#!/bin/bash

# ldd drop-in replacement for cross-compilation toolchains.

# This file is a slightly modified version of xldd.in from
# crosstool-ng 1.22.0

# In order to use it, copy it in same directory than other
# toolchain binaries and rename it with same tuple.
# (i.e. /opt/arm-sysmic-linux-gnueabihf/bin/arm-sysmic-linux-gnueabihf-ldd)
# Thus, this will automaticaly detect necessary information
# about your toolchain.

export LC_ALL=C
version="forked from crosstool-ng 1.22.0"
# Change it to 64 if necessary
bits="32"
sed="${SED:-sed}"
grep="${GREP:-grep}"

my_name="$( basename "${0}" )"
prefix="${0%-ldd}"
gcc="${prefix}-gcc"
readelf="${prefix}-readelf"
fake_load_addr_root="$((0xdeadbeef))"
fake_load_addr_rpath="$((0xdeadc0de))"
fake_load_addr_sysroot="$((0x8badf00d))"
ld_library_path="/lib:/usr/lib"

do_error() {
    printf "%s: %s\n" "${my_name}" "$*" >&2
}

do_opt_error() {
    do_error "$@"
    printf "Try \`%s --help' for more information\n" "${my_name}" >&2
}

do_trace() {
    local depth=0

    [ -z "${CT_XLDD_VERBOSE}" ] && return 0

    for((depth=0; "${#FUNCNAME[$((depth+1))]}" != 0; depth++)); do :; done
    printf "%*s" $((4*(depth-1))) "" >&2
    printf -- "$@" >&2
}

show_version() {
    # Fake a real ldd, just in case some dumb script would check
    cat <<_EOF_
ldd (crosstool-NG) ${version}
Copyright (C) 2010 "Yann E. MORIN" <yann.morin.1998@free.fr>
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Licensed under the GPLv2, see the file LICENSES in the top-directory of the
sources for this package.
_EOF_
}

show_help() {
    cat <<_EOF_
Usage: ${my_name} [OPTION]... --root DIR FILE...
      --help              print this help and exit
      --version           print version information and exit
      --root dir          treat dir as being the root of the target
  -s, --show-system       mark libs from the sysroot with a trailing '[*]'
                          and libs found via RPATH with a trailing '[+]'

_EOF_
    cat <<_EOF_ |fmt
${my_name} tries to mimick the behavior of a real native ldd, but can be
used in a cross-development environment. Here is how it differs from a
real native ldd:

If the CT_XLDD_VERBOSE variable is set and non-empty, then ${my_name} will
print a lot of debug messages, explaining how it builds the library
search path, and how each library was found and why.

The LD_LIBRARY_PATH variable is not used, as it can not reliably be
guessed except at runtime, and we can't run.

${my_name} does not scan /etc/ld.so.cache, but instead uses /etc/ld.so.conf
(it understands the include directives therein for libces that have that).

${my_name} also interprets (tries to!) the RPATH/RUNPATH records found in
the dynamic ELF section. Such paths are searched for only relative to
the specified root, not from the sysroot (see below). Also, those paths
are searched for not only for the file they appear in, but also for its
dependencies.

${my_name} will search the directory specified with --root for libraries
to resolve the NEEDED tags. If --root is not set, then ${my_name} will
use the value in the environment variable \${CT_XLDD_ROOT}. If neither
is set, then this is an error.

If NEEDED libraries can't be found in the specified root directory, then
${my_name} will also look in the sysroot of the toolchain to see if it
can find them.

For NEEDED libraries that were found, the output will look like:
        libneeded.so => /path/to/libneeded.so (0xloadaddr)

and for those that were not found, the output will look like:
        libneeded.so not found

The paths are relative to the specified root directory, or to the sysroot
(eg. /lib/libneeded.so, /usr/lib/libneeded.so, and so on...).

The expected load address 'loadaddr' is a faked address to match the output
of the real ldd, but has no actual meaning (set to some constants for now,
0x8badf00d for libraries from the sysroot, 0xdeadc0de for those found via
the RPATH/RUNPATH records, and 0xdeadbeef for others).
_EOF_

# Unimplemeted yet:
#  -d, --data-relocs       process data relocations
#  -r, --function-relocs   process data and function relocations
#  -u, --unused            print unused direct dependencies
#  -v, --verbose           print all information

# See also this thread:
#  http://sourceware.org/ml/crossgcc/2008-09/msg00057.html
}

# Parse command line options
root="${CT_XLDD_ROOT}"
show_system=
while true; do
    case "${1}" in
        --help)
            show_help
            exit 0
            ;;
        --version)
            show_version
            exit 0
            ;;
        --root)
            root="$2"
            shift
            ;;
        --root=*)
            root="${1#--root=}"
            ;;
        --show-system|-s)
            show_system=1
            ;;
        -*)
            do_opt_error "unrecognized option \`${1}'"
            exit 1
            ;;
        *)
            break
            ;;
    esac
    shift
done

# Sanity checks
sysroot="$( "${gcc}" -print-sysroot 2>/dev/null )"
if [ -z "${sysroot}" ]; then
    sysroot="$( "${gcc}" -print-file-name=libc.so 2>/dev/null \
                |${sed} -r -e 's:/usr/lib/libc.so$::;'        \
              )"
fi
if [ -z "${sysroot}" ]; then
    do_error "unable to find sysroot for \`${gcc}'"
fi

if [ -z "${root}" ]; then
    root=${sysroot}
fi
if [ ! -d "${root}" ]; then
    do_error "\`${root}': no such file or directory"
    exit 1
fi

do_report_needed_found() {
    local needed="${1}"
    local path="${2}"
    local origin="${3}"
    local loadaddr
    local sys

    case "${origin}" in
        root)
            loadaddr="${fake_load_addr_root}"
            ;;
        rpath)
            loadaddr="${fake_load_addr_rpath}"
            if [ -n "${show_system}" ]; then
                sys=" [+]"
            fi
            ;;
        sysroot)
            loadaddr="${fake_load_addr_sysroot}"
            if [ -n "${show_system}" ]; then
                sys=" [*]"
            fi
            ;;
    esac

    printf "%8s%s => %s (0x%0*x)%s\n"   \
           ""                           \
           "${needed}"                  \
           "${path}"                    \
           "$((bits/4))"                \
           "${loadaddr}"                \
           "${sys}"
}

# Search a needed file, scanning ${lib_dir} in the root directory
do_find_needed() {
    local needed="${1}"
    local -a list
    local -a dirs
    local found
    local where
    local base
    local d i

    do_trace "Searching for '%s'\n" "${needed}"

    # rpath shall come first!
    list=(                      \
        "rpath:${root}"         \
        "root:${root}"          \
        "sysroot:${sysroot}"    \
    )

    for i in "${list[@]}"; do
        where="${i%%:*}"
        base="${i#*:}"
        if [ "${where}" = "rpath" ]; then
            dirs=( "${search_rpath[@]}" )
        else
            dirs=( "${needed_search_path[@]}" )
        fi
        for d in "${dirs[@]}"; do
            do_trace "-> looking in '%s' (%s)\n" "${d}" "${where}"
            if [ -f "${base}${d}/${needed}" ]; then
                found="${d}/${needed}"
                do_trace "---> found\n"
                break 2
            fi
        done
    done

    if [ -n "${found}" ]; then
        do_report_needed_found "${needed}" "${found}" "${where}"
        do_process_file "${base}${found}"
    else
        printf "%8s%s not found\n" "" "${needed}"
    fi

    do_trace "Done searching for '%s'\n" "${needed}"
}

# Scan a file for all NEEDED tags
do_process_file() {
    local file="${1}"
    local -a save_search_rpath
    local n m
    local found

    do_trace "Parsing file '%s'\n" "${file}"

    save_search_rpath=( "${search_rpath[@]}" )
    for n in $( "${readelf}" -d "${file}"                                           \
                |"${grep}" -E '\((RPATH|RUNPATH)\)'                                 \
                |"${sed}" -r -e 's/^.*Library r(|un)path:[[:space:]]+\[(.*)\]$/\2/;'\
              ); do
        do_trace "-> adding rpath '%s'\n" "${n}"
        search_rpath+=( "${n}" )
    done
    do_trace ": search path:\n"
    for n in "${search_rpath[@]}" "${needed_search_path[@]}"; do
        do_trace ": - '%s'\n" "${n}"
    done
    do_trace ": end search path\n"

    for n in $( "${readelf}" -d "${file}"                                               \
                |"${grep}" -E '\(NEEDED\)'                                              \
                |"${sed}" -r -e 's/^.*Shared library:[[:space:]]+\[([^]]+)\].*/\1/;'    \
              ); do
        found=0
        for m in "${needed_list[@]}"; do
            [ "${n}" = "${m}" ] && found=1 && break
        done
        if [ ${found} -ne 0 ]; then
            do_trace "-> skipping already known dependency '%s'\n" "${n}"
            continue
        fi
        do_trace "-> handling new dependency '%s'\n" "${n}"
        needed_list+=( "${n}" )
        do_find_needed "${n}"
        do_trace "-> done handling dependency '%s'\n" "${n}"
    done

    search_rpath=( "${save_search_rpath[@]}" )

    do_trace "Finished parsing file '%s'\n" "${file}"
}

# Recursively scan a /etc/ld.so.conf file
do_scan_etc_ldsoconf() {
    local ldsoconf="${1}"
    local g
    local f

    [ -f "${ldsoconf}" ] || return 0
    do_trace "Parsing ld.so.conf: '%s'\n" "${ldsoconf}"

    while read line; do
        case "${line}" in
            include\ *)
                g="${root}${line#include }"
                do_trace "-> handling include directive '%s'\n" "${g}"
                for f in ${g}; do
                    do_scan_etc_ldsoconf "${f}"
                done
                do_trace "-> finished handling include directive '%s'\n" "${g}"
                ;;
            \#*|"")
                ;;
            *)
                do_trace "-> adding search dir '%s'\n" "${line}"
                needed_search_path+=( "${line}" )
                ;;
        esac
    done <"${ldsoconf}"

    do_trace "Finished parsing ld.so.conf: '%s'\n" "${ldsoconf}"
}

# Build up the full list of search directories
declare -a needed_search_path
do_trace "Adding basic lib dirs\n"
ld_library_path="${ld_library_path}:"
while [ -n "${ld_library_path}" ]; do
    d="${ld_library_path%%:*}"
    if [ -n "${d}" ]; then
        do_trace "-> adding search dir '%s'\n" "${d}"
        needed_search_path+=( "${d}" )
    fi
    ld_library_path="${ld_library_path#*:}"
done
do_trace "Done adding basic lib dirs\n"
do_trace "Scanning '/etc/ld.so.conf'\n"
do_scan_etc_ldsoconf "${root}/etc/ld.so.conf"
do_trace "Done scanning '/etc/ld.so.conf'\n"
do_trace "Search path:\n"
for p in "${needed_search_path[@]}"; do
    do_trace "-> '%s'\n" "${p}"
done

declare -a needed_list
declare -a search_rpath
do_trace "Scanning file '%s'\n" "${1}"
do_process_file "${1}"
do_trace "Done scanning file '%s'\n" "${1}"
