Build loaders reproducibly when WITH_REPRODUCIBLE_BUILD

When WITH_REPRODUCIBLE_BUILD=yes is set in src.conf(5), eliminate the
time, user, and host from the loader's version information.  This allows
builds to produce bit-for-bit identical output.

Reviewed by:	bapt
MFC after:	1 month
Relnotes:	yes
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D8842

share/mk/src.opts.mk

@@ -190,6 +190,7 @@ __DEFAULT_NO_OPTIONS = \
     OFED \
     OPENLDAP \
     RCS \
+    REPRODUCIBLE_BUILD \
     SHARED_TOOLCHAIN \
     SORT_THREADS \
     SVN \

sys/boot/common/Makefile.inc

@@ -74,5 +74,9 @@ CFLAGS+=-I${.CURDIR}/../../../../lib/libstand
 
 CLEANFILES+=	vers.c
 VERSION_FILE?=	${.CURDIR}/version
+.if ${MK_REPRODUCIBLE_BUILD} != no
+REPRO_FLAG=	-r
+.endif
 vers.c: ${SRCTOP}/sys/boot/common/newvers.sh ${VERSION_FILE}
-	sh ${SRCTOP}/sys/boot/common/newvers.sh ${VERSION_FILE} ${NEWVERSWHAT}
+	sh ${SRCTOP}/sys/boot/common/newvers.sh ${REPRO_FLAG} ${VERSION_FILE} \
+	    ${NEWVERSWHAT}

sys/boot/common/newvers.sh

@@ -35,11 +35,26 @@
 tempfile=$(mktemp tmp.XXXXXX) || exit
 trap "rm -f $tempfile" EXIT INT TERM
 
+include_metadata=true
+while getopts r opt; do
+	case "$opt" in
+	r)
+		include_metadata=
+		;;
+	esac
+done
+shift $((OPTIND - 1))
+
 LC_ALL=C; export LC_ALL
 u=${USER-root} h=${HOSTNAME-`hostname`} t=`date`
 #r=`head -n 6 $1 | tail -n 1 | awk -F: ' { print $1 } '`
 r=`awk -F: ' /^[0-9]\.[0-9]+:/ { print $1; exit }' $1`
 
-echo "char bootprog_info[] = \"FreeBSD/${3} ${2}, Revision ${r}\\n(${t} ${u}@${h})\\n\";" > $tempfile
+bootprog_info="FreeBSD/${3} ${2}, Revision ${r}\\n"
+if [ -n "${include_metadata}" ]; then
+	bootprog_info="$bootprog_info(${t} ${u}@${h})\\n"
+fi
+
+echo "char bootprog_info[] = \"$bootprog_info\";" > $tempfile
 echo "unsigned bootprog_rev = ${r%%.*}${r##*.};" >> $tempfile
 mv $tempfile vers.c

tools/build/options/WITH_REPRODUCIBLE_BUILD

@@ -1,3 +1,4 @@
 $FreeBSD$
-Set to exclude build metadata (build time, user, host and path) from the
-kernel and uname output.
+Set to exclude build metadata (such as the build time, user, or host)
+from the kernel, boot loaders, and uname output, so that builds produce
+bit-for-bit identical output.