[thirdparty/man-pages.git] / man1 / ldd.1

.\" Copyright 1995-2000 David Engel (david@ods.com)
.\" Copyright 1995 Rickard E. Faith (faith@cs.unc.edu)
.\" Copyright 2000 Ben Collins (bcollins@debian.org)
.\"    Redone for GLibc 2.2
.\" Copyright 2000 Jakub Jelinek (jakub@redhat.com)
.\"    Corrected.
.\" and Copyright (C) 2012, 2016, Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
.\" Do not restrict distribution.
.\" May be distributed under the GNU General Public License
.\" %%%LICENSE_END
.\"
.TH LDD 1 2019-03-06 "" "Linux Programmer's Manual"
.SH NAME
ldd \- print shared object dependencies
.SH SYNOPSIS
.BR ldd " [\fIoption\fP]... \fIfile\fP..."
.SH DESCRIPTION
.B ldd
prints the shared objects (shared libraries) required by each program or
shared object specified on the command line.
An example of its use and output is the following:
.PP
.in +2n
.EX
$ \fBldd /bin/ls\fP
        linux-vdso.so.1 (0x00007ffcc3563000)
        libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f87e5459000)
        libcap.so.2 => /lib64/libcap.so.2 (0x00007f87e5254000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f87e4e92000)
        libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f87e4c22000)
        libdl.so.2 => /lib64/libdl.so.2 (0x00007f87e4a1e000)
        /lib64/ld-linux-x86-64.so.2 (0x00005574bf12e000)
        libattr.so.1 => /lib64/libattr.so.1 (0x00007f87e4817000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f87e45fa000)
.EE
.in
.PP
In the usual case,
.B ldd
invokes the standard dynamic linker (see
.BR ld.so (8))
with the
.B LD_TRACE_LOADED_OBJECTS
environment variable set to 1.
This causes the dynamic linker to inspect the program's dynamic dependencies,
and find (according to the rules described in
.BR ld.so (8))
and load the objects that satisfy those dependencies.
For each dependency,
.B ldd
displays the location of the matching object
and the (hexadecimal) address at which it is loaded.
(The
.I linux-vdso
and
.I ld-linux
shared dependencies are special; see
.BR vdso (7)
and
.BR ld.so (8).)
.\"
.SS Security
Be aware that in some circumstances
(e.g., where the program specifies an ELF interpreter other than
.IR ld-linux.so ),
.\" The circumstances are where the program has an interpreter
.\" other than ld-linux.so. In this case, ldd tries to execute the
.\" program directly with LD_TRACE_LOADED_OBJECTS=1, with the
.\" result that the program interpreter gets control, and can do
.\" what it likes, or pass control to the program itself.
.\" Much more detail at
.\" http://www.catonmat.net/blog/ldd-arbitrary-code-execution/
some versions of
.B ldd
may attempt to obtain the dependency information
by attempting to directly execute the program,
which may lead to the execution of whatever code is defined
in the program's ELF interpreter,
and perhaps to execution of the program itself.
.\" Mainline glibc's ldd allows this possibility (the line
.\"      try_trace "$file"
.\" in glibc 2.15, for example), but many distro versions of
.\" ldd seem to remove that code path from the script.
(In glibc versions before 2.27,
.\" glibc commit eedca9772e99c72ab4c3c34e43cc764250aa3e3c
the upstream
.B ldd
implementation did this for example,
although most distributions provided a modified version that did not.)
.PP
Thus, you should
.I never
employ
.B ldd
on an untrusted executable,
since this may result in the execution of arbitrary code.
A safer alternative when dealing with untrusted executables is:
.PP
.in +4n
.EX
$ \fBobjdump \-p /path/to/program | grep NEEDED\fP
.EE
.in
.PP
Note, however, that this alternative shows only the direct dependencies
of the executable, while
.B ldd
shows the entire dependency tree of the executable.
.SH OPTIONS
.TP
.B \-\-version
Print the version number of
.BR ldd .
.TP
.BR \-v ", " \-\-verbose
Print all information, including, for example,
symbol versioning information.
.TP
.BR \-u ", " \-\-unused
Print unused direct dependencies.
(Since glibc 2.3.4.)
.TP
.BR \-d ", " \-\-data\-relocs
Perform relocations and report any missing objects (ELF only).
.TP
.BR \-r ", " \-\-function\-relocs
Perform relocations for both data objects and functions, and
report any missing objects or functions (ELF only).
.TP
.B \-\-help
Usage information.
.\" .SH NOTES
.\" The standard version of
.\" .B ldd
.\" comes with glibc2.
.\" Libc5 came with an older version, still present
.\" on some systems.
.\" The long options are not supported by the libc5 version.
.\" On the other hand, the glibc2 version does not support
.\" .B \-V
.\" and only has the equivalent
.\" .BR \-\-version .
.\" .LP
.\" The libc5 version of this program will use the name of a library given
.\" on the command line as-is when it contains a \(aq/\(aq; otherwise it
.\" searches for the library in the standard locations.
.\" To run it
.\" on a shared library in the current directory, prefix the name with "./".
.SH BUGS
.B ldd
does not work on a.out shared libraries.
.PP
.B ldd
does not work with some extremely old a.out programs which were
built before
.B ldd
support was added to the compiler releases.
If you use
.B ldd
on one of these programs, the program will attempt to run with
.I argc
= 0 and the results will be unpredictable.
.\" .SH AUTHOR
.\" David Engel.
.\" Roland McGrath and Ulrich Drepper.
.SH SEE ALSO
.BR pldd (1),
.BR sprof (1),
.BR ld.so (8),
.BR ldconfig (8)
Commit	Line	Data
	1	.\" Copyright 1995-2000 David Engel (david@ods.com)
	2	.\" Copyright 1995 Rickard E. Faith (faith@cs.unc.edu)
	3	.\" Copyright 2000 Ben Collins (bcollins@debian.org)
	4	.\" Redone for GLibc 2.2
	5	.\" Copyright 2000 Jakub Jelinek (jakub@redhat.com)
	6	.\" Corrected.
	7	.\" and Copyright (C) 2012, 2016, Michael Kerrisk <mtk.manpages@gmail.com>
	8	.\"
	9	.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
	10	.\" Do not restrict distribution.
	11	.\" May be distributed under the GNU General Public License
	12	.\" %%%LICENSE_END
	13	.\"
	14	.TH LDD 1 2019-03-06 "" "Linux Programmer's Manual"
	15	.SH NAME
	16	ldd \- print shared object dependencies
	17	.SH SYNOPSIS
	18	.BR ldd " [\fIoption\fP]... \fIfile\fP..."
	19	.SH DESCRIPTION
	20	.B ldd
	21	prints the shared objects (shared libraries) required by each program or
	22	shared object specified on the command line.
	23	An example of its use and output is the following:
	24	.PP
	25	.in +2n
	26	.EX
	27	$ \fBldd /bin/ls\fP
	28	linux-vdso.so.1 (0x00007ffcc3563000)
	29	libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f87e5459000)
	30	libcap.so.2 => /lib64/libcap.so.2 (0x00007f87e5254000)
	31	libc.so.6 => /lib64/libc.so.6 (0x00007f87e4e92000)
	32	libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f87e4c22000)
	33	libdl.so.2 => /lib64/libdl.so.2 (0x00007f87e4a1e000)
	34	/lib64/ld-linux-x86-64.so.2 (0x00005574bf12e000)
	35	libattr.so.1 => /lib64/libattr.so.1 (0x00007f87e4817000)
	36	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f87e45fa000)
	37	.EE
	38	.in
	39	.PP
	40	In the usual case,
	41	.B ldd
	42	invokes the standard dynamic linker (see
	43	.BR ld.so (8))
	44	with the
	45	.B LD_TRACE_LOADED_OBJECTS
	46	environment variable set to 1.
	47	This causes the dynamic linker to inspect the program's dynamic dependencies,
	48	and find (according to the rules described in
	49	.BR ld.so (8))
	50	and load the objects that satisfy those dependencies.
	51	For each dependency,
	52	.B ldd
	53	displays the location of the matching object
	54	and the (hexadecimal) address at which it is loaded.
	55	(The
	56	.I linux-vdso
	57	and
	58	.I ld-linux
	59	shared dependencies are special; see
	60	.BR vdso (7)
	61	and
	62	.BR ld.so (8).)
	63	.\"
	64	.SS Security
	65	Be aware that in some circumstances
	66	(e.g., where the program specifies an ELF interpreter other than
	67	.IR ld-linux.so ),
	68	.\" The circumstances are where the program has an interpreter
	69	.\" other than ld-linux.so. In this case, ldd tries to execute the
	70	.\" program directly with LD_TRACE_LOADED_OBJECTS=1, with the
	71	.\" result that the program interpreter gets control, and can do
	72	.\" what it likes, or pass control to the program itself.
	73	.\" Much more detail at
	74	.\" http://www.catonmat.net/blog/ldd-arbitrary-code-execution/
	75	some versions of
	76	.B ldd
	77	may attempt to obtain the dependency information
	78	by attempting to directly execute the program,
	79	which may lead to the execution of whatever code is defined
	80	in the program's ELF interpreter,
	81	and perhaps to execution of the program itself.
	82	.\" Mainline glibc's ldd allows this possibility (the line
	83	.\" try_trace "$file"
	84	.\" in glibc 2.15, for example), but many distro versions of
	85	.\" ldd seem to remove that code path from the script.
	86	(In glibc versions before 2.27,
	87	.\" glibc commit eedca9772e99c72ab4c3c34e43cc764250aa3e3c
	88	the upstream
	89	.B ldd
	90	implementation did this for example,
	91	although most distributions provided a modified version that did not.)
	92	.PP
	93	Thus, you should
	94	.I never
	95	employ
	96	.B ldd
	97	on an untrusted executable,
	98	since this may result in the execution of arbitrary code.
	99	A safer alternative when dealing with untrusted executables is:
	100	.PP
	101	.in +4n
	102	.EX
	103	$ \fBobjdump \-p /path/to/program \| grep NEEDED\fP
	104	.EE
	105	.in
	106	.PP
	107	Note, however, that this alternative shows only the direct dependencies
	108	of the executable, while
	109	.B ldd
	110	shows the entire dependency tree of the executable.
	111	.SH OPTIONS
	112	.TP
	113	.B \-\-version
	114	Print the version number of
	115	.BR ldd .
	116	.TP
	117	.BR \-v ", " \-\-verbose
	118	Print all information, including, for example,
	119	symbol versioning information.
	120	.TP
	121	.BR \-u ", " \-\-unused
	122	Print unused direct dependencies.
	123	(Since glibc 2.3.4.)
	124	.TP
	125	.BR \-d ", " \-\-data\-relocs
	126	Perform relocations and report any missing objects (ELF only).
	127	.TP
	128	.BR \-r ", " \-\-function\-relocs
	129	Perform relocations for both data objects and functions, and
	130	report any missing objects or functions (ELF only).
	131	.TP
	132	.B \-\-help
	133	Usage information.
	134	.\" .SH NOTES
	135	.\" The standard version of
	136	.\" .B ldd
	137	.\" comes with glibc2.
	138	.\" Libc5 came with an older version, still present
	139	.\" on some systems.
	140	.\" The long options are not supported by the libc5 version.
	141	.\" On the other hand, the glibc2 version does not support
	142	.\" .B \-V
	143	.\" and only has the equivalent
	144	.\" .BR \-\-version .
	145	.\" .LP
	146	.\" The libc5 version of this program will use the name of a library given
	147	.\" on the command line as-is when it contains a \(aq/\(aq; otherwise it
	148	.\" searches for the library in the standard locations.
	149	.\" To run it
	150	.\" on a shared library in the current directory, prefix the name with "./".
	151	.SH BUGS
	152	.B ldd
	153	does not work on a.out shared libraries.
	154	.PP
	155	.B ldd
	156	does not work with some extremely old a.out programs which were
	157	built before
	158	.B ldd
	159	support was added to the compiler releases.
	160	If you use
	161	.B ldd
	162	on one of these programs, the program will attempt to run with
	163	.I argc
	164	= 0 and the results will be unpredictable.
	165	.\" .SH AUTHOR
	166	.\" David Engel.
	167	.\" Roland McGrath and Ulrich Drepper.
	168	.SH SEE ALSO
	169	.BR pldd (1),
	170	.BR sprof (1),
	171	.BR ld.so (8),
	172	.BR ldconfig (8)