[PATCH v3 2/3] scripts: kconfig: merge_config.sh: use awk in checks too

[Mikko Rapeli <mikko.rapeli@linaro.org>]

Converting from shell/sed/grep loop to awk improves runtime
checks of Yocto genericarm64 kernel config from 20 seconds
to under 1 second. The checks catch this kind of issues:

WARNING: CONFIG_BLK_DEV_DM differs:
Requested value: CONFIG_BLK_DEV_DM=y
Actual value:    CONFIG_BLK_DEV_DM=m
WARNING: CONFIG_SECURITY_NETWORK differs:
Requested value: CONFIG_SECURITY_NETWORK=n
Actual value:    CONFIG_SECURITY_NETWORK=y
WARNING: Value requested for CONFIG_ARM64_BTI_KERNEL not in final .config
Requested value: CONFIG_ARM64_BTI_KERNEL=y
Actual value:

Cc: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
---
 scripts/kconfig/merge_config.sh | 97 +++++++++++++++++++++++++++++----
 1 file changed, 86 insertions(+), 11 deletions(-)

v3: use $VAR syntax for shell variables, changed output to be a bit more
    similar to the shell script version before

v2: awk from ${AWK}
    https://lore.kernel.org/linux-kbuild/20251229114447.45236-1-mikko.rapeli@linaro.org/T/#md557a7746d96920ff270448738adf96b9fa993ca

v1: https://lore.kernel.org/linux-kbuild/20251229114447.45236-1-mikko.rapeli@linaro.org/T/#t

diff --git a/scripts/kconfig/merge_config.sh b/scripts/kconfig/merge_config.sh
index de217771b78c..9eda9dbd4542 100755
--- a/scripts/kconfig/merge_config.sh
+++ b/scripts/kconfig/merge_config.sh
@@ -286,16 +286,91 @@ fi
 # allnoconfig: Fills in any missing symbols with # CONFIG_* is not set
 make KCONFIG_ALLCONFIG=$TMP_FILE $OUTPUT_ARG $ALLTARGET
 
+# Check all specified config values took effect (might have missed-dependency issues)
+if ! "$AWK" -v prefix="$CONFIG_PREFIX" \
+	-v warnoverride="$WARNOVERRIDE" \
+	-v strict="$STRICT" \
+	-v warnredun="$WARNREDUN" '
+BEGIN {
+	strict_violated = 0
+	cfg_regex = "^" prefix "[a-zA-Z0-9_]+"
+	notset_regex = "^# " prefix "[a-zA-Z0-9_]+ is not set$"
+}
 
-# Check all specified config values took (might have missed-dependency issues)
-for CFG in $(sed -n -e "$SED_CONFIG_EXP1" -e "$SED_CONFIG_EXP2" $TMP_FILE); do
+# Extract config name from a line, returns "" if not a config line
+function get_cfg(line) {
+	if (match(line, cfg_regex)) {
+		return substr(line, RSTART, RLENGTH)
+	} else if (match(line, notset_regex)) {
+		# Extract CONFIG_FOO from "# CONFIG_FOO is not set"
+		sub(/^# /, "", line)
+		sub(/ is not set$/, "", line)
+		return line
+	}
+	return ""
+}
 
-	REQUESTED_VAL=$(grep -w -e "$CFG" $TMP_FILE)
-	ACTUAL_VAL=$(grep -w -e "$CFG" "$KCONFIG_CONFIG" || true)
-	if [ "x$REQUESTED_VAL" != "x$ACTUAL_VAL" ] ; then
-		echo "Value requested for $CFG not in final .config"
-		echo "Requested value:  $REQUESTED_VAL"
-		echo "Actual value:     $ACTUAL_VAL"
-		echo ""
-	fi
-done
+function warn_mismatch(cfg, merged, final) {
+	if (warnredun == "true") return
+	if (final == "" && !(merged ~ / is not set$/ || merged ~ /=n$/)) {
+		print "WARNING: Value requested for " cfg " not in final .config"
+		print "Requested value: " merged
+		print "Actual value:    " final
+	} else if (final == "" && merged ~ / is not set$/) {
+		# not set, pass
+	} else if (merged == "" && final != "") {
+		print "WARNING: " cfg " not in merged config but added in final .config:"
+		print "Requested value: " merged
+		print "Actual value:    " final
+	} else {
+		print "WARNING: " cfg " differs:"
+		print "Requested value: " merged
+		print "Actual value:    " final
+	}
+}
+
+# First pass: read effective config file, store all lines
+FILENAME == ARGV[1] {
+	cfg = get_cfg($0)
+	if (cfg != "") {
+		config_cfg[cfg] = $0
+	}
+	next
+}
+
+# Second pass: process merged config and compare against effective config
+{
+	cfg = get_cfg($0)
+	if (cfg == "") next
+
+	# strip trailing comment
+	sub(/[[:space:]]+#.*/, "", $0)
+	merged_val = $0
+	final_val = config_cfg[cfg]
+
+	if (merged_val == final_val) next
+
+	if (merged_val ~ /=n$/ && final_val ~ / is not set$/) next
+	if (merged_val ~ /=n$/ && final_val == "") next
+
+	warn_mismatch(cfg, merged_val, final_val)
+
+	if (strict == "true") {
+		strict_violated = 1
+	}
+}
+
+END {
+	if (strict_violated) {
+		exit 1
+	}
+}' \
+"$KCONFIG_CONFIG" "$TMP_FILE"; then
+	# awk exited non-zero, strict mode was violated
+	STRICT_MODE_VIOLATED=true
+fi
+
+if [ "$STRICT" == "true" ] && [ "$STRICT_MODE_VIOLATED" == "true" ]; then
+	echo "Requested and effective config differ"
+	exit 1
+fi
-- 
2.34.1