1 .\" Copyright (c) 1995 Paul Kranenburg
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. All advertising materials mentioning features or use of this software
13 .\" must display the following acknowledgment:
14 .\" This product includes software developed by Paul Kranenburg.
15 .\" 3. The name of the author may not be used to endorse or promote products
16 .\" derived from this software without specific prior written permission
18 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
38 .Nd run-time link-editor
42 utility is a self-contained shared object providing run-time
43 support for loading and link-editing shared objects into a process'
45 It is also commonly known as the dynamic linker.
46 It uses the data structures
47 contained within dynamically linked programs to determine which shared
48 libraries are needed and loads them using the
52 After all shared libraries have been successfully loaded,
54 proceeds to resolve external references from both the main program and
56 A mechanism is provided for initialization routines
57 to be called on a per-object basis, giving a shared object an opportunity
58 to perform any extra set-up before execution of the program proper begins.
59 This is useful for C++ libraries that contain static constructors.
63 utility itself is loaded by the kernel together with any dynamically-linked
64 program that is to be executed.
65 The kernel transfers control to the
67 After the dynamic linker has finished loading,
68 relocating, and initializing the program and its required shared
69 objects, it transfers control to the entry point of the program.
71 To locate the required shared objects in the file system,
82 recognizes a number of environment variables that can be used to modify
84 On 64-bit architectures, the linker for 32-bit objects recognizes
85 all the environment variables listed below, but is being prefixed with
86 LD_32_, for example: LD_32_TRACE_LOADED_OBJECTS.
88 .Bl -tag -width ".Ev LD_LIBMAP_DISABLE"
89 .It Ev LD_DUMP_REL_POST
92 will print a table containing all relocations after symbol
93 binding and relocation.
94 .It Ev LD_DUMP_REL_PRE
97 will print a table containing all relocations before symbol
98 binding and relocation.
100 A library replacement list in the same format as
102 For convenience, the characters
106 can be used instead of a space and a newline.
107 This variable is parsed after
109 and will override its entries.
110 .It Ev LD_LIBMAP_DISABLE
111 If set, disables the use of
115 .It Ev LD_LIBRARY_PATH
116 A colon separated list of directories, overriding the default search path
117 for shared libraries.
118 This is ignored for set-user-ID and set-group-ID programs.
120 A list of shared libraries, separated by colons and/or white space,
121 to be linked in before any
122 other shared libraries.
123 If the directory is not specified then
124 the directories specified by
126 will be searched first
127 followed by the set of built-in standard directories.
128 This is ignored for set-user-ID and set-group-ID programs.
130 When set to a nonempty string, causes
132 to relocate all external function calls before starting execution of the
134 Normally, function calls are bound lazily, at the first call
137 increases the start-up time of a program, but it avoids run-time
138 surprises caused by unexpectedly undefined functions.
139 .It Ev LD_TRACE_LOADED_OBJECTS
140 When set to a nonempty string, causes
142 to exit after loading the shared objects and printing a summary which includes
143 the absolute pathnames of all objects, to standard output.
144 .It Ev LD_TRACE_LOADED_OBJECTS_ALL
145 When set to a nonempty string, causes
147 to expand the summary to indicate which objects caused each object to
149 .It Ev LD_TRACE_LOADED_OBJECTS_FMT1
150 .It Ev LD_TRACE_LOADED_OBJECTS_FMT2
151 When set, these variables are interpreted as format strings a la
153 to customize the trace output and are used by
158 to be operated as a filter more conveniently.
159 The following conversions can be used:
162 The main program's name
166 The value of the environment variable
167 .Ev LD_TRACE_LOADED_OBJECTS_PROGNAME
171 The library's major version number.
173 The full pathname as determined by
175 library search rules.
177 The library's load address.
184 are recognized and have their usual meaning.
187 .Bl -tag -width ".Pa /var/run/ld-elf32.so.hints" -compact
188 .It Pa /var/run/ld-elf.so.hints
190 .It Pa /var/run/ld-elf32.so.hints
191 Hints file for 32-bit binaries on 64-bit system.
192 .It Pa /etc/libmap.conf
193 The libmap configuration file.
194 .It Pa /etc/libmap32.conf
195 The libmap configuration file for 32-bit binaries on 64-bit system.