#!/bin/bash
# vim: tabstop=4 shiftwidth=4 expandtab
set -o nounset
set -o errexit
set -o pipefail

# TODO: log output to a file instead of /dev/null

CUR_DIR="$PWD"
SCRIPT="`basename $BASH_SOURCE`"
SCRIPT_DIR="`dirname $BASH_SOURCE`"
SCRIPT_DIR="`readlink -f \"$SCRIPT_DIR\"`"

KMOD_DIR="$SCRIPT_DIR/kmod"
KPATCH_REG="$KMOD_DIR/kpatch-register.o"
KPATCH_LDS="$KMOD_DIR/kpatch.lds"

KPATCH_GEN="$SCRIPT_DIR/kpatch-diff-gen/kpatch-diff-gen"
KPATCHGCC="$SCRIPT_DIR/kpatch-gcc"
JOBS=4
MAKE_CMD="make -j$JOBS vmlinux"
export CROSS_COMPILE="$KPATCHGCC "
# TODO make in function

PROGRESS_FILE="kpatch-in-progress"

PATCHED=
PATCH=
KERNEL_DIR=
OUTPUT_DIR=

usage ()
{
    echo "usage: $SCRIPT -p [PATCH] -k [KERNEL DIR] -o [OUTPUT DIR]" >&2
    exit 1
}


scriptecho ()
{
    echo "$SCRIPT: $*"
}

cleanup_objs ()
{
    find "$KERNEL_DIR" -name "*.orig_kpatch" -o -name "*.kpatch_gen" | while read file; do
        rm -f $file
    done
}

cleanup ()
{
    scriptecho "cleaning up..."
    rm -f "$PROGRESS_FILE"
    cleanup_objs
    if [ $PATCHED ]; then
        cd "$KERNEL_DIR"
        patch -p1 -R < "$PATCH" > /dev/null
        export CROSS_COMPILE="$KPATCHGCC "
        $MAKE_CMD > /dev/null
    fi

    rm -rf "$TMPDIR"
}

die ()
{
    echo "$SCRIPT: error: $*" >&2
    exit 1
}

while getopts "p:k:o:" arg; do
    case "$arg" in
        p) PATCH="$OPTARG" ;;
        k) KERNEL_DIR="$OPTARG" ;;
        o) OUTPUT_DIR="$OPTARG" ;;
        *) usage ;;
    esac
done

[ ! "$PATCH" ] || [ ! "$KERNEL_DIR" ] || [ ! "$OUTPUT_DIR" ] && usage

[ ! -f "$PATCH" ] && die "$PATCH doesn't exist"
[ ! -d "$KERNEL_DIR" ] && die "$KERNEL_DIR doesn't exist"
mkdir -p "$OUTPUT_DIR"

PATCH="`readlink -f \"$PATCH\"`"
KERNEL_DIR="`readlink -f \"$KERNEL_DIR\"`"
OUTPUT_DIR="`readlink -f \"$OUTPUT_DIR\"`"

TMPDIR="`mktemp -d`"
trap cleanup exit

scriptecho "compiling original kernel"
rm -f "$PROGRESS_FILE"
cleanup_objs
cd "$KERNEL_DIR"
$MAKE_CMD > /dev/null
cp vmlinux vmlinux.orig_kpatch

scriptecho "patching kernel"
patch -p1 < "$PATCH" > /dev/null
PATCHED=1

scriptecho "compiling patched kernel"
touch "$PROGRESS_FILE"
$MAKE_CMD > /dev/null
rm -f "$PROGRESS_FILE"

scriptecho "diffing binaries"
find . -type f -name '*.o.orig_kpatch' | while read file; do
    origfile="${file#./}"
    newfile="${origfile%.orig_kpatch}"
    [ ! -f "$newfile" ] && die "can't find \"$newfile\""
	num="`readelf -s \"$file\" |awk '{print $4}' |grep -c FILE`"
    [ "$num" = 0 ] && die "unsupported change in (assembly?) file \"$file\""
	[ "$num" -gt 1 ] && die "\"$newfile\" has too many FILE symbols"
    scriptecho "object changed: \"$newfile\""
    "$KPATCH_GEN" "$origfile" "$newfile" -v vmlinux.orig_kpatch -o "$newfile.kpatch_gen"
done

scriptecho "generating kpatch modules"
unset CROSS_COMPILE
cp -a "$KMOD_DIR" "$TMPDIR/kmod"

make -C "$KERNEL_DIR" M="$TMPDIR/kmod" kpatch-patch-hook.o > /dev/null

cd $TMPDIR/kmod
find "$KERNEL_DIR" -name "*.kpatch_gen" -exec ld -m elf_x86_64 -r -o kpatch-patch-foo.o kpatch-patch-hook.o kpatch.lds {} +

make -C "$KERNEL_DIR" M="$TMPDIR/kmod" kpatch.ko > /dev/null
make -C "$KERNEL_DIR" M="$TMPDIR/kmod" kpatch-patch.ko > /dev/null

cp kpatch.ko kpatch-patch.ko "$OUTPUT_DIR"

scriptecho success!