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search.c revision 1.2 
      1 /*	$NetBSD: search.c,v 1.2 1997/02/03 19:45:02 cgd Exp $	*/
      2 
      3 /*
      4  * Copyright 1996 Matt Thomas <matt (at) 3am-software.com>
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *      This product includes software developed by John Polstra.
     18  * 4. The name of the author may not be used to endorse or promote products
     19  *    derived from this software without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 /*
     34  * Dynamic linker for ELF.
     35  *
     36  * John Polstra <jdp (at) polstra.com>.
     37  */
     38 
     39 #include <err.h>
     40 #include <errno.h>
     41 #include <fcntl.h>
     42 #include <stdarg.h>
     43 #include <stdio.h>
     44 #include <stdlib.h>
     45 #include <string.h>
     46 #include <unistd.h>
     47 #include <sys/types.h>
     48 #include <sys/mman.h>
     49 #include <sys/stat.h>
     50 #include <dirent.h>
     51 
     52 #include "debug.h"
     53 #include "rtld.h"
     54 
     55 #define CONCAT(x,y)     __CONCAT(x,y)
     56 #define ELFNAME(x)      CONCAT(elf,CONCAT(ELFSIZE,CONCAT(_,x)))
     57 #define ELFNAME2(x,y)   CONCAT(x,CONCAT(_elf,CONCAT(ELFSIZE,CONCAT(_,y))))
     58 #define ELFNAMEEND(x)   CONCAT(x,CONCAT(_elf,ELFSIZE))
     59 #define ELFDEFNNAME(x)  CONCAT(ELF,CONCAT(ELFSIZE,CONCAT(_,x)))
     60 
     61 /*
     62  * Data declarations.
     63  */
     64 
     65 typedef struct {
     66     const char *si_name;
     67     const char *si_best_name;
     68     char *si_best_fullpath;
     69     const Search_Path *si_best_path;
     70     size_t si_namelen;
     71     int si_desired_major;
     72     int si_desired_minor;
     73     int si_best_major;
     74     int si_best_minor;
     75     unsigned si_exact : 1;
     76 } Search_Info;
     77 
     78 typedef enum {
     79     Search_FoundNothing,
     80     Search_FoundLower,
     81     Search_FoundHigher,
     82     Search_FoundExact
     83 } Search_Result;
     84 
     85 static bool
     86 _rtld_check_library(
     87     const Search_Path *sp,
     88     const char *name,
     89     size_t namelen,
     90     char **fullpath_p)
     91 {
     92     struct stat mystat;
     93     char *fullpath;
     94     Elf_Ehdr ehdr;
     95     int fd;
     96 
     97     fullpath = xmalloc(sp->sp_pathlen + 1 + namelen + 1);
     98     strncpy(fullpath, sp->sp_path, sp->sp_pathlen);
     99     fullpath[sp->sp_pathlen] = '/';
    100     strcpy(&fullpath[sp->sp_pathlen + 1], name);
    101 
    102     dbg("  Trying \"%s\"", fullpath);
    103     if (stat(fullpath, &mystat) >= 0 && S_ISREG(mystat.st_mode)) {
    104 	if ((fd = open(fullpath, O_RDONLY)) >= 0) {
    105 	    if (read(fd, &ehdr, sizeof(ehdr)) != sizeof(ehdr))
    106 		goto lose;
    107 
    108 	    /* Elf_e_ident includes class */
    109 	    if (memcmp(Elf_e_ident, ehdr.e_ident, Elf_e_siz) != 0)
    110 		goto lose;
    111 
    112 	    switch (ehdr.e_machine) {
    113 	    ELFDEFNNAME(MACHDEP_ID_CASES)
    114 
    115 	    default:
    116 		goto lose;
    117 	    }
    118 
    119 	    if (ehdr.e_ident[Elf_ei_version] != Elf_ev_current ||
    120 	      ehdr.e_version != Elf_ev_current ||
    121 	      ehdr.e_ident[Elf_ei_data] != ELFDEFNNAME(MACHDEP_ENDIANNESS) ||
    122 	      ehdr.e_type != Elf_et_dyn)
    123 		goto lose;
    124 
    125 	    if (*fullpath_p != NULL)
    126 		free(*fullpath_p);
    127 	    *fullpath_p = fullpath;
    128 	    close(fd);
    129 	    return true;
    130 
    131 lose:
    132 	    close(fd);
    133 	}
    134     }
    135 
    136     free(fullpath);
    137     return false;
    138 }
    139 
    140 static Search_Result
    141 _rtld_search_directory(
    142     const Search_Path *sp,
    143     Search_Info *si)
    144 {
    145     struct dirent *entry;
    146     DIR *dirp;
    147     Search_Result result = Search_FoundNothing;
    148 
    149 dbg("_rtld_search_directory");
    150     if (sp->sp_path == NULL || sp->sp_path[0] == '\0')
    151 	return result;
    152 
    153 dbg("_rtld_search_directory 2");
    154     if ((dirp = opendir(sp->sp_path)) == NULL) {
    155 	dbg("_rtld_search_directory 2.1");
    156 	return result;
    157     }
    158 
    159 dbg("_rtld_search_directory 3");
    160     while ((entry = readdir(dirp)) != NULL) {
    161 	long major = -1;
    162 	long minor = -1;
    163 	if (strncmp(entry->d_name, si->si_name, si->si_namelen))
    164 	    continue;
    165 	/*
    166 	 * We are matching libfoo.so only (no more info).  Only take
    167 	 * it as a last resort.
    168 	 */
    169 	if (si->si_exact) {
    170 	    if (strcmp(entry->d_name, si->si_name))
    171 		continue;
    172 #ifdef notyet
    173 	} else if (entry->d_namlen == si->si_namelen) {
    174 	    if (si->si_best_path != NULL || si->si_best_major != -1)
    175 		continue;
    176 #endif
    177 	} else {
    178 	    char *cp;
    179 	    /*
    180 	     * We expect (demand!) that it be of the form
    181 	     * "libfoo.so.<something>"
    182 	     */
    183 	    if (entry->d_name[si->si_namelen] != '.')
    184 		continue;
    185 	    /*
    186 	     * This file has a least a major number (well, maybe not if it
    187 	     * has a name of "libfoo.so." but treat that as equivalent to 0.
    188 	     * It had better match what we are looking for.
    189 	     */
    190 	    major = strtol(&entry->d_name[si->si_namelen+1], &cp, 10);
    191 	    if (major < 0 || (cp[0] != '\0' && cp[0] != '.')
    192 		    || &entry->d_name[si->si_namelen+1] == cp)
    193 		continue;
    194 	    if (cp[0] == '.') {
    195 		char *cp2;
    196 		minor = strtol(&cp[1], &cp2, 10);
    197 		if (minor < 0 || cp2[0] != '\0' || cp == cp2)
    198 		    continue;
    199 	    } else {
    200 		minor = 0;
    201 	    }
    202 	    if (major != si->si_desired_major || minor <= si->si_best_minor)
    203 		continue;
    204 	}
    205 	/*
    206 	 * We have a better candidate...
    207 	 */
    208 	if (!_rtld_check_library(sp, entry->d_name, entry->d_namlen,
    209 			   &si->si_best_fullpath))
    210 	    continue;
    211 
    212 	si->si_best_name = &si->si_best_fullpath[sp->sp_pathlen + 1];
    213 	si->si_best_major = major;
    214 	si->si_best_minor = minor;
    215 	si->si_best_path = sp;
    216 
    217 	if (si->si_exact || si->si_best_minor == si->si_desired_minor)
    218 	    result = Search_FoundExact;
    219 	else if (si->si_best_minor > si->si_desired_minor)
    220 	    result = Search_FoundHigher;
    221 	else
    222 	    result = Search_FoundLower;
    223 
    224 	/*
    225 	 * We were looking for, and found, an exact match.  We're done.
    226 	 */
    227 	if (si->si_exact)
    228 	    break;
    229     }
    230 
    231     dbg("found %s (%d.%d) match for %s (%d.%d) -> %s",
    232 	result == Search_FoundNothing ? "no"
    233 	: result == Search_FoundLower ? "lower"
    234 	: result == Search_FoundExact ? "exact" : "higher",
    235 	si->si_best_major, si->si_best_minor,
    236 	si->si_name,
    237 	si->si_desired_major, si->si_desired_minor,
    238 	si->si_best_fullpath ? si->si_best_fullpath : sp->sp_path);
    239 
    240     closedir(dirp);
    241     return result;
    242 }
    243 
    244 static char *
    246 _rtld_search_library_paths(
    247     const char *name,
    248     Search_Path *paths,
    249     const Search_Path *rpaths)
    250 {
    251     Search_Info info;
    252     Search_Path *path;
    253     const char *cp;
    254     Search_Result result = Search_FoundNothing;
    255 
    256     memset(&info, 0, sizeof(info));
    257     info.si_name = name;
    258     info.si_desired_major = -1;
    259     info.si_desired_minor = -1;
    260     info.si_best_major = -1;
    261     info.si_best_minor = -1;
    262 
    263     cp = strstr(name, ".so");
    264     if (cp == NULL) {
    265 	info.si_exact = true;
    266     } else {
    267 	cp += sizeof(".so") - 1;
    268 	info.si_namelen = cp - name;
    269 	if (cp[0] != '.') {
    270 	    info.si_exact = true;
    271 	} else {
    272 	    info.si_desired_major = atoi(&cp[1]);
    273 	    if ((cp = strchr(&cp[1], '.')) != NULL) {
    274 		info.si_desired_minor = atoi(&cp[1]);
    275 	    } else {
    276 		info.si_desired_minor = 0;
    277 	    }
    278 	}
    279     }
    280 
    281     if (rpaths != NULL && result < Search_FoundHigher) {	/* Exact? */
    282 	dbg("  checking rpaths..");
    283 	for (; rpaths != NULL; rpaths = rpaths->sp_next) {
    284 	    dbg("   in \"%s\"", rpaths->sp_path);
    285 	    result = _rtld_search_directory(rpaths, &info);
    286 	    if (result >= Search_FoundHigher)	/* Exact? */
    287 		break;
    288 	}
    289     }
    290     if (result < Search_FoundHigher) {	/* Exact? */
    291 	dbg("  checking default paths..");
    292 	for (path = paths; path != NULL; path = path->sp_next) {
    293 	    dbg("   in \"%s\"", path->sp_path);
    294 	    result = _rtld_search_directory(path, &info);
    295 	    if (result >= Search_FoundHigher)	/* Exact? */
    296 		break;
    297 	}
    298     }
    299 
    300     if (result >= Search_FoundHigher)
    301 	return info.si_best_fullpath;
    302 
    303     if (info.si_best_fullpath != NULL)
    304 	free(info.si_best_fullpath);
    305     return NULL;
    306 }
    307 
    308 /*
    309  * Find the library with the given name, and return its full pathname.
    310  * The returned string is dynamically allocated.  Generates an error
    311  * message and returns NULL if the library cannot be found.
    312  *
    313  * If the second argument is non-NULL, then it refers to an already-
    314  * loaded shared object, whose library search path will be searched.
    315  */
    316 char *
    317 _rtld_find_library(
    318     const char *name,
    319     const Obj_Entry *refobj)
    320 {
    321     char *pathname;
    322 
    323     if (strchr(name, '/') != NULL) {	/* Hard coded pathname */
    324 	if (name[0] != '/' && !_rtld_trust) {
    325 	    _rtld_error("Absolute pathname required for shared object \"%s\"",
    326 			name);
    327 	    return NULL;
    328 	}
    329 #ifdef SVR4_LIBDIR
    330 	if (strncmp(name, SVR4_LIBDIR, SVR4_LIBDIRLEN) == 0
    331 	        && name[SVR4_LIBDIRLEN] == '/') {	/* In "/usr/lib" */
    332 	    /* Map hard-coded "/usr/lib" onto our ELF library directory. */
    333 	    pathname = xmalloc(strlen(name) + LIBDIRLEN - SVR4_LIBDIRLEN + 1);
    334 	    strcpy(pathname, LIBDIR);
    335 	    strcpy(pathname + LIBDIRLEN, name + SVR4_LIBDIRLEN);
    336 	    return pathname;
    337 	}
    338 #endif /* SVR4_LIBDIR */
    339 	return xstrdup(name);
    340     }
    341 
    342     dbg(" Searching for \"%s\" (%p)", name, refobj);
    343 
    344     pathname = _rtld_search_library_paths(name, _rtld_paths,
    345 					  refobj ? refobj->rpaths : NULL);
    346     if (pathname == NULL)
    347 	_rtld_error("Shared object \"%s\" not found", name);
    348     return pathname;
    349 }
    350