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rtld (1)
>> rtld (1) ( FreeBSD man: Команды и прикладные программы пользовательского уровня )
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NAME
ld-elf.so.1ld.sortld
- run-time link-editor
DESCRIPTION
The
utility is a self-contained shared object providing run-time
support for loading and link-editing shared objects into a process'
address space.
It is also commonly known as the dynamic linker.
It uses the data structures
contained within dynamically linked programs to determine which shared
libraries are needed and loads them using the
mmap(2)
system call.
After all shared libraries have been successfully loaded,
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.
This is useful for C++ libraries that contain static constructors.
The
utility itself is loaded by the kernel together with any dynamically-linked
program that is to be executed.
The kernel transfers control to the
dynamic linker.
After the dynamic linker has finished loading,
relocating, and initializing the program and its required shared
objects, it transfers control to the entry point of the program.
To locate the required shared objects in the file system,
may use a
``hints''
file prepared by the
ldconfig(8)
utility.
The
utility
recognizes a number of environment variables that can be used to modify
its behaviour.
On 64-bit architectures, the linker for 32-bit objects recognizes
all the environment variables listed below, but is being prefixed with
LD_32_
for example:
LD_32_TRACE_LOADED_OBJECTS
LD_DUMP_REL_POST
If set,
will print a table containing all relocations after symbol
binding and relocation.
LD_DUMP_REL_PRE
If set,
will print a table containing all relocations before symbol
binding and relocation.
LD_LIBMAP
A library replacement list in the same format as
libmap.conf5.
For convenience, the characters
`='
and
`,'
can be used instead of a space and a newline.
This variable is parsed after
libmap.conf5,
and will override its entries.
This variable is unset for set-user-ID and set-group-ID programs.
LD_LIBMAP_DISABLE
If set, disables the use of
libmap.conf5
and
LD_LIBMAP
This variable is unset for set-user-ID and set-group-ID programs.
LD_LIBRARY_PATH
A colon separated list of directories, overriding the default search path
for shared libraries.
This variable is unset for set-user-ID and set-group-ID programs.
LD_PRELOAD
A list of shared libraries, separated by colons and/or white space,
to be linked in before any
other shared libraries.
If the directory is not specified then
the directories specified by
LD_LIBRARY_PATH
will be searched first
followed by the set of built-in standard directories.
This variable is unset for set-user-ID and set-group-ID programs.
LD_BIND_NOW
When set to a nonempty string, causes
to relocate all external function calls before starting execution of the
program.
Normally, function calls are bound lazily, at the first call
of each function.
LD_BIND_NOW
increases the start-up time of a program, but it avoids run-time
surprises caused by unexpectedly undefined functions.
LD_TRACE_LOADED_OBJECTS
When set to a nonempty string, causes
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_ALL
When set to a nonempty string, causes
to expand the summary to indicate which objects caused each object to
be loaded.
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)Ns's
-f
option and allows
ldd(1)
to be operated as a filter more conveniently.
If the dependency name starts with string
lib
LD_TRACE_LOADED_OBJECTS_FMT1
is used, otherwise
LD_TRACE_LOADED_OBJECTS_FMT2
is used.
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
%o
The library name.
%p
The full pathname as determined by
rtld 's
library search rules.
%x
The library's load address.
Additionally,
`\n'
and
`\t'
are recognized and have their usual meaning.
LD_UTRACE
If set,
will log events such as the loading and unloading of shared objects via
utrace(2).
FILES
/var/run/ld-elf.so.hints
Hints file.
/var/run/ld-elf32.so.hints
Hints file for 32-bit binaries on 64-bit system.
/etc/libmap.conf
The libmap configuration file.
/etc/libmap32.conf
The libmap configuration file for 32-bit binaries on 64-bit system.
