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Commit 7a09e1eb authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

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: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent b51d3cdf

include/linux/socket.h

+6 −0
Original line number Diff line number Diff line
@@ -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 */

net/compat.c

+2 −1
Original line number Diff line number Diff line
@@ -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,

net/socket.c

+13 −8
Original line number Diff line number Diff line
@@ -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);

}



/*
@@ -2486,7 +2491,7 @@ 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],

		err = __sys_recvfrom(a0, (void __user *)a1, a[2], a[3],

				     (struct sockaddr __user *)a[4],

				     (int __user *)a[5]);

		break;