Add memalign(3), mostly for glibc compatibility.

Reviewed by:	emaste, imp (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D24307

include/malloc_np.h

@@ -122,6 +122,9 @@ size_t	__sallocx(const void *ptr, int flags);
 void	__dallocx(void *ptr, int flags);
 void	__sdallocx(void *ptr, size_t size, int flags);
 size_t	__nallocx(size_t size, int flags);
+
+void	*memalign(size_t, size_t) __malloc_like __alloc_align(1)
+	    __alloc_size(2);
 __END_DECLS
 
 #undef __MyBool

lib/libc/gen/Makefile.inc

@@ -98,6 +98,7 @@ SRCS+=	__getosreldate.c \
 	libc_dlopen.c \
 	lockf.c \
 	lrand48.c \
+	memalign.c \
 	mrand48.c \
 	nftw.c \
 	nftw-compat11.c \

lib/libc/gen/Symbol.map

@@ -423,6 +423,7 @@ FBSD_1.5 {
 };
 
 FBSD_1.6 {
+	memalign;
 	sigandset;
 	sigisemptyset;
 	sigorset;

lib/libc/gen/memalign.c

@@ -0,0 +1,40 @@
+/*-
+ * Copyright (c) 2020 The FreeBSD Foundation
+ * All rights reserved.
+ *
+ * This software was 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, 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 <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <stdlib.h>
+
+void *
+memalign(size_t align, size_t size)
+{
+	return (aligned_alloc(align, roundup(size, align)));
+}