illumos: manual page: crle.1

CRLE(1) 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] [-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 startup.
The runtime linker attempts to read a default configuration file for all
processes. For 32-bit processes, the default configuration file is
/var/ld/ld.config. For 64-bit processes, the default configuration file
is /var/ld/64/ld.config.

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
regenerate the configuration file. When used with any other options, a
new configuration file is created or updated.

The runtime linker can also be directed to an alternative configuration
file by setting one of the LD_CONFIG family of environment variable.
LD_CONFIG applies to both 32-bit and 64-bit programs. Since 32-bit and
64-bit configuration files differ, a single configuration file cannot be
used for both class of object. Hence, LD_CONFIG can adversely affect
program execution in cases where a program of one class executes a
program of the other class. In particular, it is common practice for the
32-bit version of standard Solaris utilities to execute their 64-bit
counterpart. LD_CONFIG cannot be successfully used in this case.
Therefore, the use of the LD_CONFIG_32 and LD_CONFIG_64 environment
variables, that precisely target the appropriate class of process, is
recommended.

Creating an incorrect configuration file in the standard location,
/var/ld, can prevent programs from running, and can therefore be
difficult to recover from. To guard against this situation, it is
recommended that new configuration files first be created in a temporary
location. Then set the appropriate LD_CONFIG environment variable to this
new configuration file. This setting causes the new configuration file to
be used by the runtime linker instead of any default. After verification,
the new configuration file can be moved to the default location 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 class 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
default. See the -l and -u options.

Trusted Directories

When processing a secure application, the runtime linker restricts
the use of LD_LIBRARY_PATH searches, and $ORIGIN token expansion. See
Security in Linker and Libraries Guide. In addition, the directories
from which preload and audit libraries can be located are also
restricted. The path names that are associated with preload and audit
libraries are restricted to known trusted directories. Trusted
directories can be expressed within the configuration file.
Typically, use of this facility should be augmented with any system
defaults. See the -s and -u options.

Environment Variables

Any environment variable interpreted by the runtime linker can be
specified within the configuration file.

Directory Cache

The location of shared objects within defined directories can be
maintained as a cache within the configuration file. This directory
cache can reduce the overhead of searching for application
dependencies.

Alternative Objects

In conjunction with the directory cache, shared objects can have
alternative objects specified for use at runtime. 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
locations. These fixed alternative objects can require less
processing at runtime than their original shared object counterpart.

Defining additional 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 a suitable runpath.

The declaration of alternative objects provides a means of replacing
dependencies other than by using symbolic links or requiring
LD_LIBRARY_PATH settings.

The declaration of environment variables that are interpreted by the
runtime linker provides a means of centralizing their definition for all
applications.

The directory cache, and crle generated alternate objects, can provide a
means of reducing the runtime startup overhead of applications.
Alternative objects can be useful for applications that require many
dependencies, or whose dependencies are expensive to relocate. Shared
objects that contain position-dependent code are often expensive to
relocate. Note, the system has many caching facilities that help mitigate
expenses such as negative path lookups, and thus employing crle to create
a directory cache may have minimal effect other than for some very
specific cases.

When alternate objects that are generated by crle are specified within a
configuration file, the runtime linker performs some minimal consistency
verification. The alternative objects are verified against their
originating objects. This verification 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, and may
only show improvement in some very specific cases.

crle creates alternate objects for the shared objects that are discovered
when using the -I and -G options, using 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 by 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. Use -64 to
create a 64-bit specific configuration file.

-a name

Create an alternative path name for name. The alternative path name
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 path name for name. This alternative
path name 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 auxiliary filters. See Generating Auxiliary Filters
in 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
configuration file definitions, and process environment definitions
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 definition.

In other words, these configuration file definitions can be replaced,
or removed by the process environment at runtime.

-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
definitions, which can take one or more values, are definitions such
as LD_LIBRARY_PATH=path, and LD_DEBUG=files,details.

A singular definition that is established in a configuration file
takes precedence over a process environment definition. A list
definition that is established in a configuration file is appended to
a process environment definition. Any definition that is established
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. Multiple
occurrences of this option are permitted. name can be a shared object
or a directory. If name is a directory, each shared object within
the directory is added to the cache. If name does not exist, the name
is marked 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. Multiple 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 directory,
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 objects. Multiple
occurrences of this option are permitted.

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 /usr/lib/64.

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 objects. See
SECURITY in ld.so.1(1) for a definition of secure objects. See
Security in Linker and Libraries Guide for a discussion of runtime
restrictions imposed on secure applications.

Multiple occurrences of this option are permitted.

The default trusted directories for secure 32-bit ELF objects is
/lib/secure followed by /usr/lib/secure. For 64-bit secure ELF
objects, the default trusted directories are /lib/secure/64 followed
by /usr/lib/secure/64.

Use of this option replaces the default trusted directories.
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
configuration file. These defaults are added before the new
directories specified with the -l option.

-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 configuration 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.

The configuration file can be in the older format that lacks the
system identification information that is normally written at the
beginning of the file. In this case, crle does not place system
identification information into the resulting file, preserving
compatibility of the file with older versions of Solaris. See NOTES.

-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 configuration file
/var/ld/ld.config for each 32-bit application processed.
/var/ld/64/ld.config is read for each 64-bit application. When processing
an alternative application, the runtime linker uses a
$ORIGIN/ld.config.app-name configuration file if present. See NOTES.
Applications can reference an alternative configuration file by setting
the LD_CONFIG environment variable. An alternative configuration file can
also be specified by recording the configuration file name in the
application at the time the application is built. See the -c option of
ld(1).

EXAMPLES

Example 1: Experimenting With a Temporary Configuration File

The following example creates a temporary configuration file with a new
default search path for ELF objects. The environment variable
LD_CONFIG_32 is used to instruct the runtime linker to use this
configuration file for all 32-bit processes.

$ crle -c /tmp/ld.config -u -l /local/lib
$ crle -c /tmp/ld.config

Configuration file [version 4]: /tmp/ld.config
Platform: 32-bit MSB SPARC
Default Library Path (ELF): /lib:/usr/lib:/local/lib
Trusted Directories (ELF): /lib/secure:/usr/lib/secure \
(system default)

Command line:
crle -c /tmp/ld.config -l /lib:/usr/lib:/local/lib

$ LD_CONFIG_32=/tmp/ld.config date
Thu May 29 17:42:00 PDT 2008

Example 2: 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.

# crle -u -l /local/lib
# crle

Configuration file [version 4]: /var/ld/ld.config
Platform: 32-bit MSB SPARC
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

# crle -u -l /ISV/lib
# crle

Configuration file [version 4]: /var/ld/ld.config
Platform 32-bit MSB SPARC
Default Library Path (ELF): /lib:/usr/lib:/local/lib:/ISV/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 /ISV/lib to those paths
already established in the configuration file.

Example 3: Recovering From a Bad Configuration File

The following example creates a bad configuration file in the default
location. The file can be removed by instructing the runtime linker to
ignore any configuration file with the LD_NOCONFIG environment variable.
Note, it is recommended that temporary configuration files be created and
the environment variable LD_CONFIG used to experiment with these files.

# crle -l /local/lib
# date
ld.so.1: date: fatal: libc.so.1: open failed: \
No such file or directory
Killed
# LD_NOCONFIG=yes rm /var/ld/ld.config
# date
Thu May 29 17:52:00 PDT 2008

Note, the reason the configuration file is bad is because the system
default search paths are not present. Hence, the date utility is not able
to locate the system dependencies that it required. In this case, the -u
option should have been used.

Example 4: 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.

# crle -l /local/lib -l /lib -l /usr/lib -s /local/lib
# crle

Configuration file [version 4]: /var/ld/ld.config
Platform: 32-bit MSB SPARC
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 file, 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 5: Creating a Directory Cache for ELF Objects

The following example creates a directory cache for ELF objects.

$ crle -i /usr/dt/lib -i /usr/openwin/lib -i /lib -i /usr/lib \
-c config
$ ldd -s ./main
....
find object=libc.so.1; required by ./main
search path=/usr/dt/lib:/usr/openwin/lib (RUNPATH/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

$ LD_CONFIG=config ldd -s ./main
....
find object=libc.so.1; required by ./main
search path=/usr/dt/lib:/usr/openwin/lib (RUNPATH/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.

Example 6: Creating an Alternative Object Cache for an ELF Executable

The following example creates an alternative object cache for an ELF
executable.

$ crle -c /local/$HOST/.xterm/ld.config.xterm \
-f RTLD_REL_ALL -G /usr/openwin/bin/xterm
$ ln -s /local/$HOST/.xterm/xterm /local/$HOST/xterm
$ 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
startup 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 7: 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.

$ ldd /usr/bin/vi
libcurses.so.1 => /lib/libcurses.so.1
....

# crle -a /lib/libcurses.so.1 -o /usr/ucblib
# crle

Configuration file [version 4]: /var/ld/ld.config
Platform: 32-bit MSB SPARC
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)
....

$ 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 /usr/ucblib/libcurses.so.1.

Example 8: Setting Replaceable and Permanent Environment Variables

The following example sets replaceable and permanent environment
variables.

# crle -e LD_LIBRARY_PATH=/local/lib \
-E LD_PRELOAD=preload.so.1
# crle
.....
Environment Variables:
LD_LIBRARY_PATH=/local/lib (replaceable)
LD_PRELOAD=preload.so.1 (permanent)

.....
$ 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 definition.

EXIT STATUS

The creation or display of a configuration file results in a 0 being
returned. Otherwise, any error condition is accompanied 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 configuration file must be specified using the LD_CONFIG
environment 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 contents of a configuration
file.

$ crle

Configuration file [2]: /var/ld/ld.config
......

With a version 2 configuration file, crle is capable of constructing the
command-line arguments required to regenerate the configuration file.
This command-line construction, provides full update capabilities using
the -u option. Although a version 1 configuration file update is
possible, the configuration file contents might be insufficient for crle
to compute the entire update requirements.

Configuration files contain platform specific binary data. A given
configuration file can only be interpreted by software with the same
machine class and byte ordering. However, the information necessary to
enforce this restriction was not included in configuration files until
SXCE build 41. As of this SXCE build, configuration files have system
identification information at the beginning of the file. This additional
information is used by crle and the runtime to check their compatibility
with configuration files. This information also allows the file(1)
command to properly identify configuration files. For backward
compatibility, older files that are missing this information are still
accepted, although without the identification and error checking that
would otherwise be possible. When processing an update (-u) operation
for an older file that lacks system information, crle does not add system
identification information to the result.

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 objects.

/usr/lib/64/libcrle.so.1

Audit library that is employed to dldump(3C) 64-bit objects.

ENVIRONMENT VARIABLES

There are no environment variables that are referenced by crle. However,
several environment variables affect the runtime linkers behavior in
regard to the processing of configuration files that are created by crle.

LD_CONFIG, LD_CONFIG_32 and LD_CONFIG_64

Provide an alternative configuration file.

LD_NOCONFIG, LD_NOCONFIG_32 and LD_NOCONFIG_64

Disable configuration file processing.

LD_NODIRCONFIG, LD_NODIRCONFIG_32 and LD_NODIRCONFIG_64

Disable directory cache processing from a configuration file.

LD_NOENVCONFIG, LD_NOENVCONFIG_32 and LD_NOENVCONFIG_64

Disable environment variable processing from a configuration file.

LD_NOOBJALTER, LD_NOOBJALTER_32 and LD_NOOBJALTER_64

Disable alternative object processing from a configuration file.

ATTRIBUTES