1 files changed, 65 insertions, 0 deletions
diff --git a/scripts/check-local-export b/scripts/check-local-export
new file mode 100755
index 000000000000..2c46912be0ef
--- /dev/null
+++ b/scripts/check-local-export
@@ -0,0 +1,65 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Copyright (C) 2022 Masahiro Yamada <masahiroy@kernel.org>
+#
+# Exit with error if a local exported symbol is found.
+# EXPORT_SYMBOL should be used for global symbols.
+
+set -e
+
+declare -A symbol_types
+declare -a export_symbols
+
+exit_code=0
+
+while read value type name
+do
+	# Skip the line if the number of fields is less than 3.
+	#
+	# case 1)
+	#   For undefined symbols, the first field (value) is empty.
+	#   The outout looks like this:
+	#     "                 U _printk"
+	#   It is unneeded to record undefined symbols.
+	#
+	# case 2)
+	#   For Clang LTO, llvm-nm outputs a line with type 't' but empty name:
+	#     "---------------- t"
+	if [[ -z ${name} ]]; then
+		continue
+	fi
+
+	# save (name, type) in the associative array
+	symbol_types[${name}]=${type}
+
+	# append the exported symbol to the array
+	if [[ ${name} == __ksymtab_* ]]; then
+		export_symbols+=(${name#__ksymtab_})
+	fi
+
+	# If there is no symbol in the object, ${NM} (both GNU nm and llvm-nm)
+	# shows 'no symbols' diagnostic (but exits with 0). It is harmless and
+	# hidden by '2>/dev/null'. However, it suppresses real error messages
+	# as well. Add a hand-crafted error message here.
+	#
+	# Use --quiet instead of 2>/dev/null when we upgrade the minimum version
+	# of binutils to 2.37, llvm to 13.0.0.
+	#
+	# Then, the following line will be really simple:
+	#   done < <(${NM} --quiet ${1})
+done < <(${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; false; } )
+
+# Catch error in the process substitution
+wait $!
+
+for name in "${export_symbols[@]}"
+do
+	# nm(3) says "If lowercase, the symbol is usually local"
+	if [[ ${symbol_types[$name]} =~ [a-z] ]]; then
+		echo "$@: error: local symbol '${name}' was exported" >&2
+		exit_code=1
+	fi
+done
+
+exit ${exit_code}