.\" $NetBSD: dlinfo.3,v 1.7 2022/03/06 23:36:01 andvar Exp $ .\" .\" 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 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 pooka@NetBSD.org . .Pp The manual page for this function was written by .An Alexey Zelkin Aq Mt phantom@FreeBSD.org and adapted to .Nx by .An Kamil Rytarowski Aq Mt kamil@NetBSD.org .