How to list library dependencies of a non-native binary?
LinuxGccShared LibrariesCross CompilingBinutilsLinux Problem Overview
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-compiling, I don't know how to get the same information. The ldd is not a normal binutils utility, like strip or ar, that can be built alongside gcc for cross compiling, but instead, it is a cryptic shell script that apparently can only run on native platform.
So, using the cross-target binutils tools, is there any way to get a list of the dynamically linked dependency for of a foreign binary?
Linux Solutions
Solution 1 - Linux
> is there any way to get a list of the dynamically linked dependency for of a foreign binary
You can list direct dependencies of a binary easily enough:
readelf -d a.out | grep NEEDED
0x0000000000000001 (NEEDED) Shared library: [librt.so.1]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
I know of no way to recursively continue this to get the full list (as ldd does). You'll have to repeat the process for every NEEDED library by hand.
Solution 2 - Linux
You can do bash -x ldd /bin/ls to understand what ldd is doing. The ldd script is not that "cryptic". It basically runs
LD_TRACE_LOADED_OBJECTS=1 /lib64/ld-linux-x86-64.so.2 /bin/ls
so it uses the dynamic loader of the system (because the result of ldd depends upon your actual environment and system!). But you could examine with objdump -x /bin/ls the dynamic section of an executable, e.g.
% objdump -x /bin/ls
/bin/ls: file format elf64-x86-64
/bin/ls
architecture: i386:x86-64, flags 0x00000112:
EXEC_P, HAS_SYMS, D_PAGED
start address 0x00000000004046d4
Program Header:
PHDR off 0x0000000000000040 vaddr 0x0000000000400040 paddr 0x0000000000400040 align 2**3
filesz 0x00000000000001c0 memsz 0x00000000000001c0 flags r-x
INTERP off 0x0000000000000200 vaddr 0x0000000000400200 paddr 0x0000000000400200 align 2**0
filesz 0x000000000000001c memsz 0x000000000000001c flags r--
LOAD off 0x0000000000000000 vaddr 0x0000000000400000 paddr 0x0000000000400000 align 2**21
filesz 0x0000000000019ef4 memsz 0x0000000000019ef4 flags r-x
LOAD off 0x000000000001a000 vaddr 0x000000000061a000 paddr 0x000000000061a000 align 2**21
filesz 0x000000000000077c memsz 0x0000000000001500 flags rw-
DYNAMIC off 0x000000000001a028 vaddr 0x000000000061a028 paddr 0x000000000061a028 align 2**3
filesz 0x00000000000001d0 memsz 0x00000000000001d0 flags rw-
NOTE off 0x000000000000021c vaddr 0x000000000040021c paddr 0x000000000040021c align 2**2
filesz 0x0000000000000044 memsz 0x0000000000000044 flags r--
EH_FRAME off 0x0000000000017768 vaddr 0x0000000000417768 paddr 0x0000000000417768 align 2**2
filesz 0x00000000000006fc memsz 0x00000000000006fc flags r--
STACK off 0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**3
filesz 0x0000000000000000 memsz 0x0000000000000000 flags rw-
Dynamic Section:
NEEDED libselinux.so.1
NEEDED librt.so.1
NEEDED libacl.so.1
NEEDED libc.so.6
INIT 0x0000000000402148
FINI 0x00000000004125f8
HASH 0x0000000000400260
GNU_HASH 0x00000000004005c0
STRTAB 0x0000000000401100
SYMTAB 0x0000000000400620
STRSZ 0x00000000000004d7
SYMENT 0x0000000000000018
DEBUG 0x0000000000000000
PLTGOT 0x000000000061a208
PLTRELSZ 0x0000000000000990
PLTREL 0x0000000000000007
JMPREL 0x00000000004017b8
RELA 0x0000000000401740
RELASZ 0x0000000000000078
RELAENT 0x0000000000000018
VERNEED 0x00000000004016c0
VERNEEDNUM 0x0000000000000003
VERSYM 0x00000000004015d8
Version References:
required from librt.so.1:
0x09691a75 0x00 05 GLIBC_2.2.5
required from libacl.so.1:
0x05822452 0x00 06 ACL_1.2
0x05822450 0x00 04 ACL_1.0
required from libc.so.6:
0x09691a75 0x00 03 GLIBC_2.2.5
0x0d696913 0x00 02 GLIBC_2.3
Again, the actual dependency depends upon the system where your binary is run (e.g. because I could have an LD_LIBRARY_PATH with my own libc.so.6 somewhere, which would be a bad idea).
So you need a cross variant of objdump
Solution 3 - Linux
while in gdb, info shared is similar to ldd. It gives complete human readable runtime information of the executable.
readelf would miss path and other libraries information.
readelf is a very good tool for on the host study. Developer may choose that works.
Solution 4 - Linux
this helped me
objdump -p /path/to/program | grep NEEDED
Solution 5 - Linux
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 [ $argc -eq 0 ]
then
printf '%s: prints dependencies of a (potentially) non-native elf executable, recursively\n'
printf '\n'
printf 'usage:\n'
printf '\t%s <non-native elf executable> [ --supress-header ] [ <path> ... ]\n' "$(basename $0)"
printf '\twhere\n'
printf '\t\t<non-native elf executable> is the name of a file to find the dependencies of.\n'
printf '\t\t[ <path> ... ] 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. :)
Solution 6 - Linux
A bit late for this addition but someone might benefit/clarify. Doesn't the -A flag to readelf give the same result as ldd?
$ readelf -AW /bin/vi
Library list section '.gnu.liblist' contains 8 entries:
Library Time Stamp Checksum Version Flags
0: libselinux.so.1 2011-07-25T08:02:58 0x17a7d5f7 0 0
1: libtermcap.so.2 2011-07-25T08:02:59 0x29ae9ff7 0 0
2: libacl.so.1 2011-07-25T08:02:58 0x60748842 0 0
3: libc.so.6 2011-07-25T08:02:58 0x0c2c7eeb 0 0
4: libdl.so.2 2011-07-25T08:02:58 0xdfbfc467 0 0
5: libsepol.so.1 2011-07-25T08:02:58 0x857499cb 0 0
6: /lib64/ld-linux-x86-64.so.2 2011-07-25T08:02:58 0x9e6549b7 0 0
7: libattr.so.1 2011-07-25T08:02:58 0x862f1546 0 0
The only info missing here seems to be the full path where those libraries are located.
On the other hand, the tools mentioned so far are only useful once you have an installation known to work. My most common problems are:
- Installing a program (mostly via rpm) that then fails to start or crashes during start up. Somehow I think this is related to library incompatibilities but I haven't found an easy way of checking these thing before installing a program (nor indeed after)
- In an attemtp to overcome (1), sometimes I have resorted to downloading the sources and compiling locally. The typical configure script is partially helpful because it tells you which libraries you are missing. However, it fails to tell you what the lowest version of such libraries are required
Can anyone shed some light on these issues? BTW, I have tried reading installation instructions and release notes but they are almost always nowhere near sufficient.
A beefy example may put everything into context, so please try compiling Cinelerra.
Solution 7 - Linux
By design ldd can only been executed on target. However, it is possible to mimic ldd behavior using readelf. A script called `xldd' was developed in crosstool-ng project. An independent version of this script is available here:
https://gist.github.com/jerome-pouiller/c403786c1394f53f44a3b61214489e6f
Solution 8 - Linux
To list shared libraries dependency of a non-native binary, you can try the following tool: http://www.mathembedded.com/component/k2/item/1-cross-ldd.html
I use it on SH4 and MIPS. As reported in other answer, you can achieve the same using readelf output and a recursive loop, but I have never try by myself since cross-ldd exist.