#!/bin/bash
#
# weak-modules - determine which modules are kABI compatible with installed
#                kernels and set up the symlinks in /lib/*/weak-updates.
#

unset LANG LC_ALL LC_COLLATE

tmpdir=$(mktemp -td ${0##*/}.XXXXXX)
trap "rm -rf $tmpdir" EXIT
unset ${!changed_modules_*} ${!changed_initramfs_*}

initramfs_prefix="/boot" # can customize here
dracut="/sbin/dracut"

if [ ! -x "$dracut" ]
then
        echo "weak-modules: this tool requires a dracut-enabled kernel"
	exit 1
fi

# doit:
# A wrapper used whenever we're going to perform a real operation.
doit() {
    [ -n "$verbose" ] && echo "$@"
    [ -n "$dry_run" ] || "$@"
}

# rpmsort: The sort in coreutils can't sort the RPM list how we want it so we
# instead transform the list into a form it will sort correctly, then sort.
rpmsort() {
	local IFS=$' '
	REVERSE=""
	rpmlist=($(cat))

	if [ "-r" == "$1" ];
	then
		REVERSE="-r"
	fi

	echo ${rpmlist[@]} | \
	sed -e 's/-/../g' | \
	sort ${REVERSE} -n -t"." -k1,1 -k2,2 -k3,3 -k4,4 -k5,5 -k6,6 -k7,7 \
				 -k8,8 -k9,9 -k10,10 | \
	sed -e 's/\.\./-/g'
}

# read_modules_list:
# Read in a list of modules from standard input. Convert the filenames into
# absolute paths and compute the kernel release for each module (either using
# the modinfo section or through the absolute path.
read_modules_list() {
    local IFS=$'\n'
    modules=($(cat))

    for ((n = 0; n < ${#modules[@]}; n++)); do
        if [ ${modules[n]:0:1} != '/' ]; then
            modules[n]="$PWD/${modules[n]}"
        fi
        if [ -f "${modules[n]}" ]; then
            module_krels[n]=$(krel_of_module ${modules[n]})
        else
            # Try to extract the kernel release from the path
            set -- "${modules[n]#*/lib/modules/}"
            module_krels[n]=${1%%/*}
        fi
    done
}

decompress_initramfs() {
    local input=$1
    local output=$2

    # First, check if this is compressed at all
    if cpio -i -t < "$input" > /dev/null 2>/dev/null; then
        # If this archive contains a file early_cpio, it's a trick. Strip off
        # the early cpio archive and try again.
        if cpio -i -t < "$input" 2>/dev/null | grep -q '^early_cpio$' ; then
            /usr/lib/dracut/skipcpio "$input" > "${tmpdir}/post_early_cpio.img"
            decompress_initramfs "${tmpdir}/post_early_cpio.img" "$output"
            retval="$?"
            rm -f "${tmpdir}/post_early_cpio.img"
            return $retval
        fi

        cp "$input" "$output"
        return 0
    fi

    # Try gzip
    if gzip -cd < "$input" > "$output" 2>/dev/null ; then
        return 0
    fi

    # Next try xz
    if xz -cd < "$input" > "$output" 2>/dev/null ; then
        return 0
    fi

    echo "Unable to decompress $input: Unknown format" >&2
    return 1
}

# List all module files and modprobe configuration that could require a new
# initramfs. The current directory must be the root of the uncompressed
# initramfs. The unsorted list of files is output to stdout.
list_module_files() {
    find . -iname \*.ko 2>/dev/null
    find etc/modprobe.d usr/lib/modprobe.d -name \*.conf 2>/dev/null
}

# read_old_initramfs:
compare_initramfs_modules() {
    local old_initramfs=$1
    local new_initramfs=$2

    rm -rf "$tmpdir/old_initramfs"
    rm -rf "$tmpdir/new_initramfs"
    mkdir "$tmpdir/old_initramfs"
    mkdir "$tmpdir/new_initramfs"

    decompress_initramfs "$old_initramfs" "$tmpdir/old_initramfs.img"
    pushd "$tmpdir/old_initramfs" >/dev/null
    cpio -i < "$tmpdir/old_initramfs.img" 2>/dev/null
    rm "$tmpdir/old_initramfs.img"
    n=0; for i in `list_module_files|sort`; do
        old_initramfs_modules[n]="$i"
        n=$((n+1))
    done
    popd >/dev/null

    decompress_initramfs "$new_initramfs" "$tmpdir/new_initramfs.img"
    pushd "$tmpdir/new_initramfs" >/dev/null
    cpio -i < "$tmpdir/new_initramfs.img" 2>/dev/null
    rm "$tmpdir/new_initramfs.img"
    n=0; for i in `list_module_files|sort`; do
        new_initramfs_modules[n]="$i"
        n=$((n+1))
    done
    popd >/dev/null

    # Compare the length and contents of the arrays
    if [ "${#old_initramfs_modules[@]}" == "${#new_initramfs_modules[@]}" -a \
         "${old_initramfs_modules[*]}" == "${new_initramfs_modules[*]}" ];
    then
        # If the file lists are the same, compare each file to find any that changed
        for ((n = 0; n < ${#old_initramfs_modules[@]}; n++)); do
            if ! cmp "$tmpdir/old_initramfs/${old_initramfs_modules[n]}" \
                     "$tmpdir/new_initramfs/${new_initramfs_modules[n]}" ; then
                return 1
            fi
        done
    else
        return 1
    fi

    return 0
}

# check_initramfs:
# check and possibly also update the initramfs for changed kernels
check_initramfs() {
    local kernel=$1

    # If there is no initramfs already we will not make one here.
    if [ -e "$initramfs_prefix/initramfs-$kernel.img" ];
    then
        old_initramfs="$initramfs_prefix/initramfs-$kernel.img"
        tmp_initramfs="$initramfs_prefix/initramfs-$kernel.tmp"
        new_initramfs="$initramfs_prefix/initramfs-$kernel.img"

        $dracut -f "$tmp_initramfs" "$kernel"

        if ! $(compare_initramfs_modules "$old_initramfs" "$tmp_initramfs");
        then
            doit mv "$tmp_initramfs" "$new_initramfs"
        else
            rm -f "$tmp_initramfs"
        fi
    fi
}

# krel_of_module:
# Compute the kernel release of a module.
krel_of_module() {
    declare module=$1
    /sbin/modinfo -F vermagic "$module" | awk '{print $1}'
}

# module_is_compatible:
# Determine if a module is compatible with a particular kernel release. Also
# include any symbol deps that might be introduced by other external kmods.
module_is_compatible() {
    declare module=$1 krel=$2 module_krel=$(krel_of_module "$module")

    if [ ! -e "$tmpdir/all-symvers-$krel-$module_krel" ]; then
        # Symbols exported by the "new" kernel
        if [ ! -e $tmpdir/symvers-$krel ]; then
            # Accept '.' in the symbol name to handle the .TOC. symbol on ppc
            if [ -e /boot/symvers-$krel.gz ]; then
                zcat /boot/symvers-$krel.gz \
                | sed -r -ne 's:^(0x[0]*[0-9a-f]{8}\t[0-9a-zA-Z_.]+)\t.*:\1:p'
            fi > $tmpdir/symvers-$krel
        fi

        # Symbols exported by the add-on modules of the "new" kernel
        if [ ! -e "$tmpdir/addon-symvers-$krel" ]; then
            if [ -e /lib/modules/$krel/extra ] && \
               [ -n "`find /lib/modules/$krel/extra -type f`" ]; then
                find /lib/modules/$krel/extra -name '*.ko' \
                | xargs nm \
                | sed -nre 's:^[0]*([0-9a-f]{8}) A __crc_(.*):0x\1 \2:p'
            fi > $tmpdir/addon-symvers-$krel
        fi

        # Symbols that other add-on modules of the "old" kernel export
        # (and that this module may require)
        if [ ! -e "$tmpdir/extra-symvers-$module_krel" ]; then
            if [ -e /lib/modules/$module_krel/extra ] && \
	       [ -n "`find /lib/modules/$module_krel/extra -type f`" ]; then
                find /lib/modules/$module_krel/extra -name '*.ko' \
                | xargs nm \
                | sed -nre 's:^[0]*([0-9a-f]{8}) A __crc_(.*):0x\1 \2:p'
            fi > $tmpdir/extra-symvers-$module_krel
        fi

        sort -u $tmpdir/symvers-$krel \
                $tmpdir/extra-symvers-$module_krel \
                $tmpdir/addon-symvers-$krel \
        > "$tmpdir/all-symvers-$krel-$module_krel"
    fi

    # If the module does not have modversions enabled, $tmpdir/modvers
    # will be empty.
    /sbin/modprobe --dump-modversions "$module" \
    | sed -r -e 's:^(0x[0]*[0-9a-f]{8}\t.*):\1:' \
    | sort -u \
    > $tmpdir/modvers

    # Only include lines of the second file in the output that don't
    # match lines in the first file. (The default separator is
    # <space>, so we are matching the whole line.)
    join -j 1 -v 2 $tmpdir/all-symvers-$krel-$module_krel \
                   $tmpdir/modvers > $tmpdir/join

    if [ ! -s $tmpdir/modvers ]; then
        echo "Warning: Module ${module##*/} from kernel $module_krel has no" \
             "modversions, so it cannot be reused for kernel $krel" >&2
    elif [ -s $tmpdir/join ]; then
        [ -n "$verbose" ] &&
        echo "Module ${module##*/} from kernel $module_krel is not compatible" \             "with kernel $krel in symbols:" $(sed -e 's:.* ::' $tmpdir/join)
    else
        [ -n "$verbose" ] &&
        echo "Module ${module##*/} from kernel $module_krel is compatible" \
             "with kernel $krel"
        return 0
    fi
    return 1
}

usage() {
    echo "Usage: ${0##*/} [options] {--add-modules|--remove-modules}"
    echo "${0##*/} [options] {--add-kernel|--remove-kernel} {kernel-release}"
    cat <<'EOF'
--add-modules
        Add a list of modules read from standard input. Create
        symlinks in compatible kernel's weak-updates/ directory.
        The list of modules is read from standard input.

--remove-modules
        Remove compatibility symlinks from weak-updates/ directories
        for a list of modules.  The list of modules is read from
        standard input. Optionally specify --delete-modules to
        prevent weak-modules from attempting to locate any
        compatible modules to replace those being removed.

--add-kernel
        Add compatibility symlinks for all compatible modules to the
        specified or running kernel.

--remove-kernel
        Remove all compatibility symlinks for the specified or current
        kernel.

--no-initramfs
	Do not generate an initramfs.

--verbose
        Print the commands executed.

--dry-run
        Do not create/remove any files.
EOF
    exit $1
}

# module_has_changed:
# Mark if an actual change occured that we need to deal with later by calling
# depmod or mkinitramfs against the affected kernel.
module_has_changed() {

    declare module=$1 krel=$2

    module=${module%.ko}
    module=${module##*/}

    eval "changed_modules_${krel//[^a-zA-Z0-9]/_}=$krel"
    eval "changed_initramfs_${krel//[^a-zA-Z0-9]/_}=$krel"

}

# add_modules:
# Read in a list of modules from stdinput and process them for compatibility
# with installed kernels under /lib/modules.
add_modules() {
    read_modules_list || exit 1
    if [ ${#modules[@]} -gt 0 ]; then
        for krel in $(ls /lib/modules/); do
            [ -e "/boot/symvers-$krel.gz" ] || continue
            for ((n = 0; n < ${#modules[@]}; n++)); do
                module="${modules[n]}"
                module_krel="${module_krels[n]}"
                case "$module" in
                /lib/modules/$krel/*)
                    # Module was built against this kernel, update initramfs.
                    module_has_changed $module $krel
                    continue ;;
                esac

		# Module my also serve as a weak-update built against another
		# kernel. We need to create symlinks for compatible kernels
		# under /lib/modules and rerun depmod/dracut for those.

                subpath=`echo $module | sed -nre "s:(/usr)?/lib/modules/$module_krel/([^/]*)/(.*):\3:p"`
                weak_module="/lib/modules/$krel/weak-updates/${subpath#/}"
                if [ -r "$weak_module" ]; then
                    weak_krel=$(krel_of_module "$weak_module")
                    if [ "$weak_krel" != "$module_krel" ] &&
                       [ "$(printf "%s\n" "$weak_krel" "$module_krel" \
                            | rpmsort | (read input; echo "$input"; \
                                         while read input; do true; done))" = \
                         "$module_krel" ]; then
                        # Keep modules from more recent kernels.
                        [ -n "$verbose" ] && echo \
"Keeping module ${module##*/} from kernel $weak_krel for kernel $krel"
                        continue
                    fi
                fi
                if module_is_compatible $module $krel; then
                    doit mkdir -p $(dirname $weak_module)
                    doit ln -sf $module $weak_module
                    # Module was built against another kernel, update initramfs.
                    module_has_changed $module $krel
                fi
            done
        done
    fi
}

# remove_modules:
# Read in a list of modules from stdinput and process them for removal.
# Parameter is noreplace to delete modules, otherwise link compat.
remove_modules() {
    delete_modules=${1:-replace}

    read_modules_list || exit 1
    if [ ${#modules[@]} -gt 0 ]; then

	# Hunt for all known users of this module in /lib/modules, remove them
	# and create symlinks to other compatible modules (downgrade) if
	# possible, update initramfs for each modified kernel too.

        krels=($(ls /lib/modules/ | rpmsort -r))
        for krel in "${krels[@]}"; do
            [ -e "/boot/symvers-$krel.gz" ] || continue
            for ((n = 0; n < ${#modules[@]}; n++)); do
                module="${modules[n]}"
                module_krel="${module_krels[n]}"

		# Module is going to be removed, update initramfs.
		module_has_changed $module $krel

                subpath="${module#*/lib/modules/$module_krel/extra}"
                weak_module="/lib/modules/$krel/weak-updates/${subpath#/}"
                if [ "$module" == "`readlink $weak_module`" ]; then
                    [ -n "$verbose" ] && echo \
"Removing compatible module ${module##*/} from kernel $krel"
                    doit rm -f "$weak_module"
                    if [ "replace" == "$delete_modules" ]; then
                        for krel2 in "${krels[@]}"; do
                            if [ $krel2 != $krel ]; then
                                module="/lib/modules/$krel2/extra/${subpath#/}"
                                [ -e "$module" ] || continue
                                if module_is_compatible "$module" "$krel"; then
                                    [ -n "$verbose" ] && echo \
"Adding compatible module ${module##*/} from kernel $krel2 instead"
                                    doit ln -s "$module" "$weak_module"
			            module_has_changed $module $krel
                                    break
                                fi
                            fi
                        done
                    fi
                    # Remove the part of the directory beneath weak-updates
                    ( cd "/lib/modules/$krel/weak-updates" && \
                        doit rmdir --parents --ignore-fail-on-non-empty "$(dirname "${subpath#/}")" )
                fi
            done
        done
    fi
}

add_kernel() {
    add_krel=${1:-$(uname -r)}
    if [ ! -e "/boot/symvers-$add_krel.gz" ]; then
        echo "Symvers dump file /boot/symvers-$add_krel.gz" \
             "not found" >&2
        exit 1
    fi
    for krel in $(ls /lib/modules/ | rpmsort -r); do
        [ "$add_krel" = "$krel" ] && continue
        [ -d /lib/modules/$krel/extra ] || continue
        for module in $(find /lib/modules/$krel/extra -name '*.ko'); do
            subpath="${module#*/lib/modules/$krel/extra}"
            weak_module="/lib/modules/$add_krel/weak-updates/${subpath#/}"
            [ -e "$weak_module" ] && continue
            if module_is_compatible $module $add_krel; then
		module_has_changed $module $add_krel
                doit mkdir -p $(dirname $weak_module)
                doit ln -sf $module $weak_module
            fi
        done
    done
}

remove_kernel() {
    remove_krel=${1:-$(uname -r)}
    weak_modules="/lib/modules/$remove_krel/weak-updates"
    module_has_changed $weak_modules $remove_krel

    # Remove everything beneath the weak-updates directory
    ( cd "$weak_modules" && doit rm -rf * )
}

################################################################################
################################## MAIN GUTS ###################################
################################################################################

options=`getopt -o h --long help,add-modules,remove-modules \
                     --long add-kernel,remove-kernel \
                     --long dry-run,no-initramfs,verbose,delete-modules -- "$@"`

[ $? -eq 0 ] || usage 1

eval set -- "$options"

while :; do
    case "$1" in
    --add-modules)
        do_add_modules=1
        ;;
    --remove-modules)
        do_remove_modules=1
        ;;
    --add-kernel)
        do_add_kernel=1
        ;;
    --remove-kernel)
        do_remove_kernel=1
        ;;
    --dry-run)
        dry_run=1
        ;;
    --no-initramfs)
        no_initramfs=1
        ;;
    --verbose)
        verbose=1
        ;;
    --delete-modules)
        do_delete_modules=1
        ;;
    -h|--help)
        usage 0
        ;;
    --)
        shift
        break
        ;;
    esac
    shift
done

if [ -n "$do_add_modules" ]; then
	add_modules

elif [ -n "$do_remove_modules" ]; then
        if [ -n "$do_delete_modules" ]; then
            remove_modules "noreplace"
        else
	    remove_modules
        fi

elif [ -n "$do_add_kernel" ]; then
	kernel=${1:-$(uname -r)}
	add_kernel $kernel

elif [ -n "$do_remove_kernel" ]; then
	kernel=${1:-$(uname -r)}
	remove_kernel $kernel

	exit 0
else
	usage 1
fi

################################################################################
###################### CLEANUP POST ADD/REMOVE MODULE/KERNEL ###################
################################################################################

# run depmod and dracut as needed
for krel in ${!changed_modules_*}; do
    krel=${!krel}

    doit /sbin/depmod -ae -F /boot/System.map-$krel $krel
done

for krel in ${!changed_initramfs_*}; do
    krel=${!krel}

    if [ ! -n "$no_initramfs" ]; then
        check_initramfs $krel
    fi
done