dld.sl.5 (2012 03)

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dld.sl(5)

PA-RISC Systems Only

dld.sl(5)

/usr/lib/dld.sl: Can’t shl_load() a library containing Thread Local

Storage: /usr/lib/libcps.1

The load order and symbol resolution order may be different in a PA-RISC 32-bit program than in the

same PA-RISC 64-bit program because the dynamic loader uses depth-ﬁrst search order in PA-Risc 32-bit

mode and breadth-ﬁrst search order in PA-RISC 64-bit mode.

See Symbol Searching and Dependent Libraries in the

+help option to ld(1) or the HP-UX Linker and

Libraries User’s Guide for more information.

The dynamic loader uses the

LD_PRELOAD environment variable even if you use the

+noenvvar in the

link line. This insures that

LD_PRELOAD is enabled even in a

+compat link. The LD_PRELOAD vari-

able is always enabled except for

setuid and

setgid programs.

NOTE: If an archive library is already linked-in with the application and we try to load the shared ver-

sion of that library using

LD_PRELOAD we will have problems.

The potential problems are :

• If the library has initializers/terminators, they will be called twice

• you may end up using two different copies of the same data symbol which may cause incorrect

behavior

You can specify multiple libraries as part of the

LD_PRELOAD environment variable. Separate the

libraries by spaces or colons as in LD_LIBRARY_PATH

. (Multi-byte support is not provided as part of

parsing the

LD_PRELOAD library list). You can specify LD_PRELOAD libraries with absolute paths or

relative paths. The LD_PRELOAD libraries can also consist of just the library names, in which case the

dynamic loader uses the directory path list in the environment variables LD_LIBRARY_PATH

and/or

SHLIB_PATH or the embedded path list (if enabled) to search for the libraries.

The dynamic loader does not issue an error or warning message if it cannot ﬁnd a library speciﬁed by

LD_PRELOAD. However, if it does not ﬁnd a dependent of the LD_PRELOAD libraries, the dynamic

loader issues the same error message as if the LD_PRELOAD library is speciﬁed in the link line.

The LD_PRELOAD_ONCE Environment Variable

The

LD_PRELOAD_ONCE

feature is similar to LD_PRELOAD except that the dynamic loader, dld.sl,

unsets

LD_PRELOAD_ONCE after reading it, so that any applications invoked by the current application

do not have

LD_PRELOAD_ONCE

set. This is useful in situations where the current application needs

certain libraries preloaded while the child application is adversely affected if these are preloaded (for

example,

ksh terminates abnormally if LD_PRELOAD contains /usr/lib/libpthread.1

The libraries speciﬁed by

LD_PRELOAD_ONCE

are loaded before the ones speciﬁed by LD_PRELOAD.

The effect on symbol resolution is that the symbols from libraries speciﬁed by

LD_PRELOAD_ONCE take

precedence over symbols from libraries speciﬁed by

LD_PRELOAD.

Running setuid Programs

For looking up shared libraries for

setuid applications, the dynamic loader uses only the paths listed in

/etc/dld.sl.conf.

LD_LIBRARY_PATH and SHLIB_PATH are set, they are validated against the list of paths in

/etc/dld.sl.conf. (This allows the individual applications to appropriately order the list from the

conf ﬁle).

You can turn this feature off by setting the option _

HP_DLDOPTS to -no_setuidpath. Using this

option disables setuid programs from all dynamic path lookup.

The conﬁguration ﬁle

/etc/dld.sl.conf is expected to contain a list of shared library search paths

(delimited by either colon or newline characters). To avoid redundant searches, you should see that one

path appears only once in the ﬁle (and also in the options SHLIB_PATH and LD_LIBRARY_PATH).

The

conf ﬁle should be writeable only by root. Otherwise, the loader does not use its contents. If

/etc/dld/sl.conf does not exist or has the wrong permissions, all dynamic path lookup is disabled.

Any relative paths (paths not starting with slash (/) in the path list are ignored by the loader.

NOTE: Spaces are not allowed in the paths listed. Everything on a line that follows a space or pound (

character is ignored. You can use the pound sign (#) to comment out paths in the ﬁle.

6 Hewlett-Packard Company − 6 − HP-UX 11i Version 3: March 2012