diff --git a/config.sub b/config.sub
old mode 100755
new mode 100644
index 63c1f1c8b5e..38f3d037a78
--- a/config.sub
+++ b/config.sub
@@ -2,7 +2,9 @@
 # Configuration validation subroutine script.
 #   Copyright 1992-2021 Free Software Foundation, Inc.
 
-timestamp='2021-01-08'
+# shellcheck disable=SC2006,SC2268 # see below for rationale
+
+timestamp='2021-10-27'
 
 # This file is free software; you can redistribute it and/or modify it
 # under the terms of the GNU General Public License as published by
@@ -50,7 +52,14 @@ timestamp='2021-01-08'
 #	CPU_TYPE-MANUFACTURER-KERNEL-OPERATING_SYSTEM
 # It is wrong to echo any other type of specification.
 
-me=$(echo "$0" | sed -e 's,.*/,,')
+# The "shellcheck disable" line above the timestamp inhibits complaints
+# about features and limitations of the classic Bourne shell that were
+# superseded or lifted in POSIX.  However, this script identifies a wide
+# variety of pre-POSIX systems that do not have POSIX shells at all, and
+# even some reasonably current systems (Solaris 10 as case-in-point) still
+# have a pre-POSIX /bin/sh.
+
+me=`echo "$0" | sed -e 's,.*/,,'`
 
 usage="\
 Usage: $0 [OPTION] CPU-MFR-OPSYS or ALIAS
@@ -112,9 +121,11 @@ esac
 
 # Split fields of configuration type
 # shellcheck disable=SC2162
+saved_IFS=$IFS
 IFS="-" read field1 field2 field3 field4 <<EOF
 $1
 EOF
+IFS=$saved_IFS
 
 # Separate into logical components for further validation
 case $1 in
@@ -163,6 +174,10 @@ case $1 in
 						basic_machine=$field1
 						basic_os=$field2
 						;;
+					zephyr*)
+						basic_machine=$field1-unknown
+						basic_os=$field2
+						;;
 					# Manufacturers
 					dec* | mips* | sequent* | encore* | pc533* | sgi* | sony* \
 					| att* | 7300* | 3300* | delta* | motorola* | sun[234]* \
@@ -769,22 +784,22 @@ case $basic_machine in
 		vendor=hp
 		;;
 	i*86v32)
-		cpu=$(echo "$1" | sed -e 's/86.*/86/')
+		cpu=`echo "$1" | sed -e 's/86.*/86/'`
 		vendor=pc
 		basic_os=sysv32
 		;;
 	i*86v4*)
-		cpu=$(echo "$1" | sed -e 's/86.*/86/')
+		cpu=`echo "$1" | sed -e 's/86.*/86/'`
 		vendor=pc
 		basic_os=sysv4
 		;;
 	i*86v)
-		cpu=$(echo "$1" | sed -e 's/86.*/86/')
+		cpu=`echo "$1" | sed -e 's/86.*/86/'`
 		vendor=pc
 		basic_os=sysv
 		;;
 	i*86sol2)
-		cpu=$(echo "$1" | sed -e 's/86.*/86/')
+		cpu=`echo "$1" | sed -e 's/86.*/86/'`
 		vendor=pc
 		basic_os=solaris2
 		;;
@@ -917,14 +932,16 @@ case $basic_machine in
 		;;
 	leon-*|leon[3-9]-*)
 		cpu=sparc
-		vendor=$(echo "$basic_machine" | sed 's/-.*//')
+		vendor=`echo "$basic_machine" | sed 's/-.*//'`
 		;;
 
 	*-*)
 		# shellcheck disable=SC2162
+		saved_IFS=$IFS
 		IFS="-" read cpu vendor <<EOF
 $basic_machine
 EOF
+		IFS=$saved_IFS
 		;;
 	# We use `pc' rather than `unknown'
 	# because (1) that's what they normally are, and
@@ -1084,7 +1101,7 @@ case $cpu-$vendor in
 		cpu=mipsisa64sb1el
 		;;
 	sh5e[lb]-*)
-		cpu=$(echo "$cpu" | sed 's/^\(sh.\)e\(.\)$/\1\2e/')
+		cpu=`echo "$cpu" | sed 's/^\(sh.\)e\(.\)$/\1\2e/'`
 		;;
 	spur-*)
 		cpu=spur
@@ -1102,7 +1119,7 @@ case $cpu-$vendor in
 		cpu=x86_64
 		;;
 	xscale-* | xscalee[bl]-*)
-		cpu=$(echo "$cpu" | sed 's/^xscale/arm/')
+		cpu=`echo "$cpu" | sed 's/^xscale/arm/'`
 		;;
 	arm64-*)
 		cpu=aarch64
@@ -1165,7 +1182,7 @@ case $cpu-$vendor in
 			| alphapca5[67] | alpha64pca5[67] \
 			| am33_2.0 \
 			| amdgcn \
-			| arc | arceb \
+			| arc | arceb | arc32 | arc64 \
 			| arm | arm[lb]e | arme[lb] | armv* \
 			| avr | avr32 \
 			| asmjs \
@@ -1204,9 +1221,13 @@ case $cpu-$vendor in
 			| mips64vr5900 | mips64vr5900el \
 			| mipsisa32 | mipsisa32el \
 			| mipsisa32r2 | mipsisa32r2el \
+			| mipsisa32r3 | mipsisa32r3el \
+			| mipsisa32r5 | mipsisa32r5el \
 			| mipsisa32r6 | mipsisa32r6el \
 			| mipsisa64 | mipsisa64el \
 			| mipsisa64r2 | mipsisa64r2el \
+			| mipsisa64r3 | mipsisa64r3el \
+			| mipsisa64r5 | mipsisa64r5el \
 			| mipsisa64r6 | mipsisa64r6el \
 			| mipsisa64sb1 | mipsisa64sb1el \
 			| mipsisa64sr71k | mipsisa64sr71kel \
@@ -1283,35 +1304,37 @@ esac
 if test x$basic_os != x
 then
 
-# First recognize some ad-hoc caes, or perhaps split kernel-os, or else just
+# First recognize some ad-hoc cases, or perhaps split kernel-os, or else just
 # set os.
 case $basic_os in
 	gnu/linux*)
 		kernel=linux
-		os=$(echo $basic_os | sed -e 's|gnu/linux|gnu|')
+		os=`echo "$basic_os" | sed -e 's|gnu/linux|gnu|'`
 		;;
 	os2-emx)
 		kernel=os2
-		os=$(echo $basic_os | sed -e 's|os2-emx|emx|')
+		os=`echo "$basic_os" | sed -e 's|os2-emx|emx|'`
 		;;
 	nto-qnx*)
 		kernel=nto
-		os=$(echo $basic_os | sed -e 's|nto-qnx|qnx|')
+		os=`echo "$basic_os" | sed -e 's|nto-qnx|qnx|'`
 		;;
 	*-*)
 		# shellcheck disable=SC2162
+		saved_IFS=$IFS
 		IFS="-" read kernel os <<EOF
 $basic_os
 EOF
+		IFS=$saved_IFS
 		;;
 	# Default OS when just kernel was specified
 	nto*)
 		kernel=nto
-		os=$(echo $basic_os | sed -e 's|nto|qnx|')
+		os=`echo "$basic_os" | sed -e 's|nto|qnx|'`
 		;;
 	linux*)
 		kernel=linux
-		os=$(echo $basic_os | sed -e 's|linux|gnu|')
+		os=`echo "$basic_os" | sed -e 's|linux|gnu|'`
 		;;
 	*)
 		kernel=
@@ -1332,7 +1355,7 @@ case $os in
 		os=cnk
 		;;
 	solaris1 | solaris1.*)
-		os=$(echo $os | sed -e 's|solaris1|sunos4|')
+		os=`echo "$os" | sed -e 's|solaris1|sunos4|'`
 		;;
 	solaris)
 		os=solaris2
@@ -1361,7 +1384,7 @@ case $os in
 		os=sco3.2v4
 		;;
 	sco3.2.[4-9]*)
-		os=$(echo $os | sed -e 's/sco3.2./sco3.2v/')
+		os=`echo "$os" | sed -e 's/sco3.2./sco3.2v/'`
 		;;
 	sco*v* | scout)
 		# Don't match below
@@ -1391,7 +1414,7 @@ case $os in
 		os=lynxos
 		;;
 	mac[0-9]*)
-		os=$(echo "$os" | sed -e 's|mac|macos|')
+		os=`echo "$os" | sed -e 's|mac|macos|'`
 		;;
 	opened*)
 		os=openedition
@@ -1400,10 +1423,10 @@ case $os in
 		os=os400
 		;;
 	sunos5*)
-		os=$(echo "$os" | sed -e 's|sunos5|solaris2|')
+		os=`echo "$os" | sed -e 's|sunos5|solaris2|'`
 		;;
 	sunos6*)
-		os=$(echo "$os" | sed -e 's|sunos6|solaris3|')
+		os=`echo "$os" | sed -e 's|sunos6|solaris3|'`
 		;;
 	wince*)
 		os=wince
@@ -1437,7 +1460,7 @@ case $os in
 		;;
 	# Preserve the version number of sinix5.
 	sinix5.*)
-		os=$(echo $os | sed -e 's|sinix|sysv|')
+		os=`echo "$os" | sed -e 's|sinix|sysv|'`
 		;;
 	sinix*)
 		os=sysv4
@@ -1684,7 +1707,7 @@ fi
 # Now, validate our (potentially fixed-up) OS.
 case $os in
 	# Sometimes we do "kernel-libc", so those need to count as OSes.
-	musl* | newlib* | uclibc*)
+	musl* | newlib* | relibc* | uclibc*)
 		;;
 	# Likewise for "kernel-abi"
 	eabi* | gnueabi*)
@@ -1707,12 +1730,12 @@ case $os in
 	     | nindy* | vxsim* | vxworks* | ebmon* | hms* | mvs* \
 	     | clix* | riscos* | uniplus* | iris* | isc* | rtu* | xenix* \
 	     | mirbsd* | netbsd* | dicos* | openedition* | ose* \
-	     | bitrig* | openbsd* | solidbsd* | libertybsd* | os108* \
+	     | bitrig* | openbsd* | secbsd* | solidbsd* | libertybsd* | os108* \
 	     | ekkobsd* | freebsd* | riscix* | lynxos* | os400* \
 	     | bosx* | nextstep* | cxux* | aout* | elf* | oabi* \
 	     | ptx* | coff* | ecoff* | winnt* | domain* | vsta* \
 	     | udi* | lites* | ieee* | go32* | aux* | hcos* \
-	     | chorusrdb* | cegcc* | glidix* \
+	     | chorusrdb* | cegcc* | glidix* | serenity* \
 	     | cygwin* | msys* | pe* | moss* | proelf* | rtems* \
 	     | midipix* | mingw32* | mingw64* | mint* \
 	     | uxpv* | beos* | mpeix* | udk* | moxiebox* \
@@ -1725,7 +1748,8 @@ case $os in
 	     | skyos* | haiku* | rdos* | toppers* | drops* | es* \
 	     | onefs* | tirtos* | phoenix* | fuchsia* | redox* | bme* \
 	     | midnightbsd* | amdhsa* | unleashed* | emscripten* | wasi* \
-	     | nsk* | powerunix* | genode* | zvmoe* | qnx* | emx*)
+	     | nsk* | powerunix* | genode* | zvmoe* | qnx* | emx* | zephyr* \
+	     | fiwix* )
 		;;
 	# This one is extra strict with allowed versions
 	sco3.2v2 | sco3.2v[4-9]* | sco5v6*)
@@ -1742,11 +1766,12 @@ esac
 # As a final step for OS-related things, validate the OS-kernel combination
 # (given a valid OS), if there is a kernel.
 case $kernel-$os in
-	linux-gnu* | linux-dietlibc* | linux-android* | linux-newlib* | linux-musl* | linux-uclibc* )
+	linux-gnu* | linux-dietlibc* | linux-android* | linux-newlib* \
+		   | linux-musl* | linux-relibc* | linux-uclibc* )
 		;;
 	uclinux-uclibc* )
 		;;
-	-dietlibc* | -newlib* | -musl* | -uclibc* )
+	-dietlibc* | -newlib* | -musl* | -relibc* | -uclibc* )
 		# These are just libc implementations, not actual OSes, and thus
 		# require a kernel.
 		echo "Invalid configuration \`$1': libc \`$os' needs explicit kernel." 1>&2