#!/bin/bash
#
# weak-modules - determine which modules are kABI compatible with installed
#                kernels and set up the symlinks in /lib/*/weak-updates.
#
# This is an updated version of the script which doesn't support
# multiple installation of the same out-of-tree module (stored in the
# 'extra' subdirectory) for multiple kernels. This assumption is
# supposed to be verified at the rpm level of the packages delivering
# these modules.  There are some checks for this assumption, however we
# really don't solve this situation. This limitation allows for a much
# simpler version of the script. Previous version tried to work in this
# case but was incorrect in some cases.

unset LANG LC_ALL LC_COLLATE

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

unset BASEDIR
unset CHECK_INITRAMFS
weak_updates_dir_override=""
default_initramfs_prefix="/boot" # will be combined with BASEDIR
dracut="/usr/bin/dracut"
depmod="/sbin/depmod"
depmod_orig="$depmod"
declare -a modules
declare -A module_krels
declare -A weak_modules_before

declare -A groups
declare -A grouped_modules

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

# pr_verbose:
# print verbose -- wrapper used to print extra messages if required
pr_verbose() {
    [ -n "$verbose" ] && echo "$@"
}

# pr_warning:
# print warning
pr_warning() {
    echo "WARNING: $*"
}

# 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'
}

# krel_of_module:
# Compute the kernel release of a module.
krel_of_module() {
    local module="$1"

    if [ x"${module_krels[$module]+set}" = x"set" ]; then
        # version cached in the array already
        echo "${module_krels[$module]}"
    elif [ -f "$module" ]; then
        krel_of_module_modinfo "$module"
    else
        # Try to extract the kernel release from the path
        # delete case, the .ko already deleted
        set -- "${module#*/lib/modules/}"
        echo "${1%%/*}"
    fi
}

# krel_of_module_modinfo:
# Fetches module version from internal module info
krel_of_module_modinfo() {
    local module="$1"
    /sbin/modinfo -F vermagic "$module" | awk '{print $1}'
}

# weak_updates_dir:
# gives the root directory for the weak-updates
# We need some flexibility here because of dry-run.
weak_updates_dir() {
    local krel="$1"

    if [[ -z "$weak_updates_dir_override" ]]; then
        echo "$BASEDIR/lib/modules/$krel/weak-updates"
    else
        echo "$weak_updates_dir_override"
    fi
}

# 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.
# If used with input redirect, should be used as read_module_list < input,
# not input | read_modules_list, the latter spawns a subshell
# and the arrays are not seen in the caller
read_modules_list() {
    local IFS=$'\n'
    modules=($(cat))

    for ((n = 0; n < ${#modules[@]}; n++)); do
        if [ ${modules[n]:0:1} != '/' ]; then
            modules[n]="$PWD/${modules[n]}"
        fi
        module_krels["${modules[n]}"]=$(krel_of_module ${modules[n]})
    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 -o -iname '*.ko.xz' -o -iname '*.ko.gz' 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]}" \
                     >/dev/null 2>&1
            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
}

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. Note: it doesn't attempt 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=$2
    declare orig_module=$module

    module=${module%.ko}
    [[ $module == $orig_module ]] && module=${module%.ko.xz}
    [[ $module == $orig_module ]] && module=${module%.ko.gz}
    module=${module##*/}

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

}

# module_weak_link:
# Generate a weak link path for the module.
# Takes module file name and the target kernel release as arguments
# The way of generation intentionally left from the initial version
module_weak_link() {
    local module="$1"
    local krel="$2"
    local module_krel
    local subpath
    local module_krel_escaped

    module_krel="$(krel_of_module "$module")"
    module_krel_escaped=$(echo "$module_krel" | \
                              sed 's/\([.+?^$\/\\|()\[]\|\]\)/\\\0/g')
    subpath=$(echo $module | sed -nre "s:$BASEDIR(/usr)?/lib/modules/$module_krel_escaped/([^/]*)/(.*):\3:p")

    if [[ -z $subpath ]]; then
        # module is not in /lib/modules/$krel?
        # It's possible for example for Oracle ACFS compatibility check
        # Install it with its full path as a /lib/modules subpath
        subpath="$module"
    fi

    echo "$(weak_updates_dir $krel)/${subpath#/}"
}

# module_short_name:
# 'basename' version purely in bash, cuts off path from the filename
module_short_name() {
    echo "${1##*/}"
}

#### Helper predicates

# is_weak_for_module_valid:
# Takes real module filename and target kernel as arguments.
# Calculates weak symlink filename for the corresponding module
# for the target kernel,
# returns 'true' if the symlink filename is a symlink
# and the symlink points to a readable file
# EVEN if it points to a different filename
is_weak_for_module_valid() {
    local module="$1"
    local krel="$2"
    local weak_link

    weak_link="$(module_weak_link $module $krel)"
    [[ -L "$weak_link" ]] && [[ -r "$weak_link" ]]
}

# is_weak_link:
# Takes a filename and a kernel release.
# 'true' if the filename is symlink under weak-updates/ for the kernel.
# It doesn't matter, if it's a valid symlink (points to a real file) or not.
is_weak_link() {
    local link="$1"
    local krel="$2"

    echo $link | grep -q "$(weak_updates_dir $krel)" || return 1
    [[ -L $link ]]
}

# is_extra_exists:
# Takes a module filename, the module's kernel release and target kernel release.
# The module filename should be a real, not a symlink, filename (i.e. in extra/).
# Returns 'true' if the same module exists for the target kernel.
is_extra_exists() {
    local module="$1"
    local module_krel="$2"
    local krel="$3"
    local subpath="${module#*/lib/modules/$module_krel/extra/}"

    [[ -f $BASEDIR/lib/modules/$krel/extra/$subpath ]]
}

is_kernel_installed() {
    local krel="$1"

    find_symvers_file "$krel" > /dev/null &&
        find_systemmap_file "$krel" > /dev/null
}

is_empty_file() {
    local file="$1"

    [[ "$(wc -l "$file" | cut -f 1 -d ' ')" == 0 ]]
}

#### Helpers

# find_modules:
# Takes kernel release and a list of subdirectories.
# Produces list of module files in the subdirectories for the kernel
find_modules() {
    local krel="$1"
    shift
    local dirs="$*"

    for dir in $dirs; do
        find $BASEDIR/lib/modules/$krel/$dir \
             -name '*.ko' -o -name '*.ko.xz' -o -name '*.ko.gz' \
             2>/dev/null
    done
}

# find_modules_dirs:
# Takes a list of directories.
# Produces list of module files in the subdirectories
find_modules_dirs() {
    local dirs="$*"

    for dir in $dirs; do
        find $dir -name '*.ko' -o -name '*.ko.xz' -o -name '*.ko.gz' \
             2>/dev/null
    done
}

# find_installed_kernels:
# Produces list of kernels, which modules are still installed
find_installed_kernels() {
    ls $BASEDIR/lib/modules/
}

# find_kernels_with_extra:
# Produces list of kernels, where exists extra/ directory
find_kernels_with_extra() {
    local krel
    local extra_dir

    for krel in $(find_installed_kernels); do
        extra_dir="$BASEDIR/lib/modules/$krel/extra"
        [[ -d "$extra_dir" ]] || continue
        echo "$krel"
    done
}

# remove_weak_link_quiet:
# Takes symlink filename and target kernel release.
# Removes the symlink and the directory tree
# if it was the last file in the tree
remove_weak_link_quiet() {
    local link="$1"
    local krel="$2"
    local subpath="${link#*$(weak_updates_dir $krel)}"

    rm -f $link
    ( cd "$(weak_updates_dir $krel)" && \
          rmdir --parents --ignore-fail-on-non-empty "$(dirname "${subpath#/}")" 2>/dev/null )
}

# prepare_sandbox:
# Takes kernel release, creates temporary weak-modules directory for it
# and depmod config to operate on it.
# Sets the global state accordingly

prepare_sandbox() {
    local krel="$1"
    local orig_dir
    local dir
    local conf="$tmpdir/depmod.conf"

    #directory
    orig_dir=$(weak_updates_dir $krel)
    dir="$tmpdir/$krel/weak-updates"

    mkdir -p "$dir"
    # the orig_dir can be empty
    cp -R "$orig_dir"/* "$dir" 2>/dev/null

    weak_updates_dir_override="$dir"

    #config
    echo "search external extra built-in weak-updates" >"$conf"
    echo "external $krel $dir" >>"$conf"

    depmod="$depmod_orig -C $conf"
}


# finish_sandbox:
# restore global state after sandboxing
# copy configuration to the kernel directory if not dry run
finish_sandbox() {
    local krel="$1"
    local override="$weak_updates_dir_override"
    local wa_dir

    weak_updates_dir_override=""
    depmod="$depmod_orig"

    [[ -n "$dry_run" ]] && return

    wa_dir="$(weak_updates_dir $krel)"

    rm -rf "$wa_dir"
    mkdir -p "$wa_dir"

    cp -R "${override}"/* "$wa_dir" 2>/dev/null
}

# Auxiliary functions to find symvers file
make_kernel_file_names() {
    local krel="$1"
    local file="$2"
    local suffix="$3"

    echo "${BASEDIR}/boot/${file}-${krel}${suffix}"
    echo "${BASEDIR}/lib/modules/${krel}/${file}${suffix}"
}

find_kernel_file() {
    local krel="$1"
    local file="$2"
    local suffix="$3"
    local print="$4"
    local i

    if [[ "$print" != "" ]]; then
        make_kernel_file_names "$krel" "$file" "$suffix"
        return 0
    fi

    for i in  $(make_kernel_file_names "$krel" "$file" "$suffix"); do
        if [[ -r "$i" ]]; then
            echo "$i"
            return 0
        fi
    done

    return 1
}

# find_symvers_file:
# Since /boot/ files population process is now controlled by systemd's
# kernel-install bash script and its plug-ins, it might be the case
# that, while present, symvers file is not populated in /boot.
# Let's also check for /lib/modules/$kver/symvers.gz, since that's where
# it is populated from.
#
# $1 - krel
# return - 0 if symvers file is found, 1 otherwise.
# Prints symvers path if found, empty string otherwise.
find_symvers_file() {
    local krel="$1"
    local print="$2"

    find_kernel_file "$krel" symvers .gz "$print"
}

# find_systemmap_file:
# Same as above but for System.map
find_systemmap_file() {
    local krel="$1"
    local print="$2"
    local no_suffix=""

    find_kernel_file "$krel" System.map "$no_suffix" "$print"
}

#### Main logic

# update_modules_for_krel:
# Takes kernel release and "action" function name.
# Skips kernel without symvers,
# otherwise triggers the main logic of modules installing/removing
# for the given kernel, which is:
# - save current state of weak modules symlinks
# - install/remove the symlinks for the given (via stdin) list of modules
# - validate the state and remove invalid symlinks
#   (for the modules, which are not compatible (became incompatible) for
#   the given kernel)
# - check the state after validation to produce needed messages
#   and trigger initrd regeneration if the list changed.
update_modules_for_krel() {
    local krel="$1"
    local func="$2"
    local force_update="$3"

    is_kernel_installed "$krel" || return

    prepare_sandbox $krel

    global_link_state_save $krel

    $func $krel

    if ! validate_weak_links $krel && [[ -z "$force_update" ]]; then
        global_link_state_restore $krel
    fi

    global_link_state_announce_changes $krel

    finish_sandbox $krel
}

# update_modules:
# Common entry point for add/remove modules command
# Takes the "action" function, the module list is supplied via stdin.
# Reads the module list and triggers modules update for all installed
# kernels.
# Triggers initrd rebuild for the kernels, which modules are installed.
update_modules() {
    local func="$1"
    local force_update="$2"
    local module_krel

    read_modules_list || exit 1
    [[ ${#modules[@]} -gt 0 ]] || return

    for krel in $(find_installed_kernels); do
        update_modules_for_krel $krel $func $force_update
    done

    for module in "${modules[@]}"; do
        # Module was built against this kernel, update initramfs.
        module_krel="${module_krels[$module]}"
        module_has_changed $module $module_krel
    done
}

# add_weak_links:
# Action function for the "add-modules" command
# Takes the kernel release, where the modules are added
# and the modules[] and module_krels[] global arrays.
# Install symlinks for the kernel with minimal checks
# (just filename checks, no symbol checks)
add_weak_links() {
    local krel="$1"
    local module_krel
    local weak_link

    for module in "${modules[@]}"; do
        module_krel="$(krel_of_module $module)"

        case "$module" in
            /lib/modules/$krel/*)
                # Module already installed to the current kernel
                continue ;;
        esac

        if is_extra_exists $module $module_krel $krel; then
            pr_verbose "found $(module_short_name $module) for $krel while installing for $module_krel, update case?"
        fi

        if is_weak_for_module_valid $module $krel; then
            pr_verbose "weak module for $(module_short_name $module) already exists for kernel $krel, update case?"
            # we should update initrd in update case,
            # the change is not seen by the symlink detector
            # (global_link_state_announce_changes())
            module_has_changed $module $krel
        fi

        weak_link="$(module_weak_link $module $krel)"

        mkdir -p "$(dirname $weak_link)"
        ln -sf $module $weak_link

    done
}

# remove_weak_links:
# Action function for the "remove-modules" command
# Takes the kernel release, where the modules are removed
# and the modules[] and module_krels[] global arrays.
# Removes symlinks from the given kernel if they are installed
# for the modules in the list.
remove_weak_links() {
    local krel="$1"
    local weak_link
    local target
    local module_krel

    for module in "${modules[@]}"; do
        module_krel="$(krel_of_module $module)"

        weak_link="$(module_weak_link $module $krel)"
        target="$(readlink $weak_link)"

        if [[ "$module" != "$target" ]]; then
            pr_verbose "Skipping symlink $weak_link"
            continue
        fi
        # In update case the --remove-modules call is performed
        # after --add-modules (from postuninstall).
        # So, we shouldn't really remove the symlink in this case.
        # But in the remove case the actual target already removed.
        if ! is_weak_for_module_valid "$module" "$krel"; then
            remove_weak_link_quiet "$weak_link" "$krel"
        fi
    done
}

# validate_weak_links:
# Takes kernel release.
# Checks if all the weak symlinks are suitable for the given kernel.
# Uses depmod to perform the actual symbol checks and parses the output.
# Since depmod internally creates the module list in the beginning of its work
# accroding to the priority list in its configuration, but without symbol
# check and doesn't amend the list during the check, the function runs it
# in a loop in which it removes discovered incompatible symlinks
#
# Returns 0 (success) if proposal is fine or
#         1 (false) if some incompatible symlinks were removed
validate_weak_links() {
    local krel="$1"
    local basedir=${BASEDIR:+-b $BASEDIR}
    local tmp
    declare -A symbols
    local is_updates_changed=1
    local module
    local module_krel
    local target
    local modpath
    local symbol
    local weak_link
    # to return to caller that original proposal is not valid
    # here 0 is true, 1 is false, since it will be the return code
    local is_configuration_valid=0

    tmp=$(mktemp -p $tmpdir)

    if ! [[ -e $tmpdir/symvers-$krel ]]; then
        local symvers_path=$(find_symvers_file "$krel")

        [[ -n "$symvers_path" ]] || return
        zcat "$symvers_path" > $tmpdir/symvers-$krel
    fi

    while ((is_updates_changed)); do
        is_updates_changed=0

        # again $tmp because of subshell, see read_modules_list() comment
        # create incompatibility report by depmod
        # Shorcut if depmod finds a lot of incompatible modules elsewhere,
        # we care only about weak-updates
        $depmod $basedir -naeE $tmpdir/symvers-$krel $krel 2>&1 1>/dev/null | \
            grep "$(weak_updates_dir $krel)" 2>/dev/null >$tmp
        # parse it into symbols[] associative array in form a-la
        #   symbols["/path/to/the/module"]="list of bad symbols"
        while read line; do
            set -- $(echo $line | awk '/needs unknown symbol/{print $3 " " $NF}')
            modpath=$1
            symbol=$2
            if [[ -n "$modpath" ]]; then
                symbols[$modpath]="${symbols[$modpath]} $symbol"
                continue
            fi

            set -- $(echo $line | awk '/disagrees about version of symbol/{print $3 " " $NF}')
            modpath=$1
            symbol=$2
            if [[ -n "$modpath" ]]; then
                symbols[$modpath]="${symbols[$modpath]} $symbol"
                continue
            fi
        done < $tmp

        # loop through all the weak links from the list of incompatible
        # modules and remove them. Skips non-weak incompatibilities
        for modpath in "${!symbols[@]}"; do
            is_weak_link $modpath $krel || continue

            target=$(readlink $modpath)
            module_krel=$(krel_of_module $target)

            remove_weak_link_quiet "$modpath" "$krel"

            pr_verbose "Module $(module_short_name $modpath) from kernel $module_krel is not compatible with kernel $krel in symbols: ${symbols[$modpath]}"
            is_updates_changed=1
            is_configuration_valid=1 # inversed value
        done
    done
    rm -f $tmp

    # this loop is just to produce verbose compatibility messages
    # for the compatible modules
    for module in "${modules[@]}"; do
        is_weak_for_module_valid $module $krel || continue

        weak_link="$(module_weak_link $module $krel)"
        target="$(readlink $weak_link)"
        module_krel=$(krel_of_module $target)

        if [[ "$module" == "$target" ]]; then
            pr_verbose "Module ${module##*/} from kernel $module_krel is compatible with kernel $krel"
        fi
    done
    return $is_configuration_valid
}

# global_link_state_save:
# Takes kernel release
# Saves the given kernel's weak symlinks state into the global array
# weak_modules_before[] for later processing
global_link_state_save() {
    local krel="$1"
    local link
    local target

    weak_modules_before=()
    for link in $(find_modules_dirs $(weak_updates_dir $krel) | xargs); do
        target=$(readlink $link)
        weak_modules_before[$link]=$target
    done
}

# global_link_state_restore:
# Takes kernel release
# Restores the previous weak links state
# (for example, if incompatible modules were installed)
global_link_state_restore() {
    local krel="$1"
    local link
    local target

    pr_verbose "Falling back weak-modules state for kernel $krel"

    ( cd "$(weak_updates_dir $krel)" 2>/dev/null && rm -rf * )

    for link in "${!weak_modules_before[@]}"; do
        target=${weak_modules_before[$link]}

        mkdir -p "$(dirname $link)"
        ln -sf $target $link
    done
}

# global_link_state_announce_changes:
# Takes kernel release
# Reads the given kernel's weak symlinks state, compares to the saved,
# triggers initrd rebuild if there were changes
# and produces message on symlink removal
global_link_state_announce_changes() {
    local krel="$1"
    local link
    local target
    local new_target
    declare -A weak_modules_after

    for link in $(find_modules_dirs $(weak_updates_dir $krel) | xargs); do
        target=${weak_modules_before[$link]}
        new_target=$(readlink $link)
        weak_modules_after[$link]=$new_target

        # report change of existing link and appearing of a new link
        [[ "$target" == "$new_target" ]] || module_has_changed $new_target $krel
    done

    for link in "${!weak_modules_before[@]}"; do
        target=${weak_modules_before[$link]}
        new_target=${weak_modules_after[$link]}

        # report change of existing link and disappearing of an old link
        [[ "$target" == "$new_target" ]] && continue
        module_has_changed $target $krel
        [[ -n "$new_target" ]] ||
            pr_verbose "Removing compatible module $(module_short_name $target) from kernel $krel"
    done
}

# remove_modules:
# Read in a list of modules from stdinput and process them for removal.
# Parameter (noreplace) is deprecated, acts always as "noreplace".
# There is no sense in the "replace" functionality since according
# to the current requirements RPM will track existing of only one version
# of extra/ module (no same extra/ modules for different kernels).
remove_modules() {
    update_modules remove_weak_links force_update
}

# add_modules:
# Read in a list of modules from stdinput and process them for compatibility
# with installed kernels under /lib/modules.
add_modules() {
    no_force_update=""

    update_modules add_weak_links $no_force_update
}

# do_make_groups:
# Takes tmp file which contains preprocessed modules.dep
# output (or modules.dep)
# reads modules.dep format information from stdin
# produces groups associative array
# the group is a maximum subset of modules having at least a link
do_make_groups()
{
    local tmp="$1"
    local group_name
    local mod
    declare -a mods

    while read i; do
        mods=($i)

        # if the module already met, then its dependencies already counted
        module_group="${grouped_modules[${mods[0]}]}"
        [[ -n $module_group ]] && continue

        # new group
        group_name="${mods[0]}"

        for mod in "${mods[@]}"; do
            # if there is already such group,
            # it is a subset of the one being created
            # due to depmod output
            unset groups[$mod]

            # extra space doesn't matter, since later (in add_kernel())
            # it is expanded without quotes
            groups[$group_name]+=" $mod"
            grouped_modules[$mod]=$group_name
        done
    done < $tmp # avoid subshell
}

# filter_depmod_deps:
# preprocess output for make_groups
# depmod -n produces also aliases, so it cuts them off
# also it removes colon after the first module
filter_depmod_deps()
{
    awk 'BEGIN { pr = 1 } /^#/{ pr = 0 } pr == 1 {sub(":",""); print $0}'
}

# make_abs_path:
# Takes kernel version
# makes full path from the relative module path
# (produced by depmod for in-kernel-dir modules)
make_abs_path()
{
    local kver="$1"
    local mod
    declare -a mods

    while read i; do
        mods=($i)
        for j in "${!mods[@]}"; do
            mod="${mods[$j]}"
            [[ ${mod:0:1} == "/" ]] || mod="/lib/modules/$kver/$mod"
            mods[$j]="$mod"
        done
        echo "${mods[@]}"
    done
}

# make_groups:
# takes krel and a file with the list of modules,
# prepares and feeds to do_make_groups
# to create the module groups (global)
make_groups()
{
    local krel="$1"
    local tmp1="$2"
    local tmp2=$(mktemp -p $tmpdir)

    groups=()
    grouped_modules=()

    $depmod -n $krel $(cat $tmp1) 2>/dev/null |
        filter_depmod_deps | make_abs_path $krel > $tmp2

    do_make_groups $tmp2

    rm -f $tmp2
}

add_kernel() {
    local krel=${1:-$(uname -r)}
    local tmp
    local no_force_update=""

    tmp=$(mktemp -p $tmpdir)

    if ! find_symvers_file "$krel" > /dev/null; then
        echo "Symvers dump file is not found in" \
             $(find_symvers_file "$krel" print) >&2
        exit 1
    fi

    for k in $(find_kernels_with_extra | rpmsort); do
        [[ "$krel" == "$k" ]] && continue
        find_modules $k extra > $tmp

        is_empty_file "$tmp" || make_groups $krel $tmp

        # reuse tmp

        for g in "${groups[@]}"; do
            printf '%s\n' $g > $tmp
            # to avoid subshell, see the read_modules_list comment
            read_modules_list < $tmp
            update_modules_for_krel $krel add_weak_links $no_force_update
        done
    done

    rm -f $tmp

}

remove_kernel() {
    remove_krel=${1:-$(uname -r)}
    weak_modules="$(weak_updates_dir $remove_krel)"
    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 \
                     --long basedir:,dracut:,check-initramfs-prog: -- "$@"`

[ $? -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
        # --dry-run option is not pure dry run anymore,
        # because of depmod used internally.
        # For add/remove modules we have to add/remove the symlinks
        # and just restore the original configuration afterwards.
        ;;
    --no-initramfs)
        no_initramfs=1
        ;;
    --verbose)
        verbose=1
        ;;
    --delete-modules)
        pr_warning "--delete-modules is deprecated, no effect"
        ;;
    --basedir)
        BASEDIR="$2"
        shift
        ;;
    --dracut)
        dracut="$2"
        shift
        ;;
    --check-initramfs-prog)
        CHECK_INITRAMFS="$2"
        shift
        ;;
    -h|--help)
        usage 0
        ;;
    --)
        shift
        break
        ;;
    esac
    shift
done

if [ ! -x "$dracut" ]
then
    echo "weak-modules: could not find dracut at $dracut"
    exit 1
fi

initramfs_prefix="$BASEDIR/${default_initramfs_prefix#/}"

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

elif [ -n "$do_remove_modules" ]; then
    remove_modules

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}
    basedir=${BASEDIR:+-b $BASEDIR}

    if is_kernel_installed $krel; then
        doit $depmod $basedir -ae -F $(find_systemmap_file $krel) $krel
    else
        pr_verbose "Skipping depmod for non-installed kernel $krel"
    fi
done

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

    if [ ! -n "$no_initramfs" ]; then
        ${CHECK_INITRAMFS:-check_initramfs} $krel
    fi
done