1. 根目录:
2. arch
3. x86
4. vdso
5. checkundef.sh

#!/bin/sh
nm="$1"
file="$2"
$nm "$file" | grep '^ *U' > /dev/null 2>&1
if [ $? -eq 1 ]; then
    exit 0
else
    echo "$file: undefined symbols found" >&2
    exit 1
fi