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#!/usr/bin/env 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
# catch errors from ${NM}
set -o pipefail
# Run the last element of a pipeline in the current shell.
# Without this, the while-loop would be executed in a subshell, and
# the changes made to 'symbol_types' and 'export_symbols' would be lost.
shopt -s lastpipe
declare -A symbol_types
declare -a export_symbols
exit_code=0
# 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.
#
# TODO:
# 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:
# ${NM} --quiet ${1} |
{ ${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; false; } } |
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
done
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}
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