diff --git a/lib/Makefile b/lib/Makefile
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -210,6 +210,10 @@
 SUBDIR.${MK_BHYVE}+=	libvmmapi
 .endif
 
+.if ${MACHINE_CPUARCH} != "aarch64" && ${MACHINE_CPUARCH} != "riscv"
+SUBDIR+=		libsbrk
+.endif
+
 .if ${MACHINE_ARCH} != "powerpc" && ${MACHINE_CPUARCH} != "arm"
 SUBDIR.${MK_OPENMP}+=	libomp
 .endif
diff --git a/lib/libsbrk/Makefile b/lib/libsbrk/Makefile
new file mode 100644
--- /dev/null
+++ b/lib/libsbrk/Makefile
@@ -0,0 +1,11 @@
+PACKAGE=	clibs
+LIB=		sbrk
+SHLIB_MAJOR=	1
+
+LDFLAGS+=-Wl,--filter=libc.so.7
+VERSION_DEF=${SRCTOP}/lib/libc/Versions.def
+SYMBOL_MAPS=${.CURDIR}/Symbol.map
+
+SRCS=		${LIB}.c
+
+.include <bsd.lib.mk>
diff --git a/lib/libsbrk/Symbol.map b/lib/libsbrk/Symbol.map
new file mode 100644
--- /dev/null
+++ b/lib/libsbrk/Symbol.map
@@ -0,0 +1,3 @@
+FBSD_1.0 {
+	sbrk;
+};
diff --git a/lib/libsbrk/sbrk.c b/lib/libsbrk/sbrk.c
new file mode 100644
--- /dev/null
+++ b/lib/libsbrk/sbrk.c
@@ -0,0 +1,42 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2023 SRI International
+ *
+ * This software was developed by SRI International, the University of
+ * Cambridge Computer Laboratory (Department of Computer Science and
+ * Technology), and Capabilities Limited under Defense Advanced Research
+ * Projects Agency (DARPA) Contract No. HR001122S0003 ("MTSS").
+ *
+ * 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 <inttypes.h>
+
+void *sbrk(intptr_t);
+void *libc_sbrk(intptr_t);
+
+asm (".symver libc_sbrk, sbrk@FBSD_1.0");
+
+void *sbrk(intptr_t incr) {
+	return (libc_sbrk(incr));
+}
diff --git a/lib/libsys/brk.2 b/lib/libsys/brk.2
--- a/lib/libsys/brk.2
+++ b/lib/libsys/brk.2
@@ -33,7 +33,7 @@
 .Nm sbrk
 .Nd change data segment size
 .Sh LIBRARY
-.Lb libc
+.Lb libsbrk
 .Sh SYNOPSIS
 .In unistd.h
 .Ft int
@@ -51,6 +51,11 @@
 They are deprecated and not declared or directly linkable in libc on any
 architectures as of
 .Fx 15.0 .
+The
+.Fn sbrk
+function may be directly declared and linked by linking via the libsbrk
+library, but the kernel may not support it if backwards compatibility is
+not configured.
 They are not available on the aarch64 or riscv architectures.
 The
 .Xr mmap 2
diff --git a/rescue/rescue/Makefile b/rescue/rescue/Makefile
--- a/rescue/rescue/Makefile
+++ b/rescue/rescue/Makefile
@@ -146,7 +146,7 @@
 CRUNCH_LIBS+= -l80211 -lalias -lcam -lncursesw -ldevstat -lipsec -llzma
 CRUNCH_LIBS_camcontrol+= ${LIBNVMF}
 .if ${MK_ZFS} != "no"
-CRUNCH_LIBS+= -lavl -lpthread -luutil -lumem -ltpool -lspl -lrt
+CRUNCH_LIBS+= -lavl -lpthread -lsys -luutil -lumem -ltpool -lspl -lrt
 CRUNCH_LIBS_zfs+=	${LIBBE} \
 			${LIBZPOOL} \
 			${LIBZFS} \
@@ -167,7 +167,7 @@
 			${LIBNVPAIR}
 .else
 # liblzma needs pthread
-CRUNCH_LIBS+= -lpthread
+CRUNCH_LIBS+= -lpthread -lsys
 .endif
 CRUNCH_LIBS+= -lgeom -lbsdxml -lkiconv
 .if ${MK_OPENSSL} == "no"