ld.so - run-time link-editor
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
within dynamically linked programs to determine which
are needed and loads them at a convenient virtual
the mmap(2) system call.
After all shared libraries have been successfully loaded,
to resolve external references from both the main program
and all objects
loaded. A mechanism is provided for initialization routines
called, on a per-object basis, giving a shared object an opportunity to
perform any extra set-up, before execution of the program
ld.so is itself a shared object that is initially loaded by
To quickly locate the required shared objects in the
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,
ld.so recognises a number of environment variables that can
be used to
modify its behaviour as follows:
A colon separated list of directories, overriding
search path for shared libraries. This variable is
set-user-ID and set-group-ID executables.
A colon separate list of library names to load before any of the
regular libraries are loaded. This variable is ignored for setuser-ID
and set-group-ID executables.
Specifies that the dynamic linker should process all
before transferring control to the program. Normally, the procedure
linkage table entries are handled lazily,
lookup and relocation for unused functions. This
variable is ignored
for set-user-ID and set-group-ID executables.
When set, issue a warning whenever a link-editing
modification of the text segment of some
This is usually indicative of an incorrectly built
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>
When set, causes ld.so to exit after loading the
and printing a summary which includes the absolute
all objects, to standard output.
When set, these variables are interpreted as format
strings a la
printf(3) to customize the trace output and are used
-f option and allows ldd(1) to be operated as a filter more conveniently.
The following conversions can be used:
%a The main program's name (also known as
%A The value of the environment variable
LD_TRACE_LOADED_OBJECTS_PROGNAME. <not yet
%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
%x The library's load address.
Additionally,n ant are recognised and have their
<not yet supported>
When set, ld.so does not process any internal search
were recorded in the executable. <not yet supported>
When set, do not load shared objects or libraries
in random order. This variable is ignored for
and set-group-ID executables.
<not yet supported> When set, do not include a set
standard directory paths for searching. This might
when running on a system with a completely non-standard filesystem
When set, be verbose about what ld.so does.
/var/run/ld.so.hints library location hints built by ldconfig(8)
ld(1), link(5), ldconfig(8)
The shared library model employed first appeared in SunOS
OpenBSD 3.6 June 27, 1995
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