usr/src/lib/libc/port/gen/nss_deffinder.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #pragma ident   "%Z%%M% %I%     %E% SMI"
  28
  29 /*
  30  * Default backend-finder(s) for the name-service-switch routines.
  31  * At present there is a single finder that uses dlopen() to do its thing.
  32  *
  33  * === Could also do a finder that includes db-name in filename
  34  * === and one that does dlopen(0) to check in the executable
  35  */
  36
  37         /* Allow our finder(s) to be overridden by user-supplied ones */
  38
  39 #pragma weak _nss_default_finders = nss_default_finders
  40
  41 #include "lint.h"
  42 #include "mtlib.h"
  43 #include <nss_common.h>
  44 #include <dlfcn.h>
  45 #include <stdio.h>
  46 #include <stdlib.h>
  47 #include <string.h>
  48 #include <alloca.h>
  49
  50 /* === ? move these constants to a public header file ? */
  51 static const int  dlopen_version  = 1;
  52 #ifndef NSS_DLOPEN_FORMAT
  53 #define NSS_DLOPEN_FORMAT "nss_%s.so.%d"
  54 #endif
  55 #ifndef NSS_DLSYM_FORMAT
  56 #define NSS_DLSYM_FORMAT "_nss_%s_%s_constr"
  57 #endif
  58 static const char dlopen_format[] = NSS_DLOPEN_FORMAT;
  59 static const char dlsym_format [] = NSS_DLSYM_FORMAT;
  60 static const size_t  format_maxlen   = sizeof (dlsym_format) - 4;
  61
  62 /*ARGSUSED*/
  63 static nss_backend_constr_t
  64 SO_per_src_lookup(void *dummy, const char *db_name, const char *src_name,
  65         void **delete_privp)
  66 {
  67         char                    *name;
  68         void                    *dlhandle;
  69         void                    *sym;
  70         size_t                  len;
  71         nss_backend_constr_t    res = 0;
  72
  73         len = format_maxlen + strlen(db_name) + strlen(src_name);
  74         name = alloca(len);
  75         (void) sprintf(name, dlopen_format, src_name, dlopen_version);
  76         if ((dlhandle = dlopen(name, RTLD_LAZY)) != 0) {
  77                 (void) sprintf(name, dlsym_format, src_name, db_name);
  78                 if ((sym = dlsym(dlhandle, name)) == 0) {
  79                         (void) dlclose(dlhandle);
  80                 } else {
  81                         *delete_privp = dlhandle;
  82                         res = (nss_backend_constr_t)sym;
  83                 }
  84         }
  85         return (res);
  86 }
  87
  88 /*ARGSUSED*/
  89 static void
  90 SO_per_src_delete(void *delete_priv, nss_backend_constr_t dummy)
  91 {
  92         (void) dlclose(delete_priv);
  93 }
  94
  95 static nss_backend_finder_t SO_per_src = {
  96         SO_per_src_lookup,
  97         SO_per_src_delete,
  98         0,
  99         0
 100 };
 101
 102 nss_backend_finder_t *nss_default_finders = &SO_per_src;