\"      $NetBSD: dlinfo.3,v 1.7 2022/03/06 23:36:01 andvar Exp $
\"
\" Copyright (c) 2003 Alexey Zelkin <[email protected]>
\" All rights reserved.
\"
\" Redistribution and use in source and binary forms, with or without
\" modification, are permitted provided that the following conditions
\" are met:
\" 1. Redistributions of source code must retain the above copyright
\"    notice, this list of conditions and the following disclaimer.
\" 2. Redistributions in binary form must reproduce the above copyright
\"    notice, this list of conditions and the following disclaimer in the
\"    documentation and/or other materials provided with the distribution.
\"
\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
\" SUCH DAMAGE.
\"
\" $FreeBSD: head/lib/libc/gen/dlinfo.3 267774 2014-06-23 08:25:03Z bapt $
\"
Dd January 13, 2020
Dt DLINFO 3
Os
Sh NAME
Nm dlinfo
Nd information about a dynamically loaded object
Sh LIBRARY
(These functions are not in a library.
They are included in every
dynamically linked program automatically.)
Sh SYNOPSIS
In link.h
In dlfcn.h
Ft int
Fn dlinfo "void *handle" "int request" "void *p"
Sh DESCRIPTION
The
Fn dlinfo
function provides information about a dynamically loaded object.
The action taken by
Fn dlinfo
and exact meaning and type of
Fa p
argument depend on value of the
Fa request
argument provided by caller.
Pp
The
Fa handle
argument is either the value returned from the
Xr dlopen 3
function call or special handle
Dv RTLD_SELF .
If
Fa handle
is the value returned from
Xr dlopen 3 ,
the information returned by the
Fn dlinfo
function pertains to the specified object.
If
Fa handle
is the special handle
Dv RTLD_SELF ,
the information returned pertains to the caller itself.
Pp
Possible values for the
Fa request
argument are:
Bl -tag -width "Dv RTLD_"
It Dv RTLD_DI_LINKMAP
Retrieve the pointer to the
Vt Link_map
for the specified
Fa handle .
On successful return, the
Fa p
argument is filled with the pointer to the
Vt Link_map
structure
Pq Fa "Link_map **p"
describing a shared object specified by the
Fa handle
argument.
The
Vt Link_map
structures are maintained as a doubly linked list by
Xr ld.so 1 ,
in the same order as
Xr dlopen 3
and
Xr dlclose 3
are called.
Pp
The
Vt Link_map
structure is defined in
In link.h
and has the following members:
Bd -literal -offset indent
caddr_t         l_addr;    /* Base Address of library */
#ifdef __mips__
caddr_t         l_offs;    /* Load Offset of library */
#endif
const char      *l_name;   /* Absolute Path to Library */
void            *l_ld;     /* Pointer to .dynamic in memory */
struct link_map *l_next,   /* linked list of mapped libs */
               *l_prev;
Ed
Bl -tag -width Va
It Va l_addr
The base address of the object loaded into memory.
It Va l_name
The absolute pathname of the loaded shared object.
It Va l_ld
The address of the dynamic linking information segment
Pq Dv PT_DYNAMIC
loaded into memory.
It Va l_next
The next
Vt Link_map
structure on the link-map list.
It Va l_prev
The previous
Vt Link_map
structure on the link-map list.
El
\" .It Dv RTLD_DI_SERINFO
\" Retrieve the library search paths associated with the given
\" .Fa handle
\" argument.
\" The
\" .Fa p
\" argument should point to
\" .Vt Dl_serinfo
\" structure buffer
\" .Pq Fa "Dl_serinfo *p" .
\" The
\" .Vt Dl_serinfo
\" structure must be initialized first with the
\" .Dv RTLD_DI_SERINFOSIZE
\" request.
\" .Pp
\" The returned
\" .Vt Dl_serinfo
\" structure contains
\" .Va dls_cnt
\" .Vt Dl_serpath
\" entries.
\" Each entry's
\" .Va dlp_name
\" field points to the search path.
\" The corresponding
\" .Va dlp_info
\" field contains one of more flags indicating the origin of the path (see the
\" .Dv LA_SER_*
\" flags defined in the
\" .In link.h
\" header file).
\" See
\" .Sx EXAMPLES ,
\" example 2, for a usage example.
\" .It Dv RTLD_DI_SERINFOSIZE
\" Initialize a
\" .Vt Dl_serinfo
\" structure for use in a
\" .Dv RTLD_DI_SERINFO
\" request.
\" Both the
\" .Va dls_cnt
\" and
\" .Va dls_size
\" fields are returned to indicate the number of search paths applicable
\" to the handle, and the total size of a
\" .Vt Dl_serinfo
\" buffer required to hold
\" .Va dls_cnt
\" .Vt Dl_serpath
\" entries and the associated search path strings.
\" See
\" .Sx EXAMPLES ,
\" example 2, for a usage example.
\" .It Va RTLD_DI_ORIGIN
\" Retrieve the origin of the dynamic object associated with the handle.
\" On successful return,
\" .Fa p
\" argument is filled with the
\" .Vt char
\" pointer
\" .Pq Fa "char *p" .
El
Sh RETURN VALUES
The
Fn dlinfo
function returns 0 on success, or \-1 if an error occurred.
Whenever an error has been detected, a message detailing it can
be retrieved via a call to
Xr dlerror 3 .
Sh EXAMPLES
Using
Fn dlinfo
to retrieve
Vt Link_map
structure.
Pp
The following example shows how dynamic library can detect the list
of shared libraries loaded after caller's one.
For simplicity, error checking has been omitted.
Bd -literal -offset indent
Link_map *map;

dlinfo(RTLD_SELF, RTLD_DI_LINKMAP, &map);

while (map != NULL) {
       printf("%p: %s\\n", map->l_addr, map->l_name);
       map = map->l_next;
}
Ed
\" .Pp
\" Example 2: Using
\" .Fn dlinfo
\" to retrieve the library search paths.
\" .Pp
\" The following example shows how a dynamic object can inspect the library
\" search paths that would be used to locate a simple filename with
\" .Xr dlopen 3 .
\" For simplicity, error checking has been omitted.
\" .Bd -literal -offset indent
\" Dl_serinfo    _info, *info = &_info;
\" Dl_serpath   *path;
\" unsigned int  cnt;
\"
\" /* determine search path count and required buffer size */
\" dlinfo(RTLD_SELF, RTLD_DI_SERINFOSIZE, (void *)info);
\"
\" /* allocate new buffer and initialize */
\" info = malloc(_info.dls_size);
\" info->dls_size = _info.dls_size;
\" info->dls_cnt = _info.dls_cnt;
\"
\" /* obtain search path information */
\" dlinfo(RTLD_SELF, RTLD_DI_SERINFO, (void *)info);
\"
\" path = &info->dls_serpath[0];
\"
\" for (cnt = 1; cnt <= info->dls_cnt; cnt++, path++) {
\"      (void) printf("%2d: %s\\n", cnt, path->dls_name);
\" }
\" .Ed
Sh SEE ALSO
Xr rtld 1 ,
Xr dladdr 3 ,
Xr dlopen 3 ,
Xr dlsym 3
Sh HISTORY
The
Fn dlinfo
function first appeared in the Solaris operating system.
In
Nx ,
it first appeared in
Nx 5.1 .
Sh AUTHORS
An -nosplit
The
Nx
implementation of the
Fn dlinfo
function was written by
An Antti Kantee Aq Mt [email protected] .
Pp
The manual page for this function was written by
An Alexey Zelkin Aq Mt [email protected]
and adapted to
Nx
by
An Kamil Rytarowski Aq Mt [email protected] .

You are viewing proxied material from ftp.icm.edu.pl. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.