.\" .\" Copyright (c) 2003 Alexey Zelkin .\" 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 February 14, 2003 .Dt DLINFO 3 .Os .Sh NAME .Nm dlinfo .Nd information about dynamically loaded object .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In link.h .In dlfcn.h .Ft int .Fn dlinfo "void * restrict handle" "int request" "void * restrict p" .Sh DESCRIPTION The .Fn dlinfo function provides information about 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 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 indent .It Dv RTLD_DI_LINKMAP Retrieve the .Vt Link_map .Pq Vt "struct link_map" structure pointer 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. See .Sx EXAMPLES , example 1. .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 */ const char *l_name; /* Absolute Path to Library */ const 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 l_addr" .It Va l_addr The base address of the object loaded into memory. .It Va l_name The full name 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 Example 1: 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 sarch 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 .Fx , it first appeared in .Fx 4.8 . .Sh AUTHORS .An -nosplit The .Fx implementation of the .Fn dlinfo function was originally written by .An Alexey Zelkin Aq Mt phantom@FreeBSD.org and later extended and improved by .An Alexander Kabaev Aq Mt kan@FreeBSD.org . .Pp The manual page for this function was written by .An Alexey Zelkin Aq Mt phantom@FreeBSD.org .