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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 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 recommented 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 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 /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 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 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, and AOUT objects, are /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.

-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 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

See attributes(5) for descriptions of the following attributes.

ATTRIBUTE TYPE ATTRIBUTE VALUE Availability SUNWtoo Interface Stability

SEE ALSO

file(1), ld(1), ld.so.1(1), dldump(3C), tempnam(3C), attributes(5)

Linker and Libraries Guide

Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXAMPLES

EXIT STATUS

NOTES

FILES

ENVIRONMENT VARIABLES

ATTRIBUTES

SEE ALSO

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