#!/bin/sh
## https://github.com/dnschneid/crouton/wiki/Repack-kernel-to-Enable-VT_x-for-Virtualbox
set -e

main() {
        local part=$1
        assert matches_rx $part '^[24]$'

        check_crossystem
        sudo dd if=/dev/sda$part of=$tmp/old_kernel
        cmdline=$($hack/chromeos-files/futility vbutil_kernel --verify $tmp/old_kernel | tail -1)
        new_cmdline="$cmdline"
        echo $new_cmdline | egrep -q " rootwait rw " || {
                new_cmdline=$(echo $new_cmdline | sed 's/ rootwait ro / rootwait rw /')
        }
        echo $new_cmdline | egrep -q "disable_vmx" || {
                new_cmdline="$new_cmdline disable_vmx=off"
        }
        echo $new_cmdline | egrep -q "lsm.module_locking" || {
                new_cmdline="$new_cmdline lsm.module_locking=0"
        }
        if [ "$cmdline" = "$new_cmdline" ]; then
                fatal "no changes to apply to current cmdline: $cmdline"
        else
                echo $new_cmdline > $tmp/new_cmdline
                $hack/chromeos-files/futility vbutil_kernel \
                        --repack $tmp/new_kernel \
                        --signprivate $hack/chromeos-files/kernel_data_key.vbprivk \
                        --keyblock $hack/chromeos-files/kernel.keyblock \
                        --oldblob $tmp/old_kernel \
                        --config $tmp/new_cmdline
                $hack/chromeos-files/futility vbutil_kernel \
                        --verify $tmp/new_kernel \
                        --verbose | \
                        grep -q "Body verification succeeded" || {
                                fatal "new kernel verification failed"
                        }
                log "saving kernel with new cmdline"
                $dry_run sudo dd if=$tmp/new_kernel of=/dev/sda$part bs=512 notrunc
        fi
}

####
hack=$(readlink -f $(dirname $0))
. $hack/functions.sh
tmp=/tmp/$(basename $0).$$
mkdir $tmp

if [ "x$1" = x-f ]; then
        shift
else
        log "dry-run mode"
        dry_run=echo
fi

 [ "$1" != 2 -a "$1" != 4 ] && {
        log "Usage: $0 [24]"
        exit 2
}
main $1