x86/entry/syscalls: Wire up 32-bit direct socket calls

On x86_64, there's no socketcall syscall; instead all of the
socket calls are real syscalls.  For 32-bit programs, we're
stuck offering the socketcall syscall, but it would be nice to
expose the direct calls as well.  This will enable seccomp to
filter socket calls (for new userspace only, but that's fine for
some applications) and it will provide a tiny performance boost.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Alexander Larsson <alexl@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Cosimo Cecchi <cosimo@endlessm.com>
Cc: Dan Nicholson <nicholson@endlessm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
Cc: libc-alpha <libc-alpha@sourceware.org>
Link: http://lkml.kernel.org/r/cb5138299d37d5800e2d135b01a7667fa6115854.1436912629.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/entry/syscalls/syscall_32.tbl

@@ -365,3 +365,18 @@
 356	i386	memfd_create		sys_memfd_create
 357	i386	bpf			sys_bpf
 358	i386	execveat		sys_execveat			stub32_execveat
+359	i386	socket			sys_socket
+360	i386	socketpair		sys_socketpair
+361	i386	bind			sys_bind
+362	i386	connect			sys_connect
+363	i386	listen			sys_listen
+364	i386	accept4			sys_accept4
+365	i386	getsockopt		sys_getsockopt			compat_sys_getsockopt
+366	i386	setsockopt		sys_setsockopt			compat_sys_setsockopt
+367	i386	getsockname		sys_getsockname
+368	i386	getpeername		sys_getpeername
+369	i386	sendto			sys_sendto
+370	i386	sendmsg			sys_sendmsg			compat_sys_sendmsg
+371	i386	recvfrom		sys_recvfrom			compat_sys_recvfrom
+372	i386	recvmsg			sys_recvmsg			compat_sys_recvmsg
+373	i386	shutdown		sys_shutdown