165 lines
5.3 KiB
Groff
165 lines
5.3 KiB
Groff
.\" $FreeBSD$
|
|
.\"
|
|
.\" Copyright (c) 1995 Paul Kranenburg
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgment:
|
|
.\" This product includes software developed by Paul Kranenburg.
|
|
.\" 3. The name of the author may not be used to endorse or promote products
|
|
.\" derived from this software without specific prior written permission
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.Dd January 28, 2000
|
|
.Dt RTLD 1
|
|
.Os
|
|
.Sh NAME
|
|
.Nm ld-elf.so.1 ,
|
|
.Nm rtld
|
|
.Nd run-time link-editor
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
utility is a self-contained shared object providing run-time
|
|
support for loading and link-editing shared objects into a process'
|
|
address space.
|
|
It is also commonly known as the dynamic linker.
|
|
It uses the data structures
|
|
contained within dynamically linked programs to determine which shared
|
|
libraries are needed and loads them using the
|
|
.Xr mmap 2
|
|
system call.
|
|
.Pp
|
|
After all shared libraries have been successfully loaded,
|
|
.Nm
|
|
proceeds to resolve external references from both the main program and
|
|
all objects loaded.
|
|
A mechanism is provided for initialization routines
|
|
to be called on a per-object basis, giving a shared object an opportunity
|
|
to perform any extra set-up before execution of the program proper begins.
|
|
This is useful for C++ libraries that contain static constructors.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
utility itself is loaded by the kernel together with any dynamically-linked
|
|
program that is to be executed.
|
|
The kernel transfers control to the
|
|
dynamic linker.
|
|
After the dynamic linker has finished loading,
|
|
relocating, and initializing the program and its required shared
|
|
objects, it transfers control to the entry point of the program.
|
|
.Pp
|
|
To locate the required shared objects in the file system,
|
|
.Nm
|
|
may use a
|
|
.Dq hints
|
|
file prepared by the
|
|
.Xr ldconfig 8
|
|
utility.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
utility
|
|
recognizes a number of environment variables that can be used to modify
|
|
its behaviour as follows:
|
|
.Pp
|
|
.Bl -tag -width ".Ev LD_LIBRARY_PATH"
|
|
.It Ev LD_LIBRARY_PATH
|
|
A colon separated list of directories, overriding the default search path
|
|
for shared libraries.
|
|
This is ignored for set-user-ID and set-group-ID programs.
|
|
.It Ev LD_PRELOAD
|
|
A list of shared libraries, separated by colons and/or white space,
|
|
to be linked in before any
|
|
other shared libraries.
|
|
If the directory is not specified then
|
|
the directories specified by
|
|
.Ev LD_LIBRARY_PATH
|
|
will be searched first
|
|
followed by the set of built-in standard directories.
|
|
This is ignored for set-user-ID and set-group-ID programs.
|
|
.It Ev LD_BIND_NOW
|
|
When set to a nonempty string, causes
|
|
.Nm
|
|
to relocate all external function calls before starting execution of the
|
|
program.
|
|
Normally, function calls are bound lazily, at the first call
|
|
of each function.
|
|
.Ev LD_BIND_NOW
|
|
increases the start-up time of a program, but it avoids run-time
|
|
surprises caused by unexpectedly undefined functions.
|
|
.It Ev LD_TRACE_LOADED_OBJECTS
|
|
When set to a nonempty string, causes
|
|
.Nm
|
|
to exit after loading the shared objects and printing a summary which includes
|
|
the absolute pathnames of all objects, to standard output.
|
|
.It Ev LD_TRACE_LOADED_OBJECTS_ALL
|
|
When set to a nonempty string, causes
|
|
.Nm
|
|
to expand the summary to indicate which objects caused each object to
|
|
be loaded.
|
|
.It Ev LD_TRACE_LOADED_OBJECTS_FMT1
|
|
.It Ev LD_TRACE_LOADED_OBJECTS_FMT2
|
|
When set, these variables are interpreted as format strings a la
|
|
.Xr printf 3
|
|
to customize the trace output and are used by
|
|
.Xr ldd 1 Ns 's
|
|
.Fl f
|
|
option and allows
|
|
.Xr ldd 1
|
|
to be operated as a filter more conveniently.
|
|
The following conversions can be used:
|
|
.Bl -tag -width 4n
|
|
.It Li %a
|
|
The main program's name
|
|
(also known as
|
|
.Dq __progname ) .
|
|
.It Li \&%A
|
|
The value of the environment variable
|
|
.Ev LD_TRACE_LOADED_OBJECTS_PROGNAME
|
|
.It Li %o
|
|
The library name.
|
|
.It Li %m
|
|
The library's major version number.
|
|
.It Li %p
|
|
The full pathname as determined by
|
|
.Nm rtld Ns 's
|
|
library search rules.
|
|
.It Li %x
|
|
The library's load address.
|
|
.El
|
|
.Pp
|
|
Additionally,
|
|
.Ql \en
|
|
and
|
|
.Ql \et
|
|
are recognized and have their usual meaning.
|
|
.El
|
|
.Sh FILES
|
|
.Bl -tag -width indent
|
|
.It Pa /var/run/ld-elf.so.hints
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr ld 1 ,
|
|
.Xr ldd 1 ,
|
|
.Xr elf 5 ,
|
|
.Xr ldconfig 8
|