Windows PowerShell command on Get-command dlmopen

Manual Pages for UNIX Operating System command usage for man dlmopen

Standard C Library Functions dlopen(3C)

NAME

dlopen, dlmopen - gain access to an executable object file

SYNOPSIS

#include

void * dlopen(const char *pathname, int mode);

void * dlmopen(Lmid_t lmid, const char *pathname, int mode);

DESCRIPTION

The dlopen() function makes an executable object file avail-

able to a running process. dlopen() returns to the process a handle that the process can use on subsequent calls to dlsym(3C), dladdr(3C), dlinfo(3C), and dlclose(3C). The value of this handle should not be interpreted in any way by the process. The pathname argument is the path name of the object to be opened. A path name containing an embedded '/' is interpreted as an absolute path or relative to the current directory. Otherwise, the set of search paths currently in effect by the runtime linker are used to locate the specified file. See NOTES. If the object file referenced by dlopen() is not already loaded as part of the process, then the object file is added to the process address space. A handle for this object is created and returned to the caller. If the object file is already part of the process, a handle is also returned to the caller. Multiple references to the same object result in

returning the same handle. A reference count within the han-

dle maintains the number of callers. The dlclose() of a han-

dle results in decrementing the handles reference count.

When the reference count reaches 0 the object file is a can-

didate for unloading. Any init section within an object is called once when the object is loaded. Any fini section within an object is called once when the object is unloaded. When dlopen() causes an object to be loaded, it also loads

any non-lazy dependencies that are recorded within the

object given by pathname. These dependencies are searched in the order in which the dependencies were loaded to locate any additional dependencies. This process continues until all the dependencies of pathname are loaded. This dependency tree is referred to as a group.

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Standard C Library Functions dlopen(3C) If the value of pathname is 0, dlopen() provides a handle on a set of global symbol objects. These objects consist of the

original program image file, any dependencies loaded at pro-

gram startup, and any objects loaded using dlopen() with the

RTLD_GLOBAL flag. Because the latter set of objects can

change during process execution, the set identified by han-

dle can also change dynamically.

The mode argument describes how dlopen() operates on path-

name with respect to the processing of reference reloca-

tions. The mode also affects the scope of visibility of the symbols provided by pathname and its dependencies. This visibility can affect how the resulting handle is used. When an object is loaded, the object can contain references to symbols whose addresses are not known until the object is

loaded. These references must be relocated before the sym-

bols can be accessed. References are categorized as either

immediate or lazy. Immediate references are typically refer-

ences to data items used by the object code. Immediate

references include pointers to functions and calls to func-

tions made from position-dependent shared objects. Lazy

references are typically calls to global functions that are

made from position-independent shared objects.

Lazy references can also be identified as deferred. See the

-z deferred option of ld(1). Deferred dependencies are only

loaded during process execution, when the first binding to a deferred reference is made. These references are unaffected by the mode.

The mode argument governs when non-deferred references take

place. The mode argument can be one of the following values.

RTLD_LAZY Only immediate symbol references are relocated

when the object is first loaded. Lazy refer-

ences are not relocated until a given function is called for the first time. This value for

mode should improve performance, since a pro-

cess might not require all lazy references in

any given object. This behavior mimics the nor-

mal loading of dependencies during process ini-

tialization. See NOTES.

RTLD_NOW All non-deferred relocations are performed when

the object is first loaded. This process might waste some processing if relocations are

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Standard C Library Functions dlopen(3C) performed for lazy references that are never used. However, this mode ensures that when an

object is loaded, all non-deferred symbols that

are referenced during execution are available.

This behavior mimics the loading of dependen-

cies when the environment variable LD_BIND_NOW

is in effect. See the Linker and Libraries Guide for more information about symbol references. The visibility of symbols that are available for relocation can be affected by mode. To specify the scope of visibility for symbols that are loaded with a dlopen() call, mode

should be a bitwise-inclusive OR with one of the following

values:

RTLD_GLOBAL The object's global symbols are made avail-

able for the relocation processing of any other object. In addition, symbol lookup using dlopen(0, mode) and an associated dlsym() allows objects that are loaded with

RTLD_GLOBAL to be searched.

RTLD_LOCAL The object's globals symbols are only avail-

able for the relocation processing of other objects that include the same group. The program image file and any objects loaded at program

startup have the mode RTLD_GLOBAL. The mode RTLD_LOCAL is

the default mode for any objects that are acquired with dlo-

pen(). A local object can be a dependency of more then one

group. Any object of mode RTLD_LOCAL that is referenced as a

dependency of an object of mode RTLD_GLOBAL is promoted to

RTLD_GLOBAL. In other words, the RTLD_LOCAL mode is ignored.

Any object loaded by dlopen() that requires relocations against global symbols can reference the symbols in any

RTLD_GLOBAL object. Objects of this mode are at least the

program image file and any objects loaded at program startup. A loaded object can also reference symbols from itself, and from any dependencies the object references.

However, the mode parameter can also be a bitwise-inclusive

OR with one of the following values to affect the scope of symbol availability:

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Standard C Library Functions dlopen(3C)

RTLD_GROUP Only symbols from the associated group are

made available for relocation. A group is established from the defined object and all the dependencies of that object. A group must

be completely self-contained. All dependency

relationships between the members of the

group must be sufficient to satisfy the relo-

cation requirements of each object that defines the group.

RTLD_PARENT The symbols of the object initiating the dlo-

pen() call are made available to the objects obtained by dlopen(). This option is useful when hierarchical dlopen() families are

created. Although the parent object can sup-

ply symbols for the relocation of this object, the parent object is not available to dlsym() through the returned handle.

RTLD_WORLD Only symbols from RTLD_GLOBAL objects are

made available for relocation.

The default modes for dlopen() are both RTLD_WORLD and

RTLD_GROUP. If an object is requires additional modes, the

mode parameter can be the bitwise-inclusive OR of the

required modes together with the default modes. The following modes provide additional capabilities outside of relocation processing:

RTLD_NODELETE The specified object is tagged to prevent

its deletion from the address space as part of a dlclose().

RTLD_NOLOAD The specified object is not loaded as part

of the dlopen(). However, a valid handle is returned if the object already exists as

part of the process address space. Addi-

tional modes can be specified as a

bitwise-inclusive OR with the present mode

of the object and its dependencies. The

RTLD_NOLOAD mode provides a means of query-

ing the presence or promoting the modes of an existing dependency.

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Standard C Library Functions dlopen(3C) The default use of a handle with dlsym() allows a symbol search to inspect all objects that are associated with the group of objects that are loaded from dlopen(). The mode

parameter can also be a bitwise-inclusive OR with the fol-

lowing value to restrict this symbol search:

RTLD_FIRST Use of this handle with dlsym(), restricts the

symbol search to the first object associated with the handle. An object can be accessed from a process both with and

without RTLD_FIRST. Although the object will only be loaded

once, two different handles are created to provide for the different dlsym() requirements.

The dlmopen() function is identical to dlopen(), except that

an identifying link-map ID (lmid) is provided. This link-map

ID informs the dynamic linking facilities upon which link-

map list to load the object. See the Linker and Libraries

Guide for details about link-maps.

The lmid passed to dlmopen() identifies the link-map list on

which the object is loaded. This parameter can be any valid

Lmid_t returned by dlinfo() or one of the following special

values:

LM_ID_BASE Load the object on the applications link-map

list.

LM_ID_LDSO Load the object on the dynamic linkers

(ld.so.1) link-map list.

LM_ID_NEWLM Cause the object to create a new link-map

list as part of loading. Objects that are

opened on a new link-map list must express

all of their dependencies.

RETURN VALUES

The dlopen() function returns NULL if pathname cannot be found, cannot be opened for reading, or is not a shared object or a relocatable object. dlopen() also returns NULL if an error occurs during the process of loading pathname or relocating its symbolic references. See NOTES. Additional diagnostic information is available through dlerror().

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Standard C Library Functions dlopen(3C)

USAGE

The dlopen() and dlmopen() functions are members of a family

of functions that give the user direct access to the dynamic linking facilities. This family of functions is available

only to dynamically-linked processes. See the Linker and

Libraries Guide.

ATTRIBUTES

See attributes(5) for descriptions of the following attri-

butes:

____________________________________________________________

| ATTRIBUTE TYPE | ATTRIBUTE VALUE |

|_____________________________|_____________________________|

| Interface Stability | Committed |

|_____________________________|_____________________________|

| MT-Level | MT-Safe |

|_____________________________|_____________________________|

| Standard | See standards(5). |

|_____________________________|_____________________________|

Manual Pages for UNIX Operating System command usage for man dlmopen

NAME

dlopen, dlmopen - gain access to an executable object file

SYNOPSIS

void * dlmopen(Lmid_t lmid, const char *pathname, int mode);

DESCRIPTION

The dlmopen() function is identical to dlopen(), except that

The lmid passed to dlmopen() identifies the link-map list on

RETURN VALUES

USAGE

The dlopen() and dlmopen() functions are members of a family

ATTRIBUTES

| ATTRIBUTE TYPE | ATTRIBUTE VALUE |

SEE ALSO