add a rescue/sh sanity check before installworld on the running system

FreeBSD does not guarantee kernel forward compatibility (that is,
running a newer userland on an older kernel).  The documented upgrade
procedure specifies that installkernel should be performed, followed by
a reboot and then installworld.  As a sanity check when installing onto
the running system (DESTDIR is / or unset), attempt to run "sh echo OK"
using rescue from the objdir.  If rescue fails (e.g., because the system
has not been rebooted and the "old" kernel lacks a system call required
by the to-be-installed world), abort the installation.

This should avoid ino64 foot-shooting when the proper upgrade procedure
is not followed.

Reviewed by:	allanjude, gjb, kib
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D10987

1 files changed, 16 insertions, 0 deletions

diff --git a/Makefile.inc1 b/Makefile.inc1
index a06b1797e244..e3b778d40dda 100644
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -975,6 +975,22 @@ __installcheck_UGID: .PHONY
 	fi
 .endfor
 .endif
+#
+# If installing over the running system (DESTDIR is / or unset) and the install
+# includes rescue, try running rescue from the objdir as a sanity check.  If
+# rescue is not functional (e.g., because it depends on a system call not
+# supported by the currently running kernel), abort the installation.
+#
+.if !make(distributeworld) && ${MK_RESCUE} != "no" && \
+    (empty(DESTDIR) || ${DESTDIR} == "/") && empty(BYPASS_INSTALLCHECK_SH)
+_installcheck_world: __installcheck_sh_check
+__installcheck_sh_check: .PHONY
+	@if [ "`${OBJTREE}${.CURDIR}/rescue/rescue/rescue sh -c 'echo OK'`" != \
+	    OK ]; then \
+		echo "rescue/sh check failed, installation aborted" >&2; \
+		false; \
+	fi
+.endif
 
 #
 # Required install tools to be saved in a scratch dir for safety.