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User Commands crle(1)
NAME
crle - configure runtime linking environment
SYNOPSIS
crle [-64] [-a name] [-A name] [-c conf] [-e env] [-E env]
[-f flags] [-i name] [-I name] [-g name] [-G name] [-l dir]
[-o dir] [-s dir] [-t [ ELF | AOUT] ] [-u] [-v]
DESCRIPTION
The crle utility provides for the creation and display of a
runtime linking configuration file. The configuration file
is read and interpreted by the runtime linker, ld.so.1(1),
during process start-up. Without any arguments, or with just
the -c option, crle displays configuration information. This
information includes the contents of a configuration file,
any system defaults and the command-line required to regen-
erate the configuration file. When used with any other
options, a new configuration file is created or updated.
For 32-bit objects, the default configuration file is
/var/ld/ld.config. For 64-bit objects, the default confi-
guration file is /var/ld/64/ld.config.
When creating a new configuration file, first create the
file in a temporary location. The environment variable
LD_CONFIG can then be set to this new configuration file.
This setting causes the new configuration to be used by the
runtime linker instead of any default. After verification,
the new configuration file can be moved to the default loca-
tion if desired. At any time, the environment variable
LD_NOCONFIG can be set to any value to instruct the runtime
linker to ignore any configuration files. This setting can
prove useful during experimentation.
A configuration file can contain the following information.
Default Search Paths
The runtime linker uses a prescribed search path for
locating the dynamic dependencies of an object. This
search path starts with the components of any
LD_LIBRARY_PATH definition, followed by the components
of an object's runpath. Finally, any default search
paths specific to the object's type are used. This last
component of the search path can be expressed within the
configuration file. Typically, use of this facility
should be augmented with any system defaults. See the -l
option.
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User Commands crle(1)
Trusted Directories
When processing a secure application, the runtime linker
restricts the use of LD_LIBRARY_PATH and the directories
from which preload and audit libraries can be used. This
processing is restricted to known trusted directories.
Trusted directories can be expressed within the confi-
guration file. Typically, use of this facility should be
augmented with any system defaults. See the -s option.
Directory Cache
The location of shared objects within defined direc-
tories can be maintained as a cache within the confi-
guration file. This directory cache can reduce the over-
head of searching for application dependencies.
Alternative Objects
In conjunction with the directory cache, shared objects
can have alternative objects specified for use at run-
time. These alternate objects, can be supplied by the
user. Alternative objects can also be created by crle as
copies of shared objects fixed to known memory loca-
tions. These fixed alternative objects can require less
processing at runtime than their original shared object
counterpart.
Environment Variables
Any environment variable interpreted by the runtime
linker can be specified within the configuration file.
Defining alternative default search paths, or additional
trusted directories can be useful for administrators who
wish to install third party software in a central location,
or otherwise alter the search path of applications that
might not have been coded with suitable runpaths.
The declaration of alternative objects, provides a means of
replacing dependencies other than by using symbolic links,
or requiring LD_LIBRARY_PATH settings.
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User Commands crle(1)
The declaration of environment variables that are inter-
preted by the runtime linker, provides a means of centraliz-
ing their definition for all applications.
The directory cache, and crle generated alternate objects,
can provide a means of reducing the runtime start-up over-
head of applications. Alternative objects can be useful for
applications that require many dependencies, or whose depen-
dencies are expensive to relocate. Shared objects that con-
tain position-dependent code are often expensive to relo-
cate.
When alternate objects that are generated by crle are speci-
fied within a configuration file, ld.so.1(1) performs some
minimal consistency verification. The alternative objects
are verified against their originating objects. This verifi-
cation is intended to avert application failure should an
applications configuration information become out-of-sync
with the underlying system components. When this situation
arises the flexibility offered by dynamic linking system
components can be compromised. This type of application
failure can be very difficult to diagnose. No verification
of directory cache information is performed. Any changes to
the directory structure are not seen by a process until the
cache is rebuilt.
System shared objects are often well tuned, and can show
little benefit from being cached. The directory cache and
alternative object features are typically applicable to user
applications and shared objects.
crle creates alternate objects for the shared objects that
are discovered when using the -I and -G options, by calls to
dldump(3C). The alternate object is created in the directory
specified by the preceding -o option, or defaults to the
directory in which the configuration file is created. The
flags used for the dldump() are specified using the -f
option, or default to RTLD_REL_RELATIVE.
OPTIONS
The following options are supported.
-64
Specify to process 64-bit objects, the default is 32-
bit.
-a name
Create an alternative pathname for name. The alternative
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User Commands crle(1)
pathname is added to the configuration file.
The actual alternative file must be supplied by the
user. Multiple occurrences of this option are permitted.
If name is a directory, each shared object within the
directory is added to the cache. If name does not exist,
then name is marked in the cache as a nonexistent file.
Typically, this option is used with the -o option.
-A name
Create an optional alternative pathname for name. This
alternative pathname is added to the configuration file.
This option mimics the -a option, except that if the
alternative is unavailable at runtime, the original
object name is used. This model mimics the use of auxi-
liary filters. See the Linker and Libraries Guide.
Typically, this option is used with the -o option.
-c conf
Specify to use the configuration file name conf. If this
option is not supplied, the default configuration file
is used.
-e env
Specify a replaceable environment variable, env. Only
environment variables that are applicable to the runtime
linker are meaningful. Multiple occurrences of this
option are permitted. This option is similar to the -E
option. However, the options differs in how configura-
tion file definitions, and process environment defini-
tions of the same name are resolved at runtime.
A definition established in a configuration file can be
overridden by a process environment definition, or be
suppressed by a null-value process environment defini-
tion.
In other words, these configuration file definitions can
be replaced, or removed by the process environment at
runtime.
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User Commands crle(1)
-E env
Specify a permanent environment variable, env. Only
environment variables that are applicable to the runtime
linker are meaningful. Multiple occurrences of this
option are permitted. This option is similar to the -e
option. However, the option differs in how configuration
file definitions, and process environment definitions of
the same name are resolved at runtime.
Environment variable definitions that are meaningful to
the runtime linker fall into one of two categories.
Singular definitions are definitions such as
LD_NOLAZYLOAD=1 and LD_DEBUG_OUTPUT=file. List defini-
tions, which can take one or more values, are defini-
tions such as LD_LIBRARY_PATH=path, and
LD_DEBUG=files,details.
A singular definition that is established in a confi-
guration file takes precedence over a process environ-
ment definition. A list definition that is established
in a configuration file is appended to a process
environment definition. Any definition that is esta-
blished in a configuration file can not be suppressed by
a null-value process environment definition.
In other words, these configuration file definitions can
not be replaced, or removed by the process environment
at runtime.
-f flags
Provide the symbolic flags argument to the dldump(3C)
calls used to generate alternate objects. Any of the
RTLD_REL flags that are defined in /usr/include/dlfcn.h
can be used. Multiple flags can be or'ed together using
the "|" character. In this case, the string should be
quoted to avoid expansion by the shell. If no flags
values are provided the default flag is
RTLD_REL_RELATIVE.
-i name
Add an individual name to the configuration cache. Mul-
tiple occurrences of this option are permitted. name can
be a shared object or a directory. If name is a direc-
tory, each shared object within the directory is added
to the cache. If name does not exist, the name is marked
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User Commands crle(1)
in the cache as a nonexistent directory.
-I name
Mimic the -i, and in addition any shared object that is
processed has an alternative created using dldump(3C).
If the -f flag contains RTLD_REL_EXEC, then name can be
a dynamic executable, for which an alternative is
created. Only one dynamic executable can be specified in
this manner, as the cache that is created is specific to
this application.
-g name
Add the group name to the configuration cache. Each
object is expanded to determine its dependencies. Multi-
ple occurrences of this option are permitted. name can
be a dynamic executable, shared object or a directory.
If name is a shared object, the shared object and its
dependencies are added to the cache. If name is a direc-
tory, each shared object within the directory, and its
dependencies, are added to the cache.
-G name
Mimic the -g option, and in addition any shared object
that is processed has an alternative created using
dldump(3C). If name is a dynamic executable, and the -f
flag contains RTLD_REL_EXEC, then an alternative for the
dynamic executable is also created. Only one dynamic
executable can be specified in this manner as the cache
that is created is specific to this application.
-l dir
Specify a new default search directory dir for ELF or
AOUT objects. Multiple occurrences of this option are
permitted. The type of object that is applicable to the
search, is specified by the preceding -t option, or
defaults to ELF.
The default search paths for 32-bit ELF objects are /lib
followed by /usr/lib. For 64-bit ELF objects, the
default search paths are /lib/64 followed by
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User Commands crle(1)
/usr/lib/64.
The default search paths for AOUT objects are /usr/4lib,
followed by /usr/lib and finally /usr/local/lib.
Use of this option replaces the default search path.
Therefore, a -l option is normally required to specify
the original system default in relation to any new paths
that are being applied. However, if the -u option is in
effect, and a configuration file does not exist, the
system defaults are added to the new configuration file.
These defaults are added before the new paths specified
with the -l option.
-o dir
When used with either the -a or -A options, specifies
the directory dir in which any alternate objects exist.
When alternative objects are created by crle, this
option specified where the alternative are created.
Without this option, alternate objects exist in the
directory in which the configuration file is created.
Multiple occurrences of this option are permitted, the
directory dir being used to locate alternatives for any
following command-line options. Alternative objects are
not permitted to override their associated originals.
Typically, this option is used with the -a or -A
options.
-s dir
Specify a new trusted directory dir for secure ELF or
AOUT objects. See SECURITY in ld.so.1(1) for a defini-
tion of secure objects.
Multiple occurrences of this option are permitted. The
type of object that is applicable to the search is
specified by the preceding -t option, or defaults to
ELF.
The default trusted directories for secure 32-bit ELF
objects are /lib/secure followed by /usr/lib/secure. For
64-bit secure ELF objects, the default trusted direc-
tories are /lib/secure/64 followed by
/usr/lib/secure/64.
The default trusted directories for secure AOUT objects
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User Commands crle(1)
are /usr/4lib, followed by /usr/lib, followed by
/usr/ucblib, and finally /usr/local/lib.
Use of this option replaces the default trusted direc-
tories. Therefore, a -s option is normally required to
specify the original system default in relation to any
new directories that are being applied. However, if the
-u option is in effect, and a configuration file does
not exist, the system defaults are added to the new con-
figuration file. These defaults are added before the new
directories specified with the -l option.
-t ELF | AOUT
Toggle the object type that is applicable to any -l or
-s options that follow. The default object type is ELF.
-u
Request that a configuration file be updated, possibly
with the addition of new information. Without other
options, any existing configuration file is inspected
and its contents recomputed. Additional arguments allow
information to be appended to the recomputed contents.
See NOTES.
If a configuration file does not exist, the configura-
tion file is created as directed by the other arguments.
In the case of the -l and -s options, any system
defaults are first applied to the configuration file
before the directories specified with these options.
-v
Specify verbose mode. When creating a configuration
file, a trace of the files that are being processed is
written to the standard out. When printing the contents
of a configuration file, more extensive directory and
file information is provided.
By default, the runtime linker attempts to read the confi-
guration file /var/ld/ld.config for each 32-bit application
processesed. /var/ld/64/ld.config is read for each 64-bit
application. When processing an alternative application, the
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User Commands crle(1)
runtime linker uses a $ORIGIN/ld.config.app-name configura-
tion file if present. See NOTES. Applications can reference
an alternative configuration file by setting the LD_CONFIG
environment variable. See ld.so.1(1). An alternative confi-
guration file can also be specified by recording the confi-
guration file name in the application at the time the appli-
cation is built. See the -c option of ld(1).
EXAMPLES
Example 1: Updating and Displaying a New Default Search Path
for ELF Objects
The following example updates and displays a new default
search path for ELF objects:
example% crle -u -l /local/lib
example% crle
Configuration file [version 4]: /var/ld/ld.config
Default Library Path (ELF): /lib:/usr/lib:/local/lib
Trusted Directories (ELF): /lib/secure:/usr/lib/secure (system default)
Command line:
crle -l /lib:/usr/lib:/local/lib
example% crle -u -l /usr/local/lib
example% crle
Configuration file [version 4]: /var/ld/ld.config
Default Library Path (ELF): /lib:/usr/lib:/local/lib:/usr/local/lib
Trusted Directories (ELF): /lib/secure:/usr/lib/secure (system default)
Command line:
crle -l /lib:/usr/lib:/local/lib:/usr/local/lib
In this example, the default configuration file initially
did not exist. Therefore, the new search path /local/lib is
appended to the system default. The next update appends the
search path /usr/local/lib to those paths already esta-
blished in the configuration file.
Example 2: Creating and Displaying a New Default Search Path
and New Trusted Directory for ELF Objects
The following example creates and displays a new default
search path and new trusted directory for ELF objects:
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User Commands crle(1)
example% crle -l /local/lib -l /lib -l /usr/lib -s /local/lib
example% crle
Configuration file [version 4]: /var/ld/ld.config
Default Library Path (ELF): /local/lib:/lib:/usr/lib
Trusted Directories (ELF): /local/lib
Command line:
crle -l /local/lib:/lib:/usr/lib -s /local/lib
With this configuration, third party applications could be
installed in /local/bin and their associated dependencies in
/local/lib. The default search path allows the applications
to locate their dependencies without the need to set
LD_LIBRARY_PATH. The default trusted directories have also
been replaced with this example.
Example 3: Creating a Directory Cache for ELF Objects
The following example creates a directory cache for ELF
objects:
example% crle -i /usr/dt/lib -i /usr/openwin/lib -i /lib -i /usr/lib \
-c config
example% ldd -s ./main
....
find object=libc.so.1; required by ./main
search path=/usr/dt/lib:/usr/openwin/lib (RPATH ./main)
trying path=/usr/dt/lib/libc.so.1
trying path=/usr/openwin/lib/libc.so.1
search path=/lib (default)
trying path=/lib/libc.so.1
libc.so.1 => /lib/libc.so.1
example% LD_CONFIG=config ldd -s ./main
....
find object=libc.so.1; required by ./main
search path=/usr/dt/lib:/usr/openwin/lib (RPATH ./main)
search path=/lib (default)
trying path=/lib/libc.so.1
libc.so.1 => /lib/libc.so.1
With this configuration, the cache reflects that the system
library libc.so.1 does not exist in the directories
/usr/dt/lib or /usr/openwin/lib. Therefore, the search for
this system file ignores these directories even though the
application's runpath indicates these paths should be
searched.
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User Commands crle(1)
Example 4: Creating an Alternative Object Cache for an ELF
Executable
The following example creates an alternative object cache
for an ELF executable:
example% crle -c /local/$HOST/.xterm/ld.config.xterm \
-f RTLD_REL_ALL -G /usr/openwin/bin/xterm
example% ln -s /local/$HOST/.xterm/xterm /local/$HOST/xterm
example% ldd /usr/local/$HOST/xterm
libXaw.so.5 => /local/$HOST/.xterm/libWaw.so.5 (alternate)
libXmu.so.4 => /local/$HOST/.xterm/libXmu.so.4 (alternate)
....
libc.so.1 => /local/$HOST/.xterm/libc.so.1 (alternate)
....
With this configuration, a new xterm and its dependencies
are created. These new objects are fully relocated to each
other, and result in faster start-up than the originating
objects. The execution of this application uses its own
specific configuration file. This model is generally more
flexible than using the environment variable LD_CONFIG, as
the configuration file can not be erroneously used by other
applications such as ldd(1) or truss(1).
Example 5: Creating an Alternative Object Cache to Replace
an ELF Shared Object
The following example creates an alternative object cache to
replace an ELF shared object:
example% ldd /usr/bin/vi
libcurses.so.1 => /lib/libcurses.so.1
....
example% crle -a /lib/libcurses.so.1 -o /usr/ucblib
example% crle
Configuration file [version 4]: /var/ld/ld.config
Default Library Path (ELF): /lib:/usr/lib (system default)
Trusted Directories (ELF): /lib/secure:/usr/lib/secure (system default)
Directory: /lib
libcurses.so.1 (alternate: /usr/ucblib/libcurses.so.1)
....
example% ldd /usr/bin/vi
libcurses.so.1 => /usr/ucblib/libcurses.so.1 (alternate)
....
With this configuration, any dependency that would normally
resolve to /usr/lib/libcurses.so.1 instead resolves to
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User Commands crle(1)
/usr/ucblib/libcurses.so.1.
Example 6: Setting Replaceable and Permanent Environment
Variables
The following example sets replaceable and permanent
environment variables:
example% crle -e LD_LIBRARY_PATH=/local/lib \
-E LD_PRELOAD=preload.so.1
example% crle
.....
Environment Variables:
LD_LIBRARY_PATH=/local/lib (replaceable)
LD_PRELOAD=preload.so.1 (permanent)
.....
example% LD_DEBUG=files LD_PRELOAD=preload.so.2 ./main
.....
18764: file=preload.so.2; preloaded
18764: file=/local/lib/preload.so.2 [ ELF ]; generating link map
.....
18764: file=preload.so.1; preloaded
18764: file=/local/lib/preload.so.1 [ ELF ]; generating link map
.....
With this configuration file, a replaceable search path has
been specified together with a permanent preload object
which becomes appended to the process environment defini-
tion.
EXIT STATUS
The creation or display of a configuration file results in a
0 being returned. Otherwise, any error condition is accom-
panied with a diagnostic message and a non-zero value being
returned.
NOTES
The ability to tag an alternative application to use an
application-specific configuration file, is possible if the
original application contains one of the .dynamic tags
DT_FLAGS_1 or DT_FEATURE_1. Without these entries, a confi-
guration file must be specified using the LD_CONFIG environ-
ment variable. Care should be exercised with this latter
method as this environment variable is visible to any forked
applications.
The use of the -u option requires at least version 2 of
crle. This version level is evident from displaying the con-
tents of a configuration file:
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User Commands crle(1)
example% crle
Configuration file [2]: /var/ld/ld.config
......
With a version 2 configuration file, crle is capable of con-
structing the command-line arguments required to regenerate
the configuration file. This command-line construction, pro-
vides full update capabilities using the -u option. Although
a version 1 configuration file update is possible, the con-
figuration file contents might be insufficient for crle to
compute the entire update requirements.
FILES
/var/ld/ld.config
Default configuration file for 32-bit applications.
/var/ld/64/ld.config
Default configuration file for 64-bit applications.
/var/tmp
Default location for temporary configuration file. See
tempnam(3C).
/usr/lib/lddstub
Stub application that is employed to dldump(3C) 32-bit
objects.
/usr/lib/64/lddstub
Stub application that is employed to dldump(3C) 64-bit
objects.
/usr/lib/libcrle.so.1
Audit library that is employed to dldump(3C) 32-bit
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User Commands crle(1)
objects.
/usr/lib/64/libcrle.so.1
Audit library that is employed to dldump(3C) 64-bit
objects.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWtoo |
|_____________________________|_____________________________|
| Interface Stability | Stable |
|_____________________________|_____________________________|
SEE ALSO
ld(1), ld.so.1(1), dldump(3C), tempnam(3C), attributes(5)
SunOS 5.10 Last change: 4 Feb 2005 14
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