libsys: don't expose sigwait wrapper

Long ago (e129c18a83) __sys_sigwait was wrapped to prevent sigwait()
from returning with EINTR.  Through a series of changes this wrapper
become __libc_sigwait which was internal to libc and used solely in the
interposing table.  To support a move of sigwait back to libc, move this
wrapper into libsys and rename it with an __libsys_ prefix.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D44238

lib/libc/include/libc_private.h

@@ -414,8 +414,7 @@ int		__libc_sigaction(int, const struct sigaction *,
 int		__libc_sigprocmask(int, const __sigset_t *, __sigset_t *)
 		    __hidden;
 int		__libc_sigsuspend(const __sigset_t *) __hidden;
-int		__libc_sigwait(const __sigset_t * __restrict,
-		    int * restrict sig);
+int		__libsys_sigwait(const __sigset_t *, int *) __hidden;
 int		__libc_system(const char *);
 int		__libc_tcdrain(int);
 

lib/libsys/Makefile.sys

@@ -37,7 +37,8 @@ SRCS+=	\
 	__getosreldate.c \
 	getpagesize.c \
 	getpagesizes.c \
-	interposing_table.c
+	interposing_table.c \
+	libsys_sigwait.c
 
 SRCS+= getdents.c lstat.c mknod.c stat.c
 

lib/libsys/Symbol.sys.map

@@ -433,7 +433,6 @@ FBSD_1.8 {
 
 FBSDprivate_1.0 {
 	/* Add entries in sort(1) order */
-	__libc_sigwait;
 	__libsys_interposing_slot;
 	__set_error_selector;
 	__sigwait;

lib/libsys/interposing_table.c

@@ -59,7 +59,7 @@ interpos_func_t __libsys_interposing[INTERPOS_MAX] = {
 	SLOT(sigaction, __sys_sigaction),
 	SLOT(sigprocmask, __sys_sigprocmask),
 	SLOT(sigsuspend, __sys_sigsuspend),
-	SLOT(sigwait, __libc_sigwait),
+	SLOT(sigwait, __libsys_sigwait),
 	SLOT(sigtimedwait, __sys_sigtimedwait),
 	SLOT(sigwaitinfo, __sys_sigwaitinfo),
 	SLOT(swapcontext, __sys_swapcontext),

lib/libsys/libsys_sigwait.c

@@ -0,0 +1,45 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2010 davidxu@freebsd.org
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <errno.h>
+#include <signal.h>
+#include "libc_private.h"
+
+/* XXX: why does this symbol exist? */
+__weak_reference(__libsys_sigwait, __sigwait);
+
+int
+__libsys_sigwait(const sigset_t *set, int *sig)
+{
+	int ret;
+
+	/* POSIX does not allow EINTR to be returned */
+	do {
+		ret = __sys_sigwait(set, sig);
+	} while (ret == EINTR);
+	return (ret);
+}

lib/libsys/sigwait.c

@@ -25,12 +25,9 @@
  * SUCH DAMAGE.
  */
 
-#include <errno.h>
 #include <signal.h>
 #include "libc_private.h"
 
-__weak_reference(__libc_sigwait, __sigwait);
-
 #pragma weak sigwait
 int
 sigwait(const sigset_t *set, int *sig)
@@ -38,15 +35,3 @@ sigwait(const sigset_t *set, int *sig)
 	return (((int (*)(const sigset_t *, int *))
 	    __libsys_interposing[INTERPOS_sigwait])(set, sig));
 }
-
-int
-__libc_sigwait(const sigset_t *set, int *sig)
-{
-	int ret;
-
-	/* POSIX does not allow EINTR to be returned */
-	do  {
-		ret = __sys_sigwait(set, sig);
-	} while (ret == EINTR);
-	return (ret);
-}