How to list library dependencies of a non-native binary?

Question

When developing for native platform, I can use ldd to list all the shared libraries (.so files) a binary executable I build will try to load upon start-up. But when cross-co

Answer 1

Sorry to make a zombie thread, but I am working on some things for my OpenWRT router and wanted this to check some dependencies to see if I had enough space on my jffs2 partition to copy over just e2fsck. Short answer: nope.avi.

Anyhoo, I made a little script that uses the accepted answer plus some (probably overly verbose) grep calls and with a little hand waving and some unicorn tears (no worries, they were happy tears!) I managed to put together the following script that gives you all the dependencies. I'm sure there's lots of room for improvement especially RE: the loops and recursion, as well as the fact that it's all bashisms all the time (i.e. indexed arrays) but this is at least nominally working for me:

#!/bin/bash

declare -a search_path
declare -a found_deps

find_dependencies() {
    local file="$1"
    local -a deps
    local -a deps_to_process

    deps=( $( readelf -d "$file" | grep "NEEDED" | \
        grep -o -E "\[[^]]*\]" | grep -o -E "[^][]*" ) )

    local add_this_dep=true

    # always assume we've found $file and add it to the $found_deps list
    # if it's not there
    for found_dep in "${found_deps[@]}"
    do
        if [ "$found_dep" = "$(basename $file)" ]
        then
            add_this_dep=false
            break
        fi
    done

    # if $add_this_dep is true, go ahead and add to the found_deps list
    if $add_this_dep
    then
        found_deps+=("$(basename $file)")
    fi

    # for every dependency found by readelf (no path)
    for dep in "${deps[@]}"
    do
        local process_dep=true

        # if the basename of the file passed into the function is
        # this dep, skip processing altogether
        if [ "$dep" = "$(basename $file)" ]
        then
            break
        else
            # otherwise, if it's one of the 'found deps' don't process it
            for found_dep in "${found_deps[@]}"
            do
                if [ "$dep" = "$found_dep" ]
                then
                    process_dep=false
                    break
                fi
            done

            # it wasn't one of the 'found deps' so add 
            # it to the found_deps list
            if $process_dep
            then
                found_deps+=($dep)
            fi
        fi

        # if we are supposed to process this dep
        if $process_dep
        then
            local file_path=

            # check each search path for a file named $dep underneath it
            for dir in $search_path
            do
                file_path=$( find "$dir" -name "$dep" | head -n 1 )

                # if the $file_path is not empty, then we found
                # a copy of it, so break out of the loop
                if [ -n "$file_path" ]; then break; fi;
            done

            # if the $file_path is not empty, then we found a copy
            # of the file, place it the list of deps to be processed
            if [ -n "$file_path" ]
            then
                deps_to_process+=($file_path)
            fi
        fi
    done

    # now, go through all of our $deps_to_process (with path)
    # and run "find_dependencies" on them
    for dep_to_process in "${deps_to_process[@]}"
    do
        find_dependencies "$dep_to_process"
    done
}

argc=$#

if [ $argc -eq 0 ]
then
    printf '%s: prints dependencies of a (potentially) non-native elf executable, recursively\n'
    printf '\n'
    printf 'usage:\n'
    printf '\t%s  [ --supress-header ] [  ... ]\n' "$(basename $0)"
    printf '\twhere\n'
    printf '\t\t is the name of a file to find the dependencies of.\n'
    printf '\t\t[  ... ] is an optional list of directories under which to search for libraries.\n'
    printf '\t\t[ --supress-header ] is an optional flag that prints nothing other than the list of files to stdout.\n'
    printf '\t\t\t(without the parameter a banner is sent to stderr)'
    printf '\n'
else
    file="$1"
    shift 1

    show_header=true

    if [ "$1" = "--supress-header" ]; then show_header=false; shift 1; fi;

    if $show_header
    then
        printf ' -------------------------------------------------------------------------------------------------------------\n' 1>&2
        printf '  ldd-nonnative: find all dependencies of a (potentially) non-native binary %s\n' "$file" 1>&2
        printf ' -------------------------------------------------------------------------------------------------------------\n' 1>&2
    fi

    search_path="$@"
    find_dependencies $file

    printf '\t%s\n' "${found_deps[@]}"
fi

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So, there ya go. Hope it helps someone. Egads it's taken me a long time to even get good enough with shell scripting to be able to pull something like this off, nevermind the fact that it took me much longer than it probably should have, so please forgive what has likely shaken some of you script gurus out there to the very core of your being. :)