recvfrom(a0, compat_ptr(a1), a[2], a[3],
- compat_ptr(a[4]), compat_ptr(a[5]));
+ ret = __compat_sys_recvfrom(a0, compat_ptr(a1), a[2], a[3],
+ compat_ptr(a[4]),
+ compat_ptr(a[5]));
break;
case SYS_SHUTDOWN:
ret = __sys_shutdown(a0, a1);
--
2.16.3