libthr: wrap pdfork(2), same as fork(2).

Without wrapping, rtld services and malloc(3) are not guaranteed
to operate correctly in the forked child.

Reviewed by:	markj
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D28088

4 files changed, 50 insertions, 0 deletions

diff --git a/lib/libc/include/libc_private.h b/lib/libc/include/libc_private.h
index d26c78c21c07..363e1057986b 100644
--- a/lib/libc/include/libc_private.h
+++ b/lib/libc/include/libc_private.h
@@ -238,6 +238,7 @@ enum {
 	INTERPOS_fdatasync,
 	INTERPOS_clock_nanosleep,
 	INTERPOS_distribute_static_tls,
+	INTERPOS_pdfork,
 	INTERPOS_MAX
 };
 
@@ -353,6 +354,7 @@ int		__sys_msync(void *, __size_t, int);
 int		__sys_nanosleep(const struct timespec *, struct timespec *);
 int		__sys_open(const char *, int, ...);
 int		__sys_openat(int, const char *, int, ...);
+int		__sys_pdfork(int *, int);
 int		__sys_pselect(int, struct fd_set *, struct fd_set *,
 		    struct fd_set *, const struct timespec *,
 		    const __sigset_t *);
diff --git a/lib/libc/sys/Symbol.map b/lib/libc/sys/Symbol.map
index 847dd9cca987..0044c06fd639 100644
--- a/lib/libc/sys/Symbol.map
+++ b/lib/libc/sys/Symbol.map
@@ -804,6 +804,7 @@ FBSDprivate_1.0 {
 	__sys_openat;
 	_pathconf;
 	__sys_pathconf;
+	__sys_pdfork;
 	_pipe;
 	__sys_pipe;
 	_poll;
diff --git a/lib/libc/sys/interposing_table.c b/lib/libc/sys/interposing_table.c
index 670e9fd7dd0f..b2cfb3250cd9 100644
--- a/lib/libc/sys/interposing_table.c
+++ b/lib/libc/sys/interposing_table.c
@@ -82,6 +82,7 @@ interpos_func_t __libc_interposing[INTERPOS_MAX] = {
 	SLOT(fdatasync, __sys_fdatasync),
 	SLOT(clock_nanosleep, __sys_clock_nanosleep),
 	SLOT(distribute_static_tls, __libc_distribute_static_tls),
+	SLOT(pdfork, __sys_pdfork),
 };
 #undef SLOT
 
diff --git a/lib/libc/sys/pdfork.c b/lib/libc/sys/pdfork.c
new file mode 100644
index 000000000000..003262d1237d
--- /dev/null
+++ b/lib/libc/sys/pdfork.c
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2021 The FreeBSD Foundation.
+ * All rights reserved.
+ *
+ * Portions of this software were developed by Konstantin Belousov
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * 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(s), this list of conditions and the following disclaimer as
+ *    the first lines of this file unmodified other than the possible
+ *    addition of one or more copyright notices.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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 <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <unistd.h>
+#include "libc_private.h"
+
+#pragma weak pdfork
+pid_t
+pdfork(int *fdp, int flags)
+{
+	return (((pid_t (*)(int *, int))__libc_interposing[
+	    INTERPOS_pdfork])(fdp, flags));
+}