MirOS Manual: ld.so(1)

LD.SO(1)                     BSD Reference Manual                     LD.SO(1)

NAME

     ld.so - run-time link-editor

DESCRIPTION

     ld.so is a self-contained, position independent program image providing
     run-time support for loading and link-editing shared objects into a
     process's address space. It uses the data structures (see link(5)) con-
     tained within dynamically linked programs to determine which shared li-
     braries are needed and loads them at a convenient virtual address using
     the mmap(2) system call.

     After all shared libraries have been successfully loaded, ld.so proceeds
     to resolve external references from both the main program and all objects
     loaded. A mechanism is provided for initialization routines to be called,
     on a per-object basis, giving a shared object an opportunity to perform
     any extra set-up, before execution of the program proper begins.

     ld.so is itself a shared object that is initially loaded by the kernel.

     To quickly locate the required shared objects in the filesystem, ld.so
     may use a "hints" file, prepared by the ldconfig(8) utility, in which the
     full path specification of the shared objects can be looked up by hashing
     on the 3-tuple <library-name, major-version-number, minor-version-
     number>.

     ld.so recognises a number of environment variables that can be used to
     modify its behaviour as follows:

     LD_LIBRARY_PATH
             A colon separated list of directories, overriding the default
             search path for shared libraries. This variable is ignored for
             set-user-ID and set-group-ID executables.

     LD_PRELOAD
             A colon separate list of library names to load before any of the
             regular libraries are loaded. This variable is ignored for set-
             user-ID and set-group-ID executables.

     LD_BIND_NOW
             Specifies that the dynamic linker should process all relocations
             before transferring control to the program. Normally, the pro-
             cedure linkage table entries are handled lazily, avoiding symbol
             lookup and relocation for unused functions. This variable is ig-
             nored for set-user-ID and set-group-ID executables.

     LD_WARN_NON_PURE_CODE
             When set, issue a warning whenever a link-editing operation re-
             quires modification of the text segment of some loaded object.
             This is usually indicative of an incorrectly built library. <not
             yet supported>

     LD_SUPPRESS_WARNINGS
             When set, no warning messages of any kind are issued. Normally, a
             warning is given if a satisfactorily versioned library could not
             be found. <not yet supported>

     LD_TRACE_LOADED_OBJECTS
             When set, causes ld.so to exit after loading the shared objects
             and printing a summary which includes the absolute pathnames of
             all objects, to standard output.

     LD_TRACE_LOADED_OBJECTS_FMT1
     LD_TRACE_LOADED_OBJECTS_FMT2
             When set, these variables are interpreted as format strings a la
             printf(3) to customize the trace output and are used by ldd(1)'s
             -f option and allows ldd(1) to be operated as a filter more con-
             veniently. The following conversions can be used:

             %a    The main program's name (also known as "__progname").

             %A    The value of the environment variable
                   LD_TRACE_LOADED_OBJECTS_PROGNAME. <not yet supported>

             %o    The library name.

             %m    The library's major version number.

             %n    The library's minor version number.

             %p    The full pathname as determined by ld.so's library search
                   rules.

             %x    The library's load address.

             Additionally, \n and \t are recognised and have their usual mean-
             ing. <not yet supported>

     LD_NO_INTERN_SEARCH
             When set, ld.so does not process any internal search paths that
             were recorded in the executable. <not yet supported>

     LD_NORANDOM
             When set, do not load shared objects or libraries dependent ob-
             jects in random order. This variable is ignored for set-user-ID
             and set-group-ID executables.

     LD_NOSTD_PATH
             <not yet supported> When set, do not include a set of built-in
             standard directory paths for searching. This might be useful when
             running on a system with a completely non-standard filesystem
             layout.

     LD_DEBUG
             When set, be verbose about what ld.so does.

     LD_NOPREBIND
             When set, ignore any prebind data associated with the program or
             libraries.

     LD_PREBINDVALIDATE
             When set, perform symbol relocation of the given binary and the
             associated libraries, compare the results against the prebind
             values, then exit.

FILES

     /var/run/ld.so.hints     library location hints built by ldconfig(8)

SEE ALSO

     ld(1), link(5), ldconfig(8)

HISTORY

     The shared library model employed first appeared in SunOS 4.0.

MirOS BSD #10-current           June 27, 1995                                1

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