[v7,3/3] check-module-params: Introduce check-module-params.sh

diff --git a/scripts/check-module-params.sh b/scripts/check-module-params.sh
new file mode 100755
index 000000000000..990b271a8dbf
--- /dev/null
+++ b/scripts/check-module-params.sh
@@ -0,0 +1,371 @@ 
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+# Script to check commits for UAPI backwards compatibility
+
+set -o errexit
+set -o pipefail
+
+print_usage() {
+	name=$(basename "$0")
+	cat << EOF
+$name - check for module parameter stability across git commits.
+
+By default, the script will check to make sure the latest commit (or current
+dirty changes) did not introduce changes when compared to HEAD^1. You can
+check against additional commit ranges with the -b and -p options.
+
+Usage: $name [-b BASE_REF] [-p PAST_REF] [-j N] [-l ERROR_LOG] [-P] [-R] [-q]
+
+Options:
+    -b BASE_REF    Base git reference to use for comparison. If unspecified or empty,
+                   will use any dirty changes in tree. If there are no dirty changes,
+                   HEAD will be used.
+    -p PAST_REF    Compare BASE_REF to PAST_REF (e.g. -p v6.1). If unspecified or empty,
+                   will use BASE_REF^1. Must be an ancestor of BASE_REF. Only headers
+                   that exist on PAST_REF will be checked for compatibility.
+    -j JOBS        Number of checks to run in parallel (default: number of CPU cores).
+    -l ERROR_LOG   Write error log to file (default: no error log is generated).
+    -P             Flag all changes to permissions (even if they're compatible). This
+                   option negates the need for a host C compiler.
+    -R             Skip flagging parameter removals.
+    -q             Quiet operation (suppress stdout, still print stderr).
+
+Environmental args:
+    HOSTCC   C compiler for permission conversion to octal (default is "gcc")
+
+Exit codes:
+    $SUCCESS) Success
+    $FAILURE) Module param differences detected
+EOF
+}
+
+readonly SUCCESS=0
+readonly FAILURE=1
+
+# Print to stderr
+eprintf() {
+	# shellcheck disable=SC2059
+	printf "$@" >&2
+}
+
+# Check if git tree is dirty
+tree_is_dirty() {
+	! git diff --quiet
+}
+
+file_module_params_unmodified() {
+	local file="$1"
+	local base_ref="$2"
+	local past_ref="$3"
+	local base_params_file="${TMP_DIR}/${file}.base"
+	local past_params_file="${TMP_DIR}/${file}.past"
+	local error_log="${TMP_DIR}/${file}.error"
+
+	local -r awk_cmd='/^ *module_param.*\(/,/.*\);/'
+
+	mkdir -p "$(dirname "$error_log")"
+	git show "${past_ref}:${file}" 2> /dev/null \
+		| awk "$awk_cmd" > "$past_params_file" || true
+
+	if [ -z "$base_ref" ]; then
+		awk "$awk_cmd" "${KERNEL_SRC}/${file}" \
+			> "$base_params_file" 2> /dev/null || true
+	else
+		git show "${base_ref}:${file}" 2> /dev/null \
+			| awk "$awk_cmd" > "$base_params_file" || true
+	fi
+
+	# Ignore files that don't exist at the past ref or don't have module params
+	if [ ! -s "$past_params_file" ]; then
+		return 255 # Special return code for "no-op"
+	fi
+
+	# Process the param data to come up with an associative array of param names to param data
+	# For example:
+	#   module_param_call(foo, set_result, get_result, NULL, 0600);
+	#
+	# is processed into:
+	#   pre_change_params[foo]="set_result,get_result,NULL,0600"
+	local -A pre_change_params
+	local param_name
+	local param_params
+
+	while read -r mod_param_args; do
+		param_name="$(echo "$mod_param_args" | cut -d ',' -f 1)"
+		param_params="$(echo "$mod_param_args" | cut -d ',' -f 2-)"
+
+		pre_change_params[$param_name]=$param_params
+	done < <(tr -d '\t\n ' < "$past_params_file" | tr ';' '\n' | perl -lne '/\((.*)\)/ && print $1')
+
+	local -A post_change_params
+	while read -r mod_param_args; do
+		param_name="$(echo "$mod_param_args" | cut -d ',' -f 1)"
+		param_params="$(echo "$mod_param_args" | cut -d ',' -f 2-)"
+
+		post_change_params[$param_name]=$param_params
+	done < <(tr -d '\t\n ' < "$base_params_file" | tr ';' '\n' | perl -lne '/\((.*)\)/ && print $1')
+
+	#for param in "${!pre_change_params[@]}"; do
+	#	echo "$param: ${pre_change_params[${param}]}"
+	#done
+
+	# Flag any module param changes that:
+	#  - Remove/rename a parameter
+	#  - Change the arguments of the parameter
+	local incompat_param_changes=0
+	local pre
+	local post
+	for param_name in "${!pre_change_params[@]}"; do
+		pre="${pre_change_params[$param_name]}"
+		if [ ! "${post_change_params[$param_name]+set}" ]; then
+			if [ "$SKIP_PARAM_REMOVALS" = "true" ]; then
+				continue
+			fi
+			{
+				printf "Module parameter \"%s\" in %s removed!\n" "$param_name" "$file"
+				printf "  Original args: %s\n" "$pre"
+			} > "$error_log"
+			incompat_param_changes=$((incompat_param_changes + 1))
+			continue
+		fi
+
+		post="${post_change_params[$param_name]}"
+		if [ "$pre" != "$post" ]; then
+			if [ "$SKIP_SAFE_PERM_CHANGES" = "true" ] && perm_change_is_safe "$pre" "$post"; then
+				continue
+			fi
+			{
+				printf "Module parameter \"%s\" in %s changed!\n" "$param_name" "$file"
+				printf "  Original args: %s\n" "$pre"
+				printf "       New args: %s\n" "$post"
+			} > "$error_log"
+			incompat_param_changes=$((incompat_param_changes + 1))
+			continue
+		fi
+	done
+
+	if [ "$incompat_param_changes" -gt 0 ]; then
+		return 1
+	fi
+}
+
+perm_change_is_safe() {
+	local -r pre="$1"
+	local -r post="$2"
+
+	# Assume that the permission arg is always the last one.
+	pre_perm_arg=$(echo "$pre" | grep -o '[^,]*$')
+	post_perm_arg=$(echo "$post" | grep -o '[^,]*$')
+
+	# If the non-permission arguments are different, then
+	# don't even bother checking the permission arg.
+	if [ "${pre/,${pre_perm_arg}/}" != "${post/,${post_perm_arg}/}" ]; then
+		return 1
+	fi
+
+	# Convert both to octal representation to compare
+	pre_perm_arg_octal=$(get_octal_val "$pre_perm_arg")
+	post_perm_arg_octal=$(get_octal_val "$post_perm_arg")
+
+	if [ "$pre_perm_arg_octal" = "$post_perm_arg_octal" ]; then
+		return 0
+	else
+		return 1
+	fi
+}
+
+get_octal_val() {
+	local -r input="$1"
+
+	# Save needing to recompile for input we've seen before
+	local -r input_hash="$(echo "$input" | md5sum | cut -d ' ' -f 1)"
+
+	local -r prog="${TMP_DIR}/get_octal_val_${input_hash}"
+	local -r stat="include/linux/stat.h"
+
+	if [ ! -x "$prog" ]; then
+		cat << EOF > "${prog}.c"
+#include <stdio.h>
+#include <sys/stat.h>
+
+$(grep '#define *S_IRWXUGO' "$stat")
+$(grep '#define *S_IALLUGO' "$stat")
+$(grep '#define *S_IRUGO' "$stat")
+$(grep '#define *S_IWUGO' "$stat")
+$(grep '#define *S_IXUGO' "$stat")
+
+int main(void) { printf("%04o\\n", $input); };
+EOF
+		"${HOSTCC:-gcc}" -o "$prog" "${prog}.c"
+	fi
+
+	"$prog"
+}
+run() {
+	local base_ref="$1"
+	local past_ref="$2"
+	local param_error_log="$3"
+
+	diff_args=("$past_ref")
+	if [ -n "$base_ref" ]; then
+		diff_args+=("$base_ref")
+	fi
+
+	local -a threads=()
+	local passed=0
+	local failed=0
+	printf "Checking files between %s and %s for module parameter compatibility...\n" \
+		"$past_ref" "$base_ref"
+	while read -r modified_file; do
+		if [ "${#threads[@]}" -ge "$MAX_THREADS" ]; then
+			wait "${threads[0]}" && ret="$?" || ret="$?"
+			if [ "$ret" -eq 0 ]; then
+				passed=$((passed + 1))
+			elif [ "$ret" -eq 1 ]; then
+				failed=$((failed + 1))
+			fi
+			threads=("${threads[@]:1}")
+		fi
+
+		file_module_params_unmodified "$modified_file" "$base_ref" "$past_ref" &
+		threads+=("$!")
+	done < <(git diff --diff-filter=MCD --name-only "${diff_args[@]}" -- '*.c' '*.h')
+
+	for t in "${threads[@]}"; do
+		wait "$t" && ret="$?" || ret="$?"
+		if [ "$ret" -eq 0 ]; then
+			passed=$((passed + 1))
+		elif [ "$ret" -eq 1 ]; then
+			failed=$((failed + 1))
+		fi
+	done
+
+	total=$((passed + failed))
+	if [ "$total" -eq 0 ]; then
+		printf "No files with module parameters modified between %s and %s\n" \
+			"$past_ref" "${base_ref:-dirty tree}"
+		exit "$SUCCESS"
+	fi
+
+	if [ -n "$param_error_log" ]; then
+		printf 'Generated by "%s %s" from git ref %s\n\n' \
+			"$0" "$*" "$(git rev-parse HEAD)" > "$param_error_log"
+	fi
+
+	while read -r error_file; do
+		{
+			cat "$error_file"
+			printf "\n\n"
+		} | tee -a "${param_error_log:-/dev/null}" >&2
+	done < <(find "$TMP_DIR" -type f -name '*.error' | sort)
+
+	if [ "$failed" -gt 0 ]; then
+		eprintf "error - %d/%d files with modules parameters appear _not_ to be backwards compatible\n" \
+			"$failed" "$total"
+		if [ -n "$param_error_log" ]; then
+			eprintf "Failure summary saved to %s\n" "$param_error_log"
+		fi
+	else
+		printf "All %d files with module_parameters checked appear to be backwards compatible\n" \
+			"$total"
+	fi
+
+	exit "$failed"
+}
+
+# Make sure the git refs we have make sense
+check_refs() {
+	if ! git rev-parse --is-inside-work-tree > /dev/null 2>&1; then
+		eprintf "error - this script requires the kernel tree to be initialized with Git\n"
+		return 1
+	fi
+
+	if ! git rev-parse --verify "$past_ref" > /dev/null 2>&1; then
+		printf 'error - invalid git reference "%s"\n' "$past_ref"
+		return 1
+	fi
+
+	if [ -n "$base_ref" ]; then
+		if ! git merge-base --is-ancestor "$past_ref" "$base_ref" > /dev/null 2>&1; then
+			printf 'error - "%s" is not an ancestor of base ref "%s"\n' "$past_ref" "$base_ref"
+			return 1
+		fi
+		if [ "$(git rev-parse "$base_ref")" = "$(git rev-parse "$past_ref")" ]; then
+			printf 'error - "%s" and "%s" are the same reference\n' "$past_ref" "$base_ref"
+			return 1
+		fi
+	fi
+}
+
+main() {
+	MAX_THREADS=$(nproc)
+	SKIP_SAFE_PERM_CHANGES="true"
+	SKIP_PARAM_REMOVALS="false"
+	quiet="false"
+	local base_ref=""
+	while getopts "hb:p:j:l:PRq" opt; do
+		case $opt in
+		h)
+			print_usage
+			exit "$SUCCESS"
+			;;
+		b)
+			base_ref="$OPTARG"
+			;;
+		p)
+			past_ref="$OPTARG"
+			;;
+		j)
+			MAX_THREADS="$OPTARG"
+			;;
+		l)
+			param_error_log="$OPTARG"
+			;;
+		P)
+			SKIP_SAFE_PERM_CHANGES="false"
+			;;
+		R)
+			SKIP_PARAM_REMOVALS="true"
+			;;
+		q)
+			quiet="true"
+			;;
+		*)
+			exit "$FAILURE"
+		esac
+	done
+
+	if [ "$quiet" = "true" ]; then
+		exec > /dev/null 2>&1
+	fi
+
+	if [ -z "$KERNEL_SRC" ]; then
+		KERNEL_SRC="$(realpath "$(dirname "$0")"/..)"
+	fi
+
+	cd "$KERNEL_SRC"
+
+	if [ -z "$base_ref" ] && ! tree_is_dirty; then
+		base_ref=HEAD
+	fi
+
+	if [ -z "$past_ref" ]; then
+		if [ -n "$base_ref" ]; then
+			past_ref="${base_ref}^1"
+		else
+			past_ref=HEAD
+		fi
+	fi
+
+	if ! check_refs; then
+		exit "$FAILURE"
+	fi
+
+	TMP_DIR=$(mktemp -d)
+	readonly TMP_DIR
+	trap 'rm -rf "$TMP_DIR"' EXIT
+
+	run "$base_ref" "$past_ref" "$param_error_log"
+}
+
+main "$@"